Date: 2016-07-24T17:09:30+00:00

Actual source code: snesgs.c
petsc-3.7.3 2016-07-24
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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: }