Actual source code: tr.c

petsc-master 2020-02-23
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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: }