Actual source code: snesgs.c

petsc-3.4.4 2014-03-13
  1: #include <petsc-private/snesimpl.h>             /*I   "petscsnes.h"   I*/

  3: typedef struct {
  4:   PetscInt  sweeps;     /* number of sweeps through the local subdomain before neighbor communication */
  5:   PetscInt  max_its;    /* maximum iterations of the inner pointblock solver */
  6:   PetscReal rtol;       /* relative tolerance of the inner pointblock solver */
  7:   PetscReal abstol;     /* absolute tolerance of the inner pointblock solver */
  8:   PetscReal stol;       /* step tolerance of the inner pointblock solver */
  9: } SNES_GS;


 14: /*@
 15:    SNESGSSetTolerances - Sets various parameters used in convergence tests.

 17:    Logically Collective on SNES

 19:    Input Parameters:
 20: +  snes - the SNES context
 21: .  abstol - absolute convergence tolerance
 22: .  rtol - relative convergence tolerance
 23: .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
 24: -  maxit - maximum number of iterations


 27:    Options Database Keys:
 28: +    -snes_gs_atol <abstol> - Sets abstol
 29: .    -snes_gs_rtol <rtol> - Sets rtol
 30: .    -snes_gs_stol <stol> - Sets stol
 31: -    -snes_max_it <maxit> - Sets maxit

 33:    Level: intermediate

 35: .keywords: SNES, nonlinear, gauss-seidel, set, convergence, tolerances

 37: .seealso: SNESSetTrustRegionTolerance()
 38: @*/
 39: PetscErrorCode  SNESGSSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit)
 40: {
 41:   SNES_GS *gs = (SNES_GS*)snes->data;


 46:   if (abstol != PETSC_DEFAULT) {
 47:     if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %G must be non-negative",abstol);
 48:     gs->abstol = abstol;
 49:   }
 50:   if (rtol != PETSC_DEFAULT) {
 51:     if (rtol < 0.0 || 1.0 <= rtol) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Relative tolerance %G must be non-negative and less than 1.0",rtol);
 52:     gs->rtol = rtol;
 53:   }
 54:   if (stol != PETSC_DEFAULT) {
 55:     if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %G must be non-negative",stol);
 56:     gs->stol = stol;
 57:   }
 58:   if (maxit != PETSC_DEFAULT) {
 59:     if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
 60:     gs->max_its = maxit;
 61:   }
 62:   return(0);
 63: }

 67: /*@
 68:    SNESGSGetTolerances - Gets various parameters used in convergence tests.

 70:    Not Collective

 72:    Input Parameters:
 73: +  snes - the SNES context
 74: .  atol - absolute convergence tolerance
 75: .  rtol - relative convergence tolerance
 76: .  stol -  convergence tolerance in terms of the norm
 77:            of the change in the solution between steps
 78: -  maxit - maximum number of iterations

 80:    Notes:
 81:    The user can specify NULL for any parameter that is not needed.

 83:    Level: intermediate

 85: .keywords: SNES, nonlinear, get, convergence, tolerances

 87: .seealso: SNESSetTolerances()
 88: @*/
 89: PetscErrorCode  SNESGSGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit)
 90: {
 91:   SNES_GS *gs = (SNES_GS*)snes->data;

 95:   if (atol) *atol = gs->abstol;
 96:   if (rtol) *rtol = gs->rtol;
 97:   if (stol) *stol = gs->stol;
 98:   if (maxit) *maxit = gs->max_its;
 99:   return(0);
100: }

104: /*@
105:    SNESGSSetSweeps - Sets the number of sweeps of GS to use.

107:    Input Parameters:
108: +  snes   - the SNES context
109: -  sweeps  - the number of sweeps of GS to perform.

111:    Level: intermediate

113: .keywords: SNES, nonlinear, set, Gauss-Siedel

115: .seealso: SNESSetGS(), SNESGetGS(), SNESSetPC(), SNESGSGetSweeps()
116: @*/

118: PetscErrorCode SNESGSSetSweeps(SNES snes, PetscInt sweeps)
119: {
120:   SNES_GS *gs = (SNES_GS*)snes->data;

124:   gs->sweeps = sweeps;
125:   return(0);
126: }

130: /*@
131:    SNESGSGetSweeps - Gets the number of sweeps GS will use.

133:    Input Parameters:
134: .  snes   - the SNES context

136:    Output Parameters:
137: .  sweeps  - the number of sweeps of GS to perform.

139:    Level: intermediate

141: .keywords: SNES, nonlinear, set, Gauss-Siedel

143: .seealso: SNESSetGS(), SNESGetGS(), SNESSetPC(), SNESGSSetSweeps()
144: @*/
145: PetscErrorCode SNESGSGetSweeps(SNES snes, PetscInt * sweeps)
146: {
147:   SNES_GS *gs = (SNES_GS*)snes->data;

151:   *sweeps = gs->sweeps;
152:   return(0);
153: }


158: PetscErrorCode SNESDefaultApplyGS(SNES snes,Vec X,Vec F,void *ctx)
159: {
161:   /* see if there's a coloring on the DM */
162:   return(0);
163: }

167: PetscErrorCode SNESReset_GS(SNES snes)
168: {
170:   return(0);
171: }

175: PetscErrorCode SNESDestroy_GS(SNES snes)
176: {

180:   SNESReset_GS(snes);
181:   PetscFree(snes->data);
182:   return(0);
183: }

187: PetscErrorCode SNESSetUp_GS(SNES snes)
188: {
190:   return(0);
191: }

195: PetscErrorCode SNESSetFromOptions_GS(SNES snes)
196: {
197:   SNES_GS        *gs = (SNES_GS*)snes->data;
199:   PetscInt       sweeps,max_its=PETSC_DEFAULT;
200:   PetscReal      rtol=PETSC_DEFAULT,atol=PETSC_DEFAULT,stol=PETSC_DEFAULT;
201:   PetscBool      flg,flg1,flg2,flg3;

204:   PetscOptionsHead("SNES GS options");
205:   /* GS Options */
206:   PetscOptionsInt("-snes_gs_sweeps","Number of sweeps of GS to apply","SNESComputeGS",gs->sweeps,&sweeps,&flg);
207:   if (flg) {
208:     SNESGSSetSweeps(snes,sweeps);
209:   }
210:   PetscOptionsReal("-snes_gs_atol","Number of sweeps of GS to apply","SNESComputeGS",gs->abstol,&atol,&flg);
211:   PetscOptionsReal("-snes_gs_rtol","Number of sweeps of GS to apply","SNESComputeGS",gs->rtol,&rtol,&flg1);
212:   PetscOptionsReal("-snes_gs_stol","Number of sweeps of GS to apply","SNESComputeGS",gs->stol,&stol,&flg2);
213:   PetscOptionsInt("-snes_gs_max_it","Number of sweeps of GS to apply","SNESComputeGS",gs->max_its,&max_its,&flg3);
214:   if (flg || flg1 || flg2 || flg3) {
215:     SNESGSSetTolerances(snes,atol,rtol,stol,max_its);
216:   }
217:   PetscOptionsTail();
218:   return(0);
219: }

223: PetscErrorCode SNESView_GS(SNES snes, PetscViewer viewer)
224: {
226:   return(0);
227: }

231: PetscErrorCode SNESSolve_GS(SNES snes)
232: {
233:   Vec            F;
234:   Vec            X;
235:   Vec            B;
236:   PetscInt       i;
237:   PetscReal      fnorm;
239:   SNESNormType   normtype;

242:   X = snes->vec_sol;
243:   F = snes->vec_func;
244:   B = snes->vec_rhs;

246:   PetscObjectAMSTakeAccess((PetscObject)snes);
247:   snes->iter   = 0;
248:   snes->norm   = 0.;
249:   PetscObjectAMSGrantAccess((PetscObject)snes);
250:   snes->reason = SNES_CONVERGED_ITERATING;

252:   SNESGetNormType(snes, &normtype);
253:   if (normtype == SNES_NORM_FUNCTION || normtype == SNES_NORM_INITIAL_ONLY || normtype == SNES_NORM_INITIAL_FINAL_ONLY) {
254:     /* compute the initial function and preconditioned update delX */
255:     if (!snes->vec_func_init_set) {
256:       SNESComputeFunction(snes,X,F);
257:       if (snes->domainerror) {
258:         snes->reason = SNES_DIVERGED_FUNCTION_DOMAIN;
259:         return(0);
260:       }
261:     } else snes->vec_func_init_set = PETSC_FALSE;

263:     /* convergence test */
264:     if (!snes->norm_init_set) {
265:       VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F||  */
266:       if (PetscIsInfOrNanReal(fnorm)) {
267:         snes->reason = SNES_DIVERGED_FNORM_NAN;
268:         return(0);
269:       }
270:     } else {
271:       fnorm               = snes->norm_init;
272:       snes->norm_init_set = PETSC_FALSE;
273:     }
274:     PetscObjectAMSTakeAccess((PetscObject)snes);
275:     snes->iter = 0;
276:     snes->norm = fnorm;
277:     PetscObjectAMSGrantAccess((PetscObject)snes);
278:     SNESLogConvergenceHistory(snes,snes->norm,0);
279:     SNESMonitor(snes,0,snes->norm);

281:     /* set parameter for default relative tolerance convergence test */
282:     snes->ttol = fnorm*snes->rtol;

284:     /* test convergence */
285:     (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
286:     if (snes->reason) return(0);
287:   } else {
288:     PetscObjectAMSGrantAccess((PetscObject)snes);
289:     SNESLogConvergenceHistory(snes,snes->norm,0);
290:     SNESMonitor(snes,0,snes->norm);
291:   }


294:   /* Call general purpose update function */
295:   if (snes->ops->update) {
296:     (*snes->ops->update)(snes, snes->iter);
297:   }

299:   for (i = 0; i < snes->max_its; i++) {
300:     SNESComputeGS(snes, B, X);
301:     /* only compute norms if requested or about to exit due to maximum iterations */
302:     if (normtype == SNES_NORM_FUNCTION || ((i == snes->max_its - 1) && (normtype == SNES_NORM_INITIAL_FINAL_ONLY || normtype == SNES_NORM_FINAL_ONLY))) {
303:       SNESComputeFunction(snes,X,F);
304:       if (snes->domainerror) {
305:         snes->reason = SNES_DIVERGED_FUNCTION_DOMAIN;
306:         return(0);
307:       }
308:       VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F||  */
309:       if (PetscIsInfOrNanReal(fnorm)) {
310:         snes->reason = SNES_DIVERGED_FNORM_NAN;
311:         return(0);
312:       }
313:     }
314:     /* Monitor convergence */
315:     PetscObjectAMSTakeAccess((PetscObject)snes);
316:     snes->iter = i+1;
317:     snes->norm = fnorm;
318:     PetscObjectAMSGrantAccess((PetscObject)snes);
319:     SNESLogConvergenceHistory(snes,snes->norm,0);
320:     SNESMonitor(snes,snes->iter,snes->norm);
321:     /* Test for convergence */
322:     if (normtype == SNES_NORM_FUNCTION) (*snes->ops->converged)(snes,snes->iter,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
323:     if (snes->reason) return(0);
324:     /* Call general purpose update function */
325:     if (snes->ops->update) {
326:       (*snes->ops->update)(snes, snes->iter);
327:     }
328:   }
329:   if (normtype == SNES_NORM_FUNCTION) {
330:     if (i == snes->max_its) {
331:       PetscInfo1(snes,"Maximum number of iterations has been reached: %D\n",snes->max_its);
332:       if (!snes->reason) snes->reason = SNES_DIVERGED_MAX_IT;
333:     }
334:   } else if (!snes->reason) snes->reason = SNES_CONVERGED_ITS; /* GS is meant to be used as a preconditioner */
335:   return(0);
336: }

338: /*MC
339:   SNESGS - Just calls the user-provided solution routine provided with SNESSetGS()

341:    Level: advanced

343:   Notes:
344:   the Gauss-Seidel smoother is inherited through composition.  If a solver has been created with SNESGetPC(), it will have
345:   its parent's Gauss-Seidel routine associated with it.

347: .seealso: SNESCreate(), SNES, SNESSetType(), SNESSetGS(), SNESType (for list of available types)
348: M*/

352: PETSC_EXTERN PetscErrorCode SNESCreate_GS(SNES snes)
353: {
354:   SNES_GS        *gs;

358:   snes->ops->destroy        = SNESDestroy_GS;
359:   snes->ops->setup          = SNESSetUp_GS;
360:   snes->ops->setfromoptions = SNESSetFromOptions_GS;
361:   snes->ops->view           = SNESView_GS;
362:   snes->ops->solve          = SNESSolve_GS;
363:   snes->ops->reset          = SNESReset_GS;

365:   snes->usesksp = PETSC_FALSE;
366:   snes->usespc  = PETSC_FALSE;

368:   if (!snes->tolerancesset) {
369:     snes->max_its   = 10000;
370:     snes->max_funcs = 10000;
371:   }

373:   PetscNewLog(snes, SNES_GS, &gs);

375:   gs->sweeps  = 1;
376:   gs->rtol    = 1e-5;
377:   gs->abstol  = 1e-15;
378:   gs->stol    = 1e-12;
379:   gs->max_its = 50;

381:   snes->data = (void*) gs;
382:   return(0);
383: }