Actual source code: tr.c
petsc-3.13.6 2020-09-29
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      2:  #include <../src/snes/impls/tr/trimpl.h>

      4: typedef struct {
      5:   SNES           snes;
      6:   /*  Information on the regular SNES convergence test; which may have been user provided */
      7:   PetscErrorCode (*convtest)(KSP,PetscInt,PetscReal,KSPConvergedReason*,void*);
      8:   PetscErrorCode (*convdestroy)(void*);
      9:   void           *convctx;
     10: } SNES_TR_KSPConverged_Ctx;

     12: static PetscErrorCode SNESTR_KSPConverged_Private(KSP ksp,PetscInt n,PetscReal rnorm,KSPConvergedReason *reason,void *cctx)
     13: {
     14:   SNES_TR_KSPConverged_Ctx *ctx = (SNES_TR_KSPConverged_Ctx*)cctx;
     15:   SNES                     snes = ctx->snes;
     16:   SNES_NEWTONTR            *neP = (SNES_NEWTONTR*)snes->data;
     17:   Vec                      x;
     18:   PetscReal                nrm;
     19:   PetscErrorCode           ierr;

     22:   (*ctx->convtest)(ksp,n,rnorm,reason,ctx->convctx);
     23:   if (*reason) {
     24:     PetscInfo2(snes,"Default or user provided convergence test KSP iterations=%D, rnorm=%g\n",n,(double)rnorm);
     25:   }
     26:   /* Determine norm of solution */
     27:   KSPBuildSolution(ksp,0,&x);
     28:   VecNorm(x,NORM_2,&nrm);
     29:   if (nrm >= neP->delta) {
     30:     PetscInfo2(snes,"Ending linear iteration early, delta=%g, length=%g\n",(double)neP->delta,(double)nrm);
     31:     *reason = KSP_CONVERGED_STEP_LENGTH;
     32:   }
     33:   return(0);
     34: }

     36: static PetscErrorCode SNESTR_KSPConverged_Destroy(void *cctx)
     37: {
     38:   SNES_TR_KSPConverged_Ctx *ctx = (SNES_TR_KSPConverged_Ctx*)cctx;
     39:   PetscErrorCode           ierr;

     42:   (*ctx->convdestroy)(ctx->convctx);
     43:   PetscFree(ctx);
     44:   return(0);
     45: }

     47: /* ---------------------------------------------------------------- */
     48: /*
     49:    SNESTR_Converged_Private -test convergence JUST for
     50:    the trust region tolerance.

     52: */
     53: static PetscErrorCode SNESTR_Converged_Private(SNES snes,PetscInt it,PetscReal xnorm,PetscReal pnorm,PetscReal fnorm,SNESConvergedReason *reason,void *dummy)
     54: {
     55:   SNES_NEWTONTR  *neP = (SNES_NEWTONTR*)snes->data;

     59:   *reason = SNES_CONVERGED_ITERATING;
     60:   if (neP->delta < xnorm * snes->deltatol) {
     61:     PetscInfo3(snes,"Converged due to trust region param %g<%g*%g\n",(double)neP->delta,(double)xnorm,(double)snes->deltatol);
     62:     *reason = SNES_DIVERGED_TR_DELTA;
     63:   } else if (snes->nfuncs >= snes->max_funcs && snes->max_funcs >= 0) {
     64:     PetscInfo1(snes,"Exceeded maximum number of function evaluations: %D\n",snes->max_funcs);
     65:     *reason = SNES_DIVERGED_FUNCTION_COUNT;
     66:   }
     67:   return(0);
     68: }

     70: /*@C
     71:    SNESNewtonTRSetPreCheck - Sets a user function that is called before the search step has been determined.
     72:        Allows the user a chance to change or override the decision of the line search routine.

     74:    Logically Collective on snes

     76:    Input Parameters:
     77: +  snes - the nonlinear solver object
     78: .  func - [optional] function evaluation routine, see SNESNewtonTRPreCheck()  for the calling sequence
     79: -  ctx  - [optional] user-defined context for private data for the function evaluation routine (may be NULL)

     81:    Level: intermediate

     83:    Note: This function is called BEFORE the function evaluation within the SNESNEWTONTR solver.

     85: .seealso: SNESNewtonTRPreCheck(), SNESNewtonTRGetPreCheck(), SNESNewtonTRSetPostCheck(), SNESNewtonTRGetPostCheck()
     86: @*/
     87: PetscErrorCode  SNESNewtonTRSetPreCheck(SNES snes, PetscErrorCode (*func)(SNES,Vec,Vec,PetscBool*,void*),void *ctx)
     88: {
     89:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;

     93:   if (func) tr->precheck    = func;
     94:   if (ctx)  tr->precheckctx = ctx;
     95:   return(0);
     96: }

     98: /*@C
     99:    SNESNewtonTRGetPreCheck - Gets the pre-check function

    101:    Not collective

    103:    Input Parameter:
    104: .  snes - the nonlinear solver context

    106:    Output Parameters:
    107: +  func - [optional] function evaluation routine, see for the calling sequence SNESNewtonTRPreCheck()
    108: -  ctx  - [optional] user-defined context for private data for the function evaluation routine (may be NULL)

    110:    Level: intermediate

    112: .seealso: SNESNewtonTRSetPreCheck(), SNESNewtonTRPreCheck()
    113: @*/
    114: PetscErrorCode  SNESNewtonTRGetPreCheck(SNES snes, PetscErrorCode (**func)(SNES,Vec,Vec,PetscBool*,void*),void **ctx)
    115: {
    116:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;

    120:   if (func) *func = tr->precheck;
    121:   if (ctx)  *ctx  = tr->precheckctx;
    122:   return(0);
    123: }

    125: /*@C
    126:    SNESNewtonTRSetPostCheck - Sets a user function that is called after the search step has been determined but before the next
    127:        function evaluation. Allows the user a chance to change or override the decision of the line search routine

    129:    Logically Collective on snes

    131:    Input Parameters:
    132: +  snes - the nonlinear solver object
    133: .  func - [optional] function evaluation routine, see SNESNewtonTRPostCheck()  for the calling sequence
    134: -  ctx  - [optional] user-defined context for private data for the function evaluation routine (may be NULL)

    136:    Level: intermediate

    138:    Note: This function is called BEFORE the function evaluation within the SNESNEWTONTR solver while the function set in
    139:    SNESLineSearchSetPostCheck() is called AFTER the function evaluation.

    141: .seealso: SNESNewtonTRPostCheck(), SNESNewtonTRGetPostCheck()
    142: @*/
    143: PetscErrorCode  SNESNewtonTRSetPostCheck(SNES snes, PetscErrorCode (*func)(SNES,Vec,Vec,Vec,PetscBool*,PetscBool*,void*),void *ctx)
    144: {
    145:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;

    149:   if (func) tr->postcheck    = func;
    150:   if (ctx)  tr->postcheckctx = ctx;
    151:   return(0);
    152: }

    154: /*@C
    155:    SNESNewtonTRGetPostCheck - Gets the post-check function

    157:    Not collective

    159:    Input Parameter:
    160: .  snes - the nonlinear solver context

    162:    Output Parameters:
    163: +  func - [optional] function evaluation routine, see for the calling sequence SNESNewtonTRPostCheck()
    164: -  ctx  - [optional] user-defined context for private data for the function evaluation routine (may be NULL)

    166:    Level: intermediate

    168: .seealso: SNESNewtonTRSetPostCheck(), SNESNewtonTRPostCheck()
    169: @*/
    170: PetscErrorCode  SNESNewtonTRGetPostCheck(SNES snes, PetscErrorCode (**func)(SNES,Vec,Vec,Vec,PetscBool*,PetscBool*,void*),void **ctx)
    171: {
    172:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;

    176:   if (func) *func = tr->postcheck;
    177:   if (ctx)  *ctx  = tr->postcheckctx;
    178:   return(0);
    179: }

    181: /*@C
    182:    SNESNewtonTRPreCheck - Called before the step has been determined in SNESNEWTONTR

    184:    Logically Collective on snes

    186:    Input Parameters:
    187: +  snes - the solver
    188: .  X - The last solution
    189: -  Y - The step direction

    191:    Output Parameters:
    192: .  changed_Y - Indicator that the step direction Y has been changed.

    194:    Level: developer

    196: .seealso: SNESNewtonTRSetPreCheck(), SNESNewtonTRGetPreCheck()
    197: @*/
    198: static PetscErrorCode SNESNewtonTRPreCheck(SNES snes,Vec X,Vec Y,PetscBool *changed_Y)
    199: {
    200:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;

    204:   *changed_Y = PETSC_FALSE;
    205:   if (tr->precheck) {
    206:     (*tr->precheck)(snes,X,Y,changed_Y,tr->precheckctx);
    208:   }
    209:   return(0);
    210: }

    212: /*@C
    213:    SNESNewtonTRPostCheck - Called after the step has been determined in SNESNEWTONTR but before the function evaluation

    215:    Logically Collective on snes

    217:    Input Parameters:
    218: +  snes - the solver.  X - The last solution
    219: .  Y - The full step direction
    220: -  W - The updated solution, W = X - Y

    222:    Output Parameters:
    223: +  changed_Y - indicator if step has been changed
    224: -  changed_W - Indicator if the new candidate solution W has been changed.

    226:    Notes:
    227:      If Y is changed then W is recomputed as X - Y

    229:    Level: developer

    231: .seealso: SNESNewtonTRSetPostCheck(), SNESNewtonTRGetPostCheck()
    232: @*/
    233: static PetscErrorCode SNESNewtonTRPostCheck(SNES snes,Vec X,Vec Y,Vec W,PetscBool *changed_Y,PetscBool *changed_W)
    234: {
    235:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;

    239:   *changed_Y = PETSC_FALSE;
    240:   *changed_W = PETSC_FALSE;
    241:   if (tr->postcheck) {
    242:     (*tr->postcheck)(snes,X,Y,W,changed_Y,changed_W,tr->postcheckctx);
    245:   }
    246:   return(0);
    247: }

    249: /*
    250:    SNESSolve_NEWTONTR - Implements Newton's Method with a very simple trust
    251:    region approach for solving systems of nonlinear equations.

    254: */
    255: static PetscErrorCode SNESSolve_NEWTONTR(SNES snes)
    256: {
    257:   SNES_NEWTONTR            *neP = (SNES_NEWTONTR*)snes->data;
    258:   Vec                      X,F,Y,G,Ytmp,W;
    259:   PetscErrorCode           ierr;
    260:   PetscInt                 maxits,i,lits;
    261:   PetscReal                rho,fnorm,gnorm,gpnorm,xnorm=0,delta,nrm,ynorm,norm1;
    262:   PetscScalar              cnorm;
    263:   KSP                      ksp;
    264:   SNESConvergedReason      reason = SNES_CONVERGED_ITERATING;
    265:   PetscBool                breakout = PETSC_FALSE;
    266:   SNES_TR_KSPConverged_Ctx *ctx;
    267:   PetscErrorCode           (*convtest)(KSP,PetscInt,PetscReal,KSPConvergedReason*,void*),(*convdestroy)(void*);
    268:   void                     *convctx;

    271:   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);

    273:   maxits = snes->max_its;               /* maximum number of iterations */
    274:   X      = snes->vec_sol;               /* solution vector */
    275:   F      = snes->vec_func;              /* residual vector */
    276:   Y      = snes->work[0];               /* work vectors */
    277:   G      = snes->work[1];
    278:   Ytmp   = snes->work[2];
    279:   W      = snes->work[3];

    281:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    282:   snes->iter = 0;
    283:   PetscObjectSAWsGrantAccess((PetscObject)snes);

    285:   /* Set the linear stopping criteria to use the More' trick. */
    286:   SNESGetKSP(snes,&ksp);
    287:   KSPGetConvergenceTest(ksp,&convtest,&convctx,&convdestroy);
    288:   if (convtest != SNESTR_KSPConverged_Private) {
    289:     PetscNew(&ctx);
    290:     ctx->snes             = snes;
    291:     KSPGetAndClearConvergenceTest(ksp,&ctx->convtest,&ctx->convctx,&ctx->convdestroy);
    292:     KSPSetConvergenceTest(ksp,SNESTR_KSPConverged_Private,ctx,SNESTR_KSPConverged_Destroy);
    293:     PetscInfo(snes,"Using Krylov convergence test SNESTR_KSPConverged_Private\n");
    294:   }

    296:   if (!snes->vec_func_init_set) {
    297:     SNESComputeFunction(snes,X,F);          /* F(X) */
    298:   } else snes->vec_func_init_set = PETSC_FALSE;

    300:   VecNorm(F,NORM_2,&fnorm);             /* fnorm <- || F || */
    301:   SNESCheckFunctionNorm(snes,fnorm);
    302:   VecNorm(X,NORM_2,&xnorm);             /* fnorm <- || F || */
    303:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    304:   snes->norm = fnorm;
    305:   PetscObjectSAWsGrantAccess((PetscObject)snes);
    306:   delta      = xnorm ? neP->delta0*xnorm : neP->delta0;
    307:   neP->delta = delta;
    308:   SNESLogConvergenceHistory(snes,fnorm,0);
    309:   SNESMonitor(snes,0,fnorm);

    311:   /* test convergence */
    312:   (*snes->ops->converged)(snes,snes->iter,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
    313:   if (snes->reason) return(0);

    316:   for (i=0; i<maxits; i++) {

    318:     /* Call general purpose update function */
    319:     if (snes->ops->update) {
    320:       (*snes->ops->update)(snes, snes->iter);
    321:     }

    323:     /* Solve J Y = F, where J is Jacobian matrix */
    324:     SNESComputeJacobian(snes,X,snes->jacobian,snes->jacobian_pre);
    325:     SNESCheckJacobianDomainerror(snes);
    326:     KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);
    327:     KSPSolve(snes->ksp,F,Ytmp);
    328:     KSPGetIterationNumber(snes->ksp,&lits);

    330:     snes->linear_its += lits;

    332:     PetscInfo2(snes,"iter=%D, linear solve iterations=%D\n",snes->iter,lits);
    333:     VecNorm(Ytmp,NORM_2,&nrm);
    334:     norm1 = nrm;
    335:     while (1) {
    336:       PetscBool changed_y;
    337:       PetscBool changed_w;
    338:       VecCopy(Ytmp,Y);
    339:       nrm  = norm1;

    341:       /* Scale Y if need be and predict new value of F norm */
    342:       if (nrm >= delta) {
    343:         nrm    = delta/nrm;
    344:         gpnorm = (1.0 - nrm)*fnorm;
    345:         cnorm  = nrm;
    346:         PetscInfo1(snes,"Scaling direction by %g\n",(double)nrm);
    347:         VecScale(Y,cnorm);
    348:         nrm    = gpnorm;
    349:         ynorm  = delta;
    350:       } else {
    351:         gpnorm = 0.0;
    352:         PetscInfo(snes,"Direction is in Trust Region\n");
    353:         ynorm  = nrm;
    354:       }
    355:       /* PreCheck() allows for updates to Y prior to W <- X - Y */
    356:       SNESNewtonTRPreCheck(snes,X,Y,&changed_y);
    357:       VecWAXPY(W,-1.0,Y,X);         /* W <- X - Y */
    358:       SNESNewtonTRPostCheck(snes,X,Y,W,&changed_y,&changed_w);
    359:       if (changed_y) VecWAXPY(W,-1.0,Y,X);
    360:       VecCopy(Y,snes->vec_sol_update);
    361:       SNESComputeFunction(snes,W,G); /*  F(X) */
    362:       VecNorm(G,NORM_2,&gnorm);      /* gnorm <- || g || */
    363:       SNESCheckFunctionNorm(snes,gnorm);
    364:       if (fnorm == gpnorm) rho = 0.0;
    365:       else rho = (fnorm*fnorm - gnorm*gnorm)/(fnorm*fnorm - gpnorm*gpnorm);

    367:       /* Update size of trust region */
    368:       if      (rho < neP->mu)  delta *= neP->delta1;
    369:       else if (rho < neP->eta) delta *= neP->delta2;
    370:       else                     delta *= neP->delta3;
    371:       PetscInfo3(snes,"fnorm=%g, gnorm=%g, ynorm=%g\n",(double)fnorm,(double)gnorm,(double)ynorm);
    372:       PetscInfo3(snes,"gpred=%g, rho=%g, delta=%g\n",(double)gpnorm,(double)rho,(double)delta);

    374:       neP->delta = delta;
    375:       if (rho > neP->sigma) break;
    376:       PetscInfo(snes,"Trying again in smaller region\n");
    377:       /* check to see if progress is hopeless */
    378:       neP->itflag = PETSC_FALSE;
    379:       SNESTR_Converged_Private(snes,snes->iter,xnorm,ynorm,fnorm,&reason,snes->cnvP);
    380:       if (!reason) {(*snes->ops->converged)(snes,snes->iter,xnorm,ynorm,fnorm,&reason,snes->cnvP);}
    381:       if (reason == SNES_CONVERGED_SNORM_RELATIVE) reason = SNES_DIVERGED_INNER;
    382:       if (reason) {
    383:         /* We're not progressing, so return with the current iterate */
    384:         SNESMonitor(snes,i+1,fnorm);
    385:         breakout = PETSC_TRUE;
    386:         break;
    387:       }
    388:       snes->numFailures++;
    389:     }
    390:     if (!breakout) {
    391:       /* Update function and solution vectors */
    392:       fnorm = gnorm;
    393:       VecCopy(G,F);
    394:       VecCopy(W,X);
    395:       /* Monitor convergence */
    396:       PetscObjectSAWsTakeAccess((PetscObject)snes);
    397:       snes->iter = i+1;
    398:       snes->norm = fnorm;
    399:       snes->xnorm = xnorm;
    400:       snes->ynorm = ynorm;
    401:       PetscObjectSAWsGrantAccess((PetscObject)snes);
    402:       SNESLogConvergenceHistory(snes,snes->norm,lits);
    403:       SNESMonitor(snes,snes->iter,snes->norm);
    404:       /* Test for convergence, xnorm = || X || */
    405:       neP->itflag = PETSC_TRUE;
    406:       if (snes->ops->converged != SNESConvergedSkip) { VecNorm(X,NORM_2,&xnorm); }
    407:       (*snes->ops->converged)(snes,snes->iter,xnorm,ynorm,fnorm,&reason,snes->cnvP);
    408:       if (reason) break;
    409:     } else break;
    410:   }
    411:   if (i == maxits) {
    412:     PetscInfo1(snes,"Maximum number of iterations has been reached: %D\n",maxits);
    413:     if (!reason) reason = SNES_DIVERGED_MAX_IT;
    414:   }
    415:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    416:   snes->reason = reason;
    417:   PetscObjectSAWsGrantAccess((PetscObject)snes);
    418:   if (convtest != SNESTR_KSPConverged_Private) {
    419:     KSPGetAndClearConvergenceTest(ksp,&ctx->convtest,&ctx->convctx,&ctx->convdestroy);
    420:     PetscFree(ctx);
    421:     KSPSetConvergenceTest(ksp,convtest,convctx,convdestroy);
    422:   }
    423:   return(0);
    424: }
    425: /*------------------------------------------------------------*/
    426: static PetscErrorCode SNESSetUp_NEWTONTR(SNES snes)
    427: {

    431:   SNESSetWorkVecs(snes,4);
    432:   SNESSetUpMatrices(snes);
    433:   return(0);
    434: }

    436: PetscErrorCode SNESReset_NEWTONTR(SNES snes)
    437: {

    440:   return(0);
    441: }

    443: static PetscErrorCode SNESDestroy_NEWTONTR(SNES snes)
    444: {

    448:   SNESReset_NEWTONTR(snes);
    449:   PetscFree(snes->data);
    450:   return(0);
    451: }
    452: /*------------------------------------------------------------*/

    454: static PetscErrorCode SNESSetFromOptions_NEWTONTR(PetscOptionItems *PetscOptionsObject,SNES snes)
    455: {
    456:   SNES_NEWTONTR  *ctx = (SNES_NEWTONTR*)snes->data;

    460:   PetscOptionsHead(PetscOptionsObject,"SNES trust region options for nonlinear equations");
    461:   PetscOptionsReal("-snes_trtol","Trust region tolerance","SNESSetTrustRegionTolerance",snes->deltatol,&snes->deltatol,NULL);
    462:   PetscOptionsReal("-snes_tr_mu","mu","None",ctx->mu,&ctx->mu,NULL);
    463:   PetscOptionsReal("-snes_tr_eta","eta","None",ctx->eta,&ctx->eta,NULL);
    464:   PetscOptionsReal("-snes_tr_sigma","sigma","None",ctx->sigma,&ctx->sigma,NULL);
    465:   PetscOptionsReal("-snes_tr_delta0","delta0","None",ctx->delta0,&ctx->delta0,NULL);
    466:   PetscOptionsReal("-snes_tr_delta1","delta1","None",ctx->delta1,&ctx->delta1,NULL);
    467:   PetscOptionsReal("-snes_tr_delta2","delta2","None",ctx->delta2,&ctx->delta2,NULL);
    468:   PetscOptionsReal("-snes_tr_delta3","delta3","None",ctx->delta3,&ctx->delta3,NULL);
    469:   PetscOptionsTail();
    470:   return(0);
    471: }

    473: static PetscErrorCode SNESView_NEWTONTR(SNES snes,PetscViewer viewer)
    474: {
    475:   SNES_NEWTONTR  *tr = (SNES_NEWTONTR*)snes->data;
    477:   PetscBool      iascii;

    480:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    481:   if (iascii) {
    482:     PetscViewerASCIIPrintf(viewer,"  Trust region tolerance (-snes_trtol)\n",(double)snes->deltatol);
    483:     PetscViewerASCIIPrintf(viewer,"  mu=%g, eta=%g, sigma=%g\n",(double)tr->mu,(double)tr->eta,(double)tr->sigma);
    484:     PetscViewerASCIIPrintf(viewer,"  delta0=%g, delta1=%g, delta2=%g, delta3=%g\n",(double)tr->delta0,(double)tr->delta1,(double)tr->delta2,(double)tr->delta3);
    485:   }
    486:   return(0);
    487: }
    488: /* ------------------------------------------------------------ */
    489: /*MC
    490:       SNESNEWTONTR - Newton based nonlinear solver that uses a trust region

    492:    Options Database:
    493: +    -snes_trtol <tol> - trust region tolerance
    494: .    -snes_tr_mu <mu> - trust region parameter
    495: .    -snes_tr_eta <eta> - trust region parameter
    496: .    -snes_tr_sigma <sigma> - trust region parameter
    497: .    -snes_tr_delta0 <delta0> -  initial size of the trust region is delta0*norm2(x)
    498: .    -snes_tr_delta1 <delta1> - trust region parameter
    499: .    -snes_tr_delta2 <delta2> - trust region parameter
    500: -    -snes_tr_delta3 <delta3> - trust region parameter

    502:    The basic algorithm is taken from "The Minpack Project", by More',
    503:    Sorensen, Garbow, Hillstrom, pages 88-111 of "Sources and Development
    504:    of Mathematical Software", Wayne Cowell, editor.

    506:    Level: intermediate

    508: .seealso:  SNESCreate(), SNES, SNESSetType(), SNESNEWTONLS, SNESSetTrustRegionTolerance()

    510: M*/
    511: PETSC_EXTERN PetscErrorCode SNESCreate_NEWTONTR(SNES snes)
    512: {
    513:   SNES_NEWTONTR  *neP;

    517:   snes->ops->setup          = SNESSetUp_NEWTONTR;
    518:   snes->ops->solve          = SNESSolve_NEWTONTR;
    519:   snes->ops->destroy        = SNESDestroy_NEWTONTR;
    520:   snes->ops->setfromoptions = SNESSetFromOptions_NEWTONTR;
    521:   snes->ops->view           = SNESView_NEWTONTR;
    522:   snes->ops->reset          = SNESReset_NEWTONTR;

    524:   snes->usesksp = PETSC_TRUE;
    525:   snes->usesnpc = PETSC_FALSE;

    527:   snes->alwayscomputesfinalresidual = PETSC_TRUE;

    529:   PetscNewLog(snes,&neP);
    530:   snes->data  = (void*)neP;
    531:   neP->mu     = 0.25;
    532:   neP->eta    = 0.75;
    533:   neP->delta  = 0.0;
    534:   neP->delta0 = 0.2;
    535:   neP->delta1 = 0.3;
    536:   neP->delta2 = 0.75;
    537:   neP->delta3 = 2.0;
    538:   neP->sigma  = 0.0001;
    539:   neP->itflag = PETSC_FALSE;
    540:   neP->rnorm0 = 0.0;
    541:   neP->ttol   = 0.0;
    542:   return(0);
    543: }