Actual source code: snes.c

  1: #include <petsc/private/snesimpl.h>
  2: #include <petscdmshell.h>
  3: #include <petscdraw.h>
  4: #include <petscds.h>
  5: #include <petscdmadaptor.h>
  6: #include <petscconvest.h>

  8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
  9: PetscFunctionList SNESList              = NULL;

 11: /* Logging support */
 12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
 13: PetscLogEvent SNES_Solve, SNES_SetUp, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve, SNES_ObjectiveEval;

 15: /*@
 16:    SNESSetErrorIfNotConverged - Causes `SNESSolve()` to generate an error immediately if the solver has not converged.

 18:    Logically Collective

 20:    Input Parameters:
 21: +  snes - iterative context obtained from `SNESCreate()`
 22: -  flg - `PETSC_TRUE` indicates you want the error generated

 24:    Options Database Key:
 25: .  -snes_error_if_not_converged <true,false> - cause an immediate error condition and stop the program if the solver does not converge

 27:    Level: intermediate

 29:    Note:
 30:    Normally PETSc continues if a solver fails to converge, you can call `SNESGetConvergedReason()` after a `SNESSolve()`
 31:    to determine if it has converged. Otherwise the solution may be inaccurate or wrong

 33: .seealso: [](chapter_snes), `SNES`, `SNESGetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 34: @*/
 35: PetscErrorCode SNESSetErrorIfNotConverged(SNES snes, PetscBool flg)
 36: {
 37:   PetscFunctionBegin;
 40:   snes->errorifnotconverged = flg;
 41:   PetscFunctionReturn(PETSC_SUCCESS);
 42: }

 44: /*@
 45:    SNESGetErrorIfNotConverged - Indicates if `SNESSolve()` will generate an error if the solver does not converge?

 47:    Not Collective

 49:    Input Parameter:
 50: .  snes - iterative context obtained from `SNESCreate()`

 52:    Output Parameter:
 53: .  flag - `PETSC_TRUE` if it will generate an error, else `PETSC_FALSE`

 55:    Level: intermediate

 57: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 58: @*/
 59: PetscErrorCode SNESGetErrorIfNotConverged(SNES snes, PetscBool *flag)
 60: {
 61:   PetscFunctionBegin;
 64:   *flag = snes->errorifnotconverged;
 65:   PetscFunctionReturn(PETSC_SUCCESS);
 66: }

 68: /*@
 69:     SNESSetAlwaysComputesFinalResidual - tells the `SNES` to always compute the residual (nonlinear function value) at the final solution

 71:    Logically Collective

 73:     Input Parameters:
 74: +   snes - the shell `SNES`
 75: -   flg - `PETSC_TRUE` to always compute the residual

 77:    Level: advanced

 79:    Note:
 80:    Some solvers (such as smoothers in a `SNESFAS`) do not need the residual computed at the final solution so skip computing it
 81:    to save time.

 83: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetAlwaysComputesFinalResidual()`
 84: @*/
 85: PetscErrorCode SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
 86: {
 87:   PetscFunctionBegin;
 89:   snes->alwayscomputesfinalresidual = flg;
 90:   PetscFunctionReturn(PETSC_SUCCESS);
 91: }

 93: /*@
 94:     SNESGetAlwaysComputesFinalResidual - checks if the `SNES` always computes the residual at the final solution

 96:    Logically Collective

 98:     Input Parameter:
 99: .   snes - the `SNES` context

101:     Output Parameter:
102: .   flg - `PETSC_TRUE` if the residual is computed

104:    Level: advanced

106: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetAlwaysComputesFinalResidual()`
107: @*/
108: PetscErrorCode SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
109: {
110:   PetscFunctionBegin;
112:   *flg = snes->alwayscomputesfinalresidual;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /*@
117:    SNESSetFunctionDomainError - tells `SNES` that the input vector, a proposed new solution, to your function you provided to `SNESSetFunction()` is not
118:      in the functions domain. For example, a step with negative pressure.

120:    Logically Collective

122:    Input Parameter:
123: .  snes - the `SNES` context

125:    Level: advanced

127:    Note:
128:    You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
129:    `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

131: .seealso: [](chapter_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunction`, `SNESSetJacobianDomainError()`, `SNESVISetVariableBounds()`,
132:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`
133: @*/
134: PetscErrorCode SNESSetFunctionDomainError(SNES snes)
135: {
136:   PetscFunctionBegin;
138:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates input vector is not in the function domain");
139:   snes->domainerror = PETSC_TRUE;
140:   PetscFunctionReturn(PETSC_SUCCESS);
141: }

143: /*@
144:    SNESSetJacobianDomainError - tells `SNES` that the function you provided to `SNESSetJacobian()` at the proposed step. For example there is a negative element transformation.

146:    Logically Collective

148:    Input Parameter:
149: .  snes - the `SNES` context

151:    Level: advanced

153:    Note:
154:    You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
155:    `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

157: .seealso: [](chapter_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESVISetVariableBounds()`,
158:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`
159: @*/
160: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
161: {
162:   PetscFunctionBegin;
164:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates computeJacobian does not make sense");
165:   snes->jacobiandomainerror = PETSC_TRUE;
166:   PetscFunctionReturn(PETSC_SUCCESS);
167: }

169: /*@
170:    SNESSetCheckJacobianDomainError - tells `SNESSolve()` whether to check if the user called `SNESSetJacobianDomainError()` Jacobian domain error after
171:    each Jacobian evaluation. By default, we check Jacobian domain error in the debug mode, and do not check it in the optimized mode.

173:    Logically Collective

175:    Input Parameters:
176: +  snes - the `SNES` context
177: -  flg  - indicates if or not to check Jacobian domain error after each Jacobian evaluation

179:    Level: advanced

181:    Note:
182:    Checks require one extra parallel synchronization for each Jacobian evaluation

184: .seealso: [](chapter_snes), `SNES`, `SNESConvergedReason`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESGetCheckJacobianDomainError()`
185: @*/
186: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
187: {
188:   PetscFunctionBegin;
190:   snes->checkjacdomainerror = flg;
191:   PetscFunctionReturn(PETSC_SUCCESS);
192: }

194: /*@
195:    SNESGetCheckJacobianDomainError - Get an indicator whether or not we are checking Jacobian domain errors after each Jacobian evaluation.

197:    Logically Collective

199:    Input Parameter:
200: .  snes - the `SNES` context

202:    Output Parameter:
203: .  flg  - `PETSC_FALSE` indicates that we don't check Jacobian domain errors after each Jacobian evaluation

205:    Level: advanced

207: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESSetCheckJacobianDomainError()`
208: @*/
209: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
210: {
211:   PetscFunctionBegin;
214:   *flg = snes->checkjacdomainerror;
215:   PetscFunctionReturn(PETSC_SUCCESS);
216: }

218: /*@
219:    SNESGetFunctionDomainError - Gets the status of the domain error after a call to `SNESComputeFunction()`;

221:    Logically Collective

223:    Input Parameter:
224: .  snes - the `SNES` context

226:    Output Parameter:
227: .  domainerror - Set to `PETSC_TRUE` if there's a domain error; `PETSC_FALSE` otherwise.

229:    Level: developer

231: .seealso: [](chapter_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`
232: @*/
233: PetscErrorCode SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
234: {
235:   PetscFunctionBegin;
238:   *domainerror = snes->domainerror;
239:   PetscFunctionReturn(PETSC_SUCCESS);
240: }

242: /*@
243:    SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to `SNESComputeJacobian()`;

245:    Logically Collective

247:    Input Parameter:
248: .  snes - the `SNES` context

250:    Output Parameter:
251: .  domainerror - Set to `PETSC_TRUE` if there's a Jacobian domain error; `PETSC_FALSE` otherwise.

253:    Level: advanced

255: .seealso: [](chapter_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`, `SNESGetFunctionDomainError()`
256: @*/
257: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
258: {
259:   PetscFunctionBegin;
262:   *domainerror = snes->jacobiandomainerror;
263:   PetscFunctionReturn(PETSC_SUCCESS);
264: }

266: /*@C
267:   SNESLoad - Loads a `SNES` that has been stored in `PETSCVIEWERBINARY` with `SNESView()`.

269:   Collective

271:   Input Parameters:
272: + newdm - the newly loaded `SNES`, this needs to have been created with `SNESCreate()` or
273:            some related function before a call to `SNESLoad()`.
274: - viewer - binary file viewer, obtained from `PetscViewerBinaryOpen()`

276:    Level: intermediate

278:   Note:
279:    The type is determined by the data in the file, any type set into the `SNES` before this call is ignored.

281: .seealso: [](chapter_snes), `SNES`, `PetscViewer`, `SNESCreate()`, `SNESType`, `PetscViewerBinaryOpen()`, `SNESView()`, `MatLoad()`, `VecLoad()`
282: @*/
283: PetscErrorCode SNESLoad(SNES snes, PetscViewer viewer)
284: {
285:   PetscBool isbinary;
286:   PetscInt  classid;
287:   char      type[256];
288:   KSP       ksp;
289:   DM        dm;
290:   DMSNES    dmsnes;

292:   PetscFunctionBegin;
295:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
296:   PetscCheck(isbinary, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Invalid viewer; open viewer with PetscViewerBinaryOpen()");

298:   PetscCall(PetscViewerBinaryRead(viewer, &classid, 1, NULL, PETSC_INT));
299:   PetscCheck(classid == SNES_FILE_CLASSID, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Not SNES next in file");
300:   PetscCall(PetscViewerBinaryRead(viewer, type, 256, NULL, PETSC_CHAR));
301:   PetscCall(SNESSetType(snes, type));
302:   PetscTryTypeMethod(snes, load, viewer);
303:   PetscCall(SNESGetDM(snes, &dm));
304:   PetscCall(DMGetDMSNES(dm, &dmsnes));
305:   PetscCall(DMSNESLoad(dmsnes, viewer));
306:   PetscCall(SNESGetKSP(snes, &ksp));
307:   PetscCall(KSPLoad(ksp, viewer));
308:   PetscFunctionReturn(PETSC_SUCCESS);
309: }

311: #include <petscdraw.h>
312: #if defined(PETSC_HAVE_SAWS)
313: #include <petscviewersaws.h>
314: #endif

316: /*@C
317:    SNESViewFromOptions - View a `SNES` based on values in the options database

319:    Collective

321:    Input Parameters:
322: +  A - the `SNES` context
323: .  obj - Optional object that provides the options prefix for the checks
324: -  name - command line option

326:    Level: intermediate

328: .seealso: [](chapter_snes), `SNES`, `SNESView`, `PetscObjectViewFromOptions()`, `SNESCreate()`
329: @*/
330: PetscErrorCode SNESViewFromOptions(SNES A, PetscObject obj, const char name[])
331: {
332:   PetscFunctionBegin;
334:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
335:   PetscFunctionReturn(PETSC_SUCCESS);
336: }

338: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES, Vec, Mat, Mat, void *);

340: /*@C
341:    SNESView - Prints or visualizes the `SNES` data structure.

343:    Collective

345:    Input Parameters:
346: +  snes - the `SNES` context
347: -  viewer - the `PetscViewer`

349:    Options Database Key:
350: .  -snes_view - Calls `SNESView()` at end of `SNESSolve()`

352:    Level: beginner

354:    Notes:
355:    The available visualization contexts include
356: +     `PETSC_VIEWER_STDOUT_SELF` - standard output (default)
357: -     `PETSC_VIEWER_STDOUT_WORLD` - synchronized standard
358:          output where only the first processor opens
359:          the file.  All other processors send their
360:          data to the first processor to print.

362:    The available formats include
363: +     `PETSC_VIEWER_DEFAULT` - standard output (default)
364: -     `PETSC_VIEWER_ASCII_INFO_DETAIL` - more verbose output for `SNESNASM`

366:    The user can open an alternative visualization context with
367:    `PetscViewerASCIIOpen()` - output to a specified file.

369:   In the debugger you can do "call `SNESView`(snes,0)" to display the `SNES` solver. (The same holds for any PETSc object viewer).

371: .seealso: [](chapter_snes), `SNES`, `SNESLoad()`, `SNESCreate()`, `PetscViewerASCIIOpen()`
372: @*/
373: PetscErrorCode SNESView(SNES snes, PetscViewer viewer)
374: {
375:   SNESKSPEW     *kctx;
376:   KSP            ksp;
377:   SNESLineSearch linesearch;
378:   PetscBool      iascii, isstring, isbinary, isdraw;
379:   DMSNES         dmsnes;
380: #if defined(PETSC_HAVE_SAWS)
381:   PetscBool issaws;
382: #endif

384:   PetscFunctionBegin;
386:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &viewer));
388:   PetscCheckSameComm(snes, 1, viewer, 2);

390:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
391:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSTRING, &isstring));
392:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
393:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERDRAW, &isdraw));
394: #if defined(PETSC_HAVE_SAWS)
395:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
396: #endif
397:   if (iascii) {
398:     SNESNormSchedule normschedule;
399:     DM               dm;
400:     PetscErrorCode (*cJ)(SNES, Vec, Mat, Mat, void *);
401:     void       *ctx;
402:     const char *pre = "";

404:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)snes, viewer));
405:     if (!snes->setupcalled) PetscCall(PetscViewerASCIIPrintf(viewer, "  SNES has not been set up so information may be incomplete\n"));
406:     if (snes->ops->view) {
407:       PetscCall(PetscViewerASCIIPushTab(viewer));
408:       PetscUseTypeMethod(snes, view, viewer);
409:       PetscCall(PetscViewerASCIIPopTab(viewer));
410:     }
411:     PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=%" PetscInt_FMT "\n", snes->max_its, snes->max_funcs));
412:     PetscCall(PetscViewerASCIIPrintf(viewer, "  tolerances: relative=%g, absolute=%g, solution=%g\n", (double)snes->rtol, (double)snes->abstol, (double)snes->stol));
413:     if (snes->usesksp) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of linear solver iterations=%" PetscInt_FMT "\n", snes->linear_its));
414:     PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of function evaluations=%" PetscInt_FMT "\n", snes->nfuncs));
415:     PetscCall(SNESGetNormSchedule(snes, &normschedule));
416:     if (normschedule > 0) PetscCall(PetscViewerASCIIPrintf(viewer, "  norm schedule %s\n", SNESNormSchedules[normschedule]));
417:     if (snes->gridsequence) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of grid sequence refinements=%" PetscInt_FMT "\n", snes->gridsequence));
418:     if (snes->ksp_ewconv) {
419:       kctx = (SNESKSPEW *)snes->kspconvctx;
420:       if (kctx) {
421:         PetscCall(PetscViewerASCIIPrintf(viewer, "  Eisenstat-Walker computation of KSP relative tolerance (version %" PetscInt_FMT ")\n", kctx->version));
422:         PetscCall(PetscViewerASCIIPrintf(viewer, "    rtol_0=%g, rtol_max=%g, threshold=%g\n", (double)kctx->rtol_0, (double)kctx->rtol_max, (double)kctx->threshold));
423:         PetscCall(PetscViewerASCIIPrintf(viewer, "    gamma=%g, alpha=%g, alpha2=%g\n", (double)kctx->gamma, (double)kctx->alpha, (double)kctx->alpha2));
424:       }
425:     }
426:     if (snes->lagpreconditioner == -1) {
427:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is never rebuilt\n"));
428:     } else if (snes->lagpreconditioner > 1) {
429:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is rebuilt every %" PetscInt_FMT " new Jacobians\n", snes->lagpreconditioner));
430:     }
431:     if (snes->lagjacobian == -1) {
432:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is never rebuilt\n"));
433:     } else if (snes->lagjacobian > 1) {
434:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is rebuilt every %" PetscInt_FMT " SNES iterations\n", snes->lagjacobian));
435:     }
436:     PetscCall(SNESGetDM(snes, &dm));
437:     PetscCall(DMSNESGetJacobian(dm, &cJ, &ctx));
438:     if (snes->mf_operator) {
439:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing\n"));
440:       pre = "Preconditioning ";
441:     }
442:     if (cJ == SNESComputeJacobianDefault) {
443:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences one column at a time\n", pre));
444:     } else if (cJ == SNESComputeJacobianDefaultColor) {
445:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences with coloring\n", pre));
446:       /* it slightly breaks data encapsulation for access the DMDA information directly */
447:     } else if (cJ == SNESComputeJacobian_DMDA) {
448:       MatFDColoring fdcoloring;
449:       PetscCall(PetscObjectQuery((PetscObject)dm, "DMDASNES_FDCOLORING", (PetscObject *)&fdcoloring));
450:       if (fdcoloring) {
451:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using colored finite differences on a DMDA\n", pre));
452:       } else {
453:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using a DMDA local Jacobian\n", pre));
454:       }
455:     } else if (snes->mf && !snes->mf_operator) {
456:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing, no explicit Jacobian\n"));
457:     }
458:   } else if (isstring) {
459:     const char *type;
460:     PetscCall(SNESGetType(snes, &type));
461:     PetscCall(PetscViewerStringSPrintf(viewer, " SNESType: %-7.7s", type));
462:     PetscTryTypeMethod(snes, view, viewer);
463:   } else if (isbinary) {
464:     PetscInt    classid = SNES_FILE_CLASSID;
465:     MPI_Comm    comm;
466:     PetscMPIInt rank;
467:     char        type[256];

469:     PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
470:     PetscCallMPI(MPI_Comm_rank(comm, &rank));
471:     if (rank == 0) {
472:       PetscCall(PetscViewerBinaryWrite(viewer, &classid, 1, PETSC_INT));
473:       PetscCall(PetscStrncpy(type, ((PetscObject)snes)->type_name, sizeof(type)));
474:       PetscCall(PetscViewerBinaryWrite(viewer, type, sizeof(type), PETSC_CHAR));
475:     }
476:     PetscTryTypeMethod(snes, view, viewer);
477:   } else if (isdraw) {
478:     PetscDraw draw;
479:     char      str[36];
480:     PetscReal x, y, bottom, h;

482:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
483:     PetscCall(PetscDrawGetCurrentPoint(draw, &x, &y));
484:     PetscCall(PetscStrncpy(str, "SNES: ", sizeof(str)));
485:     PetscCall(PetscStrlcat(str, ((PetscObject)snes)->type_name, sizeof(str)));
486:     PetscCall(PetscDrawStringBoxed(draw, x, y, PETSC_DRAW_BLUE, PETSC_DRAW_BLACK, str, NULL, &h));
487:     bottom = y - h;
488:     PetscCall(PetscDrawPushCurrentPoint(draw, x, bottom));
489:     PetscTryTypeMethod(snes, view, viewer);
490: #if defined(PETSC_HAVE_SAWS)
491:   } else if (issaws) {
492:     PetscMPIInt rank;
493:     const char *name;

495:     PetscCall(PetscObjectGetName((PetscObject)snes, &name));
496:     PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
497:     if (!((PetscObject)snes)->amsmem && rank == 0) {
498:       char dir[1024];

500:       PetscCall(PetscObjectViewSAWs((PetscObject)snes, viewer));
501:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/its", name));
502:       PetscCallSAWs(SAWs_Register, (dir, &snes->iter, 1, SAWs_READ, SAWs_INT));
503:       if (!snes->conv_hist) PetscCall(SNESSetConvergenceHistory(snes, NULL, NULL, PETSC_DECIDE, PETSC_TRUE));
504:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/conv_hist", name));
505:       PetscCallSAWs(SAWs_Register, (dir, snes->conv_hist, 10, SAWs_READ, SAWs_DOUBLE));
506:     }
507: #endif
508:   }
509:   if (snes->linesearch) {
510:     PetscCall(SNESGetLineSearch(snes, &linesearch));
511:     PetscCall(PetscViewerASCIIPushTab(viewer));
512:     PetscCall(SNESLineSearchView(linesearch, viewer));
513:     PetscCall(PetscViewerASCIIPopTab(viewer));
514:   }
515:   if (snes->npc && snes->usesnpc) {
516:     PetscCall(PetscViewerASCIIPushTab(viewer));
517:     PetscCall(SNESView(snes->npc, viewer));
518:     PetscCall(PetscViewerASCIIPopTab(viewer));
519:   }
520:   PetscCall(PetscViewerASCIIPushTab(viewer));
521:   PetscCall(DMGetDMSNES(snes->dm, &dmsnes));
522:   PetscCall(DMSNESView(dmsnes, viewer));
523:   PetscCall(PetscViewerASCIIPopTab(viewer));
524:   if (snes->usesksp) {
525:     PetscCall(SNESGetKSP(snes, &ksp));
526:     PetscCall(PetscViewerASCIIPushTab(viewer));
527:     PetscCall(KSPView(ksp, viewer));
528:     PetscCall(PetscViewerASCIIPopTab(viewer));
529:   }
530:   if (isdraw) {
531:     PetscDraw draw;
532:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
533:     PetscCall(PetscDrawPopCurrentPoint(draw));
534:   }
535:   PetscFunctionReturn(PETSC_SUCCESS);
536: }

538: /*
539:   We retain a list of functions that also take SNES command
540:   line options. These are called at the end SNESSetFromOptions()
541: */
542: #define MAXSETFROMOPTIONS 5
543: static PetscInt numberofsetfromoptions;
544: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

546: /*@C
547:   SNESAddOptionsChecker - Adds an additional function to check for `SNES` options.

549:   Not Collective

551:   Input Parameter:
552: . snescheck - function that checks for options

554:   Level: developer

556: .seealso: [](chapter_snes), `SNES`, `SNESSetFromOptions()`
557: @*/
558: PetscErrorCode SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
559: {
560:   PetscFunctionBegin;
561:   PetscCheck(numberofsetfromoptions < MAXSETFROMOPTIONS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %d allowed", MAXSETFROMOPTIONS);
562:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
563:   PetscFunctionReturn(PETSC_SUCCESS);
564: }

566: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
567: {
568:   Mat          J;
569:   MatNullSpace nullsp;

571:   PetscFunctionBegin;

574:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
575:     Mat A = snes->jacobian, B = snes->jacobian_pre;
576:     PetscCall(MatCreateVecs(A ? A : B, NULL, &snes->vec_func));
577:   }

579:   PetscCheck(version == 1 || version == 2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");
580:   if (version == 1) {
581:     PetscCall(MatCreateSNESMF(snes, &J));
582:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
583:     PetscCall(MatSetFromOptions(J));
584:     /* TODO: the version 2 code should be merged into the MatCreateSNESMF() and MatCreateMFFD() infrastructure and then removed */
585:   } else /* if (version == 2) */ {
586:     PetscCheck(snes->vec_func, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "SNESSetFunction() must be called first");
587: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
588:     PetscCall(MatCreateSNESMFMore(snes, snes->vec_func, &J));
589: #else
590:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
591: #endif
592:   }

594:   /* attach any user provided null space that was on Amat to the newly created matrix free matrix */
595:   if (snes->jacobian) {
596:     PetscCall(MatGetNullSpace(snes->jacobian, &nullsp));
597:     if (nullsp) PetscCall(MatSetNullSpace(J, nullsp));
598:   }

600:   PetscCall(PetscInfo(snes, "Setting default matrix-free operator routines (version %" PetscInt_FMT ")\n", version));
601:   if (hasOperator) {
602:     /* This version replaces the user provided Jacobian matrix with a
603:        matrix-free version but still employs the user-provided preconditioner matrix. */
604:     PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
605:   } else {
606:     /* This version replaces both the user-provided Jacobian and the user-
607:      provided preconditioner Jacobian with the default matrix free version. */
608:     if (snes->npcside == PC_LEFT && snes->npc) {
609:       if (!snes->jacobian) PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
610:     } else {
611:       KSP       ksp;
612:       PC        pc;
613:       PetscBool match;

615:       PetscCall(SNESSetJacobian(snes, J, J, MatMFFDComputeJacobian, NULL));
616:       /* Force no preconditioner */
617:       PetscCall(SNESGetKSP(snes, &ksp));
618:       PetscCall(KSPGetPC(ksp, &pc));
619:       PetscCall(PetscObjectTypeCompareAny((PetscObject)pc, &match, PCSHELL, PCH2OPUS, ""));
620:       if (!match) {
621:         PetscCall(PetscInfo(snes, "Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n"));
622:         PetscCall(PCSetType(pc, PCNONE));
623:       }
624:     }
625:   }
626:   PetscCall(MatDestroy(&J));
627:   PetscFunctionReturn(PETSC_SUCCESS);
628: }

630: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine, Mat Restrict, Vec Rscale, Mat Inject, DM dmcoarse, void *ctx)
631: {
632:   SNES snes = (SNES)ctx;
633:   Vec  Xfine, Xfine_named = NULL, Xcoarse;

635:   PetscFunctionBegin;
636:   if (PetscLogPrintInfo) {
637:     PetscInt finelevel, coarselevel, fineclevel, coarseclevel;
638:     PetscCall(DMGetRefineLevel(dmfine, &finelevel));
639:     PetscCall(DMGetCoarsenLevel(dmfine, &fineclevel));
640:     PetscCall(DMGetRefineLevel(dmcoarse, &coarselevel));
641:     PetscCall(DMGetCoarsenLevel(dmcoarse, &coarseclevel));
642:     PetscCall(PetscInfo(dmfine, "Restricting SNES solution vector from level %" PetscInt_FMT "-%" PetscInt_FMT " to level %" PetscInt_FMT "-%" PetscInt_FMT "\n", finelevel, fineclevel, coarselevel, coarseclevel));
643:   }
644:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
645:   else {
646:     PetscCall(DMGetNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
647:     Xfine = Xfine_named;
648:   }
649:   PetscCall(DMGetNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
650:   if (Inject) {
651:     PetscCall(MatRestrict(Inject, Xfine, Xcoarse));
652:   } else {
653:     PetscCall(MatRestrict(Restrict, Xfine, Xcoarse));
654:     PetscCall(VecPointwiseMult(Xcoarse, Xcoarse, Rscale));
655:   }
656:   PetscCall(DMRestoreNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
657:   if (Xfine_named) PetscCall(DMRestoreNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
658:   PetscFunctionReturn(PETSC_SUCCESS);
659: }

661: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm, DM dmc, void *ctx)
662: {
663:   PetscFunctionBegin;
664:   PetscCall(DMCoarsenHookAdd(dmc, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, ctx));
665:   PetscFunctionReturn(PETSC_SUCCESS);
666: }

668: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
669:  * safely call SNESGetDM() in their residual evaluation routine. */
670: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp, Mat A, Mat B, void *ctx)
671: {
672:   SNES  snes = (SNES)ctx;
673:   Vec   X, Xnamed = NULL;
674:   DM    dmsave;
675:   void *ctxsave;
676:   PetscErrorCode (*jac)(SNES, Vec, Mat, Mat, void *) = NULL;

678:   PetscFunctionBegin;
679:   dmsave = snes->dm;
680:   PetscCall(KSPGetDM(ksp, &snes->dm));
681:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
682:   else { /* We are on a coarser level, this vec was initialized using a DM restrict hook */ PetscCall(DMGetNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
683:     X = Xnamed;
684:     PetscCall(SNESGetJacobian(snes, NULL, NULL, &jac, &ctxsave));
685:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
686:     if (jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, SNESComputeJacobianDefaultColor, NULL));
687:   }
688:   /* Make sure KSP DM has the Jacobian computation routine */
689:   {
690:     DMSNES sdm;

692:     PetscCall(DMGetDMSNES(snes->dm, &sdm));
693:     if (!sdm->ops->computejacobian) PetscCall(DMCopyDMSNES(dmsave, snes->dm));
694:   }
695:   /* Compute the operators */
696:   PetscCall(SNESComputeJacobian(snes, X, A, B));
697:   /* Put the previous context back */
698:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, jac, ctxsave));

700:   if (Xnamed) PetscCall(DMRestoreNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
701:   snes->dm = dmsave;
702:   PetscFunctionReturn(PETSC_SUCCESS);
703: }

705: /*@
706:    SNESSetUpMatrices - ensures that matrices are available for `SNES` Newton-like methods, this is called by `SNESSetUp_XXX()`

708:    Collective

710:    Input Parameter:
711: .  snes - `SNES` object to configure

713:    Level: developer

715:    Note:
716:    If the matrices do not yet exist it attempts to create them based on options previously set for the `SNES` such as `-snes_mf`

718: .seealso: [](chapter_snes), `SNES`, `SNESSetUp()`
719: @*/
720: PetscErrorCode SNESSetUpMatrices(SNES snes)
721: {
722:   DM     dm;
723:   DMSNES sdm;

725:   PetscFunctionBegin;
726:   PetscCall(SNESGetDM(snes, &dm));
727:   PetscCall(DMGetDMSNES(dm, &sdm));
728:   if (!snes->jacobian && snes->mf) {
729:     Mat   J;
730:     void *functx;
731:     PetscCall(MatCreateSNESMF(snes, &J));
732:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
733:     PetscCall(MatSetFromOptions(J));
734:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
735:     PetscCall(SNESSetJacobian(snes, J, J, NULL, NULL));
736:     PetscCall(MatDestroy(&J));
737:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
738:     Mat J, B;
739:     PetscCall(MatCreateSNESMF(snes, &J));
740:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
741:     PetscCall(MatSetFromOptions(J));
742:     PetscCall(DMCreateMatrix(snes->dm, &B));
743:     /* sdm->computejacobian was already set to reach here */
744:     PetscCall(SNESSetJacobian(snes, J, B, NULL, NULL));
745:     PetscCall(MatDestroy(&J));
746:     PetscCall(MatDestroy(&B));
747:   } else if (!snes->jacobian_pre) {
748:     PetscDS   prob;
749:     Mat       J, B;
750:     PetscBool hasPrec = PETSC_FALSE;

752:     J = snes->jacobian;
753:     PetscCall(DMGetDS(dm, &prob));
754:     if (prob) PetscCall(PetscDSHasJacobianPreconditioner(prob, &hasPrec));
755:     if (J) PetscCall(PetscObjectReference((PetscObject)J));
756:     else if (hasPrec) PetscCall(DMCreateMatrix(snes->dm, &J));
757:     PetscCall(DMCreateMatrix(snes->dm, &B));
758:     PetscCall(SNESSetJacobian(snes, J ? J : B, B, NULL, NULL));
759:     PetscCall(MatDestroy(&J));
760:     PetscCall(MatDestroy(&B));
761:   }
762:   {
763:     KSP ksp;
764:     PetscCall(SNESGetKSP(snes, &ksp));
765:     PetscCall(KSPSetComputeOperators(ksp, KSPComputeOperators_SNES, snes));
766:     PetscCall(DMCoarsenHookAdd(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
767:   }
768:   PetscFunctionReturn(PETSC_SUCCESS);
769: }

771: static PetscErrorCode SNESMonitorPauseFinal_Internal(SNES snes)
772: {
773:   PetscInt i;

775:   PetscFunctionBegin;
776:   if (!snes->pauseFinal) PetscFunctionReturn(PETSC_SUCCESS);
777:   for (i = 0; i < snes->numbermonitors; ++i) {
778:     PetscViewerAndFormat *vf = (PetscViewerAndFormat *)snes->monitorcontext[i];
779:     PetscDraw             draw;
780:     PetscReal             lpause;

782:     if (!vf) continue;
783:     if (vf->lg) {
784:       if (!PetscCheckPointer(vf->lg, PETSC_OBJECT)) continue;
785:       if (((PetscObject)vf->lg)->classid != PETSC_DRAWLG_CLASSID) continue;
786:       PetscCall(PetscDrawLGGetDraw(vf->lg, &draw));
787:       PetscCall(PetscDrawGetPause(draw, &lpause));
788:       PetscCall(PetscDrawSetPause(draw, -1.0));
789:       PetscCall(PetscDrawPause(draw));
790:       PetscCall(PetscDrawSetPause(draw, lpause));
791:     } else {
792:       PetscBool isdraw;

794:       if (!PetscCheckPointer(vf->viewer, PETSC_OBJECT)) continue;
795:       if (((PetscObject)vf->viewer)->classid != PETSC_VIEWER_CLASSID) continue;
796:       PetscCall(PetscObjectTypeCompare((PetscObject)vf->viewer, PETSCVIEWERDRAW, &isdraw));
797:       if (!isdraw) continue;
798:       PetscCall(PetscViewerDrawGetDraw(vf->viewer, 0, &draw));
799:       PetscCall(PetscDrawGetPause(draw, &lpause));
800:       PetscCall(PetscDrawSetPause(draw, -1.0));
801:       PetscCall(PetscDrawPause(draw));
802:       PetscCall(PetscDrawSetPause(draw, lpause));
803:     }
804:   }
805:   PetscFunctionReturn(PETSC_SUCCESS);
806: }

808: /*@C
809:    SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

811:    Collective

813:    Input Parameters:
814: +  snes - `SNES` object you wish to monitor
815: .  name - the monitor type one is seeking
816: .  help - message indicating what monitoring is done
817: .  manual - manual page for the monitor
818: .  monitor - the monitor function
819: -  monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the `SNES` or `PetscViewer` objects

821:    Options Database Key:
822: .  -name - trigger the use of this monitor in `SNESSetFromOptions()`

824:    Level: advanced

826: .seealso: [](chapter_snes), `PetscOptionsGetViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
827:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
828:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`, `PetscOptionsBool()`,
829:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
830:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
831:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
832:           `PetscOptionsFList()`, `PetscOptionsEList()`
833: @*/
834: PetscErrorCode SNESMonitorSetFromOptions(SNES snes, const char name[], const char help[], const char manual[], PetscErrorCode (*monitor)(SNES, PetscInt, PetscReal, PetscViewerAndFormat *), PetscErrorCode (*monitorsetup)(SNES, PetscViewerAndFormat *))
835: {
836:   PetscViewer       viewer;
837:   PetscViewerFormat format;
838:   PetscBool         flg;

840:   PetscFunctionBegin;
841:   PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, name, &viewer, &format, &flg));
842:   if (flg) {
843:     PetscViewerAndFormat *vf;
844:     PetscCall(PetscViewerAndFormatCreate(viewer, format, &vf));
845:     PetscCall(PetscObjectDereference((PetscObject)viewer));
846:     if (monitorsetup) PetscCall((*monitorsetup)(snes, vf));
847:     PetscCall(SNESMonitorSet(snes, (PetscErrorCode(*)(SNES, PetscInt, PetscReal, void *))monitor, vf, (PetscErrorCode(*)(void **))PetscViewerAndFormatDestroy));
848:   }
849:   PetscFunctionReturn(PETSC_SUCCESS);
850: }

852: PetscErrorCode SNESEWSetFromOptions_Private(SNESKSPEW *kctx, PetscBool print_api, MPI_Comm comm, const char *prefix)
853: {
854:   const char *api = print_api ? "SNESKSPSetParametersEW" : NULL;

856:   PetscFunctionBegin;
857:   PetscOptionsBegin(comm, prefix, "Eisenstat and Walker type forcing options", "KSP");
858:   PetscCall(PetscOptionsInt("-ksp_ew_version", "Version 1, 2 or 3", api, kctx->version, &kctx->version, NULL));
859:   PetscCall(PetscOptionsReal("-ksp_ew_rtol0", "0 <= rtol0 < 1", api, kctx->rtol_0, &kctx->rtol_0, NULL));
860:   kctx->rtol_max = PetscMax(kctx->rtol_0, kctx->rtol_max);
861:   PetscCall(PetscOptionsReal("-ksp_ew_rtolmax", "0 <= rtolmax < 1", api, kctx->rtol_max, &kctx->rtol_max, NULL));
862:   PetscCall(PetscOptionsReal("-ksp_ew_gamma", "0 <= gamma <= 1", api, kctx->gamma, &kctx->gamma, NULL));
863:   PetscCall(PetscOptionsReal("-ksp_ew_alpha", "1 < alpha <= 2", api, kctx->alpha, &kctx->alpha, NULL));
864:   PetscCall(PetscOptionsReal("-ksp_ew_alpha2", "alpha2", NULL, kctx->alpha2, &kctx->alpha2, NULL));
865:   PetscCall(PetscOptionsReal("-ksp_ew_threshold", "0 < threshold < 1", api, kctx->threshold, &kctx->threshold, NULL));
866:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p1", "p1", NULL, kctx->v4_p1, &kctx->v4_p1, NULL));
867:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p2", "p2", NULL, kctx->v4_p2, &kctx->v4_p2, NULL));
868:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p3", "p3", NULL, kctx->v4_p3, &kctx->v4_p3, NULL));
869:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m1", "Scaling when rk-1 in [p2,p3)", NULL, kctx->v4_m1, &kctx->v4_m1, NULL));
870:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m2", "Scaling when rk-1 in [p3,+infty)", NULL, kctx->v4_m2, &kctx->v4_m2, NULL));
871:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m3", "Threshold for successive rtol (0.1 in Eq.7)", NULL, kctx->v4_m3, &kctx->v4_m3, NULL));
872:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m4", "Adaptation scaling (0.5 in Eq.7)", NULL, kctx->v4_m4, &kctx->v4_m4, NULL));
873:   PetscOptionsEnd();
874:   PetscFunctionReturn(PETSC_SUCCESS);
875: }

877: /*@
878:    SNESSetFromOptions - Sets various `SNES` and `KSP` parameters from user options.

880:    Collective

882:    Input Parameter:
883: .  snes - the `SNES` context

885:    Options Database Keys:
886: +  -snes_type <type> - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, `SNESType` for complete list
887: .  -snes_stol - convergence tolerance in terms of the norm
888:                 of the change in the solution between steps
889: .  -snes_atol <abstol> - absolute tolerance of residual norm
890: .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
891: .  -snes_divergence_tolerance <divtol> - if the residual goes above divtol*rnorm0, exit with divergence
892: .  -snes_force_iteration <force> - force SNESSolve() to take at least one iteration
893: .  -snes_max_it <max_it> - maximum number of iterations
894: .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
895: .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
896: .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
897: .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
898: .  -snes_lag_preconditioner_persists <true,false> - retains the -snes_lag_preconditioner information across multiple SNESSolve()
899: .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
900: .  -snes_lag_jacobian_persists <true,false> - retains the -snes_lag_jacobian information across multiple SNESSolve()
901: .  -snes_tr_tol <trtol> - trust region tolerance
902: .  -snes_convergence_test - <default,skip,correct_pressure> convergence test in nonlinear solver.
903:                                default `SNESConvergedDefault()`. skip `SNESConvergedSkip()` means continue iterating until max_it or some other criterion is reached, saving expense
904:                                of convergence test. correct_pressure S`NESConvergedCorrectPressure()` has special handling of a pressure null space.
905: .  -snes_monitor [ascii][:filename][:viewer format] - prints residual norm at each iteration. if no filename given prints to stdout
906: .  -snes_monitor_solution [ascii binary draw][:filename][:viewer format] - plots solution at each iteration
907: .  -snes_monitor_residual [ascii binary draw][:filename][:viewer format] - plots residual (not its norm) at each iteration
908: .  -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
909: .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
910: .  -snes_monitor_lg_range - plots residual norm at each iteration
911: .  -snes_monitor_pause_final - Pauses all monitor drawing after the solver ends
912: .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
913: .  -snes_fd_color - use finite differences with coloring to compute Jacobian
914: .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
915: .  -snes_converged_reason - print the reason for convergence/divergence after each solve
916: .  -npc_snes_type <type> - the SNES type to use as a nonlinear preconditioner
917: .   -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
918: -   -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

920:     Options Database Keys for Eisenstat-Walker method:
921: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
922: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
923: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
924: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
925: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
926: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
927: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
928: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

930:    Level: beginner

932:    Notes:
933:    To see all options, run your program with the -help option or consult the users manual

935:    `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix free, and computing explicitly with
936:    finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

938: .seealso: [](chapter_snes), `SNESType`, `SNESSetOptionsPrefix()`, `SNESResetFromOptions()`, `SNES`, `SNESCreate()`
939: @*/
940: PetscErrorCode SNESSetFromOptions(SNES snes)
941: {
942:   PetscBool   flg, pcset, persist, set;
943:   PetscInt    i, indx, lag, grids;
944:   const char *deft        = SNESNEWTONLS;
945:   const char *convtests[] = {"default", "skip", "correct_pressure"};
946:   SNESKSPEW  *kctx        = NULL;
947:   char        type[256], monfilename[PETSC_MAX_PATH_LEN], ewprefix[256];
948:   PCSide      pcside;
949:   const char *optionsprefix;

951:   PetscFunctionBegin;
953:   PetscCall(SNESRegisterAll());
954:   PetscObjectOptionsBegin((PetscObject)snes);
955:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
956:   PetscCall(PetscOptionsFList("-snes_type", "Nonlinear solver method", "SNESSetType", SNESList, deft, type, 256, &flg));
957:   if (flg) {
958:     PetscCall(SNESSetType(snes, type));
959:   } else if (!((PetscObject)snes)->type_name) {
960:     PetscCall(SNESSetType(snes, deft));
961:   }
962:   PetscCall(PetscOptionsReal("-snes_stol", "Stop if step length less than", "SNESSetTolerances", snes->stol, &snes->stol, NULL));
963:   PetscCall(PetscOptionsReal("-snes_atol", "Stop if function norm less than", "SNESSetTolerances", snes->abstol, &snes->abstol, NULL));

965:   PetscCall(PetscOptionsReal("-snes_rtol", "Stop if decrease in function norm less than", "SNESSetTolerances", snes->rtol, &snes->rtol, NULL));
966:   PetscCall(PetscOptionsReal("-snes_divergence_tolerance", "Stop if residual norm increases by this factor", "SNESSetDivergenceTolerance", snes->divtol, &snes->divtol, NULL));
967:   PetscCall(PetscOptionsInt("-snes_max_it", "Maximum iterations", "SNESSetTolerances", snes->max_its, &snes->max_its, NULL));
968:   PetscCall(PetscOptionsInt("-snes_max_funcs", "Maximum function evaluations", "SNESSetTolerances", snes->max_funcs, &snes->max_funcs, NULL));
969:   PetscCall(PetscOptionsInt("-snes_max_fail", "Maximum nonlinear step failures", "SNESSetMaxNonlinearStepFailures", snes->maxFailures, &snes->maxFailures, NULL));
970:   PetscCall(PetscOptionsInt("-snes_max_linear_solve_fail", "Maximum failures in linear solves allowed", "SNESSetMaxLinearSolveFailures", snes->maxLinearSolveFailures, &snes->maxLinearSolveFailures, NULL));
971:   PetscCall(PetscOptionsBool("-snes_error_if_not_converged", "Generate error if solver does not converge", "SNESSetErrorIfNotConverged", snes->errorifnotconverged, &snes->errorifnotconverged, NULL));
972:   PetscCall(PetscOptionsBool("-snes_force_iteration", "Force SNESSolve() to take at least one iteration", "SNESSetForceIteration", snes->forceiteration, &snes->forceiteration, NULL));
973:   PetscCall(PetscOptionsBool("-snes_check_jacobian_domain_error", "Check Jacobian domain error after Jacobian evaluation", "SNESCheckJacobianDomainError", snes->checkjacdomainerror, &snes->checkjacdomainerror, NULL));

975:   PetscCall(PetscOptionsInt("-snes_lag_preconditioner", "How often to rebuild preconditioner", "SNESSetLagPreconditioner", snes->lagpreconditioner, &lag, &flg));
976:   if (flg) {
977:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the preconditioner must be built as least once, perhaps you mean -2");
978:     PetscCall(SNESSetLagPreconditioner(snes, lag));
979:   }
980:   PetscCall(PetscOptionsBool("-snes_lag_preconditioner_persists", "Preconditioner lagging through multiple SNES solves", "SNESSetLagPreconditionerPersists", snes->lagjac_persist, &persist, &flg));
981:   if (flg) PetscCall(SNESSetLagPreconditionerPersists(snes, persist));
982:   PetscCall(PetscOptionsInt("-snes_lag_jacobian", "How often to rebuild Jacobian", "SNESSetLagJacobian", snes->lagjacobian, &lag, &flg));
983:   if (flg) {
984:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the Jacobian must be built as least once, perhaps you mean -2");
985:     PetscCall(SNESSetLagJacobian(snes, lag));
986:   }
987:   PetscCall(PetscOptionsBool("-snes_lag_jacobian_persists", "Jacobian lagging through multiple SNES solves", "SNESSetLagJacobianPersists", snes->lagjac_persist, &persist, &flg));
988:   if (flg) PetscCall(SNESSetLagJacobianPersists(snes, persist));

990:   PetscCall(PetscOptionsInt("-snes_grid_sequence", "Use grid sequencing to generate initial guess", "SNESSetGridSequence", snes->gridsequence, &grids, &flg));
991:   if (flg) PetscCall(SNESSetGridSequence(snes, grids));

993:   PetscCall(PetscOptionsEList("-snes_convergence_test", "Convergence test", "SNESSetConvergenceTest", convtests, sizeof(convtests) / sizeof(char *), "default", &indx, &flg));
994:   if (flg) {
995:     switch (indx) {
996:     case 0:
997:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedDefault, NULL, NULL));
998:       break;
999:     case 1:
1000:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedSkip, NULL, NULL));
1001:       break;
1002:     case 2:
1003:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedCorrectPressure, NULL, NULL));
1004:       break;
1005:     }
1006:   }

1008:   PetscCall(PetscOptionsEList("-snes_norm_schedule", "SNES Norm schedule", "SNESSetNormSchedule", SNESNormSchedules, 5, "function", &indx, &flg));
1009:   if (flg) PetscCall(SNESSetNormSchedule(snes, (SNESNormSchedule)indx));

1011:   PetscCall(PetscOptionsEList("-snes_function_type", "SNES Norm schedule", "SNESSetFunctionType", SNESFunctionTypes, 2, "unpreconditioned", &indx, &flg));
1012:   if (flg) PetscCall(SNESSetFunctionType(snes, (SNESFunctionType)indx));

1014:   kctx = (SNESKSPEW *)snes->kspconvctx;

1016:   PetscCall(PetscOptionsBool("-snes_ksp_ew", "Use Eisentat-Walker linear system convergence test", "SNESKSPSetUseEW", snes->ksp_ewconv, &snes->ksp_ewconv, NULL));

1018:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1019:   PetscCall(PetscSNPrintf(ewprefix, sizeof(ewprefix), "%s%s", optionsprefix ? optionsprefix : "", "snes_"));
1020:   PetscCall(SNESEWSetFromOptions_Private(kctx, PETSC_TRUE, PetscObjectComm((PetscObject)snes), ewprefix));

1022:   flg = PETSC_FALSE;
1023:   PetscCall(PetscOptionsBool("-snes_monitor_cancel", "Remove all monitors", "SNESMonitorCancel", flg, &flg, &set));
1024:   if (set && flg) PetscCall(SNESMonitorCancel(snes));

1026:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor", "Monitor norm of function", "SNESMonitorDefault", SNESMonitorDefault, SNESMonitorDefaultSetUp));
1027:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_short", "Monitor norm of function with fewer digits", "SNESMonitorDefaultShort", SNESMonitorDefaultShort, NULL));
1028:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_range", "Monitor range of elements of function", "SNESMonitorRange", SNESMonitorRange, NULL));

1030:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_ratio", "Monitor ratios of the norm of function for consecutive steps", "SNESMonitorRatio", SNESMonitorRatio, SNESMonitorRatioSetUp));
1031:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_field", "Monitor norm of function (split into fields)", "SNESMonitorDefaultField", SNESMonitorDefaultField, NULL));
1032:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution", "View solution at each iteration", "SNESMonitorSolution", SNESMonitorSolution, NULL));
1033:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution_update", "View correction at each iteration", "SNESMonitorSolutionUpdate", SNESMonitorSolutionUpdate, NULL));
1034:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_residual", "View residual at each iteration", "SNESMonitorResidual", SNESMonitorResidual, NULL));
1035:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_jacupdate_spectrum", "Print the change in the spectrum of the Jacobian", "SNESMonitorJacUpdateSpectrum", SNESMonitorJacUpdateSpectrum, NULL));
1036:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_fields", "Monitor norm of function per field", "SNESMonitorSet", SNESMonitorFields, NULL));
1037:   PetscCall(PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL));

1039:   PetscCall(PetscOptionsString("-snes_monitor_python", "Use Python function", "SNESMonitorSet", NULL, monfilename, sizeof(monfilename), &flg));
1040:   if (flg) PetscCall(PetscPythonMonitorSet((PetscObject)snes, monfilename));

1042:   flg = PETSC_FALSE;
1043:   PetscCall(PetscOptionsBool("-snes_monitor_lg_range", "Plot function range at each iteration", "SNESMonitorLGRange", flg, &flg, NULL));
1044:   if (flg) {
1045:     PetscViewer ctx;

1047:     PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, NULL, PETSC_DECIDE, PETSC_DECIDE, 400, 300, &ctx));
1048:     PetscCall(SNESMonitorSet(snes, SNESMonitorLGRange, ctx, (PetscErrorCode(*)(void **))PetscViewerDestroy));
1049:   }

1051:   flg = PETSC_FALSE;
1052:   PetscCall(PetscOptionsBool("-snes_converged_reason_view_cancel", "Remove all converged reason viewers", "SNESConvergedReasonViewCancel", flg, &flg, &set));
1053:   if (set && flg) PetscCall(SNESConvergedReasonViewCancel(snes));

1055:   flg = PETSC_FALSE;
1056:   PetscCall(PetscOptionsBool("-snes_fd", "Use finite differences (slow) to compute Jacobian", "SNESComputeJacobianDefault", flg, &flg, NULL));
1057:   if (flg) {
1058:     void *functx;
1059:     DM    dm;
1060:     PetscCall(SNESGetDM(snes, &dm));
1061:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1062:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
1063:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefault, functx));
1064:     PetscCall(PetscInfo(snes, "Setting default finite difference Jacobian matrix\n"));
1065:   }

1067:   flg = PETSC_FALSE;
1068:   PetscCall(PetscOptionsBool("-snes_fd_function", "Use finite differences (slow) to compute function from user objective", "SNESObjectiveComputeFunctionDefaultFD", flg, &flg, NULL));
1069:   if (flg) PetscCall(SNESSetFunction(snes, NULL, SNESObjectiveComputeFunctionDefaultFD, NULL));

1071:   flg = PETSC_FALSE;
1072:   PetscCall(PetscOptionsBool("-snes_fd_color", "Use finite differences with coloring to compute Jacobian", "SNESComputeJacobianDefaultColor", flg, &flg, NULL));
1073:   if (flg) {
1074:     DM dm;
1075:     PetscCall(SNESGetDM(snes, &dm));
1076:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1077:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefaultColor, NULL));
1078:     PetscCall(PetscInfo(snes, "Setting default finite difference coloring Jacobian matrix\n"));
1079:   }

1081:   flg = PETSC_FALSE;
1082:   PetscCall(PetscOptionsBool("-snes_mf_operator", "Use a Matrix-Free Jacobian with user-provided preconditioner matrix", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf_operator, &flg));
1083:   if (flg && snes->mf_operator) {
1084:     snes->mf_operator = PETSC_TRUE;
1085:     snes->mf          = PETSC_TRUE;
1086:   }
1087:   flg = PETSC_FALSE;
1088:   PetscCall(PetscOptionsBool("-snes_mf", "Use a Matrix-Free Jacobian with no preconditioner matrix", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf, &flg));
1089:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
1090:   PetscCall(PetscOptionsInt("-snes_mf_version", "Matrix-Free routines version 1 or 2", "None", snes->mf_version, &snes->mf_version, NULL));

1092:   flg = PETSC_FALSE;
1093:   PetscCall(SNESGetNPCSide(snes, &pcside));
1094:   PetscCall(PetscOptionsEnum("-snes_npc_side", "SNES nonlinear preconditioner side", "SNESSetNPCSide", PCSides, (PetscEnum)pcside, (PetscEnum *)&pcside, &flg));
1095:   if (flg) PetscCall(SNESSetNPCSide(snes, pcside));

1097: #if defined(PETSC_HAVE_SAWS)
1098:   /*
1099:     Publish convergence information using SAWs
1100:   */
1101:   flg = PETSC_FALSE;
1102:   PetscCall(PetscOptionsBool("-snes_monitor_saws", "Publish SNES progress using SAWs", "SNESMonitorSet", flg, &flg, NULL));
1103:   if (flg) {
1104:     void *ctx;
1105:     PetscCall(SNESMonitorSAWsCreate(snes, &ctx));
1106:     PetscCall(SNESMonitorSet(snes, SNESMonitorSAWs, ctx, SNESMonitorSAWsDestroy));
1107:   }
1108: #endif
1109: #if defined(PETSC_HAVE_SAWS)
1110:   {
1111:     PetscBool set;
1112:     flg = PETSC_FALSE;
1113:     PetscCall(PetscOptionsBool("-snes_saws_block", "Block for SAWs at end of SNESSolve", "PetscObjectSAWsBlock", ((PetscObject)snes)->amspublishblock, &flg, &set));
1114:     if (set) PetscCall(PetscObjectSAWsSetBlock((PetscObject)snes, flg));
1115:   }
1116: #endif

1118:   for (i = 0; i < numberofsetfromoptions; i++) PetscCall((*othersetfromoptions[i])(snes));

1120:   PetscTryTypeMethod(snes, setfromoptions, PetscOptionsObject);

1122:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
1123:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)snes, PetscOptionsObject));
1124:   PetscOptionsEnd();

1126:   if (snes->linesearch) {
1127:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
1128:     PetscCall(SNESLineSearchSetFromOptions(snes->linesearch));
1129:   }

1131:   if (snes->usesksp) {
1132:     if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
1133:     PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
1134:     PetscCall(KSPSetFromOptions(snes->ksp));
1135:   }

1137:   /* if user has set the SNES NPC type via options database, create it. */
1138:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1139:   PetscCall(PetscOptionsHasName(((PetscObject)snes)->options, optionsprefix, "-npc_snes_type", &pcset));
1140:   if (pcset && (!snes->npc)) PetscCall(SNESGetNPC(snes, &snes->npc));
1141:   if (snes->npc) PetscCall(SNESSetFromOptions(snes->npc));
1142:   snes->setfromoptionscalled++;
1143:   PetscFunctionReturn(PETSC_SUCCESS);
1144: }

1146: /*@
1147:    SNESResetFromOptions - Sets various `SNES` and `KSP` parameters from user options ONLY if the `SNESSetFromOptions()` was previously set from options

1149:    Collective

1151:    Input Parameter:
1152: .  snes - the `SNES` context

1154:    Level: beginner

1156: .seealso: [](chapter_snes), `SNES`, `SNESSetFromOptions()`, `SNESSetOptionsPrefix()`
1157: @*/
1158: PetscErrorCode SNESResetFromOptions(SNES snes)
1159: {
1160:   PetscFunctionBegin;
1161:   if (snes->setfromoptionscalled) PetscCall(SNESSetFromOptions(snes));
1162:   PetscFunctionReturn(PETSC_SUCCESS);
1163: }

1165: /*@C
1166:    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
1167:    the nonlinear solvers.

1169:    Logically Collective; No Fortran Support

1171:    Input Parameters:
1172: +  snes - the `SNES` context
1173: .  compute - function to compute the context
1174: -  destroy - function to destroy the context

1176:    Level: intermediate

1178:    Note:
1179:    This routine is useful if you are performing grid sequencing or using `SNESFAS` and need the appropriate context generated for each level.

1181:    Use `SNESSetApplicationContext()` to see the context immediately

1183: .seealso: [](chapter_snes), `SNESGetApplicationContext()`, `SNESSetComputeApplicationContext()`, `SNESSetApplicationContext()`
1184: @*/
1185: PetscErrorCode SNESSetComputeApplicationContext(SNES snes, PetscErrorCode (*compute)(SNES, void **), PetscErrorCode (*destroy)(void **))
1186: {
1187:   PetscFunctionBegin;
1189:   snes->ops->usercompute = compute;
1190:   snes->ops->userdestroy = destroy;
1191:   PetscFunctionReturn(PETSC_SUCCESS);
1192: }

1194: /*@
1195:    SNESSetApplicationContext - Sets the optional user-defined context for the nonlinear solvers.

1197:    Logically Collective

1199:    Input Parameters:
1200: +  snes - the `SNES` context
1201: -  usrP - optional user context

1203:    Level: intermediate

1205:    Notes:
1206:    Users can provide a context when constructing the `SNES` options and then access it inside their function, Jacobian, or other evaluation function
1207:    with `SNESGetApplicationContext()`

1209:    To provide a function that computes the context for you use `SNESSetComputeApplicationContext()`

1211:    Fortran Note:
1212:     You must write a Fortran interface definition for this
1213:     function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

1215: .seealso: [](chapter_snes), `SNES`, `SNESSetComputeApplicationContext()`, `SNESGetApplicationContext()`
1216: @*/
1217: PetscErrorCode SNESSetApplicationContext(SNES snes, void *usrP)
1218: {
1219:   KSP ksp;

1221:   PetscFunctionBegin;
1223:   PetscCall(SNESGetKSP(snes, &ksp));
1224:   PetscCall(KSPSetApplicationContext(ksp, usrP));
1225:   snes->user = usrP;
1226:   PetscFunctionReturn(PETSC_SUCCESS);
1227: }

1229: /*@
1230:    SNESGetApplicationContext - Gets the user-defined context for the
1231:    nonlinear solvers set with `SNESGetApplicationContext()` or with `SNESSetComputeApplicationContext()`

1233:    Not Collective

1235:    Input Parameter:
1236: .  snes - `SNES` context

1238:    Output Parameter:
1239: .  usrP - user context

1241:    Level: intermediate

1243:    Fortran Note:
1244:    You must write a Fortran interface definition for this
1245:    function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

1247: .seealso: [](chapter_snes), `SNESSetApplicationContext()`
1248: @*/
1249: PetscErrorCode SNESGetApplicationContext(SNES snes, void *usrP)
1250: {
1251:   PetscFunctionBegin;
1253:   *(void **)usrP = snes->user;
1254:   PetscFunctionReturn(PETSC_SUCCESS);
1255: }

1257: /*@
1258:    SNESSetUseMatrixFree - indicates that `SNES` should use matrix free finite difference matrix vector products to apply the Jacobian.

1260:    Logically Collective

1262:    Input Parameters:
1263: +  snes - `SNES` context
1264: .  mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1265: -  mf - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored. With
1266:    this option no matrix element based preconditioners can be used in the linear solve since the matrix won't be explicitly available

1268:    Options Database Keys:
1269: + -snes_mf_operator - use matrix free only for the mat operator
1270: . -snes_mf - use matrix-free for both the mat and pmat operator
1271: . -snes_fd_color - compute the Jacobian via coloring and finite differences.
1272: - -snes_fd - compute the Jacobian via finite differences (slow)

1274:    Level: intermediate

1276:    Note:
1277:    `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free, and computing explicitly with
1278:    finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

1280: .seealso: [](chapter_snes), `SNES`, `SNESGetUseMatrixFree()`, `MatCreateSNESMF()`, `SNESComputeJacobianDefaultColor()`
1281: @*/
1282: PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)
1283: {
1284:   PetscFunctionBegin;
1288:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
1289:   snes->mf_operator = mf_operator;
1290:   PetscFunctionReturn(PETSC_SUCCESS);
1291: }

1293: /*@
1294:    SNESGetUseMatrixFree - indicates if the `SNES` uses matrix-free finite difference matrix vector products to apply the Jacobian.

1296:    Not Collective, but the resulting flags will be the same on all MPI ranks

1298:    Input Parameter:
1299: .  snes - `SNES` context

1301:    Output Parameters:
1302: +  mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1303: -  mf - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored

1305:    Level: intermediate

1307: .seealso: [](chapter_snes), `SNES`, `SNESSetUseMatrixFree()`, `MatCreateSNESMF()`
1308: @*/
1309: PetscErrorCode SNESGetUseMatrixFree(SNES snes, PetscBool *mf_operator, PetscBool *mf)
1310: {
1311:   PetscFunctionBegin;
1313:   if (mf) *mf = snes->mf;
1314:   if (mf_operator) *mf_operator = snes->mf_operator;
1315:   PetscFunctionReturn(PETSC_SUCCESS);
1316: }

1318: /*@
1319:    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
1320:    at this time.

1322:    Not Collective

1324:    Input Parameter:
1325: .  snes - `SNES` context

1327:    Output Parameter:
1328: .  iter - iteration number

1330:    Level: intermediate

1332:    Notes:
1333:    For example, during the computation of iteration 2 this would return 1.

1335:    This is useful for using lagged Jacobians (where one does not recompute the
1336:    Jacobian at each `SNES` iteration). For example, the code
1337: .vb
1338:       ierr = SNESGetIterationNumber(snes,&it);
1339:       if (!(it % 2)) {
1340:         [compute Jacobian here]
1341:       }
1342: .ve
1343:    can be used in your function that computes the Jacobian to cause the Jacobian to be
1344:    recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

1346:    After the `SNES` solve is complete this will return the number of nonlinear iterations used.

1348: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`
1349: @*/
1350: PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)
1351: {
1352:   PetscFunctionBegin;
1355:   *iter = snes->iter;
1356:   PetscFunctionReturn(PETSC_SUCCESS);
1357: }

1359: /*@
1360:    SNESSetIterationNumber - Sets the current iteration number.

1362:    Not Collective

1364:    Input Parameters:
1365: +  snes - `SNES` context
1366: -  iter - iteration number

1368:    Level: developer

1370: .seealso: [](chapter_snes), `SNESGetLinearSolveIterations()`
1371: @*/
1372: PetscErrorCode SNESSetIterationNumber(SNES snes, PetscInt iter)
1373: {
1374:   PetscFunctionBegin;
1376:   PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
1377:   snes->iter = iter;
1378:   PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
1379:   PetscFunctionReturn(PETSC_SUCCESS);
1380: }

1382: /*@
1383:    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1384:    attempted by the nonlinear solver.

1386:    Not Collective

1388:    Input Parameter:
1389: .  snes - `SNES` context

1391:    Output Parameter:
1392: .  nfails - number of unsuccessful steps attempted

1394:    Level: intermediate

1396:    Note:
1397:    This counter is reset to zero for each successive call to `SNESSolve()`.

1399: .seealso: [](chapter_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1400:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetMaxNonlinearStepFailures()`
1401: @*/
1402: PetscErrorCode SNESGetNonlinearStepFailures(SNES snes, PetscInt *nfails)
1403: {
1404:   PetscFunctionBegin;
1407:   *nfails = snes->numFailures;
1408:   PetscFunctionReturn(PETSC_SUCCESS);
1409: }

1411: /*@
1412:    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1413:    attempted by the nonlinear solver before it gives up and generates an error

1415:    Not Collective

1417:    Input Parameters:
1418: +  snes     - `SNES` context
1419: -  maxFails - maximum of unsuccessful steps

1421:    Level: intermediate

1423: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1424:           `SNESGetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1425: @*/
1426: PetscErrorCode SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1427: {
1428:   PetscFunctionBegin;
1430:   snes->maxFailures = maxFails;
1431:   PetscFunctionReturn(PETSC_SUCCESS);
1432: }

1434: /*@
1435:    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1436:    attempted by the nonlinear solver before it gives up and generates an error

1438:    Not Collective

1440:    Input Parameter:
1441: .  snes     - `SNES` context

1443:    Output Parameter:
1444: .  maxFails - maximum of unsuccessful steps

1446:    Level: intermediate

1448: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1449:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1450: @*/
1451: PetscErrorCode SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1452: {
1453:   PetscFunctionBegin;
1456:   *maxFails = snes->maxFailures;
1457:   PetscFunctionReturn(PETSC_SUCCESS);
1458: }

1460: /*@
1461:    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1462:      done by the `SNES` object

1464:    Not Collective

1466:    Input Parameter:
1467: .  snes     - `SNES` context

1469:    Output Parameter:
1470: .  nfuncs - number of evaluations

1472:    Level: intermediate

1474:    Note:
1475:     Reset every time `SNESSolve()` is called unless `SNESSetCountersReset()` is used.

1477: .seealso: [](chapter_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`, `SNESSetCountersReset()`
1478: @*/
1479: PetscErrorCode SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1480: {
1481:   PetscFunctionBegin;
1484:   *nfuncs = snes->nfuncs;
1485:   PetscFunctionReturn(PETSC_SUCCESS);
1486: }

1488: /*@
1489:    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1490:    linear solvers.

1492:    Not Collective

1494:    Input Parameter:
1495: .  snes - `SNES` context

1497:    Output Parameter:
1498: .  nfails - number of failed solves

1500:    Options Database Key:
1501: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1503:    Level: intermediate

1505:    Note:
1506:    This counter is reset to zero for each successive call to `SNESSolve()`.

1508: .seealso: [](chapter_snes), `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`
1509: @*/
1510: PetscErrorCode SNESGetLinearSolveFailures(SNES snes, PetscInt *nfails)
1511: {
1512:   PetscFunctionBegin;
1515:   *nfails = snes->numLinearSolveFailures;
1516:   PetscFunctionReturn(PETSC_SUCCESS);
1517: }

1519: /*@
1520:    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1521:    allowed before `SNES` returns with a diverged reason of `SNES_DIVERGED_LINEAR_SOLVE`

1523:    Logically Collective

1525:    Input Parameters:
1526: +  snes     - `SNES` context
1527: -  maxFails - maximum allowed linear solve failures

1529:    Options Database Key:
1530: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1532:    Level: intermediate

1534:    Note:
1535:     By default this is 0; that is `SNES` returns on the first failed linear solve

1537: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`
1538: @*/
1539: PetscErrorCode SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1540: {
1541:   PetscFunctionBegin;
1544:   snes->maxLinearSolveFailures = maxFails;
1545:   PetscFunctionReturn(PETSC_SUCCESS);
1546: }

1548: /*@
1549:    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1550:      are allowed before `SNES` returns as unsuccessful

1552:    Not Collective

1554:    Input Parameter:
1555: .  snes     - `SNES` context

1557:    Output Parameter:
1558: .  maxFails - maximum of unsuccessful solves allowed

1560:    Level: intermediate

1562:    Note:
1563:     By default this is 1; that is `SNES` returns on the first failed linear solve

1565: .seealso: [](chapter_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`,
1566: @*/
1567: PetscErrorCode SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1568: {
1569:   PetscFunctionBegin;
1572:   *maxFails = snes->maxLinearSolveFailures;
1573:   PetscFunctionReturn(PETSC_SUCCESS);
1574: }

1576: /*@
1577:    SNESGetLinearSolveIterations - Gets the total number of linear iterations
1578:    used by the nonlinear solver.

1580:    Not Collective

1582:    Input Parameter:
1583: .  snes - `SNES` context

1585:    Output Parameter:
1586: .  lits - number of linear iterations

1588:    Level: intermediate

1590:    Notes:
1591:    This counter is reset to zero for each successive call to `SNESSolve()` unless `SNESSetCountersReset()` is used.

1593:    If the linear solver fails inside the `SNESSolve()` the iterations for that call to the linear solver are not included. If you wish to count them
1594:    then call `KSPGetIterationNumber()` after the failed solve.

1596: .seealso: [](chapter_snes), `SNES`, `SNESGetIterationNumber()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESSetCountersReset()`
1597: @*/
1598: PetscErrorCode SNESGetLinearSolveIterations(SNES snes, PetscInt *lits)
1599: {
1600:   PetscFunctionBegin;
1603:   *lits = snes->linear_its;
1604:   PetscFunctionReturn(PETSC_SUCCESS);
1605: }

1607: /*@
1608:    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1609:    are reset every time `SNESSolve()` is called.

1611:    Logically Collective

1613:    Input Parameters:
1614: +  snes - `SNES` context
1615: -  reset - whether to reset the counters or not, defaults to `PETSC_TRUE`

1617:    Level: developer

1619: .seealso: [](chapter_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1620: @*/
1621: PetscErrorCode SNESSetCountersReset(SNES snes, PetscBool reset)
1622: {
1623:   PetscFunctionBegin;
1626:   snes->counters_reset = reset;
1627:   PetscFunctionReturn(PETSC_SUCCESS);
1628: }

1630: /*@
1631:    SNESSetKSP - Sets a `KSP` context for the `SNES` object to use

1633:    Not Collective, but the `SNES` and `KSP` objects must live on the same MPI_Comm

1635:    Input Parameters:
1636: +  snes - the `SNES` context
1637: -  ksp - the `KSP` context

1639:    Level: developer

1641:    Notes:
1642:    The `SNES` object already has its `KSP` object, you can obtain with `SNESGetKSP()`
1643:    so this routine is rarely needed.

1645:    The `KSP` object that is already in the `SNES` object has its reference count
1646:    decreased by one.

1648: .seealso: [](chapter_snes), `SNES`, `KSP`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
1649: @*/
1650: PetscErrorCode SNESSetKSP(SNES snes, KSP ksp)
1651: {
1652:   PetscFunctionBegin;
1655:   PetscCheckSameComm(snes, 1, ksp, 2);
1656:   PetscCall(PetscObjectReference((PetscObject)ksp));
1657:   if (snes->ksp) PetscCall(PetscObjectDereference((PetscObject)snes->ksp));
1658:   snes->ksp = ksp;
1659:   PetscFunctionReturn(PETSC_SUCCESS);
1660: }

1662: /*@
1663:    SNESCreate - Creates a nonlinear solver context used to manage a set of nonlinear solves

1665:    Collective

1667:    Input Parameter:
1668: .  comm - MPI communicator

1670:    Output Parameter:
1671: .  outsnes - the new `SNES` context

1673:    Options Database Keys:
1674: +   -snes_mf - Activates default matrix-free Jacobian-vector products, and no preconditioning matrix
1675: .   -snes_mf_operator - Activates default matrix-free Jacobian-vector products, and a user-provided preconditioning matrix
1676:                as set by `SNESSetJacobian()`
1677: .   -snes_fd_coloring - uses a relative fast computation of the Jacobian using finite differences and a graph coloring
1678: -   -snes_fd - Uses (slow!) finite differences to compute Jacobian

1680:    Level: beginner

1682:    Developer Notes:
1683:    `SNES` always creates a `KSP` object even though many `SNES` methods do not use it. This is
1684:    unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
1685:    particular method does use `KSP` and regulates if the information about the `KSP` is printed
1686:    in `SNESView()`.

1688:    `TSSetFromOptions()` does call `SNESSetFromOptions()` which can lead to users being confused
1689:    by help messages about meaningless `SNES` options.

1691:    `SNES` always creates the snes->kspconvctx even though it is used by only one type. This should be fixed.

1693: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNES`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
1694: @*/
1695: PetscErrorCode SNESCreate(MPI_Comm comm, SNES *outsnes)
1696: {
1697:   SNES       snes;
1698:   SNESKSPEW *kctx;

1700:   PetscFunctionBegin;
1702:   *outsnes = NULL;
1703:   PetscCall(SNESInitializePackage());

1705:   PetscCall(PetscHeaderCreate(snes, SNES_CLASSID, "SNES", "Nonlinear solver", "SNES", comm, SNESDestroy, SNESView));

1707:   snes->ops->converged       = SNESConvergedDefault;
1708:   snes->usesksp              = PETSC_TRUE;
1709:   snes->tolerancesset        = PETSC_FALSE;
1710:   snes->max_its              = 50;
1711:   snes->max_funcs            = 10000;
1712:   snes->norm                 = 0.0;
1713:   snes->xnorm                = 0.0;
1714:   snes->ynorm                = 0.0;
1715:   snes->normschedule         = SNES_NORM_ALWAYS;
1716:   snes->functype             = SNES_FUNCTION_DEFAULT;
1717:   snes->rtol                 = PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8;
1718:   snes->ttol                 = 0.0;
1719:   snes->abstol               = PetscDefined(USE_REAL_SINGLE) ? 1.e-25 : 1.e-50;
1720:   snes->stol                 = PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8;
1721:   snes->deltatol             = PetscDefined(USE_REAL_SINGLE) ? 1.e-6 : 1.e-12;
1722:   snes->divtol               = 1.e4;
1723:   snes->rnorm0               = 0;
1724:   snes->nfuncs               = 0;
1725:   snes->numFailures          = 0;
1726:   snes->maxFailures          = 1;
1727:   snes->linear_its           = 0;
1728:   snes->lagjacobian          = 1;
1729:   snes->jac_iter             = 0;
1730:   snes->lagjac_persist       = PETSC_FALSE;
1731:   snes->lagpreconditioner    = 1;
1732:   snes->pre_iter             = 0;
1733:   snes->lagpre_persist       = PETSC_FALSE;
1734:   snes->numbermonitors       = 0;
1735:   snes->numberreasonviews    = 0;
1736:   snes->data                 = NULL;
1737:   snes->setupcalled          = PETSC_FALSE;
1738:   snes->ksp_ewconv           = PETSC_FALSE;
1739:   snes->nwork                = 0;
1740:   snes->work                 = NULL;
1741:   snes->nvwork               = 0;
1742:   snes->vwork                = NULL;
1743:   snes->conv_hist_len        = 0;
1744:   snes->conv_hist_max        = 0;
1745:   snes->conv_hist            = NULL;
1746:   snes->conv_hist_its        = NULL;
1747:   snes->conv_hist_reset      = PETSC_TRUE;
1748:   snes->counters_reset       = PETSC_TRUE;
1749:   snes->vec_func_init_set    = PETSC_FALSE;
1750:   snes->reason               = SNES_CONVERGED_ITERATING;
1751:   snes->npcside              = PC_RIGHT;
1752:   snes->setfromoptionscalled = 0;

1754:   snes->mf          = PETSC_FALSE;
1755:   snes->mf_operator = PETSC_FALSE;
1756:   snes->mf_version  = 1;

1758:   snes->numLinearSolveFailures = 0;
1759:   snes->maxLinearSolveFailures = 1;

1761:   snes->vizerotolerance     = 1.e-8;
1762:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

1764:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
1765:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

1767:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1768:   PetscCall(PetscNew(&kctx));

1770:   snes->kspconvctx  = (void *)kctx;
1771:   kctx->version     = 2;
1772:   kctx->rtol_0      = 0.3; /* Eisenstat and Walker suggest rtol_0=.5, but
1773:                              this was too large for some test cases */
1774:   kctx->rtol_last   = 0.0;
1775:   kctx->rtol_max    = 0.9;
1776:   kctx->gamma       = 1.0;
1777:   kctx->alpha       = 0.5 * (1.0 + PetscSqrtReal(5.0));
1778:   kctx->alpha2      = kctx->alpha;
1779:   kctx->threshold   = 0.1;
1780:   kctx->lresid_last = 0.0;
1781:   kctx->norm_last   = 0.0;

1783:   kctx->rk_last     = 0.0;
1784:   kctx->rk_last_2   = 0.0;
1785:   kctx->rtol_last_2 = 0.0;
1786:   kctx->v4_p1       = 0.1;
1787:   kctx->v4_p2       = 0.4;
1788:   kctx->v4_p3       = 0.7;
1789:   kctx->v4_m1       = 0.8;
1790:   kctx->v4_m2       = 0.5;
1791:   kctx->v4_m3       = 0.1;
1792:   kctx->v4_m4       = 0.5;

1794:   *outsnes = snes;
1795:   PetscFunctionReturn(PETSC_SUCCESS);
1796: }

1798: /*MC
1799:     SNESFunction - Functional form used to convey the nonlinear function to `SNES` in `SNESSetFunction()`

1801:      Synopsis:
1802:      #include "petscsnes.h"
1803:      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);

1805:      Collective

1807:      Input Parameters:
1808: +     snes - the `SNES` context
1809: .     x    - state at which to evaluate residual
1810: -     ctx     - optional user-defined function context, passed in with `SNESSetFunction()`

1812:      Output Parameter:
1813: .     f  - vector to put residual (function value)

1815:    Level: intermediate

1817: .seealso: [](chapter_snes), `SNESSetFunction()`, `SNESGetFunction()`
1818: M*/

1820: /*@C
1821:    SNESSetFunction - Sets the function evaluation routine and function
1822:    vector for use by the `SNES` routines in solving systems of nonlinear
1823:    equations.

1825:    Logically Collective

1827:    Input Parameters:
1828: +  snes - the `SNES` context
1829: .  r - vector to store function values, may be `NULL`
1830: .  f - function evaluation routine;  for calling sequence see `SNESFunction`
1831: -  ctx - [optional] user-defined context for private data for the
1832:          function evaluation routine (may be `NULL`)

1834:    Level: beginner

1836: .seealso: [](chapter_snes), `SNES`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetPicard()`, `SNESFunction`
1837: @*/
1838: PetscErrorCode SNESSetFunction(SNES snes, Vec r, PetscErrorCode (*f)(SNES, Vec, Vec, void *), void *ctx)
1839: {
1840:   DM dm;

1842:   PetscFunctionBegin;
1844:   if (r) {
1846:     PetscCheckSameComm(snes, 1, r, 2);
1847:     PetscCall(PetscObjectReference((PetscObject)r));
1848:     PetscCall(VecDestroy(&snes->vec_func));
1849:     snes->vec_func = r;
1850:   }
1851:   PetscCall(SNESGetDM(snes, &dm));
1852:   PetscCall(DMSNESSetFunction(dm, f, ctx));
1853:   if (f == SNESPicardComputeFunction) PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
1854:   PetscFunctionReturn(PETSC_SUCCESS);
1855: }

1857: /*@C
1858:    SNESSetInitialFunction - Sets the function vector to be used as the
1859:    initial function value at the initialization of the method.  In some
1860:    instances, the user has precomputed the function before calling
1861:    `SNESSolve()`.  This function allows one to avoid a redundant call
1862:    to `SNESComputeFunction()` in that case.

1864:    Logically Collective

1866:    Input Parameters:
1867: +  snes - the `SNES` context
1868: -  f - vector to store function value

1870:    Level: developer

1872:    Notes:
1873:    This should not be modified during the solution procedure.

1875:    This is used extensively in the `SNESFAS` hierarchy and in nonlinear preconditioning.

1877: .seealso: [](chapter_snes), `SNES`, `SNESFAS`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetInitialFunctionNorm()`
1878: @*/
1879: PetscErrorCode SNESSetInitialFunction(SNES snes, Vec f)
1880: {
1881:   Vec vec_func;

1883:   PetscFunctionBegin;
1886:   PetscCheckSameComm(snes, 1, f, 2);
1887:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
1888:     snes->vec_func_init_set = PETSC_FALSE;
1889:     PetscFunctionReturn(PETSC_SUCCESS);
1890:   }
1891:   PetscCall(SNESGetFunction(snes, &vec_func, NULL, NULL));
1892:   PetscCall(VecCopy(f, vec_func));

1894:   snes->vec_func_init_set = PETSC_TRUE;
1895:   PetscFunctionReturn(PETSC_SUCCESS);
1896: }

1898: /*@
1899:    SNESSetNormSchedule - Sets the `SNESNormSchedule` used in convergence and monitoring
1900:    of the `SNES` method, when norms are computed in the solving process

1902:    Logically Collective

1904:    Input Parameters:
1905: +  snes - the `SNES` context
1906: -  normschedule - the frequency of norm computation

1908:    Options Database Key:
1909: .  -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

1911:    Level: advanced

1913:    Notes:
1914:    Only certain `SNES` methods support certain `SNESNormSchedules`.  Most require evaluation
1915:    of the nonlinear function and the taking of its norm at every iteration to
1916:    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1917:    `SNESNGS` and the like do not require the norm of the function to be computed, and therefore
1918:    may either be monitored for convergence or not.  As these are often used as nonlinear
1919:    preconditioners, monitoring the norm of their error is not a useful enterprise within
1920:    their solution.

1922: .seealso: [](chapter_snes), `SNESNormSchedule`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1923: @*/
1924: PetscErrorCode SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
1925: {
1926:   PetscFunctionBegin;
1928:   snes->normschedule = normschedule;
1929:   PetscFunctionReturn(PETSC_SUCCESS);
1930: }

1932: /*@
1933:    SNESGetNormSchedule - Gets the `SNESNormSchedule` used in convergence and monitoring
1934:    of the `SNES` method.

1936:    Logically Collective

1938:    Input Parameters:
1939: +  snes - the `SNES` context
1940: -  normschedule - the type of the norm used

1942:    Level: advanced

1944: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1945: @*/
1946: PetscErrorCode SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
1947: {
1948:   PetscFunctionBegin;
1950:   *normschedule = snes->normschedule;
1951:   PetscFunctionReturn(PETSC_SUCCESS);
1952: }

1954: /*@
1955:   SNESSetFunctionNorm - Sets the last computed residual norm.

1957:   Logically Collective

1959:   Input Parameters:
1960: +  snes - the `SNES` context
1961: -  norm - the value of the norm

1963:   Level: developer

1965: .seealso: [](chapter_snes), `SNES`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1966: @*/
1967: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
1968: {
1969:   PetscFunctionBegin;
1971:   snes->norm = norm;
1972:   PetscFunctionReturn(PETSC_SUCCESS);
1973: }

1975: /*@
1976:   SNESGetFunctionNorm - Gets the last computed norm of the residual

1978:   Not Collective

1980:   Input Parameter:
1981: . snes - the `SNES` context

1983:   Output Parameter:
1984: . norm - the last computed residual norm

1986:   Level: developer

1988: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1989: @*/
1990: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
1991: {
1992:   PetscFunctionBegin;
1995:   *norm = snes->norm;
1996:   PetscFunctionReturn(PETSC_SUCCESS);
1997: }

1999: /*@
2000:   SNESGetUpdateNorm - Gets the last computed norm of the solution update

2002:   Not Collective

2004:   Input Parameter:
2005: . snes - the `SNES` context

2007:   Output Parameter:
2008: . ynorm - the last computed update norm

2010:   Level: developer

2012:   Note:
2013:   The new solution is the current solution plus the update, so this norm is an indication of the size of the update

2015: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`
2016: @*/
2017: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
2018: {
2019:   PetscFunctionBegin;
2022:   *ynorm = snes->ynorm;
2023:   PetscFunctionReturn(PETSC_SUCCESS);
2024: }

2026: /*@
2027:   SNESGetSolutionNorm - Gets the last computed norm of the solution

2029:   Not Collective

2031:   Input Parameter:
2032: . snes - the `SNES` context

2034:   Output Parameter:
2035: . xnorm - the last computed solution norm

2037:   Level: developer

2039: .seealso: [](chapter_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`, `SNESGetUpdateNorm()`
2040: @*/
2041: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
2042: {
2043:   PetscFunctionBegin;
2046:   *xnorm = snes->xnorm;
2047:   PetscFunctionReturn(PETSC_SUCCESS);
2048: }

2050: /*@C
2051:    SNESSetFunctionType - Sets the `SNESFunctionType`
2052:    of the `SNES` method.

2054:    Logically Collective

2056:    Input Parameters:
2057: +  snes - the `SNES` context
2058: -  type - the function type

2060:    Level: developer

2062:    Notes:
2063:    Possible values of the function type
2064: +  `SNES_FUNCTION_DEFAULT` - the default for the given `SNESType`
2065: .  `SNES_FUNCTION_UNPRECONDITIONED` - an unpreconditioned function evaluation (this is the function provided with `SNESSetFunction()`
2066: -  `SNES_FUNCTION_PRECONDITIONED` - a transformation of the function provided with `SNESSetFunction()`

2068:    Different `SNESType`s use this value in different ways

2070: .seealso: [](chapter_snes), `SNES`, `SNESFunctionType`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2071: @*/
2072: PetscErrorCode SNESSetFunctionType(SNES snes, SNESFunctionType type)
2073: {
2074:   PetscFunctionBegin;
2076:   snes->functype = type;
2077:   PetscFunctionReturn(PETSC_SUCCESS);
2078: }

2080: /*@C
2081:    SNESGetFunctionType - Gets the `SNESFunctionType` used in convergence and monitoring set with `SNESSetFunctionType()`
2082:    of the SNES method.

2084:    Logically Collective

2086:    Input Parameters:
2087: +  snes - the `SNES` context
2088: -  type - the type of the function evaluation, see `SNESSetFunctionType()`

2090:    Level: advanced

2092: .seealso: [](chapter_snes), `SNESSetFunctionType()`, `SNESFunctionType`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2093: @*/
2094: PetscErrorCode SNESGetFunctionType(SNES snes, SNESFunctionType *type)
2095: {
2096:   PetscFunctionBegin;
2098:   *type = snes->functype;
2099:   PetscFunctionReturn(PETSC_SUCCESS);
2100: }

2102: /*MC
2103:     SNESNGSFunction - function used to apply a Gauss-Seidel sweep on the nonlinear function

2105:      Synopsis:
2106: #include <petscsnes.h>
2107: $    SNESNGSFunction(SNES snes,Vec x,Vec b,void *ctx);

2109:      Collective

2111:      Input Parameters:
2112: +  X   - solution vector
2113: .  B   - RHS vector
2114: -  ctx - optional user-defined Gauss-Seidel context

2116:      Output Parameter:
2117: .  X   - solution vector

2119:    Level: intermediate

2121: .seealso: [](chapter_snes), `SNESNGS`, `SNESSetNGS()`, `SNESGetNGS()`
2122: M*/

2124: /*@C
2125:    SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
2126:    use with composed nonlinear solvers.

2128:    Input Parameters:
2129: +  snes   - the `SNES` context
2130: .  f - function evaluation routine to apply Gauss-Seidel see `SNESNGSFunction`
2131: -  ctx    - [optional] user-defined context for private data for the
2132:             smoother evaluation routine (may be `NULL`)

2134:    Calling sequence of `f`:
2135: $  PetscErrorCode f(SNES snes, Vec X, Vec B, void *ctx)
2136: +  snes - the `SNES` context
2137: .  X - the current solution
2138: .  B - the right hand side vector (which may be `NULL`)
2139: -  ctx - a user provided context

2141:    Level: intermediate

2143:    Note:
2144:    The `SNESNGS` routines are used by the composed nonlinear solver to generate
2145:     a problem appropriate update to the solution, particularly `SNESFAS`.

2147: .seealso: [](chapter_snes), `SNESGetNGS()`, `SNESNGSFunction`, `SNESNCG`, `SNESGetFunction()`, `SNESComputeNGS()`
2148: @*/
2149: PetscErrorCode SNESSetNGS(SNES snes, PetscErrorCode (*f)(SNES, Vec, Vec, void *), void *ctx)
2150: {
2151:   DM dm;

2153:   PetscFunctionBegin;
2155:   PetscCall(SNESGetDM(snes, &dm));
2156:   PetscCall(DMSNESSetNGS(dm, f, ctx));
2157:   PetscFunctionReturn(PETSC_SUCCESS);
2158: }

2160: /*
2161:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
2162:    changed during the KSPSolve()
2163: */
2164: PetscErrorCode SNESPicardComputeMFFunction(SNES snes, Vec x, Vec f, void *ctx)
2165: {
2166:   DM     dm;
2167:   DMSNES sdm;

2169:   PetscFunctionBegin;
2170:   PetscCall(SNESGetDM(snes, &dm));
2171:   PetscCall(DMGetDMSNES(dm, &sdm));
2172:   /*  A(x)*x - b(x) */
2173:   if (sdm->ops->computepfunction) {
2174:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2175:     PetscCall(VecScale(f, -1.0));
2176:     /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
2177:     if (!snes->picard) PetscCall(MatDuplicate(snes->jacobian_pre, MAT_DO_NOT_COPY_VALUES, &snes->picard));
2178:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2179:     PetscCall(MatMultAdd(snes->picard, x, f, f));
2180:   } else {
2181:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2182:     PetscCall(MatMult(snes->picard, x, f));
2183:   }
2184:   PetscFunctionReturn(PETSC_SUCCESS);
2185: }

2187: PetscErrorCode SNESPicardComputeFunction(SNES snes, Vec x, Vec f, void *ctx)
2188: {
2189:   DM     dm;
2190:   DMSNES sdm;

2192:   PetscFunctionBegin;
2193:   PetscCall(SNESGetDM(snes, &dm));
2194:   PetscCall(DMGetDMSNES(dm, &sdm));
2195:   /*  A(x)*x - b(x) */
2196:   if (sdm->ops->computepfunction) {
2197:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2198:     PetscCall(VecScale(f, -1.0));
2199:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2200:     PetscCall(MatMultAdd(snes->jacobian_pre, x, f, f));
2201:   } else {
2202:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2203:     PetscCall(MatMult(snes->jacobian_pre, x, f));
2204:   }
2205:   PetscFunctionReturn(PETSC_SUCCESS);
2206: }

2208: PetscErrorCode SNESPicardComputeJacobian(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
2209: {
2210:   PetscFunctionBegin;
2211:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
2212:   /* must assembly if matrix-free to get the last SNES solution */
2213:   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
2214:   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
2215:   PetscFunctionReturn(PETSC_SUCCESS);
2216: }

2218: /*@C
2219:    SNESSetPicard - Use `SNES` to solve the system A(x) x = bp(x) + b via a Picard type iteration (Picard linearization)

2221:    Logically Collective

2223:    Input Parameters:
2224: +  snes - the `SNES` context
2225: .  r - vector to store function values, may be `NULL`
2226: .  bp - function evaluation routine, may be `NULL`
2227: .  Amat - matrix with which A(x) x - bp(x) - b is to be computed
2228: .  Pmat - matrix from which preconditioner is computed (usually the same as `Amat`)
2229: .  J  - function to compute matrix values, for the calling sequence see `SNESJacobianFunction()`
2230: -  ctx - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

2232:    Level: intermediate

2234:    Notes:
2235:     It is often better to provide the nonlinear function F() and some approximation to its Jacobian directly and use
2236:     an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

2238:     One can call `SNESSetPicard()` or `SNESSetFunction()` (and possibly `SNESSetJacobian()`) but cannot call both

2240:      Solves the equation A(x) x = bp(x) - b via the defect correction algorithm A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}.
2241:      When an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = bp(x^{n}) + b iteration.

2243:      Run with `-snes_mf_operator` to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.

2245:    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
2246:    the direct Picard iteration A(x^n) x^{n+1} = bp(x^n) + b

2248:    There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
2249:    believe it is the iteration  A(x^{n}) x^{n+1} = b(x^{n}) hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
2250:    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).

2252:    When used with `-snes_mf_operator` this will run matrix-free Newton's method where the matrix-vector product is of the true Jacobian of A(x)x - bp(x) -b and
2253:     A(x^{n}) is used to build the preconditioner

2255:    When used with `-snes_fd` this will compute the true Jacobian (very slowly one column at at time) and thus represent Newton's method.

2257:    When used with `-snes_fd_coloring` this will compute the Jacobian via coloring and thus represent a faster implementation of Newton's method. But the
2258:    the nonzero structure of the Jacobian is, in general larger than that of the Picard matrix A so you must provide in A the needed nonzero structure for the correct
2259:    coloring. When using `DMDA` this may mean creating the matrix A with `DMCreateMatrix()` using a wider stencil than strictly needed for A or with a `DMDA_STENCIL_BOX`.
2260:    See the comment in src/snes/tutorials/ex15.c.

2262: .seealso: [](chapter_snes), `SNES`, `SNESGetFunction()`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESGetPicard()`, `SNESLineSearchPreCheckPicard()`, `SNESJacobianFunction`
2263: @*/
2264: PetscErrorCode SNESSetPicard(SNES snes, Vec r, PetscErrorCode (*bp)(SNES, Vec, Vec, void *), Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
2265: {
2266:   DM dm;

2268:   PetscFunctionBegin;
2270:   PetscCall(SNESGetDM(snes, &dm));
2271:   PetscCall(DMSNESSetPicard(dm, bp, J, ctx));
2272:   PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
2273:   PetscCall(SNESSetFunction(snes, r, SNESPicardComputeFunction, ctx));
2274:   PetscCall(SNESSetJacobian(snes, Amat, Pmat, SNESPicardComputeJacobian, ctx));
2275:   PetscFunctionReturn(PETSC_SUCCESS);
2276: }

2278: /*@C
2279:    SNESGetPicard - Returns the context for the Picard iteration

2281:    Not Collective, but `Vec` is parallel if `SNES` is parallel. Collective if `Vec` is requested, but has not been created yet.

2283:    Input Parameter:
2284: .  snes - the `SNES` context

2286:    Output Parameters:
2287: +  r - the function (or `NULL`)
2288: .  f - the function (or `NULL`);  for calling sequence see `SNESFunction`
2289: .  Amat - the matrix used to defined the operation A(x) x - b(x) (or `NULL`)
2290: .  Pmat  - the matrix from which the preconditioner will be constructed (or `NULL`)
2291: .  J - the function for matrix evaluation (or `NULL`);  for calling sequence see `SNESJacobianFunction`
2292: -  ctx - the function context (or `NULL`)

2294:    Level: advanced

2296: .seealso: [](chapter_snes), `SNESSetFunction()`, `SNESSetPicard()`, `SNESGetFunction()`, `SNESGetJacobian()`, `SNESGetDM()`, `SNESFunction`, `SNESJacobianFunction`
2297: @*/
2298: PetscErrorCode SNESGetPicard(SNES snes, Vec *r, PetscErrorCode (**f)(SNES, Vec, Vec, void *), Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES, Vec, Mat, Mat, void *), void **ctx)
2299: {
2300:   DM dm;

2302:   PetscFunctionBegin;
2304:   PetscCall(SNESGetFunction(snes, r, NULL, NULL));
2305:   PetscCall(SNESGetJacobian(snes, Amat, Pmat, NULL, NULL));
2306:   PetscCall(SNESGetDM(snes, &dm));
2307:   PetscCall(DMSNESGetPicard(dm, f, J, ctx));
2308:   PetscFunctionReturn(PETSC_SUCCESS);
2309: }

2311: /*@C
2312:    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the nonlinear problem

2314:    Logically Collective

2316:    Input Parameters:
2317: +  snes - the `SNES` context
2318: .  func - function evaluation routine
2319: -  ctx - [optional] user-defined context for private data for the
2320:          function evaluation routine (may be `NULL`)

2322:    Calling sequence of `func`:
2323: $    PetscErrorCode func(SNES snes, Vec x, void *ctx);
2324: +  snes - the `SNES` solver
2325: .  x - vector to put initial guess
2326: -  ctx - optional user-defined function context

2328:    Level: intermediate

2330: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`
2331: @*/
2332: PetscErrorCode SNESSetComputeInitialGuess(SNES snes, PetscErrorCode (*func)(SNES, Vec, void *), void *ctx)
2333: {
2334:   PetscFunctionBegin;
2336:   if (func) snes->ops->computeinitialguess = func;
2337:   if (ctx) snes->initialguessP = ctx;
2338:   PetscFunctionReturn(PETSC_SUCCESS);
2339: }

2341: /*@C
2342:    SNESGetRhs - Gets the vector for solving F(x) = `rhs`. If `rhs` is not set
2343:    it assumes a zero right hand side.

2345:    Logically Collective

2347:    Input Parameter:
2348: .  snes - the `SNES` context

2350:    Output Parameter:
2351: .  rhs - the right hand side vector or `NULL` if the right hand side vector is null

2353:    Level: intermediate

2355: .seealso: [](chapter_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetFunction()`
2356: @*/
2357: PetscErrorCode SNESGetRhs(SNES snes, Vec *rhs)
2358: {
2359:   PetscFunctionBegin;
2362:   *rhs = snes->vec_rhs;
2363:   PetscFunctionReturn(PETSC_SUCCESS);
2364: }

2366: /*@
2367:    SNESComputeFunction - Calls the function that has been set with `SNESSetFunction()`.

2369:    Collective

2371:    Input Parameters:
2372: +  snes - the `SNES` context
2373: -  x - input vector

2375:    Output Parameter:
2376: .  y - function vector, as set by `SNESSetFunction()`

2378:    Level: developer

2380:    Note:
2381:    `SNESComputeFunction()` is typically used within nonlinear solvers
2382:    implementations, so users would not generally call this routine themselves.

2384: .seealso: [](chapter_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeMFFunction()`
2385: @*/
2386: PetscErrorCode SNESComputeFunction(SNES snes, Vec x, Vec y)
2387: {
2388:   DM     dm;
2389:   DMSNES sdm;

2391:   PetscFunctionBegin;
2395:   PetscCheckSameComm(snes, 1, x, 2);
2396:   PetscCheckSameComm(snes, 1, y, 3);
2397:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2399:   PetscCall(SNESGetDM(snes, &dm));
2400:   PetscCall(DMGetDMSNES(dm, &sdm));
2401:   PetscCheck(sdm->ops->computefunction || snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2402:   if (sdm->ops->computefunction) {
2403:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2404:     PetscCall(VecLockReadPush(x));
2405:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2406:     snes->domainerror = PETSC_FALSE;
2407:     {
2408:       void *ctx;
2409:       PetscErrorCode (*computefunction)(SNES, Vec, Vec, void *);
2410:       PetscCall(DMSNESGetFunction(dm, &computefunction, &ctx));
2411:       PetscCallBack("SNES callback function", (*computefunction)(snes, x, y, ctx));
2412:     }
2413:     PetscCall(VecLockReadPop(x));
2414:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2415:   } else /* if (snes->vec_rhs) */ {
2416:     PetscCall(MatMult(snes->jacobian, x, y));
2417:   }
2418:   if (snes->vec_rhs) PetscCall(VecAXPY(y, -1.0, snes->vec_rhs));
2419:   snes->nfuncs++;
2420:   /*
2421:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2422:      propagate the value to all processes
2423:   */
2424:   if (snes->domainerror) PetscCall(VecSetInf(y));
2425:   PetscFunctionReturn(PETSC_SUCCESS);
2426: }

2428: /*@
2429:    SNESComputeMFFunction - Calls the function that has been set with `SNESSetMFFunction()`.

2431:    Collective

2433:    Input Parameters:
2434: +  snes - the `SNES` context
2435: -  x - input vector

2437:    Output Parameter:
2438: .  y - function vector, as set by `SNESSetMFFunction()`

2440:    Level: developer

2442:    Notes:
2443:    `SNESComputeMFFunction()` is used within the matrix vector products called by the matrix created with `MatCreateSNESMF()`
2444:    so users would not generally call this routine themselves.

2446:     Since this function is intended for use with finite differencing it does not subtract the right hand side vector provided with `SNESSolve()`
2447:     while `SNESComputeFunction()` does. As such, this routine cannot be used with  `MatMFFDSetBase()` with a provided F function value even if it applies the
2448:     same function as `SNESComputeFunction()` if a `SNESSolve()` right hand side vector is use because the two functions difference would include this right hand side function.

2450: .seealso: [](chapter_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `MatCreateSNESMF`
2451: @*/
2452: PetscErrorCode SNESComputeMFFunction(SNES snes, Vec x, Vec y)
2453: {
2454:   DM     dm;
2455:   DMSNES sdm;

2457:   PetscFunctionBegin;
2461:   PetscCheckSameComm(snes, 1, x, 2);
2462:   PetscCheckSameComm(snes, 1, y, 3);
2463:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2465:   PetscCall(SNESGetDM(snes, &dm));
2466:   PetscCall(DMGetDMSNES(dm, &sdm));
2467:   PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2468:   PetscCall(VecLockReadPush(x));
2469:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2470:   snes->domainerror = PETSC_FALSE;
2471:   PetscCallBack("SNES callback function", (*sdm->ops->computemffunction)(snes, x, y, sdm->mffunctionctx));
2472:   PetscCall(VecLockReadPop(x));
2473:   PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2474:   snes->nfuncs++;
2475:   /*
2476:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2477:      propagate the value to all processes
2478:   */
2479:   if (snes->domainerror) PetscCall(VecSetInf(y));
2480:   PetscFunctionReturn(PETSC_SUCCESS);
2481: }

2483: /*@
2484:    SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  `SNESSetNGS()`.

2486:    Collective

2488:    Input Parameters:
2489: +  snes - the `SNES` context
2490: .  x - input vector
2491: -  b - rhs vector

2493:    Output Parameter:
2494: .  x - new solution vector

2496:    Level: developer

2498:    Note:
2499:    `SNESComputeNGS()` is typically used within composed nonlinear solver
2500:    implementations, so most users would not generally call this routine
2501:    themselves.

2503: .seealso: [](chapter_snes), `SNESNGS`, `SNESSetNGS()`, `SNESComputeFunction()`
2504: @*/
2505: PetscErrorCode SNESComputeNGS(SNES snes, Vec b, Vec x)
2506: {
2507:   DM     dm;
2508:   DMSNES sdm;

2510:   PetscFunctionBegin;
2514:   PetscCheckSameComm(snes, 1, x, 3);
2515:   if (b) PetscCheckSameComm(snes, 1, b, 2);
2516:   if (b) PetscCall(VecValidValues_Internal(b, 2, PETSC_TRUE));
2517:   PetscCall(PetscLogEventBegin(SNES_NGSEval, snes, x, b, 0));
2518:   PetscCall(SNESGetDM(snes, &dm));
2519:   PetscCall(DMGetDMSNES(dm, &sdm));
2520:   PetscCheck(sdm->ops->computegs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2521:   if (b) PetscCall(VecLockReadPush(b));
2522:   PetscCallBack("SNES callback NGS", (*sdm->ops->computegs)(snes, x, b, sdm->gsctx));
2523:   if (b) PetscCall(VecLockReadPop(b));
2524:   PetscCall(PetscLogEventEnd(SNES_NGSEval, snes, x, b, 0));
2525:   PetscFunctionReturn(PETSC_SUCCESS);
2526: }

2528: PetscErrorCode SNESTestJacobian(SNES snes)
2529: {
2530:   Mat               A, B, C, D, jacobian;
2531:   Vec               x = snes->vec_sol, f = snes->vec_func;
2532:   PetscReal         nrm, gnorm;
2533:   PetscReal         threshold = 1.e-5;
2534:   MatType           mattype;
2535:   PetscInt          m, n, M, N;
2536:   void             *functx;
2537:   PetscBool         complete_print = PETSC_FALSE, threshold_print = PETSC_FALSE, test = PETSC_FALSE, flg, istranspose;
2538:   PetscViewer       viewer, mviewer;
2539:   MPI_Comm          comm;
2540:   PetscInt          tabs;
2541:   static PetscBool  directionsprinted = PETSC_FALSE;
2542:   PetscViewerFormat format;

2544:   PetscFunctionBegin;
2545:   PetscObjectOptionsBegin((PetscObject)snes);
2546:   PetscCall(PetscOptionsName("-snes_test_jacobian", "Compare hand-coded and finite difference Jacobians", "None", &test));
2547:   PetscCall(PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold, NULL));
2548:   PetscCall(PetscOptionsViewer("-snes_test_jacobian_view", "View difference between hand-coded and finite difference Jacobians element entries", "None", &mviewer, &format, &complete_print));
2549:   if (!complete_print) {
2550:     PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display", "-snes_test_jacobian_view", "3.13", NULL));
2551:     PetscCall(PetscOptionsViewer("-snes_test_jacobian_display", "Display difference between hand-coded and finite difference Jacobians", "None", &mviewer, &format, &complete_print));
2552:   }
2553:   /* for compatibility with PETSc 3.9 and older. */
2554:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display_threshold", "-snes_test_jacobian", "3.13", "-snes_test_jacobian accepts an optional threshold (since v3.10)"));
2555:   PetscCall(PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print));
2556:   PetscOptionsEnd();
2557:   if (!test) PetscFunctionReturn(PETSC_SUCCESS);

2559:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2560:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2561:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2562:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2563:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian -------------\n"));
2564:   if (!complete_print && !directionsprinted) {
2565:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n"));
2566:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n"));
2567:   }
2568:   if (!directionsprinted) {
2569:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n"));
2570:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Jacobian is probably correct.\n"));
2571:     directionsprinted = PETSC_TRUE;
2572:   }
2573:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2575:   PetscCall(PetscObjectTypeCompare((PetscObject)snes->jacobian, MATMFFD, &flg));
2576:   if (!flg) jacobian = snes->jacobian;
2577:   else jacobian = snes->jacobian_pre;

2579:   if (!x) {
2580:     PetscCall(MatCreateVecs(jacobian, &x, NULL));
2581:   } else {
2582:     PetscCall(PetscObjectReference((PetscObject)x));
2583:   }
2584:   if (!f) {
2585:     PetscCall(VecDuplicate(x, &f));
2586:   } else {
2587:     PetscCall(PetscObjectReference((PetscObject)f));
2588:   }
2589:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
2590:   PetscCall(SNESComputeFunction(snes, x, f));
2591:   PetscCall(VecDestroy(&f));
2592:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, SNESKSPTRANSPOSEONLY, &istranspose));
2593:   while (jacobian) {
2594:     Mat JT = NULL, Jsave = NULL;

2596:     if (istranspose) {
2597:       PetscCall(MatCreateTranspose(jacobian, &JT));
2598:       Jsave    = jacobian;
2599:       jacobian = JT;
2600:     }
2601:     PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)jacobian, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, ""));
2602:     if (flg) {
2603:       A = jacobian;
2604:       PetscCall(PetscObjectReference((PetscObject)A));
2605:     } else {
2606:       PetscCall(MatComputeOperator(jacobian, MATAIJ, &A));
2607:     }

2609:     PetscCall(MatGetType(A, &mattype));
2610:     PetscCall(MatGetSize(A, &M, &N));
2611:     PetscCall(MatGetLocalSize(A, &m, &n));
2612:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
2613:     PetscCall(MatSetType(B, mattype));
2614:     PetscCall(MatSetSizes(B, m, n, M, N));
2615:     PetscCall(MatSetBlockSizesFromMats(B, A, A));
2616:     PetscCall(MatSetUp(B));
2617:     PetscCall(MatSetOption(B, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2619:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
2620:     PetscCall(SNESComputeJacobianDefault(snes, x, B, B, functx));

2622:     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &D));
2623:     PetscCall(MatAYPX(D, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2624:     PetscCall(MatNorm(D, NORM_FROBENIUS, &nrm));
2625:     PetscCall(MatNorm(A, NORM_FROBENIUS, &gnorm));
2626:     PetscCall(MatDestroy(&D));
2627:     if (!gnorm) gnorm = 1; /* just in case */
2628:     PetscCall(PetscViewerASCIIPrintf(viewer, "  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n", (double)(nrm / gnorm), (double)nrm));

2630:     if (complete_print) {
2631:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded Jacobian ----------\n"));
2632:       PetscCall(MatView(A, mviewer));
2633:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference Jacobian ----------\n"));
2634:       PetscCall(MatView(B, mviewer));
2635:     }

2637:     if (threshold_print || complete_print) {
2638:       PetscInt           Istart, Iend, *ccols, bncols, cncols, j, row;
2639:       PetscScalar       *cvals;
2640:       const PetscInt    *bcols;
2641:       const PetscScalar *bvals;

2643:       PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &C));
2644:       PetscCall(MatSetType(C, mattype));
2645:       PetscCall(MatSetSizes(C, m, n, M, N));
2646:       PetscCall(MatSetBlockSizesFromMats(C, A, A));
2647:       PetscCall(MatSetUp(C));
2648:       PetscCall(MatSetOption(C, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2650:       PetscCall(MatAYPX(B, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2651:       PetscCall(MatGetOwnershipRange(B, &Istart, &Iend));

2653:       for (row = Istart; row < Iend; row++) {
2654:         PetscCall(MatGetRow(B, row, &bncols, &bcols, &bvals));
2655:         PetscCall(PetscMalloc2(bncols, &ccols, bncols, &cvals));
2656:         for (j = 0, cncols = 0; j < bncols; j++) {
2657:           if (PetscAbsScalar(bvals[j]) > threshold) {
2658:             ccols[cncols] = bcols[j];
2659:             cvals[cncols] = bvals[j];
2660:             cncols += 1;
2661:           }
2662:         }
2663:         if (cncols) PetscCall(MatSetValues(C, 1, &row, cncols, ccols, cvals, INSERT_VALUES));
2664:         PetscCall(MatRestoreRow(B, row, &bncols, &bcols, &bvals));
2665:         PetscCall(PetscFree2(ccols, cvals));
2666:       }
2667:       PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
2668:       PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
2669:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n", (double)threshold));
2670:       PetscCall(MatView(C, complete_print ? mviewer : viewer));
2671:       PetscCall(MatDestroy(&C));
2672:     }
2673:     PetscCall(MatDestroy(&A));
2674:     PetscCall(MatDestroy(&B));
2675:     PetscCall(MatDestroy(&JT));
2676:     if (Jsave) jacobian = Jsave;
2677:     if (jacobian != snes->jacobian_pre) {
2678:       jacobian = snes->jacobian_pre;
2679:       PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian for preconditioner -------------\n"));
2680:     } else jacobian = NULL;
2681:   }
2682:   PetscCall(VecDestroy(&x));
2683:   if (complete_print) PetscCall(PetscViewerPopFormat(mviewer));
2684:   if (mviewer) PetscCall(PetscViewerDestroy(&mviewer));
2685:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2686:   PetscFunctionReturn(PETSC_SUCCESS);
2687: }

2689: /*@
2690:    SNESComputeJacobian - Computes the Jacobian matrix that has been set with `SNESSetJacobian()`.

2692:    Collective

2694:    Input Parameters:
2695: +  snes - the `SNES` context
2696: -  x - input vector

2698:    Output Parameters:
2699: +  A - Jacobian matrix
2700: -  B - optional matrix for building the preconditioner

2702:   Options Database Keys:
2703: +    -snes_lag_preconditioner <lag> - how often to rebuild preconditioner
2704: .    -snes_lag_jacobian <lag> - how often to rebuild Jacobian
2705: .    -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
2706: .    -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
2707: .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2708: .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2709: .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2710: .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
2711: .    -snes_compare_coloring - Compute the finite difference Jacobian using coloring and display norms of difference
2712: .    -snes_compare_coloring_display - Compute the finite difference Jacobian using coloring and display verbose differences
2713: .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
2714: .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2715: .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2716: .    -snes_compare_coloring_draw - Compute the finite difference Jacobian using coloring and draw differences
2717: -    -snes_compare_coloring_draw_contour - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

2719:    Level: developer

2721:    Note:
2722:    Most users should not need to explicitly call this routine, as it
2723:    is used internally within the nonlinear solvers.

2725:    Developer Note:
2726:     This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine `SNESTestJacobian()` use to used
2727:       for with the `SNESType` of test that has been removed.

2729: .seealso: [](chapter_snes), `SNESSetJacobian()`, `KSPSetOperators()`, `MatStructure`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
2730: @*/
2731: PetscErrorCode SNESComputeJacobian(SNES snes, Vec X, Mat A, Mat B)
2732: {
2733:   PetscBool flag;
2734:   DM        dm;
2735:   DMSNES    sdm;
2736:   KSP       ksp;

2738:   PetscFunctionBegin;
2741:   PetscCheckSameComm(snes, 1, X, 2);
2742:   PetscCall(VecValidValues_Internal(X, 2, PETSC_TRUE));
2743:   PetscCall(SNESGetDM(snes, &dm));
2744:   PetscCall(DMGetDMSNES(dm, &sdm));

2746:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */
2747:   if (snes->lagjacobian == -2) {
2748:     snes->lagjacobian = -1;

2750:     PetscCall(PetscInfo(snes, "Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n"));
2751:   } else if (snes->lagjacobian == -1) {
2752:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is -1\n"));
2753:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2754:     if (flag) {
2755:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2756:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2757:     }
2758:     PetscFunctionReturn(PETSC_SUCCESS);
2759:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2760:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagjacobian, snes->iter));
2761:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2762:     if (flag) {
2763:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2764:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2765:     }
2766:     PetscFunctionReturn(PETSC_SUCCESS);
2767:   }
2768:   if (snes->npc && snes->npcside == PC_LEFT) {
2769:     PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2770:     PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2771:     PetscFunctionReturn(PETSC_SUCCESS);
2772:   }

2774:   PetscCall(PetscLogEventBegin(SNES_JacobianEval, snes, X, A, B));
2775:   PetscCall(VecLockReadPush(X));
2776:   {
2777:     void *ctx;
2778:     PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *);
2779:     PetscCall(DMSNESGetJacobian(dm, &J, &ctx));
2780:     PetscCallBack("SNES callback Jacobian", (*J)(snes, X, A, B, ctx));
2781:   }
2782:   PetscCall(VecLockReadPop(X));
2783:   PetscCall(PetscLogEventEnd(SNES_JacobianEval, snes, X, A, B));

2785:   /* attach latest linearization point to the preconditioning matrix */
2786:   PetscCall(PetscObjectCompose((PetscObject)B, "__SNES_latest_X", (PetscObject)X));

2788:   /* the next line ensures that snes->ksp exists */
2789:   PetscCall(SNESGetKSP(snes, &ksp));
2790:   if (snes->lagpreconditioner == -2) {
2791:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner exactly once since lag is -2\n"));
2792:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2793:     snes->lagpreconditioner = -1;
2794:   } else if (snes->lagpreconditioner == -1) {
2795:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is -1\n"));
2796:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2797:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2798:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagpreconditioner, snes->iter));
2799:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2800:   } else {
2801:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner\n"));
2802:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2803:   }

2805:   PetscCall(SNESTestJacobian(snes));
2806:   /* make sure user returned a correct Jacobian and preconditioner */
2809:   {
2810:     PetscBool flag = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_operator = PETSC_FALSE;
2811:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit", NULL, NULL, &flag));
2812:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw", NULL, NULL, &flag_draw));
2813:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw_contour", NULL, NULL, &flag_contour));
2814:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_operator", NULL, NULL, &flag_operator));
2815:     if (flag || flag_draw || flag_contour) {
2816:       Mat         Bexp_mine = NULL, Bexp, FDexp;
2817:       PetscViewer vdraw, vstdout;
2818:       PetscBool   flg;
2819:       if (flag_operator) {
2820:         PetscCall(MatComputeOperator(A, MATAIJ, &Bexp_mine));
2821:         Bexp = Bexp_mine;
2822:       } else {
2823:         /* See if the preconditioning matrix can be viewed and added directly */
2824:         PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)B, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPIBAIJ, ""));
2825:         if (flg) Bexp = B;
2826:         else {
2827:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
2828:           PetscCall(MatComputeOperator(B, MATAIJ, &Bexp_mine));
2829:           Bexp = Bexp_mine;
2830:         }
2831:       }
2832:       PetscCall(MatConvert(Bexp, MATSAME, MAT_INITIAL_MATRIX, &FDexp));
2833:       PetscCall(SNESComputeJacobianDefault(snes, X, FDexp, FDexp, NULL));
2834:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
2835:       if (flag_draw || flag_contour) {
2836:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Explicit Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
2837:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2838:       } else vdraw = NULL;
2839:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit %s\n", flag_operator ? "Jacobian" : "preconditioning Jacobian"));
2840:       if (flag) PetscCall(MatView(Bexp, vstdout));
2841:       if (vdraw) PetscCall(MatView(Bexp, vdraw));
2842:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Finite difference Jacobian\n"));
2843:       if (flag) PetscCall(MatView(FDexp, vstdout));
2844:       if (vdraw) PetscCall(MatView(FDexp, vdraw));
2845:       PetscCall(MatAYPX(FDexp, -1.0, Bexp, SAME_NONZERO_PATTERN));
2846:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian\n"));
2847:       if (flag) PetscCall(MatView(FDexp, vstdout));
2848:       if (vdraw) { /* Always use contour for the difference */
2849:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2850:         PetscCall(MatView(FDexp, vdraw));
2851:         PetscCall(PetscViewerPopFormat(vdraw));
2852:       }
2853:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));
2854:       PetscCall(PetscViewerDestroy(&vdraw));
2855:       PetscCall(MatDestroy(&Bexp_mine));
2856:       PetscCall(MatDestroy(&FDexp));
2857:     }
2858:   }
2859:   {
2860:     PetscBool flag = PETSC_FALSE, flag_display = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_threshold = PETSC_FALSE;
2861:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON, threshold_rtol = 10 * PETSC_SQRT_MACHINE_EPSILON;
2862:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring", NULL, NULL, &flag));
2863:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_display", NULL, NULL, &flag_display));
2864:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw", NULL, NULL, &flag_draw));
2865:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw_contour", NULL, NULL, &flag_contour));
2866:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold", NULL, NULL, &flag_threshold));
2867:     if (flag_threshold) {
2868:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_rtol", &threshold_rtol, NULL));
2869:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_atol", &threshold_atol, NULL));
2870:     }
2871:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
2872:       Mat           Bfd;
2873:       PetscViewer   vdraw, vstdout;
2874:       MatColoring   coloring;
2875:       ISColoring    iscoloring;
2876:       MatFDColoring matfdcoloring;
2877:       PetscErrorCode (*func)(SNES, Vec, Vec, void *);
2878:       void     *funcctx;
2879:       PetscReal norm1, norm2, normmax;

2881:       PetscCall(MatDuplicate(B, MAT_DO_NOT_COPY_VALUES, &Bfd));
2882:       PetscCall(MatColoringCreate(Bfd, &coloring));
2883:       PetscCall(MatColoringSetType(coloring, MATCOLORINGSL));
2884:       PetscCall(MatColoringSetFromOptions(coloring));
2885:       PetscCall(MatColoringApply(coloring, &iscoloring));
2886:       PetscCall(MatColoringDestroy(&coloring));
2887:       PetscCall(MatFDColoringCreate(Bfd, iscoloring, &matfdcoloring));
2888:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
2889:       PetscCall(MatFDColoringSetUp(Bfd, iscoloring, matfdcoloring));
2890:       PetscCall(ISColoringDestroy(&iscoloring));

2892:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
2893:       PetscCall(SNESGetFunction(snes, NULL, &func, &funcctx));
2894:       PetscCall(MatFDColoringSetFunction(matfdcoloring, (PetscErrorCode(*)(void))func, funcctx));
2895:       PetscCall(PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring, ((PetscObject)snes)->prefix));
2896:       PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring, "coloring_"));
2897:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
2898:       PetscCall(MatFDColoringApply(Bfd, matfdcoloring, X, snes));
2899:       PetscCall(MatFDColoringDestroy(&matfdcoloring));

2901:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
2902:       if (flag_draw || flag_contour) {
2903:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Colored Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
2904:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2905:       } else vdraw = NULL;
2906:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit preconditioning Jacobian\n"));
2907:       if (flag_display) PetscCall(MatView(B, vstdout));
2908:       if (vdraw) PetscCall(MatView(B, vdraw));
2909:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Colored Finite difference Jacobian\n"));
2910:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
2911:       if (vdraw) PetscCall(MatView(Bfd, vdraw));
2912:       PetscCall(MatAYPX(Bfd, -1.0, B, SAME_NONZERO_PATTERN));
2913:       PetscCall(MatNorm(Bfd, NORM_1, &norm1));
2914:       PetscCall(MatNorm(Bfd, NORM_FROBENIUS, &norm2));
2915:       PetscCall(MatNorm(Bfd, NORM_MAX, &normmax));
2916:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n", (double)norm1, (double)norm2, (double)normmax));
2917:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
2918:       if (vdraw) { /* Always use contour for the difference */
2919:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2920:         PetscCall(MatView(Bfd, vdraw));
2921:         PetscCall(PetscViewerPopFormat(vdraw));
2922:       }
2923:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));

2925:       if (flag_threshold) {
2926:         PetscInt bs, rstart, rend, i;
2927:         PetscCall(MatGetBlockSize(B, &bs));
2928:         PetscCall(MatGetOwnershipRange(B, &rstart, &rend));
2929:         for (i = rstart; i < rend; i++) {
2930:           const PetscScalar *ba, *ca;
2931:           const PetscInt    *bj, *cj;
2932:           PetscInt           bn, cn, j, maxentrycol = -1, maxdiffcol = -1, maxrdiffcol = -1;
2933:           PetscReal          maxentry = 0, maxdiff = 0, maxrdiff = 0;
2934:           PetscCall(MatGetRow(B, i, &bn, &bj, &ba));
2935:           PetscCall(MatGetRow(Bfd, i, &cn, &cj, &ca));
2936:           PetscCheck(bn == cn, ((PetscObject)A)->comm, PETSC_ERR_PLIB, "Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
2937:           for (j = 0; j < bn; j++) {
2938:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
2939:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
2940:               maxentrycol = bj[j];
2941:               maxentry    = PetscRealPart(ba[j]);
2942:             }
2943:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
2944:               maxdiffcol = bj[j];
2945:               maxdiff    = PetscRealPart(ca[j]);
2946:             }
2947:             if (rdiff > maxrdiff) {
2948:               maxrdiffcol = bj[j];
2949:               maxrdiff    = rdiff;
2950:             }
2951:           }
2952:           if (maxrdiff > 1) {
2953:             PetscCall(PetscViewerASCIIPrintf(vstdout, "row %" PetscInt_FMT " (maxentry=%g at %" PetscInt_FMT ", maxdiff=%g at %" PetscInt_FMT ", maxrdiff=%g at %" PetscInt_FMT "):", i, (double)maxentry, maxentrycol, (double)maxdiff, maxdiffcol, (double)maxrdiff, maxrdiffcol));
2954:             for (j = 0; j < bn; j++) {
2955:               PetscReal rdiff;
2956:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
2957:               if (rdiff > 1) PetscCall(PetscViewerASCIIPrintf(vstdout, " (%" PetscInt_FMT ",%g:%g)", bj[j], (double)PetscRealPart(ba[j]), (double)PetscRealPart(ca[j])));
2958:             }
2959:             PetscCall(PetscViewerASCIIPrintf(vstdout, "\n"));
2960:           }
2961:           PetscCall(MatRestoreRow(B, i, &bn, &bj, &ba));
2962:           PetscCall(MatRestoreRow(Bfd, i, &cn, &cj, &ca));
2963:         }
2964:       }
2965:       PetscCall(PetscViewerDestroy(&vdraw));
2966:       PetscCall(MatDestroy(&Bfd));
2967:     }
2968:   }
2969:   PetscFunctionReturn(PETSC_SUCCESS);
2970: }

2972: /*MC
2973:     SNESJacobianFunction - Function used by `SNES` to compute the nonlinear Jacobian of the function to be solved by `SNES`

2975:      Synopsis:
2976:      #include "petscsnes.h"
2977:      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);

2979:      Collective

2981:     Input Parameters:
2982: +  x - input vector, the Jacobian is to be computed at this value
2983: -  ctx - [optional] user-defined Jacobian context

2985:     Output Parameters:
2986: +  Amat - the matrix that defines the (approximate) Jacobian
2987: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.

2989:    Level: intermediate

2991: .seealso: [](chapter_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESSetJacobian()`, `SNESGetJacobian()`
2992: M*/

2994: /*@C
2995:    SNESSetJacobian - Sets the function to compute Jacobian as well as the
2996:    location to store the matrix.

2998:    Logically Collective

3000:    Input Parameters:
3001: +  snes - the `SNES` context
3002: .  Amat - the matrix that defines the (approximate) Jacobian
3003: .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
3004: .  J - Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFunction` for details
3005: -  ctx - [optional] user-defined context for private data for the
3006:          Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)

3008:    Level: beginner

3010:    Notes:
3011:    If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
3012:    each matrix.

3014:    If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
3015:    space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

3017:    If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
3018:    must be a `MatFDColoring`.

3020:    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
3021:    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`

3023: .seealso: [](chapter_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
3024:           `SNESSetPicard()`, `SNESJacobianFunction`
3025: @*/
3026: PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
3027: {
3028:   DM dm;

3030:   PetscFunctionBegin;
3034:   if (Amat) PetscCheckSameComm(snes, 1, Amat, 2);
3035:   if (Pmat) PetscCheckSameComm(snes, 1, Pmat, 3);
3036:   PetscCall(SNESGetDM(snes, &dm));
3037:   PetscCall(DMSNESSetJacobian(dm, J, ctx));
3038:   if (Amat) {
3039:     PetscCall(PetscObjectReference((PetscObject)Amat));
3040:     PetscCall(MatDestroy(&snes->jacobian));

3042:     snes->jacobian = Amat;
3043:   }
3044:   if (Pmat) {
3045:     PetscCall(PetscObjectReference((PetscObject)Pmat));
3046:     PetscCall(MatDestroy(&snes->jacobian_pre));

3048:     snes->jacobian_pre = Pmat;
3049:   }
3050:   PetscFunctionReturn(PETSC_SUCCESS);
3051: }

3053: /*@C
3054:    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
3055:    provided context for evaluating the Jacobian.

3057:    Not Collective, but `Mat` object will be parallel if `SNES` object is

3059:    Input Parameter:
3060: .  snes - the nonlinear solver context

3062:    Output Parameters:
3063: +  Amat - location to stash (approximate) Jacobian matrix (or `NULL`)
3064: .  Pmat - location to stash matrix used to compute the preconditioner (or `NULL`)
3065: .  J - location to put Jacobian function (or `NULL`), for calling sequence see `SNESJacobianFunction`
3066: -  ctx - location to stash Jacobian ctx (or `NULL`)

3068:    Level: advanced

3070: .seealso: [](chapter_snes), `SNES`, `Mat`, `SNESSetJacobian()`, `SNESComputeJacobian()`, `SNESJacobianFunction`, `SNESGetFunction()`
3071: @*/
3072: PetscErrorCode SNESGetJacobian(SNES snes, Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES, Vec, Mat, Mat, void *), void **ctx)
3073: {
3074:   DM dm;

3076:   PetscFunctionBegin;
3078:   if (Amat) *Amat = snes->jacobian;
3079:   if (Pmat) *Pmat = snes->jacobian_pre;
3080:   PetscCall(SNESGetDM(snes, &dm));
3081:   PetscCall(DMSNESGetJacobian(dm, J, ctx));
3082:   PetscFunctionReturn(PETSC_SUCCESS);
3083: }

3085: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
3086: {
3087:   DM     dm;
3088:   DMSNES sdm;

3090:   PetscFunctionBegin;
3091:   PetscCall(SNESGetDM(snes, &dm));
3092:   PetscCall(DMGetDMSNES(dm, &sdm));
3093:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
3094:     DM        dm;
3095:     PetscBool isdense, ismf;

3097:     PetscCall(SNESGetDM(snes, &dm));
3098:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &isdense, MATSEQDENSE, MATMPIDENSE, MATDENSE, NULL));
3099:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &ismf, MATMFFD, MATSHELL, NULL));
3100:     if (isdense) {
3101:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefault, NULL));
3102:     } else if (!ismf) {
3103:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefaultColor, NULL));
3104:     }
3105:   }
3106:   PetscFunctionReturn(PETSC_SUCCESS);
3107: }

3109: /*@
3110:    SNESSetUp - Sets up the internal data structures for the later use
3111:    of a nonlinear solver.

3113:    Collective

3115:    Input Parameter:
3116: .  snes - the `SNES` context

3118:    Level: advanced

3120:    Note:
3121:    For basic use of the `SNES` solvers the user need not explicitly call
3122:    `SNESSetUp()`, since these actions will automatically occur during
3123:    the call to `SNESSolve()`.  However, if one wishes to control this
3124:    phase separately, `SNESSetUp()` should be called after `SNESCreate()`
3125:    and optional routines of the form SNESSetXXX(), but before `SNESSolve()`.

3127: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESSolve()`, `SNESDestroy()`
3128: @*/
3129: PetscErrorCode SNESSetUp(SNES snes)
3130: {
3131:   DM             dm;
3132:   DMSNES         sdm;
3133:   SNESLineSearch linesearch, pclinesearch;
3134:   void          *lsprectx, *lspostctx;
3135:   PetscBool      mf_operator, mf;
3136:   Vec            f, fpc;
3137:   void          *funcctx;
3138:   void          *jacctx, *appctx;
3139:   Mat            j, jpre;
3140:   PetscErrorCode (*precheck)(SNESLineSearch, Vec, Vec, PetscBool *, void *);
3141:   PetscErrorCode (*postcheck)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
3142:   PetscErrorCode (*func)(SNES, Vec, Vec, void *);
3143:   PetscErrorCode (*jac)(SNES, Vec, Mat, Mat, void *);

3145:   PetscFunctionBegin;
3147:   if (snes->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
3148:   PetscCall(PetscLogEventBegin(SNES_SetUp, snes, 0, 0, 0));

3150:   if (!((PetscObject)snes)->type_name) PetscCall(SNESSetType(snes, SNESNEWTONLS));

3152:   PetscCall(SNESGetFunction(snes, &snes->vec_func, NULL, NULL));

3154:   PetscCall(SNESGetDM(snes, &dm));
3155:   PetscCall(DMGetDMSNES(dm, &sdm));
3156:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3158:   if (!snes->vec_func) PetscCall(DMCreateGlobalVector(dm, &snes->vec_func));

3160:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));

3162:   if (snes->linesearch) {
3163:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
3164:     PetscCall(SNESLineSearchSetFunction(snes->linesearch, SNESComputeFunction));
3165:   }

3167:   PetscCall(SNESGetUseMatrixFree(snes, &mf_operator, &mf));
3168:   if (snes->npc && snes->npcside == PC_LEFT) {
3169:     snes->mf          = PETSC_TRUE;
3170:     snes->mf_operator = PETSC_FALSE;
3171:   }

3173:   if (snes->npc) {
3174:     /* copy the DM over */
3175:     PetscCall(SNESGetDM(snes, &dm));
3176:     PetscCall(SNESSetDM(snes->npc, dm));

3178:     PetscCall(SNESGetFunction(snes, &f, &func, &funcctx));
3179:     PetscCall(VecDuplicate(f, &fpc));
3180:     PetscCall(SNESSetFunction(snes->npc, fpc, func, funcctx));
3181:     PetscCall(SNESGetJacobian(snes, &j, &jpre, &jac, &jacctx));
3182:     PetscCall(SNESSetJacobian(snes->npc, j, jpre, jac, jacctx));
3183:     PetscCall(SNESGetApplicationContext(snes, &appctx));
3184:     PetscCall(SNESSetApplicationContext(snes->npc, appctx));
3185:     PetscCall(SNESSetUseMatrixFree(snes->npc, mf_operator, mf));
3186:     PetscCall(VecDestroy(&fpc));

3188:     /* copy the function pointers over */
3189:     PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)snes->npc));

3191:     /* default to 1 iteration */
3192:     PetscCall(SNESSetTolerances(snes->npc, 0.0, 0.0, 0.0, 1, snes->npc->max_funcs));
3193:     if (snes->npcside == PC_RIGHT) {
3194:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_FINAL_ONLY));
3195:     } else {
3196:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_NONE));
3197:     }
3198:     PetscCall(SNESSetFromOptions(snes->npc));

3200:     /* copy the line search context over */
3201:     if (snes->linesearch && snes->npc->linesearch) {
3202:       PetscCall(SNESGetLineSearch(snes, &linesearch));
3203:       PetscCall(SNESGetLineSearch(snes->npc, &pclinesearch));
3204:       PetscCall(SNESLineSearchGetPreCheck(linesearch, &precheck, &lsprectx));
3205:       PetscCall(SNESLineSearchGetPostCheck(linesearch, &postcheck, &lspostctx));
3206:       PetscCall(SNESLineSearchSetPreCheck(pclinesearch, precheck, lsprectx));
3207:       PetscCall(SNESLineSearchSetPostCheck(pclinesearch, postcheck, lspostctx));
3208:       PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch));
3209:     }
3210:   }
3211:   if (snes->mf) PetscCall(SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version));
3212:   if (snes->ops->usercompute && !snes->user) PetscCall((*snes->ops->usercompute)(snes, (void **)&snes->user));

3214:   snes->jac_iter = 0;
3215:   snes->pre_iter = 0;

3217:   PetscTryTypeMethod(snes, setup);

3219:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3221:   if (snes->npc && snes->npcside == PC_LEFT) {
3222:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
3223:       if (snes->linesearch) {
3224:         PetscCall(SNESGetLineSearch(snes, &linesearch));
3225:         PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunctionDefaultNPC));
3226:       }
3227:     }
3228:   }
3229:   PetscCall(PetscLogEventEnd(SNES_SetUp, snes, 0, 0, 0));
3230:   snes->setupcalled = PETSC_TRUE;
3231:   PetscFunctionReturn(PETSC_SUCCESS);
3232: }

3234: /*@
3235:    SNESReset - Resets a `SNES` context to the snessetupcalled = 0 state and removes any allocated `Vec`s and `Mat`s

3237:    Collective

3239:    Input Parameter:
3240: .  snes - iterative context obtained from `SNESCreate()`

3242:    Level: intermediate

3244:    Notes:
3245:    Call this if you wish to reuse a `SNES` but with different size vectors

3247:    Also calls the application context destroy routine set with `SNESSetComputeApplicationContext()`

3249: .seealso: [](chapter_snes), `SNES`, `SNESDestroy()`, `SNESCreate()`, `SNESSetUp()`, `SNESSolve()`
3250: @*/
3251: PetscErrorCode SNESReset(SNES snes)
3252: {
3253:   PetscFunctionBegin;
3255:   if (snes->ops->userdestroy && snes->user) {
3256:     PetscCall((*snes->ops->userdestroy)((void **)&snes->user));
3257:     snes->user = NULL;
3258:   }
3259:   if (snes->npc) PetscCall(SNESReset(snes->npc));

3261:   PetscTryTypeMethod(snes, reset);
3262:   if (snes->ksp) PetscCall(KSPReset(snes->ksp));

3264:   if (snes->linesearch) PetscCall(SNESLineSearchReset(snes->linesearch));

3266:   PetscCall(VecDestroy(&snes->vec_rhs));
3267:   PetscCall(VecDestroy(&snes->vec_sol));
3268:   PetscCall(VecDestroy(&snes->vec_sol_update));
3269:   PetscCall(VecDestroy(&snes->vec_func));
3270:   PetscCall(MatDestroy(&snes->jacobian));
3271:   PetscCall(MatDestroy(&snes->jacobian_pre));
3272:   PetscCall(MatDestroy(&snes->picard));
3273:   PetscCall(VecDestroyVecs(snes->nwork, &snes->work));
3274:   PetscCall(VecDestroyVecs(snes->nvwork, &snes->vwork));

3276:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

3278:   snes->nwork = snes->nvwork = 0;
3279:   snes->setupcalled          = PETSC_FALSE;
3280:   PetscFunctionReturn(PETSC_SUCCESS);
3281: }

3283: /*@
3284:    SNESConvergedReasonViewCancel - Clears all the reason view functions for a `SNES` object.

3286:    Collective

3288:    Input Parameter:
3289: .  snes - iterative context obtained from `SNESCreate()`

3291:    Level: intermediate

3293: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESReset()`
3294: @*/
3295: PetscErrorCode SNESConvergedReasonViewCancel(SNES snes)
3296: {
3297:   PetscInt i;

3299:   PetscFunctionBegin;
3301:   for (i = 0; i < snes->numberreasonviews; i++) {
3302:     if (snes->reasonviewdestroy[i]) PetscCall((*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]));
3303:   }
3304:   snes->numberreasonviews = 0;
3305:   PetscFunctionReturn(PETSC_SUCCESS);
3306: }

3308: /*@C
3309:    SNESDestroy - Destroys the nonlinear solver context that was created
3310:    with `SNESCreate()`.

3312:    Collective

3314:    Input Parameter:
3315: .  snes - the `SNES` context

3317:    Level: beginner

3319: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESSolve()`
3320: @*/
3321: PetscErrorCode SNESDestroy(SNES *snes)
3322: {
3323:   PetscFunctionBegin;
3324:   if (!*snes) PetscFunctionReturn(PETSC_SUCCESS);
3326:   if (--((PetscObject)(*snes))->refct > 0) {
3327:     *snes = NULL;
3328:     PetscFunctionReturn(PETSC_SUCCESS);
3329:   }

3331:   PetscCall(SNESReset((*snes)));
3332:   PetscCall(SNESDestroy(&(*snes)->npc));

3334:   /* if memory was published with SAWs then destroy it */
3335:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*snes));
3336:   PetscTryTypeMethod((*snes), destroy);

3338:   if ((*snes)->dm) PetscCall(DMCoarsenHookRemove((*snes)->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, *snes));
3339:   PetscCall(DMDestroy(&(*snes)->dm));
3340:   PetscCall(KSPDestroy(&(*snes)->ksp));
3341:   PetscCall(SNESLineSearchDestroy(&(*snes)->linesearch));

3343:   PetscCall(PetscFree((*snes)->kspconvctx));
3344:   if ((*snes)->ops->convergeddestroy) PetscCall((*(*snes)->ops->convergeddestroy)((*snes)->cnvP));
3345:   if ((*snes)->conv_hist_alloc) PetscCall(PetscFree2((*snes)->conv_hist, (*snes)->conv_hist_its));
3346:   PetscCall(SNESMonitorCancel((*snes)));
3347:   PetscCall(SNESConvergedReasonViewCancel((*snes)));
3348:   PetscCall(PetscHeaderDestroy(snes));
3349:   PetscFunctionReturn(PETSC_SUCCESS);
3350: }

3352: /* ----------- Routines to set solver parameters ---------- */

3354: /*@
3355:    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.

3357:    Logically Collective

3359:    Input Parameters:
3360: +  snes - the `SNES` context
3361: -  lag - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3362:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3364:    Options Database Keys:
3365: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3366: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3367: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3368: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3370:    Notes:
3371:    Level: intermediate

3373:    The default is 1
3374:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagPreconditionerPersists()` was called

3376:    `SNESSetLagPreconditionerPersists()` allows using the same uniform lagging (for example every second linear solve) across multiple nonlinear solves.

3378: .seealso: [](chapter_snes), `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetLagPreconditionerPersists()`,
3379:           `SNESSetLagJacobianPersists()`, `SNES`, `SNESSolve()`
3380: @*/
3381: PetscErrorCode SNESSetLagPreconditioner(SNES snes, PetscInt lag)
3382: {
3383:   PetscFunctionBegin;
3385:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3386:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3388:   snes->lagpreconditioner = lag;
3389:   PetscFunctionReturn(PETSC_SUCCESS);
3390: }

3392: /*@
3393:    SNESSetGridSequence - sets the number of steps of grid sequencing that `SNES` will do

3395:    Logically Collective

3397:    Input Parameters:
3398: +  snes - the `SNES` context
3399: -  steps - the number of refinements to do, defaults to 0

3401:    Options Database Key:
3402: .    -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

3404:    Level: intermediate

3406:    Note:
3407:    Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3409: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetGridSequence()`
3410: @*/
3411: PetscErrorCode SNESSetGridSequence(SNES snes, PetscInt steps)
3412: {
3413:   PetscFunctionBegin;
3416:   snes->gridsequence = steps;
3417:   PetscFunctionReturn(PETSC_SUCCESS);
3418: }

3420: /*@
3421:    SNESGetGridSequence - gets the number of steps of grid sequencing that `SNES` will do

3423:    Logically Collective

3425:    Input Parameter:
3426: .  snes - the `SNES` context

3428:    Output Parameter:
3429: .  steps - the number of refinements to do, defaults to 0

3431:    Options Database Key:
3432: .    -snes_grid_sequence <steps> - set number of refinements

3434:    Level: intermediate

3436:    Note:
3437:    Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3439: .seealso: [](chapter_snes), `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetGridSequence()`
3440: @*/
3441: PetscErrorCode SNESGetGridSequence(SNES snes, PetscInt *steps)
3442: {
3443:   PetscFunctionBegin;
3445:   *steps = snes->gridsequence;
3446:   PetscFunctionReturn(PETSC_SUCCESS);
3447: }

3449: /*@
3450:    SNESGetLagPreconditioner - Return how often the preconditioner is rebuilt

3452:    Not Collective

3454:    Input Parameter:
3455: .  snes - the `SNES` context

3457:    Output Parameter:
3458: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3459:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3461:    Options Database Keys:
3462: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3463: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3464: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3465: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3467:    Level: intermediate

3469:    Notes:
3470:    The default is 1

3472:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3474: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3475: @*/
3476: PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)
3477: {
3478:   PetscFunctionBegin;
3480:   *lag = snes->lagpreconditioner;
3481:   PetscFunctionReturn(PETSC_SUCCESS);
3482: }

3484: /*@
3485:    SNESSetLagJacobian - Set when the Jacobian is rebuilt in the nonlinear solve. See `SNESSetLagPreconditioner()` for determining how
3486:      often the preconditioner is rebuilt.

3488:    Logically Collective

3490:    Input Parameters:
3491: +  snes - the `SNES` context
3492: -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3493:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

3495:    Options Database Keys:
3496: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3497: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3498: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3499: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag.

3501:    Level: intermediate

3503:    Notes:
3504:    The default is 1

3506:    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3508:    If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
3509:    at the next Newton step but never again (unless it is reset to another value)

3511: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagPreconditioner()`, `SNESGetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3512: @*/
3513: PetscErrorCode SNESSetLagJacobian(SNES snes, PetscInt lag)
3514: {
3515:   PetscFunctionBegin;
3517:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3518:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3520:   snes->lagjacobian = lag;
3521:   PetscFunctionReturn(PETSC_SUCCESS);
3522: }

3524: /*@
3525:    SNESGetLagJacobian - Get how often the Jacobian is rebuilt. See `SNESGetLagPreconditioner()` to determine when the preconditioner is rebuilt

3527:    Not Collective

3529:    Input Parameter:
3530: .  snes - the `SNES` context

3532:    Output Parameter:
3533: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3534:          the Jacobian is built etc.

3536:    Level: intermediate

3538:    Notes:
3539:    The default is 1

3541:    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagJacobianPersists()` was called.

3543: .seealso: [](chapter_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetLagJacobian()`, `SNESSetLagPreconditioner()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`

3545: @*/
3546: PetscErrorCode SNESGetLagJacobian(SNES snes, PetscInt *lag)
3547: {
3548:   PetscFunctionBegin;
3550:   *lag = snes->lagjacobian;
3551:   PetscFunctionReturn(PETSC_SUCCESS);
3552: }

3554: /*@
3555:    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple nonlinear solves

3557:    Logically collective

3559:    Input Parameters:
3560: +  snes - the `SNES` context
3561: -   flg - jacobian lagging persists if true

3563:    Options Database Keys:
3564: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3565: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3566: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3567: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3569:    Level: advanced

3571:    Notes:
3572:     Normally when `SNESSetLagJacobian()` is used, the Jacobian is always rebuilt at the beginning of each new nonlinear solve, this removes that.

3574:     This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3575:    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3576:    timesteps may present huge efficiency gains.

3578: .seealso: [](chapter_snes), `SNES, `SNESSetLagPreconditionerPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagJacobianPersists()`
3579: @*/
3580: PetscErrorCode SNESSetLagJacobianPersists(SNES snes, PetscBool flg)
3581: {
3582:   PetscFunctionBegin;
3585:   snes->lagjac_persist = flg;
3586:   PetscFunctionReturn(PETSC_SUCCESS);
3587: }

3589: /*@
3590:    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

3592:    Logically Collective

3594:    Input Parameters:
3595: +  snes - the `SNES` context
3596: -   flg - preconditioner lagging persists if true

3598:    Options Database Keys:
3599: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
3600: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
3601: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
3602: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

3604:    Level: developer

3606:    Notes:
3607:     Normally when `SNESSetLagPreconditioner()` is used, the preconditioner is always rebuilt at the beginning of each new nonlinear solve, this removes that.

3609:    This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3610:    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3611:    several timesteps may present huge efficiency gains.

3613: .seealso: [](chapter_snes), `SNES`, `SNESSetLagJacobianPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagPreconditioner()`
3614: @*/
3615: PetscErrorCode SNESSetLagPreconditionerPersists(SNES snes, PetscBool flg)
3616: {
3617:   PetscFunctionBegin;
3620:   snes->lagpre_persist = flg;
3621:   PetscFunctionReturn(PETSC_SUCCESS);
3622: }

3624: /*@
3625:    SNESSetForceIteration - force `SNESSolve()` to take at least one iteration regardless of the initial residual norm

3627:    Logically Collective

3629:    Input Parameters:
3630: +  snes - the `SNES` context
3631: -  force - `PETSC_TRUE` require at least one iteration

3633:    Options Database Key:
3634: .    -snes_force_iteration <force> - Sets forcing an iteration

3636:    Level: intermediate

3638:    Note:
3639:    This is used sometimes with `TS` to prevent `TS` from detecting a false steady state solution

3641: .seealso: [](chapter_snes), `SNES`, `TS`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`
3642: @*/
3643: PetscErrorCode SNESSetForceIteration(SNES snes, PetscBool force)
3644: {
3645:   PetscFunctionBegin;
3647:   snes->forceiteration = force;
3648:   PetscFunctionReturn(PETSC_SUCCESS);
3649: }

3651: /*@
3652:    SNESGetForceIteration - Check whether or not `SNESSolve()` take at least one iteration regardless of the initial residual norm

3654:    Logically Collective

3656:    Input Parameter:
3657: .  snes - the `SNES` context

3659:    Output Parameter:
3660: .  force - `PETSC_TRUE` requires at least one iteration.

3662:    Level: intermediate

3664: .seealso: [](chapter_snes), `SNES`, `SNESSetForceIteration()`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`
3665: @*/
3666: PetscErrorCode SNESGetForceIteration(SNES snes, PetscBool *force)
3667: {
3668:   PetscFunctionBegin;
3670:   *force = snes->forceiteration;
3671:   PetscFunctionReturn(PETSC_SUCCESS);
3672: }

3674: /*@
3675:    SNESSetTolerances - Sets `SNES` various parameters used in convergence tests.

3677:    Logically Collective

3679:    Input Parameters:
3680: +  snes - the `SNES` context
3681: .  abstol - absolute convergence tolerance
3682: .  rtol - relative convergence tolerance
3683: .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3684: .  maxit - maximum number of iterations, default 50.
3685: -  maxf - maximum number of function evaluations (-1 indicates no limit), default 1000

3687:    Options Database Keys:
3688: +    -snes_atol <abstol> - Sets abstol
3689: .    -snes_rtol <rtol> - Sets rtol
3690: .    -snes_stol <stol> - Sets stol
3691: .    -snes_max_it <maxit> - Sets maxit
3692: -    -snes_max_funcs <maxf> - Sets maxf

3694:    Level: intermediate

3696: .seealso: [](chapter_snes), `SNESolve()`, `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`, `SNESSetForceIteration()`
3697: @*/
3698: PetscErrorCode SNESSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit, PetscInt maxf)
3699: {
3700:   PetscFunctionBegin;

3708:   if (abstol != (PetscReal)PETSC_DEFAULT) {
3709:     PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
3710:     snes->abstol = abstol;
3711:   }
3712:   if (rtol != (PetscReal)PETSC_DEFAULT) {
3713:     PetscCheck(rtol >= 0.0 && 1.0 > rtol, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %g must be non-negative and less than 1.0", (double)rtol);
3714:     snes->rtol = rtol;
3715:   }
3716:   if (stol != (PetscReal)PETSC_DEFAULT) {
3717:     PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
3718:     snes->stol = stol;
3719:   }
3720:   if (maxit != PETSC_DEFAULT) {
3721:     PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
3722:     snes->max_its = maxit;
3723:   }
3724:   if (maxf != PETSC_DEFAULT) {
3725:     PetscCheck(maxf >= -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of function evaluations %" PetscInt_FMT " must be -1 or nonnegative", maxf);
3726:     snes->max_funcs = maxf;
3727:   }
3728:   snes->tolerancesset = PETSC_TRUE;
3729:   PetscFunctionReturn(PETSC_SUCCESS);
3730: }

3732: /*@
3733:    SNESSetDivergenceTolerance - Sets the divergence tolerance used for the `SNES` divergence test.

3735:    Logically Collective

3737:    Input Parameters:
3738: +  snes - the `SNES` context
3739: -  divtol - the divergence tolerance. Use -1 to deactivate the test, default is 1e4

3741:    Options Database Key:
3742: .    -snes_divergence_tolerance <divtol> - Sets `divtol`

3744:    Level: intermediate

3746: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetTolerances()`, `SNESGetDivergenceTolerance`
3747: @*/
3748: PetscErrorCode SNESSetDivergenceTolerance(SNES snes, PetscReal divtol)
3749: {
3750:   PetscFunctionBegin;

3754:   if (divtol != (PetscReal)PETSC_DEFAULT) {
3755:     snes->divtol = divtol;
3756:   } else {
3757:     snes->divtol = 1.0e4;
3758:   }
3759:   PetscFunctionReturn(PETSC_SUCCESS);
3760: }

3762: /*@
3763:    SNESGetTolerances - Gets various parameters used in convergence tests.

3765:    Not Collective

3767:    Input Parameters:
3768: +  snes - the `SNES` context
3769: .  atol - absolute convergence tolerance
3770: .  rtol - relative convergence tolerance
3771: .  stol -  convergence tolerance in terms of the norm
3772:            of the change in the solution between steps
3773: .  maxit - maximum number of iterations
3774: -  maxf - maximum number of function evaluations

3776:    Level: intermediate

3778:    Note:
3779:    The user can specify `NULL` for any parameter that is not needed.

3781: .seealso: [](chapter_snes), `SNES`, `SNESSetTolerances()`
3782: @*/
3783: PetscErrorCode SNESGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit, PetscInt *maxf)
3784: {
3785:   PetscFunctionBegin;
3787:   if (atol) *atol = snes->abstol;
3788:   if (rtol) *rtol = snes->rtol;
3789:   if (stol) *stol = snes->stol;
3790:   if (maxit) *maxit = snes->max_its;
3791:   if (maxf) *maxf = snes->max_funcs;
3792:   PetscFunctionReturn(PETSC_SUCCESS);
3793: }

3795: /*@
3796:    SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

3798:    Not Collective

3800:    Input Parameters:
3801: +  snes - the `SNES` context
3802: -  divtol - divergence tolerance

3804:    Level: intermediate

3806: .seealso: [](chapter_snes), `SNES`, `SNESSetDivergenceTolerance()`
3807: @*/
3808: PetscErrorCode SNESGetDivergenceTolerance(SNES snes, PetscReal *divtol)
3809: {
3810:   PetscFunctionBegin;
3812:   if (divtol) *divtol = snes->divtol;
3813:   PetscFunctionReturn(PETSC_SUCCESS);
3814: }

3816: /*@
3817:    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.

3819:    Logically Collective

3821:    Input Parameters:
3822: +  snes - the `SNES` context
3823: -  tol - tolerance

3825:    Options Database Key:
3826: .  -snes_tr_tol <tol> - Sets tol

3828:    Level: intermediate

3830: .seealso: [](chapter_snes), `SNES`, `SNESNEWTONTR`, `SNESSetTolerances()`
3831: @*/
3832: PetscErrorCode SNESSetTrustRegionTolerance(SNES snes, PetscReal tol)
3833: {
3834:   PetscFunctionBegin;
3837:   snes->deltatol = tol;
3838:   PetscFunctionReturn(PETSC_SUCCESS);
3839: }

3841: PETSC_INTERN PetscErrorCode SNESMonitorRange_Private(SNES, PetscInt, PetscReal *);

3843: PetscErrorCode SNESMonitorLGRange(SNES snes, PetscInt n, PetscReal rnorm, void *monctx)
3844: {
3845:   PetscDrawLG      lg;
3846:   PetscReal        x, y, per;
3847:   PetscViewer      v = (PetscViewer)monctx;
3848:   static PetscReal prev; /* should be in the context */
3849:   PetscDraw        draw;

3851:   PetscFunctionBegin;
3853:   PetscCall(PetscViewerDrawGetDrawLG(v, 0, &lg));
3854:   if (!n) PetscCall(PetscDrawLGReset(lg));
3855:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3856:   PetscCall(PetscDrawSetTitle(draw, "Residual norm"));
3857:   x = (PetscReal)n;
3858:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
3859:   else y = -15.0;
3860:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3861:   if (n < 20 || !(n % 5) || snes->reason) {
3862:     PetscCall(PetscDrawLGDraw(lg));
3863:     PetscCall(PetscDrawLGSave(lg));
3864:   }

3866:   PetscCall(PetscViewerDrawGetDrawLG(v, 1, &lg));
3867:   if (!n) PetscCall(PetscDrawLGReset(lg));
3868:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3869:   PetscCall(PetscDrawSetTitle(draw, "% elements > .2*max element"));
3870:   PetscCall(SNESMonitorRange_Private(snes, n, &per));
3871:   x = (PetscReal)n;
3872:   y = 100.0 * per;
3873:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3874:   if (n < 20 || !(n % 5) || snes->reason) {
3875:     PetscCall(PetscDrawLGDraw(lg));
3876:     PetscCall(PetscDrawLGSave(lg));
3877:   }

3879:   PetscCall(PetscViewerDrawGetDrawLG(v, 2, &lg));
3880:   if (!n) {
3881:     prev = rnorm;
3882:     PetscCall(PetscDrawLGReset(lg));
3883:   }
3884:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3885:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm"));
3886:   x = (PetscReal)n;
3887:   y = (prev - rnorm) / prev;
3888:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3889:   if (n < 20 || !(n % 5) || snes->reason) {
3890:     PetscCall(PetscDrawLGDraw(lg));
3891:     PetscCall(PetscDrawLGSave(lg));
3892:   }

3894:   PetscCall(PetscViewerDrawGetDrawLG(v, 3, &lg));
3895:   if (!n) PetscCall(PetscDrawLGReset(lg));
3896:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3897:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm*(% > .2 max)"));
3898:   x = (PetscReal)n;
3899:   y = (prev - rnorm) / (prev * per);
3900:   if (n > 2) { /*skip initial crazy value */
3901:     PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3902:   }
3903:   if (n < 20 || !(n % 5) || snes->reason) {
3904:     PetscCall(PetscDrawLGDraw(lg));
3905:     PetscCall(PetscDrawLGSave(lg));
3906:   }
3907:   prev = rnorm;
3908:   PetscFunctionReturn(PETSC_SUCCESS);
3909: }

3911: /*@
3912:    SNESMonitor - runs the user provided monitor routines, if they exist

3914:    Collective

3916:    Input Parameters:
3917: +  snes - nonlinear solver context obtained from `SNESCreate()`
3918: .  iter - iteration number
3919: -  rnorm - relative norm of the residual

3921:    Level: developer

3923:    Note:
3924:    This routine is called by the `SNES` implementations.
3925:    It does not typically need to be called by the user.

3927: .seealso: [](chapter_snes), `SNES`, `SNESMonitorSet()`
3928: @*/
3929: PetscErrorCode SNESMonitor(SNES snes, PetscInt iter, PetscReal rnorm)
3930: {
3931:   PetscInt i, n = snes->numbermonitors;

3933:   PetscFunctionBegin;
3934:   PetscCall(VecLockReadPush(snes->vec_sol));
3935:   for (i = 0; i < n; i++) PetscCall((*snes->monitor[i])(snes, iter, rnorm, snes->monitorcontext[i]));
3936:   PetscCall(VecLockReadPop(snes->vec_sol));
3937:   PetscFunctionReturn(PETSC_SUCCESS);
3938: }

3940: /* ------------ Routines to set performance monitoring options ----------- */

3942: /*MC
3943:     SNESMonitorFunction - functional form passed to `SNESMonitorSet()` to monitor convergence of nonlinear solver

3945:      Synopsis:
3946: #include <petscsnes.h>
3947: $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)

3949:      Collective

3951:     Input Parameters:
3952: +    snes - the `SNES` context
3953: .    its - iteration number
3954: .    norm - 2-norm function value (may be estimated)
3955: -    mctx - [optional] monitoring context

3957:    Level: advanced

3959: .seealso: [](chapter_snes), `SNESMonitorSet()`, `SNESMonitorSet()`, `SNESMonitorGet()`
3960: M*/

3962: /*@C
3963:    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
3964:    iteration of the nonlinear solver to display the iteration's
3965:    progress.

3967:    Logically Collective

3969:    Input Parameters:
3970: +  snes - the `SNES` context
3971: .  f - the monitor function,  for the calling sequence see `SNESMonitorFunction`
3972: .  mctx - [optional] user-defined context for private data for the
3973:           monitor routine (use `NULL` if no context is desired)
3974: -  monitordestroy - [optional] routine that frees monitor context (may be `NULL`)

3976:    Options Database Keys:
3977: +    -snes_monitor        - sets `SNESMonitorDefault()`
3978: .    -snes_monitor draw::draw_lg - sets line graph monitor,
3979: -    -snes_monitor_cancel - cancels all monitors that have been hardwired into a code by calls to `SNESMonitorSet()`, but does not cancel those set via
3980:                             the options database.

3982:    Level: intermediate

3984:    Note:
3985:    Several different monitoring routines may be set by calling
3986:    `SNESMonitorSet()` multiple times; all will be called in the
3987:    order in which they were set.

3989:    Fortran Note:
3990:    Only a single monitor function can be set for each `SNES` object

3992: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESMonitorDefault()`, `SNESMonitorCancel()`, `SNESMonitorFunction`
3993: @*/
3994: PetscErrorCode SNESMonitorSet(SNES snes, PetscErrorCode (*f)(SNES, PetscInt, PetscReal, void *), void *mctx, PetscErrorCode (*monitordestroy)(void **))
3995: {
3996:   PetscInt  i;
3997:   PetscBool identical;

3999:   PetscFunctionBegin;
4001:   for (i = 0; i < snes->numbermonitors; i++) {
4002:     PetscCall(PetscMonitorCompare((PetscErrorCode(*)(void))f, mctx, monitordestroy, (PetscErrorCode(*)(void))snes->monitor[i], snes->monitorcontext[i], snes->monitordestroy[i], &identical));
4003:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4004:   }
4005:   PetscCheck(snes->numbermonitors < MAXSNESMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
4006:   snes->monitor[snes->numbermonitors]          = f;
4007:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
4008:   snes->monitorcontext[snes->numbermonitors++] = (void *)mctx;
4009:   PetscFunctionReturn(PETSC_SUCCESS);
4010: }

4012: /*@
4013:    SNESMonitorCancel - Clears all the monitor functions for a `SNES` object.

4015:    Logically Collective

4017:    Input Parameter:
4018: .  snes - the `SNES` context

4020:    Options Database Key:
4021: .  -snes_monitor_cancel - cancels all monitors that have been hardwired
4022:     into a code by calls to `SNESMonitorSet()`, but does not cancel those
4023:     set via the options database

4025:    Level: intermediate

4027:    Note:
4028:    There is no way to clear one specific monitor from a `SNES` object.

4030: .seealso: [](chapter_snes), `SNES`, `SNESMonitorGet()`, `SNESMonitorDefault()`, `SNESMonitorSet()`
4031: @*/
4032: PetscErrorCode SNESMonitorCancel(SNES snes)
4033: {
4034:   PetscInt i;

4036:   PetscFunctionBegin;
4038:   for (i = 0; i < snes->numbermonitors; i++) {
4039:     if (snes->monitordestroy[i]) PetscCall((*snes->monitordestroy[i])(&snes->monitorcontext[i]));
4040:   }
4041:   snes->numbermonitors = 0;
4042:   PetscFunctionReturn(PETSC_SUCCESS);
4043: }

4045: /*MC
4046:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

4048:      Synopsis:
4049: #include <petscsnes.h>
4050: $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)

4052:      Collective

4054:     Input Parameters:
4055: +    snes - the `SNES` context
4056: .    it - current iteration (0 is the first and is before any Newton step)
4057: .    xnorm - 2-norm of current iterate
4058: .    gnorm - 2-norm of current step
4059: .    f - 2-norm of function
4060: -    cctx - [optional] convergence context

4062:     Output Parameter:
4063: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

4065:    Level: intermediate

4067: .seealso: [](chapter_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`, `SNESGetConvergenceTest()`
4068: M*/

4070: /*@C
4071:    SNESSetConvergenceTest - Sets the function that is to be used
4072:    to test for convergence of the nonlinear iterative solution.

4074:    Logically Collective

4076:    Input Parameters:
4077: +  snes - the `SNES` context
4078: .  `SNESConvergenceTestFunction` - routine to test for convergence
4079: .  cctx - [optional] context for private data for the convergence routine  (may be `NULL`)
4080: -  destroy - [optional] destructor for the context (may be `NULL`; `PETSC_NULL_FUNCTION` in Fortran)

4082:    Level: advanced

4084: .seealso: [](chapter_snes), `SNES`, `SNESConvergedDefault()`, `SNESConvergedSkip()`, `SNESConvergenceTestFunction`
4085: @*/
4086: PetscErrorCode SNESSetConvergenceTest(SNES snes, PetscErrorCode (*SNESConvergenceTestFunction)(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))
4087: {
4088:   PetscFunctionBegin;
4090:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
4091:   if (snes->ops->convergeddestroy) PetscCall((*snes->ops->convergeddestroy)(snes->cnvP));
4092:   snes->ops->converged        = SNESConvergenceTestFunction;
4093:   snes->ops->convergeddestroy = destroy;
4094:   snes->cnvP                  = cctx;
4095:   PetscFunctionReturn(PETSC_SUCCESS);
4096: }

4098: /*@
4099:    SNESGetConvergedReason - Gets the reason the `SNES` iteration was stopped.

4101:    Not Collective

4103:    Input Parameter:
4104: .  snes - the `SNES` context

4106:    Output Parameter:
4107: .  reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` for the individual convergence tests for complete lists

4109:    Options Database Key:
4110: .   -snes_converged_reason - prints the reason to standard out

4112:    Level: intermediate

4114:    Note:
4115:     Should only be called after the call the `SNESSolve()` is complete, if it is called earlier it returns the value `SNES__CONVERGED_ITERATING`.

4117: .seealso: [](chapter_snes), `SNESSolve()`, `SNESSetConvergenceTest()`, `SNESSetConvergedReason()`, `SNESConvergedReason`, `SNESGetConvergedReasonString()`
4118: @*/
4119: PetscErrorCode SNESGetConvergedReason(SNES snes, SNESConvergedReason *reason)
4120: {
4121:   PetscFunctionBegin;
4124:   *reason = snes->reason;
4125:   PetscFunctionReturn(PETSC_SUCCESS);
4126: }

4128: /*@C
4129:    SNESGetConvergedReasonString - Return a human readable string for `SNESConvergedReason`

4131:    Not Collective

4133:    Input Parameter:
4134: .  snes - the `SNES` context

4136:    Output Parameter:
4137: .  strreason - a human readable string that describes `SNES` converged reason

4139:    Level: beginner

4141: .seealso: [](chapter_snes), `SNES`, `SNESGetConvergedReason()`
4142: @*/
4143: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char **strreason)
4144: {
4145:   PetscFunctionBegin;
4148:   *strreason = SNESConvergedReasons[snes->reason];
4149:   PetscFunctionReturn(PETSC_SUCCESS);
4150: }

4152: /*@
4153:    SNESSetConvergedReason - Sets the reason the `SNES` iteration was stopped.

4155:    Not Collective

4157:    Input Parameters:
4158: +  snes - the `SNES` context
4159: -  reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` or the
4160:             manual pages for the individual convergence tests for complete lists

4162:    Level: developer

4164:    Developer Note:
4165:    Called inside the various `SNESSolve()` implementations

4167: .seealso: [](chapter_snes), `SNESGetConvergedReason()`, `SNESSetConvergenceTest()`, `SNESConvergedReason`
4168: @*/
4169: PetscErrorCode SNESSetConvergedReason(SNES snes, SNESConvergedReason reason)
4170: {
4171:   PetscFunctionBegin;
4173:   snes->reason = reason;
4174:   PetscFunctionReturn(PETSC_SUCCESS);
4175: }

4177: /*@
4178:    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.

4180:    Logically Collective

4182:    Input Parameters:
4183: +  snes - iterative context obtained from `SNESCreate()`
4184: .  a   - array to hold history, this array will contain the function norms computed at each step
4185: .  its - integer array holds the number of linear iterations for each solve.
4186: .  na  - size of a and its
4187: -  reset - `PETSC_TRUE` indicates each new nonlinear solve resets the history counter to zero,
4188:            else it continues storing new values for new nonlinear solves after the old ones

4190:    Level: intermediate

4192:    Notes:
4193:    If 'a' and 'its' are `NULL` then space is allocated for the history. If 'na' `PETSC_DECIDE` or `PETSC_DEFAULT` then a
4194:    default array of length 10000 is allocated.

4196:    This routine is useful, e.g., when running a code for purposes
4197:    of accurate performance monitoring, when no I/O should be done
4198:    during the section of code that is being timed.

4200: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetConvergenceHistory()`
4201: @*/
4202: PetscErrorCode SNESSetConvergenceHistory(SNES snes, PetscReal a[], PetscInt its[], PetscInt na, PetscBool reset)
4203: {
4204:   PetscFunctionBegin;
4208:   if (!a) {
4209:     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
4210:     PetscCall(PetscCalloc2(na, &a, na, &its));
4211:     snes->conv_hist_alloc = PETSC_TRUE;
4212:   }
4213:   snes->conv_hist       = a;
4214:   snes->conv_hist_its   = its;
4215:   snes->conv_hist_max   = (size_t)na;
4216:   snes->conv_hist_len   = 0;
4217:   snes->conv_hist_reset = reset;
4218:   PetscFunctionReturn(PETSC_SUCCESS);
4219: }

4221: #if defined(PETSC_HAVE_MATLAB)
4222:   #include <engine.h> /* MATLAB include file */
4223:   #include <mex.h>    /* MATLAB include file */

4225: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
4226: {
4227:   mxArray   *mat;
4228:   PetscInt   i;
4229:   PetscReal *ar;

4231:   mat = mxCreateDoubleMatrix(snes->conv_hist_len, 1, mxREAL);
4232:   ar  = (PetscReal *)mxGetData(mat);
4233:   for (i = 0; i < snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
4234:   return mat;
4235: }
4236: #endif

4238: /*@C
4239:    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.

4241:    Not Collective

4243:    Input Parameter:
4244: .  snes - iterative context obtained from `SNESCreate()`

4246:    Output Parameters:
4247: +  a   - array to hold history, usually was set with `SNESSetConvergenceHistory()`
4248: .  its - integer array holds the number of linear iterations (or
4249:          negative if not converged) for each solve.
4250: -  na  - size of `a` and `its`

4252:    Level: intermediate

4254:    Note:
4255:    This routine is useful, e.g., when running a code for purposes
4256:    of accurate performance monitoring, when no I/O should be done
4257:    during the section of code that is being timed.

4259:    Fortran Note:
4260:     The calling sequence for this routine in Fortran is
4261: .vb
4262:     call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)
4263: .ve

4265: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetConvergenceHistory()`
4266: @*/
4267: PetscErrorCode SNESGetConvergenceHistory(SNES snes, PetscReal *a[], PetscInt *its[], PetscInt *na)
4268: {
4269:   PetscFunctionBegin;
4271:   if (a) *a = snes->conv_hist;
4272:   if (its) *its = snes->conv_hist_its;
4273:   if (na) *na = (PetscInt)snes->conv_hist_len;
4274:   PetscFunctionReturn(PETSC_SUCCESS);
4275: }

4277: /*@C
4278:   SNESSetUpdate - Sets the general-purpose update function called
4279:   at the beginning of every iteration of the nonlinear solve. Specifically
4280:   it is called just before the Jacobian is "evaluated".

4282:   Logically Collective

4284:   Input Parameters:
4285: + snes - The nonlinear solver context
4286: - func - The function

4288:   Calling sequence of `func`:
4289: $ PetscErrorCode func(SNES snes, PetscInt step);
4290: + snes - the nonlinear solver context
4291: - step - The current step of the iteration

4293:   Level: advanced

4295:   Note:
4296:      This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your function provided
4297:      to `SNESSetFunction()`, or `SNESSetPicard()`
4298:      This is not used by most users.

4300:      There are a variety of function hooks one many set that are called at different stages of the nonlinear solution process, see the functions listed below.

4302: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESSetJacobian()`, `SNESSolve()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRSetPostCheck()`,
4303:          `SNESMonitorSet()`, `SNESSetDivergenceTest()`
4304: @*/
4305: PetscErrorCode SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
4306: {
4307:   PetscFunctionBegin;
4309:   snes->ops->update = func;
4310:   PetscFunctionReturn(PETSC_SUCCESS);
4311: }

4313: /*
4314:    SNESScaleStep_Private - Scales a step so that its length is less than the
4315:    positive parameter delta.

4317:     Input Parameters:
4318: +   snes - the `SNES` context
4319: .   y - approximate solution of linear system
4320: .   fnorm - 2-norm of current function
4321: -   delta - trust region size

4323:     Output Parameters:
4324: +   gpnorm - predicted function norm at the new point, assuming local
4325:     linearization.  The value is zero if the step lies within the trust
4326:     region, and exceeds zero otherwise.
4327: -   ynorm - 2-norm of the step

4329:     Level: developer

4331:     Note:
4332:     For non-trust region methods such as `SNESNEWTONLS`, the parameter delta
4333:     is set to be the maximum allowable step size.
4334: */
4335: PetscErrorCode SNESScaleStep_Private(SNES snes, Vec y, PetscReal *fnorm, PetscReal *delta, PetscReal *gpnorm, PetscReal *ynorm)
4336: {
4337:   PetscReal   nrm;
4338:   PetscScalar cnorm;

4340:   PetscFunctionBegin;
4343:   PetscCheckSameComm(snes, 1, y, 2);

4345:   PetscCall(VecNorm(y, NORM_2, &nrm));
4346:   if (nrm > *delta) {
4347:     nrm     = *delta / nrm;
4348:     *gpnorm = (1.0 - nrm) * (*fnorm);
4349:     cnorm   = nrm;
4350:     PetscCall(VecScale(y, cnorm));
4351:     *ynorm = *delta;
4352:   } else {
4353:     *gpnorm = 0.0;
4354:     *ynorm  = nrm;
4355:   }
4356:   PetscFunctionReturn(PETSC_SUCCESS);
4357: }

4359: /*@C
4360:    SNESConvergedReasonView - Displays the reason a `SNES` solve converged or diverged to a viewer

4362:    Collective

4364:    Parameter:
4365: +  snes - iterative context obtained from `SNESCreate()`
4366: -  viewer - the viewer to display the reason

4368:    Options Database Keys:
4369: +  -snes_converged_reason - print reason for converged or diverged, also prints number of iterations
4370: -  -snes_converged_reason ::failed - only print reason and number of iterations when diverged

4372:   Note:
4373:      To change the format of the output call `PetscViewerPushFormat`(viewer,format) before this call. Use `PETSC_VIEWER_DEFAULT` for the default,
4374:      use `PETSC_VIEWER_FAILED` to only display a reason if it fails.

4376:    Level: beginner

4378: .seealso: [](chapter_snes), `SNESConvergedReason`, `PetscViewer`, `SNES`,
4379:           `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`, `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`,
4380:           `SNESConvergedReasonViewFromOptions()`,
4381:           `PetscViewerPushFormat()`, `PetscViewerPopFormat()`
4382: @*/
4383: PetscErrorCode SNESConvergedReasonView(SNES snes, PetscViewer viewer)
4384: {
4385:   PetscViewerFormat format;
4386:   PetscBool         isAscii;

4388:   PetscFunctionBegin;
4389:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
4390:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isAscii));
4391:   if (isAscii) {
4392:     PetscCall(PetscViewerGetFormat(viewer, &format));
4393:     PetscCall(PetscViewerASCIIAddTab(viewer, ((PetscObject)snes)->tablevel));
4394:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
4395:       DM       dm;
4396:       Vec      u;
4397:       PetscDS  prob;
4398:       PetscInt Nf, f;
4399:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
4400:       void    **exactCtx;
4401:       PetscReal error;

4403:       PetscCall(SNESGetDM(snes, &dm));
4404:       PetscCall(SNESGetSolution(snes, &u));
4405:       PetscCall(DMGetDS(dm, &prob));
4406:       PetscCall(PetscDSGetNumFields(prob, &Nf));
4407:       PetscCall(PetscMalloc2(Nf, &exactSol, Nf, &exactCtx));
4408:       for (f = 0; f < Nf; ++f) PetscCall(PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]));
4409:       PetscCall(DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error));
4410:       PetscCall(PetscFree2(exactSol, exactCtx));
4411:       if (error < 1.0e-11) PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n"));
4412:       else PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", (double)error));
4413:     }
4414:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
4415:       if (((PetscObject)snes)->prefix) {
4416:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve converged due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4417:       } else {
4418:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve converged due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4419:       }
4420:     } else if (snes->reason <= 0) {
4421:       if (((PetscObject)snes)->prefix) {
4422:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve did not converge due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4423:       } else {
4424:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve did not converge due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4425:       }
4426:     }
4427:     PetscCall(PetscViewerASCIISubtractTab(viewer, ((PetscObject)snes)->tablevel));
4428:   }
4429:   PetscFunctionReturn(PETSC_SUCCESS);
4430: }

4432: /*@C
4433:    SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
4434:     end of the nonlinear solver to display the convergence reason of the nonlinear solver.

4436:    Logically Collective

4438:    Input Parameters:
4439: +  snes - the `SNES` context
4440: .  f - the snes converged reason view function
4441: .  vctx - [optional] user-defined context for private data for the
4442:           snes converged reason view routine (use `NULL` if no context is desired)
4443: -  reasonviewdestroy - [optional] routine that frees reasonview context (may be `NULL`)

4445:    Options Database Keys:
4446: +    -snes_converged_reason        - sets a default `SNESConvergedReasonView()`
4447: -    -snes_converged_reason_view_cancel - cancels all converged reason viewers that have
4448:                             been hardwired into a code by
4449:                             calls to `SNESConvergedReasonViewSet()`, but
4450:                             does not cancel those set via
4451:                             the options database.

4453:    Level: intermediate

4455:    Note:
4456:    Several different converged reason view routines may be set by calling
4457:    `SNESConvergedReasonViewSet()` multiple times; all will be called in the
4458:    order in which they were set.

4460: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESConvergedReason`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`, `SNESConvergedReasonViewCancel()`
4461: @*/
4462: PetscErrorCode SNESConvergedReasonViewSet(SNES snes, PetscErrorCode (*f)(SNES, void *), void *vctx, PetscErrorCode (*reasonviewdestroy)(void **))
4463: {
4464:   PetscInt  i;
4465:   PetscBool identical;

4467:   PetscFunctionBegin;
4469:   for (i = 0; i < snes->numberreasonviews; i++) {
4470:     PetscCall(PetscMonitorCompare((PetscErrorCode(*)(void))f, vctx, reasonviewdestroy, (PetscErrorCode(*)(void))snes->reasonview[i], snes->reasonviewcontext[i], snes->reasonviewdestroy[i], &identical));
4471:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4472:   }
4473:   PetscCheck(snes->numberreasonviews < MAXSNESREASONVIEWS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many SNES reasonview set");
4474:   snes->reasonview[snes->numberreasonviews]          = f;
4475:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
4476:   snes->reasonviewcontext[snes->numberreasonviews++] = (void *)vctx;
4477:   PetscFunctionReturn(PETSC_SUCCESS);
4478: }

4480: /*@
4481:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a `SNESConvergedReason` is to be viewed.
4482:                                        All the user-provided convergedReasonView routines will be involved as well, if they exist.

4484:   Collective

4486:   Input Parameter:
4487: . snes   - the `SNES` object

4489:   Level: advanced

4491: .seealso: [](chapter_snes), `SNES`, `SNESConvergedReason`, `SNESConvergedReasonViewSet()`, `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`,
4492:           `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`
4493: @*/
4494: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
4495: {
4496:   PetscViewer       viewer;
4497:   PetscBool         flg;
4498:   static PetscBool  incall = PETSC_FALSE;
4499:   PetscViewerFormat format;
4500:   PetscInt          i;

4502:   PetscFunctionBegin;
4503:   if (incall) PetscFunctionReturn(PETSC_SUCCESS);
4504:   incall = PETSC_TRUE;

4506:   /* All user-provided viewers are called first, if they exist. */
4507:   for (i = 0; i < snes->numberreasonviews; i++) PetscCall((*snes->reasonview[i])(snes, snes->reasonviewcontext[i]));

4509:   /* Call PETSc default routine if users ask for it */
4510:   PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_converged_reason", &viewer, &format, &flg));
4511:   if (flg) {
4512:     PetscCall(PetscViewerPushFormat(viewer, format));
4513:     PetscCall(SNESConvergedReasonView(snes, viewer));
4514:     PetscCall(PetscViewerPopFormat(viewer));
4515:     PetscCall(PetscViewerDestroy(&viewer));
4516:   }
4517:   incall = PETSC_FALSE;
4518:   PetscFunctionReturn(PETSC_SUCCESS);
4519: }

4521: /*@
4522:    SNESSolve - Solves a nonlinear system F(x) = b.
4523:    Call `SNESSolve()` after calling `SNESCreate()` and optional routines of the form `SNESSetXXX()`.

4525:    Collective

4527:    Input Parameters:
4528: +  snes - the `SNES` context
4529: .  b - the constant part of the equation F(x) = b, or `NULL` to use zero.
4530: -  x - the solution vector.

4532:    Level: beginner

4534:    Note:
4535:    The user should initialize the vector,x, with the initial guess
4536:    for the nonlinear solve prior to calling `SNESSolve()`.  In particular,
4537:    to employ an initial guess of zero, the user should explicitly set
4538:    this vector to zero by calling `VecSet()`.

4540: .seealso: [](chapter_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESSetFunction()`, `SNESSetJacobian()`, `SNESSetGridSequence()`, `SNESGetSolution()`,
4541:           `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRGetPreCheck()`, `SNESNewtonTRSetPostCheck()`, `SNESNewtonTRGetPostCheck()`,
4542:           `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`
4543: @*/
4544: PetscErrorCode SNESSolve(SNES snes, Vec b, Vec x)
4545: {
4546:   PetscBool flg;
4547:   PetscInt  grid;
4548:   Vec       xcreated = NULL;
4549:   DM        dm;

4551:   PetscFunctionBegin;
4554:   if (x) PetscCheckSameComm(snes, 1, x, 3);
4556:   if (b) PetscCheckSameComm(snes, 1, b, 2);

4558:   /* High level operations using the nonlinear solver */
4559:   {
4560:     PetscViewer       viewer;
4561:     PetscViewerFormat format;
4562:     PetscInt          num;
4563:     PetscBool         flg;
4564:     static PetscBool  incall = PETSC_FALSE;

4566:     if (!incall) {
4567:       /* Estimate the convergence rate of the discretization */
4568:       PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg));
4569:       if (flg) {
4570:         PetscConvEst conv;
4571:         DM           dm;
4572:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
4573:         PetscInt     Nf;

4575:         incall = PETSC_TRUE;
4576:         PetscCall(SNESGetDM(snes, &dm));
4577:         PetscCall(DMGetNumFields(dm, &Nf));
4578:         PetscCall(PetscCalloc1(Nf, &alpha));
4579:         PetscCall(PetscConvEstCreate(PetscObjectComm((PetscObject)snes), &conv));
4580:         PetscCall(PetscConvEstSetSolver(conv, (PetscObject)snes));
4581:         PetscCall(PetscConvEstSetFromOptions(conv));
4582:         PetscCall(PetscConvEstSetUp(conv));
4583:         PetscCall(PetscConvEstGetConvRate(conv, alpha));
4584:         PetscCall(PetscViewerPushFormat(viewer, format));
4585:         PetscCall(PetscConvEstRateView(conv, alpha, viewer));
4586:         PetscCall(PetscViewerPopFormat(viewer));
4587:         PetscCall(PetscViewerDestroy(&viewer));
4588:         PetscCall(PetscConvEstDestroy(&conv));
4589:         PetscCall(PetscFree(alpha));
4590:         incall = PETSC_FALSE;
4591:       }
4592:       /* Adaptively refine the initial grid */
4593:       num = 1;
4594:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_initial", &num, &flg));
4595:       if (flg) {
4596:         DMAdaptor adaptor;

4598:         incall = PETSC_TRUE;
4599:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4600:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4601:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4602:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4603:         PetscCall(DMAdaptorSetUp(adaptor));
4604:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x));
4605:         PetscCall(DMAdaptorDestroy(&adaptor));
4606:         incall = PETSC_FALSE;
4607:       }
4608:       /* Use grid sequencing to adapt */
4609:       num = 0;
4610:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_sequence", &num, NULL));
4611:       if (num) {
4612:         DMAdaptor adaptor;

4614:         incall = PETSC_TRUE;
4615:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4616:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4617:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4618:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4619:         PetscCall(DMAdaptorSetUp(adaptor));
4620:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x));
4621:         PetscCall(DMAdaptorDestroy(&adaptor));
4622:         incall = PETSC_FALSE;
4623:       }
4624:     }
4625:   }
4626:   if (!x) x = snes->vec_sol;
4627:   if (!x) {
4628:     PetscCall(SNESGetDM(snes, &dm));
4629:     PetscCall(DMCreateGlobalVector(dm, &xcreated));
4630:     x = xcreated;
4631:   }
4632:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view_pre"));

4634:   for (grid = 0; grid < snes->gridsequence; grid++) PetscCall(PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4635:   for (grid = 0; grid < snes->gridsequence + 1; grid++) {
4636:     /* set solution vector */
4637:     if (!grid) PetscCall(PetscObjectReference((PetscObject)x));
4638:     PetscCall(VecDestroy(&snes->vec_sol));
4639:     snes->vec_sol = x;
4640:     PetscCall(SNESGetDM(snes, &dm));

4642:     /* set affine vector if provided */
4643:     if (b) PetscCall(PetscObjectReference((PetscObject)b));
4644:     PetscCall(VecDestroy(&snes->vec_rhs));
4645:     snes->vec_rhs = b;

4647:     if (snes->vec_rhs) PetscCheck(snes->vec_func != snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Right hand side vector cannot be function vector");
4648:     PetscCheck(snes->vec_func != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be function vector");
4649:     PetscCheck(snes->vec_rhs != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be right hand side vector");
4650:     if (!snes->vec_sol_update /* && snes->vec_sol */) PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_sol_update));
4651:     PetscCall(DMShellSetGlobalVector(dm, snes->vec_sol));
4652:     PetscCall(SNESSetUp(snes));

4654:     if (!grid) {
4655:       if (snes->ops->computeinitialguess) PetscCallBack("SNES callback initial guess", (*snes->ops->computeinitialguess)(snes, snes->vec_sol, snes->initialguessP));
4656:     }

4658:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
4659:     if (snes->counters_reset) {
4660:       snes->nfuncs      = 0;
4661:       snes->linear_its  = 0;
4662:       snes->numFailures = 0;
4663:     }

4665:     PetscCall(PetscLogEventBegin(SNES_Solve, snes, 0, 0, 0));
4666:     PetscUseTypeMethod(snes, solve);
4667:     PetscCall(PetscLogEventEnd(SNES_Solve, snes, 0, 0, 0));
4668:     PetscCheck(snes->reason, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Internal error, solver returned without setting converged reason");
4669:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

4671:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
4672:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

4674:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_test_local_min", NULL, NULL, &flg));
4675:     if (flg && !PetscPreLoadingOn) PetscCall(SNESTestLocalMin(snes));
4676:     /* Call converged reason views. This may involve user-provided viewers as well */
4677:     PetscCall(SNESConvergedReasonViewFromOptions(snes));

4679:     if (snes->errorifnotconverged) PetscCheck(snes->reason >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_NOT_CONVERGED, "SNESSolve has not converged");
4680:     if (snes->reason < 0) break;
4681:     if (grid < snes->gridsequence) {
4682:       DM  fine;
4683:       Vec xnew;
4684:       Mat interp;

4686:       PetscCall(DMRefine(snes->dm, PetscObjectComm((PetscObject)snes), &fine));
4687:       PetscCheck(fine, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_INCOMP, "DMRefine() did not perform any refinement, cannot continue grid sequencing");
4688:       PetscCall(DMCreateInterpolation(snes->dm, fine, &interp, NULL));
4689:       PetscCall(DMCreateGlobalVector(fine, &xnew));
4690:       PetscCall(MatInterpolate(interp, x, xnew));
4691:       PetscCall(DMInterpolate(snes->dm, interp, fine));
4692:       PetscCall(MatDestroy(&interp));
4693:       x = xnew;

4695:       PetscCall(SNESReset(snes));
4696:       PetscCall(SNESSetDM(snes, fine));
4697:       PetscCall(SNESResetFromOptions(snes));
4698:       PetscCall(DMDestroy(&fine));
4699:       PetscCall(PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4700:     }
4701:   }
4702:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view"));
4703:   PetscCall(VecViewFromOptions(snes->vec_sol, (PetscObject)snes, "-snes_view_solution"));
4704:   PetscCall(DMMonitor(snes->dm));
4705:   PetscCall(SNESMonitorPauseFinal_Internal(snes));

4707:   PetscCall(VecDestroy(&xcreated));
4708:   PetscCall(PetscObjectSAWsBlock((PetscObject)snes));
4709:   PetscFunctionReturn(PETSC_SUCCESS);
4710: }

4712: /* --------- Internal routines for SNES Package --------- */

4714: /*@C
4715:    SNESSetType - Sets the method for the nonlinear solver.

4717:    Collective

4719:    Input Parameters:
4720: +  snes - the `SNES` context
4721: -  type - a known method

4723:    Options Database Key:
4724: .  -snes_type <type> - Sets the method; use -help for a list
4725:    of available methods (for instance, newtonls or newtontr)

4727:   Level: intermediate

4729:    Notes:
4730:    See "petsc/include/petscsnes.h" for available methods (for instance)
4731: +    `SNESNEWTONLS` - Newton's method with line search
4732:      (systems of nonlinear equations)
4733: -    `SNESNEWTONTR` - Newton's method with trust region
4734:      (systems of nonlinear equations)

4736:   Normally, it is best to use the `SNESSetFromOptions()` command and then
4737:   set the `SNES` solver type from the options database rather than by using
4738:   this routine.  Using the options database provides the user with
4739:   maximum flexibility in evaluating the many nonlinear solvers.
4740:   The `SNESSetType()` routine is provided for those situations where it
4741:   is necessary to set the nonlinear solver independently of the command
4742:   line or options database.  This might be the case, for example, when
4743:   the choice of solver changes during the execution of the program,
4744:   and the user's application is taking responsibility for choosing the
4745:   appropriate method.

4747:     Developer Note:
4748:     `SNESRegister()` adds a constructor for a new `SNESType` to `SNESList`, `SNESSetType()` locates
4749:     the constructor in that list and calls it to create the specific object.

4751: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESType`, `SNESCreate()`, `SNESDestroy()`, `SNESGetType()`, `SNESSetFromOptions()`
4752: @*/
4753: PetscErrorCode SNESSetType(SNES snes, SNESType type)
4754: {
4755:   PetscBool match;
4756:   PetscErrorCode (*r)(SNES);

4758:   PetscFunctionBegin;

4762:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, type, &match));
4763:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

4765:   PetscCall(PetscFunctionListFind(SNESList, type, &r));
4766:   PetscCheck(r, PETSC_COMM_SELF, PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested SNES type %s", type);
4767:   /* Destroy the previous private SNES context */
4768:   PetscTryTypeMethod(snes, destroy);
4769:   /* Reinitialize function pointers in SNESOps structure */
4770:   snes->ops->setup          = NULL;
4771:   snes->ops->solve          = NULL;
4772:   snes->ops->view           = NULL;
4773:   snes->ops->setfromoptions = NULL;
4774:   snes->ops->destroy        = NULL;

4776:   /* It may happen the user has customized the line search before calling SNESSetType */
4777:   if (((PetscObject)snes)->type_name) PetscCall(SNESLineSearchDestroy(&snes->linesearch));

4779:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
4780:   snes->setupcalled = PETSC_FALSE;

4782:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, type));
4783:   PetscCall((*r)(snes));
4784:   PetscFunctionReturn(PETSC_SUCCESS);
4785: }

4787: /*@C
4788:    SNESGetType - Gets the `SNES` method type and name (as a string).

4790:    Not Collective

4792:    Input Parameter:
4793: .  snes - nonlinear solver context

4795:    Output Parameter:
4796: .  type - `SNES` method (a character string)

4798:    Level: intermediate

4800: .seealso: [](chapter_snes), `SNESSetType()`, `SNESType`, `SNESSetFromOptions()`, `SNES`
4801: @*/
4802: PetscErrorCode SNESGetType(SNES snes, SNESType *type)
4803: {
4804:   PetscFunctionBegin;
4807:   *type = ((PetscObject)snes)->type_name;
4808:   PetscFunctionReturn(PETSC_SUCCESS);
4809: }

4811: /*@
4812:   SNESSetSolution - Sets the solution vector for use by the `SNES` routines.

4814:   Logically Collective

4816:   Input Parameters:
4817: + snes - the `SNES` context obtained from `SNESCreate()`
4818: - u    - the solution vector

4820:   Level: beginner

4822: .seealso: [](chapter_snes), `SNES`, `SNESSolve()`, `SNESGetSolution()`, `Vec`
4823: @*/
4824: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
4825: {
4826:   DM dm;

4828:   PetscFunctionBegin;
4831:   PetscCall(PetscObjectReference((PetscObject)u));
4832:   PetscCall(VecDestroy(&snes->vec_sol));

4834:   snes->vec_sol = u;

4836:   PetscCall(SNESGetDM(snes, &dm));
4837:   PetscCall(DMShellSetGlobalVector(dm, u));
4838:   PetscFunctionReturn(PETSC_SUCCESS);
4839: }

4841: /*@
4842:    SNESGetSolution - Returns the vector where the approximate solution is
4843:    stored. This is the fine grid solution when using `SNESSetGridSequence()`.

4845:    Not Collective, but x is parallel if snes is parallel

4847:    Input Parameter:
4848: .  snes - the `SNES` context

4850:    Output Parameter:
4851: .  x - the solution

4853:    Level: intermediate

4855: .seealso: [](chapter_snes), `SNESSetSolution()`, `SNESSolve()`, `SNES`, `SNESGetSolutionUpdate()`, `SNESGetFunction()`
4856: @*/
4857: PetscErrorCode SNESGetSolution(SNES snes, Vec *x)
4858: {
4859:   PetscFunctionBegin;
4862:   *x = snes->vec_sol;
4863:   PetscFunctionReturn(PETSC_SUCCESS);
4864: }

4866: /*@
4867:    SNESGetSolutionUpdate - Returns the vector where the solution update is
4868:    stored.

4870:    Not Collective, but x is parallel if snes is parallel

4872:    Input Parameter:
4873: .  snes - the `SNES` context

4875:    Output Parameter:
4876: .  x - the solution update

4878:    Level: advanced

4880: .seealso: [](chapter_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`
4881: @*/
4882: PetscErrorCode SNESGetSolutionUpdate(SNES snes, Vec *x)
4883: {
4884:   PetscFunctionBegin;
4887:   *x = snes->vec_sol_update;
4888:   PetscFunctionReturn(PETSC_SUCCESS);
4889: }

4891: /*@C
4892:    SNESGetFunction - Returns the function that defines the nonlinear system set with `SNESSetFunction()`

4894:    Not Collective, but r is parallel if snes is parallel. Collective if r is requested, but has not been created yet.

4896:    Input Parameter:
4897: .  snes - the `SNES` context

4899:    Output Parameters:
4900: +  r - the vector that is used to store residuals (or `NULL` if you don't want it)
4901: .  f - the function (or `NULL` if you don't want it);  for calling sequence see `SNESFunction`
4902: -  ctx - the function context (or `NULL` if you don't want it)

4904:    Level: advanced

4906:     Note:
4907:    The vector `r` DOES NOT, in general, contain the current value of the `SNES` nonlinear function

4909: .seealso: [](chapter_snes), `SNES, `SNESSolve()`, `SNESSetFunction()`, `SNESGetSolution()`, `SNESFunction`
4910: @*/
4911: PetscErrorCode SNESGetFunction(SNES snes, Vec *r, PetscErrorCode (**f)(SNES, Vec, Vec, void *), void **ctx)
4912: {
4913:   DM dm;

4915:   PetscFunctionBegin;
4917:   if (r) {
4918:     if (!snes->vec_func) {
4919:       if (snes->vec_rhs) {
4920:         PetscCall(VecDuplicate(snes->vec_rhs, &snes->vec_func));
4921:       } else if (snes->vec_sol) {
4922:         PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_func));
4923:       } else if (snes->dm) {
4924:         PetscCall(DMCreateGlobalVector(snes->dm, &snes->vec_func));
4925:       }
4926:     }
4927:     *r = snes->vec_func;
4928:   }
4929:   PetscCall(SNESGetDM(snes, &dm));
4930:   PetscCall(DMSNESGetFunction(dm, f, ctx));
4931:   PetscFunctionReturn(PETSC_SUCCESS);
4932: }

4934: /*@C
4935:    SNESGetNGS - Returns the `SNESNGS` function and context set with `SNESSetNGS()`

4937:    Input Parameter:
4938: .  snes - the `SNES` context

4940:    Output Parameters:
4941: +  f - the function (or `NULL`) see `SNESNGSFunction` for details
4942: -  ctx    - the function context (or `NULL`)

4944:    Level: advanced

4946: .seealso: [](chapter_snes), `SNESSetNGS()`, `SNESGetFunction()`
4947: @*/

4949: PetscErrorCode SNESGetNGS(SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void *), void **ctx)
4950: {
4951:   DM dm;

4953:   PetscFunctionBegin;
4955:   PetscCall(SNESGetDM(snes, &dm));
4956:   PetscCall(DMSNESGetNGS(dm, f, ctx));
4957:   PetscFunctionReturn(PETSC_SUCCESS);
4958: }

4960: /*@C
4961:    SNESSetOptionsPrefix - Sets the prefix used for searching for all
4962:    `SNES` options in the database.

4964:    Logically Collective

4966:    Input Parameters:
4967: +  snes - the `SNES` context
4968: -  prefix - the prefix to prepend to all option names

4970:    Level: advanced

4972:    Note:
4973:    A hyphen (-) must NOT be given at the beginning of the prefix name.
4974:    The first character of all runtime options is AUTOMATICALLY the hyphen.

4976: .seealso: [](chapter_snes), `SNES`, `SNESSetFromOptions()`, `SNESAppendOptionsPrefix()`
4977: @*/
4978: PetscErrorCode SNESSetOptionsPrefix(SNES snes, const char prefix[])
4979: {
4980:   PetscFunctionBegin;
4982:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes, prefix));
4983:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
4984:   if (snes->linesearch) {
4985:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
4986:     PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch, prefix));
4987:   }
4988:   PetscCall(KSPSetOptionsPrefix(snes->ksp, prefix));
4989:   PetscFunctionReturn(PETSC_SUCCESS);
4990: }

4992: /*@C
4993:    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
4994:    `SNES` options in the database.

4996:    Logically Collective

4998:    Input Parameters:
4999: +  snes - the `SNES` context
5000: -  prefix - the prefix to prepend to all option names

5002:    Level: advanced

5004:    Note:
5005:    A hyphen (-) must NOT be given at the beginning of the prefix name.
5006:    The first character of all runtime options is AUTOMATICALLY the hyphen.

5008: .seealso: [](chapter_snes), `SNESGetOptionsPrefix()`, `SNESSetOptionsPrefix()`
5009: @*/
5010: PetscErrorCode SNESAppendOptionsPrefix(SNES snes, const char prefix[])
5011: {
5012:   PetscFunctionBegin;
5014:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes, prefix));
5015:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5016:   if (snes->linesearch) {
5017:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5018:     PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch, prefix));
5019:   }
5020:   PetscCall(KSPAppendOptionsPrefix(snes->ksp, prefix));
5021:   PetscFunctionReturn(PETSC_SUCCESS);
5022: }

5024: /*@C
5025:    SNESGetOptionsPrefix - Gets the prefix used for searching for all
5026:    `SNES` options in the database.

5028:    Not Collective

5030:    Input Parameter:
5031: .  snes - the `SNES` context

5033:    Output Parameter:
5034: .  prefix - pointer to the prefix string used

5036:    Level: advanced

5038:    Fortran Note:
5039:     The user should pass in a string 'prefix' of
5040:    sufficient length to hold the prefix.

5042: .seealso: [](chapter_snes), `SNES`, `SNESSetOptionsPrefix()`, `SNESAppendOptionsPrefix()`
5043: @*/
5044: PetscErrorCode SNESGetOptionsPrefix(SNES snes, const char *prefix[])
5045: {
5046:   PetscFunctionBegin;
5048:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)snes, prefix));
5049:   PetscFunctionReturn(PETSC_SUCCESS);
5050: }

5052: /*@C
5053:   SNESRegister - Adds a method to the nonlinear solver package.

5055:    Not Collective

5057:    Input Parameters:
5058: +  sname - name of a new user-defined solver
5059: -  function - routine to create method context

5061:    Level: advanced

5063:    Note:
5064:    `SNESRegister()` may be called multiple times to add several user-defined solvers.

5066:    Sample usage:
5067: .vb
5068:    SNESRegister("my_solver",MySolverCreate);
5069: .ve

5071:    Then, your solver can be chosen with the procedural interface via
5072: $     SNESSetType(snes,"my_solver")
5073:    or at runtime via the option
5074: $     -snes_type my_solver

5076: .seealso: [](chapter_snes), `SNESRegisterAll()`, `SNESRegisterDestroy()`
5077: @*/
5078: PetscErrorCode SNESRegister(const char sname[], PetscErrorCode (*function)(SNES))
5079: {
5080:   PetscFunctionBegin;
5081:   PetscCall(SNESInitializePackage());
5082:   PetscCall(PetscFunctionListAdd(&SNESList, sname, function));
5083:   PetscFunctionReturn(PETSC_SUCCESS);
5084: }

5086: PetscErrorCode SNESTestLocalMin(SNES snes)
5087: {
5088:   PetscInt    N, i, j;
5089:   Vec         u, uh, fh;
5090:   PetscScalar value;
5091:   PetscReal   norm;

5093:   PetscFunctionBegin;
5094:   PetscCall(SNESGetSolution(snes, &u));
5095:   PetscCall(VecDuplicate(u, &uh));
5096:   PetscCall(VecDuplicate(u, &fh));

5098:   /* currently only works for sequential */
5099:   PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "Testing FormFunction() for local min\n"));
5100:   PetscCall(VecGetSize(u, &N));
5101:   for (i = 0; i < N; i++) {
5102:     PetscCall(VecCopy(u, uh));
5103:     PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "i = %" PetscInt_FMT "\n", i));
5104:     for (j = -10; j < 11; j++) {
5105:       value = PetscSign(j) * PetscExpReal(PetscAbs(j) - 10.0);
5106:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5107:       PetscCall(SNESComputeFunction(snes, uh, fh));
5108:       PetscCall(VecNorm(fh, NORM_2, &norm));
5109:       PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "       j norm %" PetscInt_FMT " %18.16e\n", j, (double)norm));
5110:       value = -value;
5111:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5112:     }
5113:   }
5114:   PetscCall(VecDestroy(&uh));
5115:   PetscCall(VecDestroy(&fh));
5116:   PetscFunctionReturn(PETSC_SUCCESS);
5117: }

5119: /*@
5120:    SNESKSPSetUseEW - Sets `SNES` to the use Eisenstat-Walker method for
5121:    computing relative tolerance for linear solvers within an inexact
5122:    Newton method.

5124:    Logically Collective

5126:    Input Parameters:
5127: +  snes - `SNES` context
5128: -  flag - `PETSC_TRUE` or `PETSC_FALSE`

5130:     Options Database Keys:
5131: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
5132: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
5133: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
5134: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
5135: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
5136: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
5137: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
5138: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

5140:    Level: advanced

5142:    Note:
5143:    The default is to use a constant relative tolerance for
5144:    the inner linear solvers.  Alternatively, one can use the
5145:    Eisenstat-Walker method, where the relative convergence tolerance
5146:    is reset at each Newton iteration according progress of the nonlinear
5147:    solver.

5149:    Reference:
5150: .  - * S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an inexact Newton method", SISC 17 (1), pp.16-32, 1996.

5152: .seealso: [](chapter_snes), `KSP`, `SNES`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5153: @*/
5154: PetscErrorCode SNESKSPSetUseEW(SNES snes, PetscBool flag)
5155: {
5156:   PetscFunctionBegin;
5159:   snes->ksp_ewconv = flag;
5160:   PetscFunctionReturn(PETSC_SUCCESS);
5161: }

5163: /*@
5164:    SNESKSPGetUseEW - Gets if `SNES` is using Eisenstat-Walker method
5165:    for computing relative tolerance for linear solvers within an
5166:    inexact Newton method.

5168:    Not Collective

5170:    Input Parameter:
5171: .  snes - `SNES` context

5173:    Output Parameter:
5174: .  flag - `PETSC_TRUE` or `PETSC_FALSE`

5176:    Level: advanced

5178: .seealso: [](chapter_snes), `SNESKSPSetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5179: @*/
5180: PetscErrorCode SNESKSPGetUseEW(SNES snes, PetscBool *flag)
5181: {
5182:   PetscFunctionBegin;
5185:   *flag = snes->ksp_ewconv;
5186:   PetscFunctionReturn(PETSC_SUCCESS);
5187: }

5189: /*@
5190:    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
5191:    convergence criteria for the linear solvers within an inexact
5192:    Newton method.

5194:    Logically Collective

5196:    Input Parameters:
5197: +    snes - `SNES` context
5198: .    version - version 1, 2 (default is 2), 3 or 4
5199: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
5200: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
5201: .    gamma - multiplicative factor for version 2 rtol computation
5202:              (0 <= gamma2 <= 1)
5203: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
5204: .    alpha2 - power for safeguard
5205: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

5207:    Level: advanced

5209:    Notes:
5210:    Version 3 was contributed by Luis Chacon, June 2006.

5212:    Use `PETSC_DEFAULT` to retain the default for any of the parameters.

5214: .seealso: [](chapter_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`
5215: @*/
5216: PetscErrorCode SNESKSPSetParametersEW(SNES snes, PetscInt version, PetscReal rtol_0, PetscReal rtol_max, PetscReal gamma, PetscReal alpha, PetscReal alpha2, PetscReal threshold)
5217: {
5218:   SNESKSPEW *kctx;

5220:   PetscFunctionBegin;
5222:   kctx = (SNESKSPEW *)snes->kspconvctx;
5223:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");

5232:   if (version != PETSC_DEFAULT) kctx->version = version;
5233:   if (rtol_0 != (PetscReal)PETSC_DEFAULT) kctx->rtol_0 = rtol_0;
5234:   if (rtol_max != (PetscReal)PETSC_DEFAULT) kctx->rtol_max = rtol_max;
5235:   if (gamma != (PetscReal)PETSC_DEFAULT) kctx->gamma = gamma;
5236:   if (alpha != (PetscReal)PETSC_DEFAULT) kctx->alpha = alpha;
5237:   if (alpha2 != (PetscReal)PETSC_DEFAULT) kctx->alpha2 = alpha2;
5238:   if (threshold != (PetscReal)PETSC_DEFAULT) kctx->threshold = threshold;

5240:   PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1 to 4 are supported: %" PetscInt_FMT, kctx->version);
5241:   PetscCheck(kctx->rtol_0 >= 0.0 && kctx->rtol_0 < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_0 < 1.0: %g", (double)kctx->rtol_0);
5242:   PetscCheck(kctx->rtol_max >= 0.0 && kctx->rtol_max < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_max (%g) < 1.0", (double)kctx->rtol_max);
5243:   PetscCheck(kctx->gamma >= 0.0 && kctx->gamma <= 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= gamma (%g) <= 1.0", (double)kctx->gamma);
5244:   PetscCheck(kctx->alpha > 1.0 && kctx->alpha <= 2.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "1.0 < alpha (%g) <= 2.0", (double)kctx->alpha);
5245:   PetscCheck(kctx->threshold > 0.0 && kctx->threshold < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 < threshold (%g) < 1.0", (double)kctx->threshold);
5246:   PetscFunctionReturn(PETSC_SUCCESS);
5247: }

5249: /*@
5250:    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
5251:    convergence criteria for the linear solvers within an inexact
5252:    Newton method.

5254:    Not Collective

5256:    Input Parameter:
5257: .    snes - `SNES` context

5259:    Output Parameters:
5260: +    version - version 1, 2 (default is 2), 3 or 4
5261: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
5262: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
5263: .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
5264: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
5265: .    alpha2 - power for safeguard
5266: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

5268:    Level: advanced

5270: .seealso: [](chapter_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPSetParametersEW()`
5271: @*/
5272: PetscErrorCode SNESKSPGetParametersEW(SNES snes, PetscInt *version, PetscReal *rtol_0, PetscReal *rtol_max, PetscReal *gamma, PetscReal *alpha, PetscReal *alpha2, PetscReal *threshold)
5273: {
5274:   SNESKSPEW *kctx;

5276:   PetscFunctionBegin;
5278:   kctx = (SNESKSPEW *)snes->kspconvctx;
5279:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");
5280:   if (version) *version = kctx->version;
5281:   if (rtol_0) *rtol_0 = kctx->rtol_0;
5282:   if (rtol_max) *rtol_max = kctx->rtol_max;
5283:   if (gamma) *gamma = kctx->gamma;
5284:   if (alpha) *alpha = kctx->alpha;
5285:   if (alpha2) *alpha2 = kctx->alpha2;
5286:   if (threshold) *threshold = kctx->threshold;
5287:   PetscFunctionReturn(PETSC_SUCCESS);
5288: }

5290: PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
5291: {
5292:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5293:   PetscReal  rtol = PETSC_DEFAULT, stol;

5295:   PetscFunctionBegin;
5296:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5297:   if (!snes->iter) {
5298:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
5299:     PetscCall(VecNorm(snes->vec_func, NORM_2, &kctx->norm_first));
5300:   } else {
5301:     PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1-4 are supported: %" PetscInt_FMT, kctx->version);
5302:     if (kctx->version == 1) {
5303:       rtol = PetscAbsReal(snes->norm - kctx->lresid_last) / kctx->norm_last;
5304:       stol = PetscPowReal(kctx->rtol_last, kctx->alpha2);
5305:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5306:     } else if (kctx->version == 2) {
5307:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5308:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5309:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5310:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
5311:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5312:       /* safeguard: avoid sharp decrease of rtol */
5313:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5314:       stol = PetscMax(rtol, stol);
5315:       rtol = PetscMin(kctx->rtol_0, stol);
5316:       /* safeguard: avoid oversolving */
5317:       stol = kctx->gamma * (kctx->norm_first * snes->rtol) / snes->norm;
5318:       stol = PetscMax(rtol, stol);
5319:       rtol = PetscMin(kctx->rtol_0, stol);
5320:     } else /* if (kctx->version == 4) */ {
5321:       /* H.-B. An et al. Journal of Computational and Applied Mathematics 200 (2007) 47-60 */
5322:       PetscReal ared = PetscAbsReal(kctx->norm_last - snes->norm);
5323:       PetscReal pred = PetscAbsReal(kctx->norm_last - kctx->lresid_last);
5324:       PetscReal rk   = ared / pred;
5325:       if (rk < kctx->v4_p1) rtol = 1. - 2. * kctx->v4_p1;
5326:       else if (rk < kctx->v4_p2) rtol = kctx->rtol_last;
5327:       else if (rk < kctx->v4_p3) rtol = kctx->v4_m1 * kctx->rtol_last;
5328:       else rtol = kctx->v4_m2 * kctx->rtol_last;

5330:       if (kctx->rtol_last_2 > kctx->v4_m3 && kctx->rtol_last > kctx->v4_m3 && kctx->rk_last_2 < kctx->v4_p1 && kctx->rk_last < kctx->v4_p1) rtol = kctx->v4_m4 * kctx->rtol_last;
5331:       kctx->rtol_last_2 = kctx->rtol_last;
5332:       kctx->rk_last_2   = kctx->rk_last;
5333:       kctx->rk_last     = rk;
5334:     }
5335:   }
5336:   /* safeguard: avoid rtol greater than rtol_max */
5337:   rtol = PetscMin(rtol, kctx->rtol_max);
5338:   PetscCall(KSPSetTolerances(ksp, rtol, PETSC_DEFAULT, PETSC_DEFAULT, PETSC_DEFAULT));
5339:   PetscCall(PetscInfo(snes, "iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g\n", snes->iter, kctx->version, (double)rtol));
5340:   PetscFunctionReturn(PETSC_SUCCESS);
5341: }

5343: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
5344: {
5345:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5346:   PCSide     pcside;
5347:   Vec        lres;

5349:   PetscFunctionBegin;
5350:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5351:   PetscCall(KSPGetTolerances(ksp, &kctx->rtol_last, NULL, NULL, NULL));
5352:   kctx->norm_last = snes->norm;
5353:   if (kctx->version == 1 || kctx->version == 4) {
5354:     PC        pc;
5355:     PetscBool getRes;

5357:     PetscCall(KSPGetPC(ksp, &pc));
5358:     PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCNONE, &getRes));
5359:     if (!getRes) {
5360:       KSPNormType normtype;

5362:       PetscCall(KSPGetNormType(ksp, &normtype));
5363:       getRes = (PetscBool)(normtype == KSP_NORM_UNPRECONDITIONED);
5364:     }
5365:     PetscCall(KSPGetPCSide(ksp, &pcside));
5366:     if (pcside == PC_RIGHT || getRes) { /* KSP residual is true linear residual */
5367:       PetscCall(KSPGetResidualNorm(ksp, &kctx->lresid_last));
5368:     } else {
5369:       /* KSP residual is preconditioned residual */
5370:       /* compute true linear residual norm */
5371:       Mat J;
5372:       PetscCall(KSPGetOperators(ksp, &J, NULL));
5373:       PetscCall(VecDuplicate(b, &lres));
5374:       PetscCall(MatMult(J, x, lres));
5375:       PetscCall(VecAYPX(lres, -1.0, b));
5376:       PetscCall(VecNorm(lres, NORM_2, &kctx->lresid_last));
5377:       PetscCall(VecDestroy(&lres));
5378:     }
5379:   }
5380:   PetscFunctionReturn(PETSC_SUCCESS);
5381: }

5383: /*@
5384:    SNESGetKSP - Returns the `KSP` context for a `SNES` solver.

5386:    Not Collective, but if snes is parallel, then ksp is parallel

5388:    Input Parameter:
5389: .  snes - the `SNES` context

5391:    Output Parameter:
5392: .  ksp - the `KSP` context

5394:    Level: beginner

5396:    Notes:
5397:    The user can then directly manipulate the `KSP` context to set various
5398:    options, etc.  Likewise, the user can then extract and manipulate the
5399:    `PC` contexts as well.

5401:    Some `SNESType`s do not use a `KSP` but a `KSP` is still returned by this function

5403: .seealso: [](chapter_snes), `SNES`, `KSP`, `PC`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
5404: @*/
5405: PetscErrorCode SNESGetKSP(SNES snes, KSP *ksp)
5406: {
5407:   PetscFunctionBegin;

5411:   if (!snes->ksp) {
5412:     PetscCall(KSPCreate(PetscObjectComm((PetscObject)snes), &snes->ksp));
5413:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->ksp, (PetscObject)snes, 1));

5415:     PetscCall(KSPSetPreSolve(snes->ksp, (PetscErrorCode(*)(KSP, Vec, Vec, void *))KSPPreSolve_SNESEW, snes));
5416:     PetscCall(KSPSetPostSolve(snes->ksp, (PetscErrorCode(*)(KSP, Vec, Vec, void *))KSPPostSolve_SNESEW, snes));

5418:     PetscCall(KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes));
5419:     PetscCall(PetscObjectSetOptions((PetscObject)snes->ksp, ((PetscObject)snes)->options));
5420:   }
5421:   *ksp = snes->ksp;
5422:   PetscFunctionReturn(PETSC_SUCCESS);
5423: }

5425: #include <petsc/private/dmimpl.h>
5426: /*@
5427:    SNESSetDM - Sets the `DM` that may be used by some nonlinear solvers or their underlying preconditioners

5429:    Logically Collective

5431:    Input Parameters:
5432: +  snes - the nonlinear solver context
5433: -  dm - the dm, cannot be `NULL`

5435:    Level: intermediate

5437:    Note:
5438:    A `DM` can only be used for solving one problem at a time because information about the problem is stored on the `DM`,
5439:    even when not using interfaces like `DMSNESSetFunction()`.  Use `DMClone()` to get a distinct `DM` when solving different
5440:    problems using the same function space.

5442: .seealso: [](chapter_snes), `DM`, `SNESGetDM()`, `KSPSetDM()`, `KSPGetDM()`
5443: @*/
5444: PetscErrorCode SNESSetDM(SNES snes, DM dm)
5445: {
5446:   KSP    ksp;
5447:   DMSNES sdm;

5449:   PetscFunctionBegin;
5452:   PetscCall(PetscObjectReference((PetscObject)dm));
5453:   if (snes->dm) { /* Move the DMSNES context over to the new DM unless the new DM already has one */
5454:     if (snes->dm->dmsnes && !dm->dmsnes) {
5455:       PetscCall(DMCopyDMSNES(snes->dm, dm));
5456:       PetscCall(DMGetDMSNES(snes->dm, &sdm));
5457:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
5458:     }
5459:     PetscCall(DMCoarsenHookRemove(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
5460:     PetscCall(DMDestroy(&snes->dm));
5461:   }
5462:   snes->dm     = dm;
5463:   snes->dmAuto = PETSC_FALSE;

5465:   PetscCall(SNESGetKSP(snes, &ksp));
5466:   PetscCall(KSPSetDM(ksp, dm));
5467:   PetscCall(KSPSetDMActive(ksp, PETSC_FALSE));
5468:   if (snes->npc) {
5469:     PetscCall(SNESSetDM(snes->npc, snes->dm));
5470:     PetscCall(SNESSetNPCSide(snes, snes->npcside));
5471:   }
5472:   PetscFunctionReturn(PETSC_SUCCESS);
5473: }

5475: /*@
5476:    SNESGetDM - Gets the `DM` that may be used by some preconditioners

5478:    Not Collective but dm obtained is parallel on snes

5480:    Input Parameter:
5481: . snes - the preconditioner context

5483:    Output Parameter:
5484: .  dm - the dm

5486:    Level: intermediate

5488: .seealso: [](chapter_snes), `DM`, `SNESSetDM()`, `KSPSetDM()`, `KSPGetDM()`
5489: @*/
5490: PetscErrorCode SNESGetDM(SNES snes, DM *dm)
5491: {
5492:   PetscFunctionBegin;
5494:   if (!snes->dm) {
5495:     PetscCall(DMShellCreate(PetscObjectComm((PetscObject)snes), &snes->dm));
5496:     snes->dmAuto = PETSC_TRUE;
5497:   }
5498:   *dm = snes->dm;
5499:   PetscFunctionReturn(PETSC_SUCCESS);
5500: }

5502: /*@
5503:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

5505:   Collective

5507:   Input Parameters:
5508: + snes - iterative context obtained from `SNESCreate()`
5509: - npc   - the preconditioner object

5511:   Level: developer

5513:   Notes:
5514:   Use `SNESGetNPC()` to retrieve the preconditioner context (for example,
5515:   to configure it using the API).

5517:   Only some `SNESType` can use a nonlinear preconditioner

5519: .seealso: [](chapter_snes), `SNESNGS`, `SNESFAS`, `SNESGetNPC()`, `SNESHasNPC()`
5520: @*/
5521: PetscErrorCode SNESSetNPC(SNES snes, SNES npc)
5522: {
5523:   PetscFunctionBegin;
5526:   PetscCheckSameComm(snes, 1, npc, 2);
5527:   PetscCall(PetscObjectReference((PetscObject)npc));
5528:   PetscCall(SNESDestroy(&snes->npc));
5529:   snes->npc = npc;
5530:   PetscFunctionReturn(PETSC_SUCCESS);
5531: }

5533: /*@
5534:   SNESGetNPC - Gets a nonlinear preconditioning solver SNES` to be used to precondition the original nonlinear solver.

5536:   Not Collective; but any changes to the obtained the npc object must be applied collectively

5538:   Input Parameter:
5539: . snes - iterative context obtained from `SNESCreate()`

5541:   Output Parameter:
5542: . npc - preconditioner context

5544:   Options Database Key:
5545: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5547:   Level: developer

5549:   Notes:
5550:     If a `SNES` was previously set with `SNESSetNPC()` then that value is returned, otherwise a new `SNES` object is created.

5552:     The (preconditioner) `SNES` returned automatically inherits the same nonlinear function and Jacobian supplied to the original
5553:     `SNES`

5555: .seealso: [](chapter_snes), `SNESSetNPC()`, `SNESHasNPC()`, `SNES`, `SNESCreate()`
5556: @*/
5557: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
5558: {
5559:   const char *optionsprefix;

5561:   PetscFunctionBegin;
5564:   if (!snes->npc) {
5565:     void *ctx;

5567:     PetscCall(SNESCreate(PetscObjectComm((PetscObject)snes), &snes->npc));
5568:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->npc, (PetscObject)snes, 1));
5569:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5570:     PetscCall(SNESSetOptionsPrefix(snes->npc, optionsprefix));
5571:     PetscCall(SNESAppendOptionsPrefix(snes->npc, "npc_"));
5572:     PetscCall(SNESGetApplicationContext(snes, &ctx));
5573:     PetscCall(SNESSetApplicationContext(snes->npc, ctx));
5574:     PetscCall(SNESSetCountersReset(snes->npc, PETSC_FALSE));
5575:   }
5576:   *pc = snes->npc;
5577:   PetscFunctionReturn(PETSC_SUCCESS);
5578: }

5580: /*@
5581:   SNESHasNPC - Returns whether a nonlinear preconditioner exists

5583:   Not Collective

5585:   Input Parameter:
5586: . snes - iterative context obtained from `SNESCreate()`

5588:   Output Parameter:
5589: . has_npc - whether the `SNES` has an NPC or not

5591:   Level: developer

5593: .seealso: [](chapter_snes), `SNESSetNPC()`, `SNESGetNPC()`
5594: @*/
5595: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
5596: {
5597:   PetscFunctionBegin;
5599:   *has_npc = (PetscBool)(snes->npc ? PETSC_TRUE : PETSC_FALSE);
5600:   PetscFunctionReturn(PETSC_SUCCESS);
5601: }

5603: /*@
5604:     SNESSetNPCSide - Sets the preconditioning side.

5606:     Logically Collective

5608:     Input Parameter:
5609: .   snes - iterative context obtained from `SNESCreate()`

5611:     Output Parameter:
5612: .   side - the preconditioning side, where side is one of
5613: .vb
5614:       PC_LEFT - left preconditioning
5615:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
5616: .ve

5618:     Options Database Key:
5619: .   -snes_npc_side <right,left> - nonlinear preconditioner side

5621:     Level: intermediate

5623:     Note:
5624:     `SNESNRICHARDSON` and `SNESNCG` only support left preconditioning.

5626: .seealso: [](chapter_snes), `SNESType`, `SNESGetNPCSide()`, `KSPSetPCSide()`
5627: @*/
5628: PetscErrorCode SNESSetNPCSide(SNES snes, PCSide side)
5629: {
5630:   PetscFunctionBegin;
5633:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
5634:   PetscCheck((side == PC_LEFT) || (side == PC_RIGHT), PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Only PC_LEFT and PC_RIGHT are supported");
5635:   snes->npcside = side;
5636:   PetscFunctionReturn(PETSC_SUCCESS);
5637: }

5639: /*@
5640:     SNESGetNPCSide - Gets the preconditioning side.

5642:     Not Collective

5644:     Input Parameter:
5645: .   snes - iterative context obtained from `SNESCreate()`

5647:     Output Parameter:
5648: .   side - the preconditioning side, where side is one of
5649: .vb
5650:       `PC_LEFT` - left preconditioning
5651:       `PC_RIGHT` - right preconditioning (default for most nonlinear solvers)
5652: .ve

5654:     Level: intermediate

5656: .seealso: [](chapter_snes), `SNES`, `SNESSetNPCSide()`, `KSPGetPCSide()`
5657: @*/
5658: PetscErrorCode SNESGetNPCSide(SNES snes, PCSide *side)
5659: {
5660:   PetscFunctionBegin;
5663:   *side = snes->npcside;
5664:   PetscFunctionReturn(PETSC_SUCCESS);
5665: }

5667: /*@
5668:   SNESSetLineSearch - Sets the linesearch on the `SNES` instance.

5670:   Collective

5672:   Input Parameters:
5673: + snes - iterative context obtained from `SNESCreate()`
5674: - linesearch   - the linesearch object

5676:   Level: developer

5678:   Note:
5679:   Use `SNESGetLineSearch()` to retrieve the preconditioner context (for example,
5680:   to configure it using the API).

5682: .seealso: [](chapter_snes), `SNESGetLineSearch()`
5683: @*/
5684: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5685: {
5686:   PetscFunctionBegin;
5689:   PetscCheckSameComm(snes, 1, linesearch, 2);
5690:   PetscCall(PetscObjectReference((PetscObject)linesearch));
5691:   PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5693:   snes->linesearch = linesearch;

5695:   PetscFunctionReturn(PETSC_SUCCESS);
5696: }

5698: /*@
5699:   SNESGetLineSearch - Returns the line search context set with `SNESSetLineSearch()`
5700:   or creates a default line search instance associated with the `SNES` and returns it.

5702:   Not Collective

5704:   Input Parameter:
5705: . snes - iterative context obtained from `SNESCreate()`

5707:   Output Parameter:
5708: . linesearch - linesearch context

5710:   Level: beginner

5712: .seealso: [](chapter_snes), `SNESLineSearch`, `SNESSetLineSearch()`, `SNESLineSearchCreate()`
5713: @*/
5714: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5715: {
5716:   const char *optionsprefix;

5718:   PetscFunctionBegin;
5721:   if (!snes->linesearch) {
5722:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5723:     PetscCall(SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch));
5724:     PetscCall(SNESLineSearchSetSNES(snes->linesearch, snes));
5725:     PetscCall(SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix));
5726:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->linesearch, (PetscObject)snes, 1));
5727:   }
5728:   *linesearch = snes->linesearch;
5729:   PetscFunctionReturn(PETSC_SUCCESS);
5730: }