2: /*
3: This file implements FGMRES (a Generalized Minimal Residual) method.
4: Reference: Saad, 1993.
6: Preconditioning: If the preconditioner is constant then this fgmres
7: code is equivalent to RIGHT-PRECONDITIONED GMRES.
8: FGMRES is a modification of gmres that allows the preconditioner to change
9: at each iteration.
11: Restarts: Restarts are basically solves with x0 not equal to zero.
13: Contributed by Allison Baker
15: */
17: #include <../src/ksp/ksp/impls/gmres/fgmres/fgmresimpl.h> 18: #define FGMRES_DELTA_DIRECTIONS 10 19: #define FGMRES_DEFAULT_MAXK 30 20: static PetscErrorCode KSPFGMRESGetNewVectors(KSP,PetscInt);
21: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP,PetscInt,PetscBool,PetscReal*);
22: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar*,Vec,Vec,KSP,PetscInt);
24: /*
26: KSPSetUp_FGMRES - Sets up the workspace needed by fgmres.
28: This is called once, usually automatically by KSPSolve() or KSPSetUp(),
29: but can be called directly by KSPSetUp().
31: */
32: PetscErrorCode KSPSetUp_FGMRES(KSP ksp) 33: {
35: PetscInt max_k,k;
36: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
39: max_k = fgmres->max_k;
41: KSPSetUp_GMRES(ksp);
43: PetscMalloc1(max_k+2,&fgmres->prevecs);
44: PetscMalloc1(max_k+2,&fgmres->prevecs_user_work);
45: PetscLogObjectMemory((PetscObject)ksp,(max_k+2)*(2*sizeof(void*)));
47: /* fgmres->vv_allocated includes extra work vectors, which are not used in the additional
48: block of vectors used to store the preconditioned directions, hence the -VEC_OFFSET
49: term for this first allocation of vectors holding preconditioned directions */
50: KSPCreateVecs(ksp,fgmres->vv_allocated-VEC_OFFSET,&fgmres->prevecs_user_work[0],0,NULL);
51: PetscLogObjectParents(ksp,fgmres->vv_allocated-VEC_OFFSET,fgmres->prevecs_user_work[0]);
52: for (k=0; k < fgmres->vv_allocated - VEC_OFFSET ; k++) {
53: fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
54: }
55: return(0);
56: }
58: /*
59: KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
60: */
61: static PetscErrorCode KSPFGMRESResidual(KSP ksp) 62: {
63: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
64: Mat Amat,Pmat;
68: PCGetOperators(ksp->pc,&Amat,&Pmat);
70: /* put A*x into VEC_TEMP */
71: KSP_MatMult(ksp,Amat,ksp->vec_sol,VEC_TEMP);
72: /* now put residual (-A*x + f) into vec_vv(0) */
73: VecWAXPY(VEC_VV(0),-1.0,VEC_TEMP,ksp->vec_rhs);
74: return(0);
75: }
77: /*
79: KSPFGMRESCycle - Run fgmres, possibly with restart. Return residual
80: history if requested.
82: input parameters:
83: . fgmres - structure containing parameters and work areas
85: output parameters:
86: . itcount - number of iterations used. If null, ignored.
87: . converged - 0 if not converged
90: Notes:
91: On entry, the value in vector VEC_VV(0) should be
92: the initial residual.
95: */
96: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount,KSP ksp) 97: {
99: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
100: PetscReal res_norm;
101: PetscReal hapbnd,tt;
102: PetscBool hapend = PETSC_FALSE; /* indicates happy breakdown ending */
104: PetscInt loc_it; /* local count of # of dir. in Krylov space */
105: PetscInt max_k = fgmres->max_k; /* max # of directions Krylov space */
106: Mat Amat,Pmat;
109: /* Number of pseudo iterations since last restart is the number
110: of prestart directions */
111: loc_it = 0;
113: /* note: (fgmres->it) is always set one less than (loc_it) It is used in
114: KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
115: Note that when KSPFGMRESBuildSoln is called from this function,
116: (loc_it -1) is passed, so the two are equivalent */
117: fgmres->it = (loc_it - 1);
119: /* initial residual is in VEC_VV(0) - compute its norm*/
120: VecNorm(VEC_VV(0),NORM_2,&res_norm);
121: KSPCheckNorm(ksp,res_norm);
123: /* first entry in right-hand-side of hessenberg system is just
124: the initial residual norm */
125: *RS(0) = res_norm;
127: ksp->rnorm = res_norm;
128: KSPLogResidualHistory(ksp,res_norm);
129: KSPMonitor(ksp,ksp->its,res_norm);
131: /* check for the convergence - maybe the current guess is good enough */
132: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
133: if (ksp->reason) {
134: if (itcount) *itcount = 0;
135: return(0);
136: }
138: /* scale VEC_VV (the initial residual) */
139: VecScale(VEC_VV(0),1.0/res_norm);
141: /* MAIN ITERATION LOOP BEGINNING*/
142: /* keep iterating until we have converged OR generated the max number
143: of directions OR reached the max number of iterations for the method */
144: while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
145: if (loc_it) {
146: KSPLogResidualHistory(ksp,res_norm);
147: KSPMonitor(ksp,ksp->its,res_norm);
148: }
149: fgmres->it = (loc_it - 1);
151: /* see if more space is needed for work vectors */
152: if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
153: KSPFGMRESGetNewVectors(ksp,loc_it+1);
154: /* (loc_it+1) is passed in as number of the first vector that should
155: be allocated */
156: }
158: /* CHANGE THE PRECONDITIONER? */
159: /* ModifyPC is the callback function that can be used to
160: change the PC or its attributes before its applied */
161: (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);
164: /* apply PRECONDITIONER to direction vector and store with
165: preconditioned vectors in prevec */
166: KSP_PCApply(ksp,VEC_VV(loc_it),PREVEC(loc_it));
168: PCGetOperators(ksp->pc,&Amat,&Pmat);
169: /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
170: KSP_MatMult(ksp,Amat,PREVEC(loc_it),VEC_VV(1+loc_it));
173: /* update hessenberg matrix and do Gram-Schmidt - new direction is in
174: VEC_VV(1+loc_it)*/
175: (*fgmres->orthog)(ksp,loc_it);
177: /* new entry in hessenburg is the 2-norm of our new direction */
178: VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);
180: *HH(loc_it+1,loc_it) = tt;
181: *HES(loc_it+1,loc_it) = tt;
183: /* Happy Breakdown Check */
184: hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
185: /* RS(loc_it) contains the res_norm from the last iteration */
186: hapbnd = PetscMin(fgmres->haptol,hapbnd);
187: if (tt > hapbnd) {
188: /* scale new direction by its norm */
189: VecScale(VEC_VV(loc_it+1),1.0/tt);
190: } else {
191: /* This happens when the solution is exactly reached. */
192: /* So there is no new direction... */
193: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP to 0 */
194: hapend = PETSC_TRUE;
195: }
196: /* note that for FGMRES we could get HES(loc_it+1, loc_it) = 0 and the
197: current solution would not be exact if HES was singular. Note that
198: HH non-singular implies that HES is no singular, and HES is guaranteed
199: to be nonsingular when PREVECS are linearly independent and A is
200: nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
201: of HES). So we should really add a check to verify that HES is nonsingular.*/
204: /* Now apply rotations to new col of hessenberg (and right side of system),
205: calculate new rotation, and get new residual norm at the same time*/
206: KSPFGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
207: if (ksp->reason) break;
209: loc_it++;
210: fgmres->it = (loc_it-1); /* Add this here in case it has converged */
212: PetscObjectSAWsTakeAccess((PetscObject)ksp);
213: ksp->its++;
214: ksp->rnorm = res_norm;
215: PetscObjectSAWsGrantAccess((PetscObject)ksp);
217: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
219: /* Catch error in happy breakdown and signal convergence and break from loop */
220: if (hapend) {
221: if (!ksp->reason) {
222: if (ksp->errorifnotconverged) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"You reached the happy break down, but convergence was not indicated. Residual norm = %g",(double)res_norm);
223: else {
224: ksp->reason = KSP_DIVERGED_BREAKDOWN;
225: break;
226: }
227: }
228: }
229: }
230: /* END OF ITERATION LOOP */
231: KSPLogResidualHistory(ksp,res_norm);
233: /*
234: Monitor if we know that we will not return for a restart */
235: if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) {
236: KSPMonitor(ksp,ksp->its,res_norm);
237: }
239: if (itcount) *itcount = loc_it;
241: /*
242: Down here we have to solve for the "best" coefficients of the Krylov
243: columns, add the solution values together, and possibly unwind the
244: preconditioning from the solution
245: */
247: /* Form the solution (or the solution so far) */
248: /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
249: properly navigates */
251: KSPFGMRESBuildSoln(RS(0),ksp->vec_sol,ksp->vec_sol,ksp,loc_it-1);
252: return(0);
253: }
255: /*
256: KSPSolve_FGMRES - This routine applies the FGMRES method.
259: Input Parameter:
260: . ksp - the Krylov space object that was set to use fgmres
262: Output Parameter:
263: . outits - number of iterations used
265: */
267: PetscErrorCode KSPSolve_FGMRES(KSP ksp)268: {
270: PetscInt cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
271: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
272: PetscBool diagonalscale;
275: PCGetDiagonalScale(ksp->pc,&diagonalscale);
276: if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);
278: PetscObjectSAWsTakeAccess((PetscObject)ksp);
279: ksp->its = 0;
280: PetscObjectSAWsGrantAccess((PetscObject)ksp);
282: /* Compute the initial (NOT preconditioned) residual */
283: if (!ksp->guess_zero) {
284: KSPFGMRESResidual(ksp);
285: } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
286: VecCopy(ksp->vec_rhs,VEC_VV(0));
287: }
288: /* now the residual is in VEC_VV(0) - which is what
289: KSPFGMRESCycle expects... */
291: KSPFGMRESCycle(&cycle_its,ksp);
292: while (!ksp->reason) {
293: KSPFGMRESResidual(ksp);
294: if (ksp->its >= ksp->max_it) break;
295: KSPFGMRESCycle(&cycle_its,ksp);
296: }
297: /* mark lack of convergence */
298: if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
299: return(0);
300: }
302: extern PetscErrorCode KSPReset_FGMRES(KSP);
303: /*
305: KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.
307: */
308: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)309: {
313: KSPReset_FGMRES(ksp);
314: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",NULL);
315: KSPDestroy_GMRES(ksp);
316: return(0);
317: }
319: /*
320: KSPFGMRESBuildSoln - create the solution from the starting vector and the
321: current iterates.
323: Input parameters:
324: nrs - work area of size it + 1.
325: vguess - index of initial guess
326: vdest - index of result. Note that vguess may == vdest (replace
327: guess with the solution).
328: it - HH upper triangular part is a block of size (it+1) x (it+1)
330: This is an internal routine that knows about the FGMRES internals.
331: */
332: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs,Vec vguess,Vec vdest,KSP ksp,PetscInt it)333: {
334: PetscScalar tt;
336: PetscInt ii,k,j;
337: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
340: /* Solve for solution vector that minimizes the residual */
342: /* If it is < 0, no fgmres steps have been performed */
343: if (it < 0) {
344: VecCopy(vguess,vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
345: return(0);
346: }
348: /* so fgmres steps HAVE been performed */
350: /* solve the upper triangular system - RS is the right side and HH is
351: the upper triangular matrix - put soln in nrs */
352: if (*HH(it,it) != 0.0) {
353: nrs[it] = *RS(it) / *HH(it,it);
354: } else {
355: nrs[it] = 0.0;
356: }
357: for (ii=1; ii<=it; ii++) {
358: k = it - ii;
359: tt = *RS(k);
360: for (j=k+1; j<=it; j++) tt = tt - *HH(k,j) * nrs[j];
361: nrs[k] = tt / *HH(k,k);
362: }
364: /* Accumulate the correction to the soln of the preconditioned prob. in
365: VEC_TEMP - note that we use the preconditioned vectors */
366: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP components to 0 */
367: VecMAXPY(VEC_TEMP,it+1,nrs,&PREVEC(0));
369: /* put updated solution into vdest.*/
370: if (vdest != vguess) {
371: VecCopy(VEC_TEMP,vdest);
372: VecAXPY(vdest,1.0,vguess);
373: } else { /* replace guess with solution */
374: VecAXPY(vdest,1.0,VEC_TEMP);
375: }
376: return(0);
377: }
379: /*
381: KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
382: Return new residual.
384: input parameters:
386: . ksp - Krylov space object
387: . it - plane rotations are applied to the (it+1)th column of the
388: modified hessenberg (i.e. HH(:,it))
389: . hapend - PETSC_FALSE not happy breakdown ending.
391: output parameters:
392: . res - the new residual
394: */
395: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp,PetscInt it,PetscBool hapend,PetscReal *res)396: {
397: PetscScalar *hh,*cc,*ss,tt;
398: PetscInt j;
399: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
402: hh = HH(0,it); /* pointer to beginning of column to update - so
403: incrementing hh "steps down" the (it+1)th col of HH*/
404: cc = CC(0); /* beginning of cosine rotations */
405: ss = SS(0); /* beginning of sine rotations */
407: /* Apply all the previously computed plane rotations to the new column
408: of the Hessenberg matrix */
409: /* Note: this uses the rotation [conj(c) s ; -s c], c= cos(theta), s= sin(theta),
410: and some refs have [c s ; -conj(s) c] (don't be confused!) */
412: for (j=1; j<=it; j++) {
413: tt = *hh;
414: *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
415: hh++;
416: *hh = *cc++ * *hh - (*ss++ * tt);
417: /* hh, cc, and ss have all been incremented one by end of loop */
418: }
420: /*
421: compute the new plane rotation, and apply it to:
422: 1) the right-hand-side of the Hessenberg system (RS)
423: note: it affects RS(it) and RS(it+1)
424: 2) the new column of the Hessenberg matrix
425: note: it affects HH(it,it) which is currently pointed to
426: by hh and HH(it+1, it) (*(hh+1))
427: thus obtaining the updated value of the residual...
428: */
430: /* compute new plane rotation */
432: if (!hapend) {
433: tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
434: if (tt == 0.0) {
435: ksp->reason = KSP_DIVERGED_NULL;
436: return(0);
437: }
439: *cc = *hh / tt; /* new cosine value */
440: *ss = *(hh+1) / tt; /* new sine value */
442: /* apply to 1) and 2) */
443: *RS(it+1) = -(*ss * *RS(it));
444: *RS(it) = PetscConj(*cc) * *RS(it);
445: *hh = PetscConj(*cc) * *hh + *ss * *(hh+1);
447: /* residual is the last element (it+1) of right-hand side! */
448: *res = PetscAbsScalar(*RS(it+1));
450: } else { /* happy breakdown: HH(it+1, it) = 0, therfore we don't need to apply
451: another rotation matrix (so RH doesn't change). The new residual is
452: always the new sine term times the residual from last time (RS(it)),
453: but now the new sine rotation would be zero...so the residual should
454: be zero...so we will multiply "zero" by the last residual. This might
455: not be exactly what we want to do here -could just return "zero". */
457: *res = 0.0;
458: }
459: return(0);
460: }
462: /*
464: KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
465: VEC_VV(it), and more preconditioned work vectors, starting
466: from PREVEC(i).
468: */
469: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp,PetscInt it)470: {
471: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
472: PetscInt nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
473: PetscInt nalloc; /* number to allocate */
475: PetscInt k;
478: nalloc = fgmres->delta_allocate; /* number of vectors to allocate
479: in a single chunk */
481: /* Adjust the number to allocate to make sure that we don't exceed the
482: number of available slots (fgmres->vecs_allocated)*/
483: if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) {
484: nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
485: }
486: if (!nalloc) return(0);
488: fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */
490: /* work vectors */
491: KSPCreateVecs(ksp,nalloc,&fgmres->user_work[nwork],0,NULL);
492: PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
493: for (k=0; k < nalloc; k++) {
494: fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
495: }
496: /* specify size of chunk allocated */
497: fgmres->mwork_alloc[nwork] = nalloc;
499: /* preconditioned vectors */
500: KSPCreateVecs(ksp,nalloc,&fgmres->prevecs_user_work[nwork],0,NULL);
501: PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
502: for (k=0; k < nalloc; k++) {
503: fgmres->prevecs[it+k] = fgmres->prevecs_user_work[nwork][k];
504: }
506: /* increment the number of work vector chunks */
507: fgmres->nwork_alloc++;
508: return(0);
509: }
511: /*
513: KSPBuildSolution_FGMRES
515: Input Parameter:
516: . ksp - the Krylov space object
517: . ptr-
519: Output Parameter:
520: . result - the solution
522: Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
523: calls directly.
525: */
526: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)527: {
528: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
532: if (!ptr) {
533: if (!fgmres->sol_temp) {
534: VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
535: PetscLogObjectParent((PetscObject)ksp,(PetscObject)fgmres->sol_temp);
536: }
537: ptr = fgmres->sol_temp;
538: }
539: if (!fgmres->nrs) {
540: /* allocate the work area */
541: PetscMalloc1(fgmres->max_k,&fgmres->nrs);
542: PetscLogObjectMemory((PetscObject)ksp,fgmres->max_k*sizeof(PetscScalar));
543: }
545: KSPFGMRESBuildSoln(fgmres->nrs,ksp->vec_sol,ptr,ksp,fgmres->it);
546: if (result) *result = ptr;
547: return(0);
548: }
550: PetscErrorCode KSPSetFromOptions_FGMRES(PetscOptionItems *PetscOptionsObject,KSP ksp)551: {
553: PetscBool flg;
556: KSPSetFromOptions_GMRES(PetscOptionsObject,ksp);
557: PetscOptionsHead(PetscOptionsObject,"KSP flexible GMRES Options");
558: PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
559: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,0,0);}
560: PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp","vary the KSP based preconditioner","KSPFGMRESSetModifyPC",&flg);
561: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCKSP,0,0);}
562: PetscOptionsTail();
563: return(0);
564: }
566: typedef PetscErrorCode (*FCN1)(KSP,PetscInt,PetscInt,PetscReal,void*); /* force argument to next function to not be extern C*/
567: typedef PetscErrorCode (*FCN2)(void*);
569: static PetscErrorCode KSPFGMRESSetModifyPC_FGMRES(KSP ksp,FCN1 fcn,void *ctx,FCN2 d)570: {
573: ((KSP_FGMRES*)ksp->data)->modifypc = fcn;
574: ((KSP_FGMRES*)ksp->data)->modifydestroy = d;
575: ((KSP_FGMRES*)ksp->data)->modifyctx = ctx;
576: return(0);
577: }
580: PetscErrorCode KSPReset_FGMRES(KSP ksp)581: {
582: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
584: PetscInt i;
587: PetscFree (fgmres->prevecs);
588: if(fgmres->nwork_alloc>0){
589: i=0;
590: /* In the first allocation we allocated VEC_OFFSET fewer vectors in prevecs */
591: VecDestroyVecs(fgmres->mwork_alloc[i]-VEC_OFFSET,&fgmres->prevecs_user_work[i]);
592: for (i=1; i<fgmres->nwork_alloc; i++) {
593: VecDestroyVecs(fgmres->mwork_alloc[i],&fgmres->prevecs_user_work[i]);
594: }
595: }
596: PetscFree(fgmres->prevecs_user_work);
597: if (fgmres->modifydestroy) {
598: (*fgmres->modifydestroy)(fgmres->modifyctx);
599: }
600: KSPReset_GMRES(ksp);
601: return(0);
602: }
604: PetscErrorCode KSPGMRESSetRestart_FGMRES(KSP ksp,PetscInt max_k)605: {
606: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
610: if (max_k < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
611: if (!ksp->setupstage) {
612: gmres->max_k = max_k;
613: } else if (gmres->max_k != max_k) {
614: gmres->max_k = max_k;
615: ksp->setupstage = KSP_SETUP_NEW;
616: /* free the data structures, then create them again */
617: KSPReset_FGMRES(ksp);
618: }
619: return(0);
620: }
622: PetscErrorCode KSPGMRESGetRestart_FGMRES(KSP ksp,PetscInt *max_k)623: {
624: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
627: *max_k = gmres->max_k;
628: return(0);
629: }
631: /*MC
632: KSPFGMRES - Implements the Flexible Generalized Minimal Residual method.
633: developed by Saad with restart
636: Options Database Keys:
637: + -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
638: . -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
639: . -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
640: vectors are allocated as needed)
641: . -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
642: . -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
643: . -ksp_gmres_cgs_refinement_type <never,ifneeded,always> - determine if iterative refinement is used to increase the
644: stability of the classical Gram-Schmidt orthogonalization.
645: . -ksp_gmres_krylov_monitor - plot the Krylov space generated
646: . -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
647: - -ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()
649: Level: beginner
651: Notes:
652: See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations
653: Only right preconditioning is supported.
655: Notes:
656: The following options -ksp_type fgmres -pc_type ksp -ksp_ksp_type bcgs -ksp_view -ksp_pc_type jacobi make the preconditioner (or inner solver)
657: be bi-CG-stab with a preconditioner of Jacobi.
659: Developer Notes:
660: This object is subclassed off of KSPGMRES662: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
663: KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(),
664: KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(),
665: KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(), KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(),
666: KSPFGMRESModifyPCKSP()
668: M*/
670: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)671: {
672: KSP_FGMRES *fgmres;
676: PetscNewLog(ksp,&fgmres);
678: ksp->data = (void*)fgmres;
679: ksp->ops->buildsolution = KSPBuildSolution_FGMRES;
680: ksp->ops->setup = KSPSetUp_FGMRES;
681: ksp->ops->solve = KSPSolve_FGMRES;
682: ksp->ops->reset = KSPReset_FGMRES;
683: ksp->ops->destroy = KSPDestroy_FGMRES;
684: ksp->ops->view = KSPView_GMRES;
685: ksp->ops->setfromoptions = KSPSetFromOptions_FGMRES;
686: ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
687: ksp->ops->computeeigenvalues = KSPComputeEigenvalues_GMRES;
689: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,3);
690: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);
692: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",KSPGMRESSetPreAllocateVectors_GMRES);
693: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",KSPGMRESSetOrthogonalization_GMRES);
694: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetOrthogonalization_C",KSPGMRESGetOrthogonalization_GMRES);
695: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetRestart_C",KSPGMRESSetRestart_FGMRES);
696: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetRestart_C",KSPGMRESGetRestart_FGMRES);
697: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",KSPFGMRESSetModifyPC_FGMRES);
698: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetCGSRefinementType_C",KSPGMRESSetCGSRefinementType_GMRES);
699: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetCGSRefinementType_C",KSPGMRESGetCGSRefinementType_GMRES);
702: fgmres->haptol = 1.0e-30;
703: fgmres->q_preallocate = 0;
704: fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
705: fgmres->orthog = KSPGMRESClassicalGramSchmidtOrthogonalization;
706: fgmres->nrs = 0;
707: fgmres->sol_temp = 0;
708: fgmres->max_k = FGMRES_DEFAULT_MAXK;
709: fgmres->Rsvd = 0;
710: fgmres->orthogwork = 0;
711: fgmres->modifypc = KSPFGMRESModifyPCNoChange;
712: fgmres->modifyctx = NULL;
713: fgmres->modifydestroy = NULL;
714: fgmres->cgstype = KSP_GMRES_CGS_REFINE_NEVER;
715: return(0);
716: }