Actual source code: snesngmres.c

petsc-3.12.0 2019-09-29
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  1:  #include <../src/snes/impls/ngmres/snesngmres.h>
  2:  #include <petscblaslapack.h>
  3:  #include <petscdm.h>

  5: const char *const SNESNGMRESRestartTypes[] = {"NONE","PERIODIC","DIFFERENCE","SNESNGMRESRestartType","SNES_NGMRES_RESTART_",0};
  6: const char *const SNESNGMRESSelectTypes[] = {"NONE","DIFFERENCE","LINESEARCH","SNESNGMRESSelectType","SNES_NGMRES_SELECT_",0};

  8: PetscErrorCode SNESReset_NGMRES(SNES snes)
  9: {
 10:   SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;

 14:   VecDestroyVecs(ngmres->msize,&ngmres->Fdot);
 15:   VecDestroyVecs(ngmres->msize,&ngmres->Xdot);
 16:   SNESLineSearchDestroy(&ngmres->additive_linesearch);
 17:   return(0);
 18: }

 20: PetscErrorCode SNESDestroy_NGMRES(SNES snes)
 21: {
 23:   SNES_NGMRES    *ngmres = (SNES_NGMRES*)snes->data;

 26:   SNESReset_NGMRES(snes);
 27:   PetscFree4(ngmres->h,ngmres->beta,ngmres->xi,ngmres->q);
 28:   PetscFree3(ngmres->xnorms,ngmres->fnorms,ngmres->s);
 29: #if defined(PETSC_USE_COMPLEX)
 30:   PetscFree(ngmres->rwork);
 31: #endif
 32:   PetscFree(ngmres->work);
 33:   PetscFree(snes->data);
 34:   return(0);
 35: }

 37: PetscErrorCode SNESSetUp_NGMRES(SNES snes)
 38: {
 39:   SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
 40:   const char     *optionsprefix;
 41:   PetscInt       msize,hsize;
 43:   DM             dm;

 46:   if (snes->npc && snes->npcside== PC_LEFT && snes->functype == SNES_FUNCTION_UNPRECONDITIONED) {
 47:     SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"SNESNGMRES does not support left preconditioning with unpreconditioned function");
 48:   }
 49:   if (snes->npcside== PC_LEFT && snes->functype == SNES_FUNCTION_DEFAULT) snes->functype = SNES_FUNCTION_PRECONDITIONED;
 50:   SNESSetWorkVecs(snes,5);

 52:   if (!snes->vec_sol) {
 53:     SNESGetDM(snes,&dm);
 54:     DMCreateGlobalVector(dm,&snes->vec_sol);
 55:   }

 57:   if (!ngmres->Xdot) {VecDuplicateVecs(snes->vec_sol,ngmres->msize,&ngmres->Xdot);}
 58:   if (!ngmres->Fdot) {VecDuplicateVecs(snes->vec_sol,ngmres->msize,&ngmres->Fdot);}
 59:   if (!ngmres->setup_called) {
 60:     msize = ngmres->msize;          /* restart size */
 61:     hsize = msize * msize;

 63:     /* explicit least squares minimization solve */
 64:     PetscCalloc4(hsize,&ngmres->h, msize,&ngmres->beta, msize,&ngmres->xi, hsize,&ngmres->q);
 65:     PetscMalloc3(msize,&ngmres->xnorms,msize,&ngmres->fnorms,msize,&ngmres->s);
 66:     ngmres->nrhs  = 1;
 67:     ngmres->lda   = msize;
 68:     ngmres->ldb   = msize;
 69:     ngmres->lwork = 12*msize;
 70: #if defined(PETSC_USE_COMPLEX)
 71:     PetscMalloc1(ngmres->lwork,&ngmres->rwork);
 72: #endif
 73:     PetscMalloc1(ngmres->lwork,&ngmres->work);
 74:   }

 76:   /* linesearch setup */
 77:   SNESGetOptionsPrefix(snes,&optionsprefix);

 79:   if (ngmres->select_type == SNES_NGMRES_SELECT_LINESEARCH) {
 80:     SNESLineSearchCreate(PetscObjectComm((PetscObject)snes),&ngmres->additive_linesearch);
 81:     SNESLineSearchSetSNES(ngmres->additive_linesearch,snes);
 82:     SNESLineSearchSetType(ngmres->additive_linesearch,SNESLINESEARCHL2);
 83:     SNESLineSearchAppendOptionsPrefix(ngmres->additive_linesearch,"additive_");
 84:     SNESLineSearchAppendOptionsPrefix(ngmres->additive_linesearch,optionsprefix);
 85:     SNESLineSearchSetFromOptions(ngmres->additive_linesearch);
 86:   }

 88:   ngmres->setup_called = PETSC_TRUE;
 89:   return(0);
 90: }

 92: PetscErrorCode SNESSetFromOptions_NGMRES(PetscOptionItems *PetscOptionsObject,SNES snes)
 93: {
 94:   SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
 96:   PetscBool      debug = PETSC_FALSE;

 99:   PetscOptionsHead(PetscOptionsObject,"SNES NGMRES options");
100:   PetscOptionsEnum("-snes_ngmres_select_type","Select type","SNESNGMRESSetSelectType",SNESNGMRESSelectTypes,
101:                           (PetscEnum)ngmres->select_type,(PetscEnum*)&ngmres->select_type,NULL);
102:   PetscOptionsEnum("-snes_ngmres_restart_type","Restart type","SNESNGMRESSetRestartType",SNESNGMRESRestartTypes,
103:                           (PetscEnum)ngmres->restart_type,(PetscEnum*)&ngmres->restart_type,NULL);
104:   PetscOptionsBool("-snes_ngmres_candidate", "Use candidate storage",              "SNES",ngmres->candidate,&ngmres->candidate,NULL);
105:   PetscOptionsBool("-snes_ngmres_approxfunc","Linearly approximate the function", "SNES",ngmres->approxfunc,&ngmres->approxfunc,NULL);
106:   PetscOptionsInt("-snes_ngmres_m",          "Number of directions",               "SNES",ngmres->msize,&ngmres->msize,NULL);
107:   PetscOptionsInt("-snes_ngmres_restart",    "Iterations before forced restart",   "SNES",ngmres->restart_periodic,&ngmres->restart_periodic,NULL);
108:   PetscOptionsInt("-snes_ngmres_restart_it", "Tolerance iterations before restart","SNES",ngmres->restart_it,&ngmres->restart_it,NULL);
109:   PetscOptionsBool("-snes_ngmres_monitor",   "Monitor actions of NGMRES",          "SNES",ngmres->monitor ? PETSC_TRUE : PETSC_FALSE,&debug,NULL);
110:   if (debug) {
111:     ngmres->monitor = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
112:   }
113:   PetscOptionsReal("-snes_ngmres_gammaA",    "Residual selection constant",   "SNES",ngmres->gammaA,&ngmres->gammaA,NULL);
114:   PetscOptionsReal("-snes_ngmres_gammaC",    "Residual restart constant",     "SNES",ngmres->gammaC,&ngmres->gammaC,NULL);
115:   PetscOptionsReal("-snes_ngmres_epsilonB",  "Difference selection constant", "SNES",ngmres->epsilonB,&ngmres->epsilonB,NULL);
116:   PetscOptionsReal("-snes_ngmres_deltaB",    "Difference residual selection constant", "SNES",ngmres->deltaB,&ngmres->deltaB,NULL);
117:   PetscOptionsBool("-snes_ngmres_single_reduction", "Aggregate reductions",  "SNES",ngmres->singlereduction,&ngmres->singlereduction,NULL);
118:   PetscOptionsBool("-snes_ngmres_restart_fm_rise", "Restart on F_M residual rise",  "SNESNGMRESSetRestartFmRise",ngmres->restart_fm_rise,&ngmres->restart_fm_rise,NULL);
119:   PetscOptionsTail();
120:   if ((ngmres->gammaA > ngmres->gammaC) && (ngmres->gammaC > 2.)) ngmres->gammaC = ngmres->gammaA;
121:   return(0);
122: }

124: PetscErrorCode SNESView_NGMRES(SNES snes,PetscViewer viewer)
125: {
126:   SNES_NGMRES    *ngmres = (SNES_NGMRES*) snes->data;
127:   PetscBool      iascii;

131:   PetscObjectTypeCompare((PetscObject) viewer,PETSCVIEWERASCII,&iascii);
132:   if (iascii) {
133:     PetscViewerASCIIPrintf(viewer,"  Number of stored past updates: %d\n", ngmres->msize);
134:     PetscViewerASCIIPrintf(viewer,"  Residual selection: gammaA=%1.0e, gammaC=%1.0e\n",ngmres->gammaA,ngmres->gammaC);
135:     PetscViewerASCIIPrintf(viewer,"  Difference restart: epsilonB=%1.0e, deltaB=%1.0e\n",ngmres->epsilonB,ngmres->deltaB);
136:     PetscViewerASCIIPrintf(viewer,"  Restart on F_M residual increase: %s\n",ngmres->restart_fm_rise?"TRUE":"FALSE");
137:   }
138:   return(0);
139: }

141: PetscErrorCode SNESSolve_NGMRES(SNES snes)
142: {
143:   SNES_NGMRES          *ngmres = (SNES_NGMRES*) snes->data;
144:   /* present solution, residual, and preconditioned residual */
145:   Vec                  X,F,B,D,Y;

147:   /* candidate linear combination answers */
148:   Vec                  XA,FA,XM,FM;

150:   /* coefficients and RHS to the minimization problem */
151:   PetscReal            fnorm,fMnorm,fAnorm;
152:   PetscReal            xnorm,xMnorm,xAnorm;
153:   PetscReal            ynorm,yMnorm,yAnorm;
154:   PetscInt             k,k_restart,l,ivec,restart_count = 0;

156:   /* solution selection data */
157:   PetscBool            selectRestart;
158:   /*
159:       These two variables are initialized to prevent compilers/analyzers from producing false warnings about these variables being passed
160:       to SNESNGMRESSelect_Private() without being set when SNES_NGMRES_RESTART_DIFFERENCE, the values are not used in the subroutines in that case
161:       so the code is correct as written.
162:   */
163:   PetscReal            dnorm = 0.0,dminnorm = 0.0;
164:   PetscReal            fminnorm;

166:   SNESConvergedReason  reason;
167:   SNESLineSearchReason lssucceed;
168:   PetscErrorCode       ierr;

171:   if (snes->xl || snes->xu || snes->ops->computevariablebounds) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);

173:   PetscCitationsRegister(SNESCitation,&SNEScite);
174:   /* variable initialization */
175:   snes->reason = SNES_CONVERGED_ITERATING;
176:   X            = snes->vec_sol;
177:   F            = snes->vec_func;
178:   B            = snes->vec_rhs;
179:   XA           = snes->vec_sol_update;
180:   FA           = snes->work[0];
181:   D            = snes->work[1];

183:   /* work for the line search */
184:   Y  = snes->work[2];
185:   XM = snes->work[3];
186:   FM = snes->work[4];

188:   PetscObjectSAWsTakeAccess((PetscObject)snes);
189:   snes->iter = 0;
190:   snes->norm = 0.;
191:   PetscObjectSAWsGrantAccess((PetscObject)snes);

193:   /* initialization */

195:   if (snes->npc && snes->npcside== PC_LEFT) {
196:     SNESApplyNPC(snes,X,NULL,F);
197:     SNESGetConvergedReason(snes->npc,&reason);
198:     if (reason < 0  && reason != SNES_DIVERGED_MAX_IT) {
199:       snes->reason = SNES_DIVERGED_INNER;
200:       return(0);
201:     }
202:     VecNorm(F,NORM_2,&fnorm);
203:   } else {
204:     if (!snes->vec_func_init_set) {
205:       SNESComputeFunction(snes,X,F);
206:     } else snes->vec_func_init_set = PETSC_FALSE;

208:     VecNorm(F,NORM_2,&fnorm);
209:     SNESCheckFunctionNorm(snes,fnorm);
210:   }
211:   fminnorm = fnorm;

213:   PetscObjectSAWsTakeAccess((PetscObject)snes);
214:   snes->norm = fnorm;
215:   PetscObjectSAWsGrantAccess((PetscObject)snes);
216:   SNESLogConvergenceHistory(snes,fnorm,0);
217:   SNESMonitor(snes,0,fnorm);
218:   (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
219:   if (snes->reason) return(0);
220:   SNESNGMRESUpdateSubspace_Private(snes,0,0,F,fnorm,X);

222:   k_restart = 1;
223:   l         = 1;
224:   ivec      = 0;
225:   for (k=1; k < snes->max_its+1; k++) {
226:     /* Computation of x^M */
227:     if (snes->npc && snes->npcside== PC_RIGHT) {
228:       VecCopy(X,XM);
229:       SNESSetInitialFunction(snes->npc,F);

231:       PetscLogEventBegin(SNES_NPCSolve,snes->npc,XM,B,0);
232:       SNESSolve(snes->npc,B,XM);
233:       PetscLogEventEnd(SNES_NPCSolve,snes->npc,XM,B,0);

235:       SNESGetConvergedReason(snes->npc,&reason);
236:       if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
237:         snes->reason = SNES_DIVERGED_INNER;
238:         return(0);
239:       }
240:       SNESGetNPCFunction(snes,FM,&fMnorm);
241:     } else {
242:       /* no preconditioner -- just take gradient descent with line search */
243:       VecCopy(F,Y);
244:       VecCopy(F,FM);
245:       VecCopy(X,XM);

247:       fMnorm = fnorm;

249:       SNESLineSearchApply(snes->linesearch,XM,FM,&fMnorm,Y);
250:       SNESLineSearchGetReason(snes->linesearch,&lssucceed);
251:       if (lssucceed) {
252:         if (++snes->numFailures >= snes->maxFailures) {
253:           snes->reason = SNES_DIVERGED_LINE_SEARCH;
254:           return(0);
255:         }
256:       }
257:     }

259:     SNESNGMRESFormCombinedSolution_Private(snes,ivec,l,XM,FM,fMnorm,X,XA,FA);
260:     /* r = F(x) */
261:     if (fminnorm > fMnorm) fminnorm = fMnorm;  /* the minimum norm is now of F^M */

263:     /* differences for selection and restart */
264:     if (ngmres->restart_type == SNES_NGMRES_RESTART_DIFFERENCE || ngmres->select_type == SNES_NGMRES_SELECT_DIFFERENCE) {
265:       SNESNGMRESNorms_Private(snes,l,X,F,XM,FM,XA,FA,D,&dnorm,&dminnorm,&xMnorm,NULL,&yMnorm,&xAnorm,&fAnorm,&yAnorm);
266:     } else {
267:       SNESNGMRESNorms_Private(snes,l,X,F,XM,FM,XA,FA,D,NULL,NULL,&xMnorm,NULL,&yMnorm,&xAnorm,&fAnorm,&yAnorm);
268:     }
269:     SNESCheckFunctionNorm(snes,fnorm);

271:     /* combination (additive) or selection (multiplicative) of the N-GMRES solution */
272:     SNESNGMRESSelect_Private(snes,k_restart,XM,FM,xMnorm,fMnorm,yMnorm,XA,FA,xAnorm,fAnorm,yAnorm,dnorm,fminnorm,dminnorm,X,F,Y,&xnorm,&fnorm,&ynorm);
273:     selectRestart = PETSC_FALSE;

275:     if (ngmres->restart_type == SNES_NGMRES_RESTART_DIFFERENCE) {
276:       SNESNGMRESSelectRestart_Private(snes,l,fMnorm,fAnorm,dnorm,fminnorm,dminnorm,&selectRestart);

278:       /* if the restart conditions persist for more than restart_it iterations, restart. */
279:       if (selectRestart) restart_count++;
280:       else restart_count = 0;
281:     } else if (ngmres->restart_type == SNES_NGMRES_RESTART_PERIODIC) {
282:       if (k_restart > ngmres->restart_periodic) {
283:         if (ngmres->monitor) PetscViewerASCIIPrintf(ngmres->monitor,"periodic restart after %D iterations\n",k_restart);
284:         restart_count = ngmres->restart_it;
285:       }
286:     }

288:     ivec = k_restart % ngmres->msize; /* replace the last used part of the subspace */

290:     /* restart after restart conditions have persisted for a fixed number of iterations */
291:     if (restart_count >= ngmres->restart_it) {
292:       if (ngmres->monitor) {
293:         PetscViewerASCIIPrintf(ngmres->monitor,"Restarted at iteration %d\n",k_restart);
294:       }
295:       restart_count = 0;
296:       k_restart     = 1;
297:       l             = 1;
298:       ivec          = 0;
299:       /* q_{00} = nu */
300:       SNESNGMRESUpdateSubspace_Private(snes,0,0,FM,fMnorm,XM);
301:     } else {
302:       /* select the current size of the subspace */
303:       if (l < ngmres->msize) l++;
304:       k_restart++;
305:       /* place the current entry in the list of previous entries */
306:       if (ngmres->candidate) {
307:         if (fminnorm > fMnorm) fminnorm = fMnorm;
308:         SNESNGMRESUpdateSubspace_Private(snes,ivec,l,FM,fMnorm,XM);
309:       } else {
310:         if (fminnorm > fnorm) fminnorm = fnorm;
311:         SNESNGMRESUpdateSubspace_Private(snes,ivec,l,F,fnorm,X);
312:       }
313:     }

315:     PetscObjectSAWsTakeAccess((PetscObject)snes);
316:     snes->iter = k;
317:     snes->norm = fnorm;
318:     PetscObjectSAWsGrantAccess((PetscObject)snes);
319:     SNESLogConvergenceHistory(snes,snes->norm,snes->iter);
320:     SNESMonitor(snes,snes->iter,snes->norm);
321:     (*snes->ops->converged)(snes,snes->iter,0,0,fnorm,&snes->reason,snes->cnvP);
322:     if (snes->reason) return(0);
323:   }
324:   snes->reason = SNES_DIVERGED_MAX_IT;
325:   return(0);
326: }

328: /*@
329:  SNESNGMRESSetRestartFmRise - Increase the restart count if the step x_M increases the residual F_M

331:   Input Parameters:
332:   +  snes - the SNES context.
333:   -  flg  - boolean value deciding whether to use the option or not

335:   Options Database:
336:   + -snes_ngmres_restart_fm_rise - Increase the restart count if the step x_M increases the residual F_M

338:   Level: intermediate

340:   Notes:
341:   If the proposed step x_M increases the residual F_M, it might be trying to get out of a stagnation area.
342:   To help the solver do that, reset the Krylov subspace whenever F_M increases.

344:   This option must be used with SNES_NGMRES_RESTART_DIFFERENCE

346:   The default is FALSE.
347:   .seealso: SNES_NGMRES_RESTART_DIFFERENCE
348:   @*/
349: PetscErrorCode SNESNGMRESSetRestartFmRise(SNES snes,PetscBool flg)
350: {
351:     PetscErrorCode (*f)(SNES,PetscBool);

355:     PetscObjectQueryFunction((PetscObject)snes,"SNESNGMRESSetRestartFmRise_C",&f);
356:     if (f) {(f)(snes,flg);}
357:     return(0);
358: }

360: PetscErrorCode SNESNGMRESSetRestartFmRise_NGMRES(SNES snes,PetscBool flg)
361: {
362:   SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

365:   ngmres->restart_fm_rise = flg;
366:   return(0);
367: }

369: PetscErrorCode SNESNGMRESGetRestartFmRise(SNES snes,PetscBool *flg)
370: {
371:     PetscErrorCode (*f)(SNES,PetscBool*);

375:     PetscObjectQueryFunction((PetscObject)snes,"SNESNGMRESGetRestartFmRise_C",&f);
376:     if (f) {(f)(snes,flg);}
377:     return(0);
378: }

380: PetscErrorCode SNESNGMRESGetRestartFmRise_NGMRES(SNES snes,PetscBool *flg)
381: {
382:   SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

385:   *flg = ngmres->restart_fm_rise;
386:   return(0);
387: }


390: /*@
391:     SNESNGMRESSetRestartType - Sets the restart type for SNESNGMRES.

393:     Logically Collective on SNES

395:     Input Parameters:
396: +   snes - the iterative context
397: -   rtype - restart type

399:     Options Database:
400: +   -snes_ngmres_restart_type<difference,periodic,none> - set the restart type
401: -   -snes_ngmres_restart[30] - sets the number of iterations before restart for periodic

403:     Level: intermediate

405:     SNESNGMRESRestartTypes:
406: +   SNES_NGMRES_RESTART_NONE - never restart
407: .   SNES_NGMRES_RESTART_DIFFERENCE - restart based upon difference criteria
408: -   SNES_NGMRES_RESTART_PERIODIC - restart after a fixed number of iterations

410:     Notes:
411:     The default line search used is the L2 line search and it requires two additional function evaluations.

413: @*/
414: PetscErrorCode SNESNGMRESSetRestartType(SNES snes,SNESNGMRESRestartType rtype)
415: {

420:   PetscTryMethod(snes,"SNESNGMRESSetRestartType_C",(SNES,SNESNGMRESRestartType),(snes,rtype));
421:   return(0);
422: }

424: /*@
425:     SNESNGMRESSetSelectType - Sets the selection type for SNESNGMRES.  This determines how the candidate solution and
426:     combined solution are used to create the next iterate.

428:     Logically Collective on SNES

430:     Input Parameters:
431: +   snes - the iterative context
432: -   stype - selection type

434:     Options Database:
435: .   -snes_ngmres_select_type<difference,none,linesearch>

437:     Level: intermediate

439:     SNESNGMRESSelectTypes:
440: +   SNES_NGMRES_SELECT_NONE - choose the combined solution all the time
441: .   SNES_NGMRES_SELECT_DIFFERENCE - choose based upon the selection criteria
442: -   SNES_NGMRES_SELECT_LINESEARCH - choose based upon line search combination

444:     Notes:
445:     The default line search used is the L2 line search and it requires two additional function evaluations.

447: @*/
448: PetscErrorCode SNESNGMRESSetSelectType(SNES snes,SNESNGMRESSelectType stype)
449: {

454:   PetscTryMethod(snes,"SNESNGMRESSetSelectType_C",(SNES,SNESNGMRESSelectType),(snes,stype));
455:   return(0);
456: }

458: PetscErrorCode SNESNGMRESSetSelectType_NGMRES(SNES snes,SNESNGMRESSelectType stype)
459: {
460:   SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

463:   ngmres->select_type = stype;
464:   return(0);
465: }

467: PetscErrorCode SNESNGMRESSetRestartType_NGMRES(SNES snes,SNESNGMRESRestartType rtype)
468: {
469:   SNES_NGMRES *ngmres = (SNES_NGMRES*)snes->data;

472:   ngmres->restart_type = rtype;
473:   return(0);
474: }

476: /*MC
477:   SNESNGMRES - The Nonlinear Generalized Minimum Residual method.

479:    Level: beginner

481:    Options Database:
482: +  -snes_ngmres_select_type<difference,none,linesearch> - choose the select between candidate and combined solution
483: .  -snes_ngmres_restart_type<difference,none,periodic> - choose the restart conditions
484: .  -snes_ngmres_candidate        - Use NGMRES variant which combines candidate solutions instead of actual solutions
485: .  -snes_ngmres_m                - Number of stored previous solutions and residuals
486: .  -snes_ngmres_restart_it       - Number of iterations the restart conditions hold before restart
487: .  -snes_ngmres_gammaA           - Residual tolerance for solution select between the candidate and combination
488: .  -snes_ngmres_gammaC           - Residual tolerance for restart
489: .  -snes_ngmres_epsilonB         - Difference tolerance between subsequent solutions triggering restart
490: .  -snes_ngmres_deltaB           - Difference tolerance between residuals triggering restart
491: .  -snes_ngmres_restart_fm_rise  - Restart on residual rise from x_M step
492: .  -snes_ngmres_monitor          - Prints relevant information about the ngmres iteration
493: .  -snes_linesearch_type <basic,l2,cp> - Line search type used for the default smoother
494: -  -additive_snes_linesearch_type - linesearch type used to select between the candidate and combined solution with additive select type

496:    Notes:

498:    The N-GMRES method combines m previous solutions into a minimum-residual solution by solving a small linearized
499:    optimization problem at each iteration.

501:    Very similar to the SNESANDERSON algorithm.

503:    References:
504: +  1. - C. W. Oosterlee and T. Washio, "Krylov Subspace Acceleration of Nonlinear Multigrid with Application to Recirculating Flows", 
505:    SIAM Journal on Scientific Computing, 21(5), 2000.
506: -  2. - Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, "Composing Scalable Nonlinear Algebraic Solvers", 
507:    SIAM Review, 57(4), 2015


510: .seealso: SNESCreate(), SNES, SNESSetType(), SNESType (for list of available types)
511: M*/

513: PETSC_EXTERN PetscErrorCode SNESCreate_NGMRES(SNES snes)
514: {
515:   SNES_NGMRES    *ngmres;
517:   SNESLineSearch linesearch;

520:   snes->ops->destroy        = SNESDestroy_NGMRES;
521:   snes->ops->setup          = SNESSetUp_NGMRES;
522:   snes->ops->setfromoptions = SNESSetFromOptions_NGMRES;
523:   snes->ops->view           = SNESView_NGMRES;
524:   snes->ops->solve          = SNESSolve_NGMRES;
525:   snes->ops->reset          = SNESReset_NGMRES;

527:   snes->usesnpc  = PETSC_TRUE;
528:   snes->usesksp  = PETSC_FALSE;
529:   snes->npcside  = PC_RIGHT;

531:   snes->alwayscomputesfinalresidual = PETSC_TRUE;

533:   PetscNewLog(snes,&ngmres);
534:   snes->data    = (void*) ngmres;
535:   ngmres->msize = 30;

537:   if (!snes->tolerancesset) {
538:     snes->max_funcs = 30000;
539:     snes->max_its   = 10000;
540:   }

542:   ngmres->candidate = PETSC_FALSE;

544:  SNESGetLineSearch(snes,&linesearch);
545:  SNESLineSearchSetType(linesearch,SNESLINESEARCHBASIC);

547:   ngmres->additive_linesearch = NULL;
548:   ngmres->approxfunc          = PETSC_FALSE;
549:   ngmres->restart_it          = 2;
550:   ngmres->restart_periodic    = 30;
551:   ngmres->gammaA              = 2.0;
552:   ngmres->gammaC              = 2.0;
553:   ngmres->deltaB              = 0.9;
554:   ngmres->epsilonB            = 0.1;
555:   ngmres->restart_fm_rise     = PETSC_FALSE;

557:   ngmres->restart_type = SNES_NGMRES_RESTART_DIFFERENCE;
558:   ngmres->select_type  = SNES_NGMRES_SELECT_DIFFERENCE;

560:   PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESSetSelectType_C",SNESNGMRESSetSelectType_NGMRES);
561:   PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESSetRestartType_C",SNESNGMRESSetRestartType_NGMRES);
562:   PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESSetRestartFmRise_C",SNESNGMRESSetRestartFmRise_NGMRES);
563:   PetscObjectComposeFunction((PetscObject)snes,"SNESNGMRESGetRestartFmRise_C",SNESNGMRESGetRestartFmRise_NGMRES);
564:   return(0);
565: }