Actual source code: snesgs.c

petsc-3.7.0 2016-04-25
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  1: #include <../src/snes/impls/gs/gsimpl.h>      /*I "petscsnes.h"  I*/

  5: /*@
  6:    SNESNGSSetTolerances - Sets various parameters used in convergence tests.

  8:    Logically Collective on SNES

 10:    Input Parameters:
 11: +  snes - the SNES context
 12: .  abstol - absolute convergence tolerance
 13: .  rtol - relative convergence tolerance
 14: .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
 15: -  maxit - maximum number of iterations


 18:    Options Database Keys:
 19: +    -snes_ngs_atol <abstol> - Sets abstol
 20: .    -snes_ngs_rtol <rtol> - Sets rtol
 21: .    -snes_ngs_stol <stol> - Sets stol
 22: -    -snes_max_it <maxit> - Sets maxit

 24:    Level: intermediate

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

 28: .seealso: SNESSetTrustRegionTolerance()
 29: @*/
 30: PetscErrorCode  SNESNGSSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit)
 31: {
 32:   SNES_NGS *gs = (SNES_NGS*)snes->data;


 37:   if (abstol != PETSC_DEFAULT) {
 38:     if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %g must be non-negative",(double)abstol);
 39:     gs->abstol = abstol;
 40:   }
 41:   if (rtol != PETSC_DEFAULT) {
 42:     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",(double)rtol);
 43:     gs->rtol = rtol;
 44:   }
 45:   if (stol != PETSC_DEFAULT) {
 46:     if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %g must be non-negative",(double)stol);
 47:     gs->stol = stol;
 48:   }
 49:   if (maxit != PETSC_DEFAULT) {
 50:     if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
 51:     gs->max_its = maxit;
 52:   }
 53:   return(0);
 54: }

 58: /*@
 59:    SNESNGSGetTolerances - Gets various parameters used in convergence tests.

 61:    Not Collective

 63:    Input Parameters:
 64: +  snes - the SNES context
 65: .  atol - absolute convergence tolerance
 66: .  rtol - relative convergence tolerance
 67: .  stol -  convergence tolerance in terms of the norm
 68:            of the change in the solution between steps
 69: -  maxit - maximum number of iterations

 71:    Notes:
 72:    The user can specify NULL for any parameter that is not needed.

 74:    Level: intermediate

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

 78: .seealso: SNESSetTolerances()
 79: @*/
 80: PetscErrorCode  SNESNGSGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit)
 81: {
 82:   SNES_NGS *gs = (SNES_NGS*)snes->data;

 86:   if (atol) *atol = gs->abstol;
 87:   if (rtol) *rtol = gs->rtol;
 88:   if (stol) *stol = gs->stol;
 89:   if (maxit) *maxit = gs->max_its;
 90:   return(0);
 91: }

 95: /*@
 96:    SNESNGSSetSweeps - Sets the number of sweeps of GS to use.

 98:    Input Parameters:
 99: +  snes   - the SNES context
100: -  sweeps  - the number of sweeps of GS to perform.

102:    Level: intermediate

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

106: .seealso: SNESSetNGS(), SNESGetNGS(), SNESSetPC(), SNESNGSGetSweeps()
107: @*/

109: PetscErrorCode SNESNGSSetSweeps(SNES snes, PetscInt sweeps)
110: {
111:   SNES_NGS *gs = (SNES_NGS*)snes->data;

115:   gs->sweeps = sweeps;
116:   return(0);
117: }

121: /*@
122:    SNESNGSGetSweeps - Gets the number of sweeps GS will use.

124:    Input Parameters:
125: .  snes   - the SNES context

127:    Output Parameters:
128: .  sweeps  - the number of sweeps of GS to perform.

130:    Level: intermediate

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

134: .seealso: SNESSetNGS(), SNESGetNGS(), SNESSetPC(), SNESNGSSetSweeps()
135: @*/
136: PetscErrorCode SNESNGSGetSweeps(SNES snes, PetscInt * sweeps)
137: {
138:   SNES_NGS *gs = (SNES_NGS*)snes->data;

142:   *sweeps = gs->sweeps;
143:   return(0);
144: }


149: PetscErrorCode SNESDefaultApplyNGS(SNES snes,Vec X,Vec F,void *ctx)
150: {
152:   /* see if there's a coloring on the DM */
153:   return(0);
154: }

158: PetscErrorCode SNESReset_NGS(SNES snes)
159: {
161:   return(0);
162: }

166: PetscErrorCode SNESDestroy_NGS(SNES snes)
167: {

171:   SNESReset_NGS(snes);
172:   PetscFree(snes->data);
173:   return(0);
174: }

178: PetscErrorCode SNESSetUp_NGS(SNES snes)
179: {
181:   PetscErrorCode (*f)(SNES,Vec,Vec,void*);

184:   SNESGetNGS(snes,&f,NULL);
185:   if (!f) {
186:     SNESSetNGS(snes,SNESComputeNGSDefaultSecant,NULL);
187:   }
188:   return(0);
189: }

193: PetscErrorCode SNESSetFromOptions_NGS(PetscOptionItems *PetscOptionsObject,SNES snes)
194: {
195:   SNES_NGS       *gs = (SNES_NGS*)snes->data;
197:   PetscInt       sweeps,max_its=PETSC_DEFAULT;
198:   PetscReal      rtol=PETSC_DEFAULT,atol=PETSC_DEFAULT,stol=PETSC_DEFAULT;
199:   PetscBool      flg,flg1,flg2,flg3;

202:   PetscOptionsHead(PetscOptionsObject,"SNES GS options");
203:   /* GS Options */
204:   PetscOptionsInt("-snes_ngs_sweeps","Number of sweeps of GS to apply","SNESComputeGS",gs->sweeps,&sweeps,&flg);
205:   if (flg) {
206:     SNESNGSSetSweeps(snes,sweeps);
207:   }
208:   PetscOptionsReal("-snes_ngs_atol","Absolute residual tolerance for GS iteration","SNESComputeGS",gs->abstol,&atol,&flg);
209:   PetscOptionsReal("-snes_ngs_rtol","Relative residual tolerance for GS iteration","SNESComputeGS",gs->rtol,&rtol,&flg1);
210:   PetscOptionsReal("-snes_ngs_stol","Absolute update tolerance for GS iteration","SNESComputeGS",gs->stol,&stol,&flg2);
211:   PetscOptionsInt("-snes_ngs_max_it","Maximum number of sweeps of GS to apply","SNESComputeGS",gs->max_its,&max_its,&flg3);
212:   if (flg || flg1 || flg2 || flg3) {
213:     SNESNGSSetTolerances(snes,atol,rtol,stol,max_its);
214:   }
215:   flg  = PETSC_FALSE;
216:   PetscOptionsBool("-snes_ngs_secant","Use pointwise secant local Jacobian approximation","",flg,&flg,NULL);
217:   if (flg) {
218:     SNESSetNGS(snes,SNESComputeNGSDefaultSecant,NULL);
219:     PetscInfo(snes,"Setting default finite difference coloring Jacobian matrix\n");
220:   }
221:   PetscOptionsReal("-snes_ngs_secant_h","Differencing parameter for secant search","",gs->h,&gs->h,NULL);
222:   PetscOptionsBool("-snes_ngs_secant_mat_coloring","Use the Jacobian coloring for the secant GS","",gs->secant_mat,&gs->secant_mat,&flg);

224:   PetscOptionsTail();
225:   return(0);
226: }

230: PetscErrorCode SNESView_NGS(SNES snes, PetscViewer viewer)
231: {
233:   return(0);
234: }

238: PetscErrorCode SNESSolve_NGS(SNES snes)
239: {
240:   Vec              F;
241:   Vec              X;
242:   Vec              B;
243:   PetscInt         i;
244:   PetscReal        fnorm;
245:   PetscErrorCode   ierr;
246:   SNESNormSchedule normschedule;


250:   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);

252:   PetscCitationsRegister(SNESCitation,&SNEScite);
253:   X = snes->vec_sol;
254:   F = snes->vec_func;
255:   B = snes->vec_rhs;

257:   PetscObjectSAWsTakeAccess((PetscObject)snes);
258:   snes->iter   = 0;
259:   snes->norm   = 0.;
260:   PetscObjectSAWsGrantAccess((PetscObject)snes);
261:   snes->reason = SNES_CONVERGED_ITERATING;

263:   SNESGetNormSchedule(snes, &normschedule);
264:   if (normschedule == SNES_NORM_ALWAYS || normschedule == SNES_NORM_INITIAL_ONLY || normschedule == SNES_NORM_INITIAL_FINAL_ONLY) {
265:     /* compute the initial function and preconditioned update delX */
266:     if (!snes->vec_func_init_set) {
267:       SNESComputeFunction(snes,X,F);
268:     } else snes->vec_func_init_set = PETSC_FALSE;

270:     VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F||  */
271:     SNESCheckFunctionNorm(snes,fnorm);
272:     PetscObjectSAWsTakeAccess((PetscObject)snes);
273:     snes->iter = 0;
274:     snes->norm = fnorm;
275:     PetscObjectSAWsGrantAccess((PetscObject)snes);
276:     SNESLogConvergenceHistory(snes,snes->norm,0);
277:     SNESMonitor(snes,0,snes->norm);

279:     /* test convergence */
280:     (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
281:     if (snes->reason) return(0);
282:   } else {
283:     PetscObjectSAWsGrantAccess((PetscObject)snes);
284:     SNESLogConvergenceHistory(snes,snes->norm,0);
285:   }

287:   /* Call general purpose update function */
288:   if (snes->ops->update) {
289:     (*snes->ops->update)(snes, snes->iter);
290:   }

292:   for (i = 0; i < snes->max_its; i++) {
293:     SNESComputeNGS(snes, B, X);
294:     /* only compute norms if requested or about to exit due to maximum iterations */
295:     if (normschedule == SNES_NORM_ALWAYS || ((i == snes->max_its - 1) && (normschedule == SNES_NORM_INITIAL_FINAL_ONLY || normschedule == SNES_NORM_FINAL_ONLY))) {
296:       SNESComputeFunction(snes,X,F);
297:       VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F||  */
298:       SNESCheckFunctionNorm(snes,fnorm);
299:       /* Monitor convergence */
300:       PetscObjectSAWsTakeAccess((PetscObject)snes);
301:       snes->iter = i+1;
302:       snes->norm = fnorm;
303:       PetscObjectSAWsGrantAccess((PetscObject)snes);
304:       SNESLogConvergenceHistory(snes,snes->norm,0);
305:       SNESMonitor(snes,snes->iter,snes->norm);
306:     }
307:     /* Test for convergence */
308:     if (normschedule == SNES_NORM_ALWAYS) (*snes->ops->converged)(snes,snes->iter,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
309:     if (snes->reason) return(0);
310:     /* Call general purpose update function */
311:     if (snes->ops->update) {
312:       (*snes->ops->update)(snes, snes->iter);
313:     }
314:   }
315:   if (normschedule == SNES_NORM_ALWAYS) {
316:     if (i == snes->max_its) {
317:       PetscInfo1(snes,"Maximum number of iterations has been reached: %D\n",snes->max_its);
318:       if (!snes->reason) snes->reason = SNES_DIVERGED_MAX_IT;
319:     }
320:   } else if (!snes->reason) snes->reason = SNES_CONVERGED_ITS; /* GS is meant to be used as a preconditioner */
321:   return(0);
322: }

324: /*MC
325:   SNESNGS - Just calls the user-provided solution routine provided with SNESSetNGS()

327:    Level: advanced

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

333:    References:
334: .  1. - Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, "Composing Scalable Nonlinear Algebraic Solvers",
335:    SIAM Review, 57(4), 2015

337: .seealso: SNESCreate(), SNES, SNESSetType(), SNESSetNGS(), SNESType (for list of available types)
338: M*/

342: PETSC_EXTERN PetscErrorCode SNESCreate_NGS(SNES snes)
343: {
344:   SNES_NGS        *gs;

348:   snes->ops->destroy        = SNESDestroy_NGS;
349:   snes->ops->setup          = SNESSetUp_NGS;
350:   snes->ops->setfromoptions = SNESSetFromOptions_NGS;
351:   snes->ops->view           = SNESView_NGS;
352:   snes->ops->solve          = SNESSolve_NGS;
353:   snes->ops->reset          = SNESReset_NGS;

355:   snes->usesksp = PETSC_FALSE;
356:   snes->usespc  = PETSC_FALSE;

358:   if (!snes->tolerancesset) {
359:     snes->max_its   = 10000;
360:     snes->max_funcs = 10000;
361:   }

363:   PetscNewLog(snes,&gs);

365:   gs->sweeps  = 1;
366:   gs->rtol    = 1e-5;
367:   gs->abstol  = 1e-15;
368:   gs->stol    = 1e-12;
369:   gs->max_its = 50;
370:   gs->h       = 1e-8;

372:   snes->data = (void*) gs;
373:   return(0);
374: }