Actual source code: bcgsl.c
petsc-3.13.6 2020-09-29
1: /*
2: * Implementation of BiCGstab(L) the paper by D.R. Fokkema,
3: * "Enhanced implementation of BiCGStab(L) for solving linear systems
4: * of equations". This uses tricky delayed updating ideas to prevent
5: * round-off buildup.
6: *
7: * This has not been completely cleaned up into PETSc style.
8: *
9: * All the BLAS and LAPACK calls below should be removed and replaced with
10: * loops and the macros for block solvers converted from LINPACK; there is no way
11: * calls to BLAS/LAPACK make sense for size 2, 3, 4, etc.
12: */
13: #include <petsc/private/kspimpl.h>
14: #include <../src/ksp/ksp/impls/bcgsl/bcgslimpl.h>
15: #include <petscblaslapack.h>
18: static PetscErrorCode KSPSolve_BCGSL(KSP ksp)
19: {
20: KSP_BCGSL *bcgsl = (KSP_BCGSL*) ksp->data;
21: PetscScalar alpha, beta, omega, sigma;
22: PetscScalar rho0, rho1;
23: PetscReal kappa0, kappaA, kappa1;
24: PetscReal ghat;
25: PetscReal zeta, zeta0, rnmax_computed, rnmax_true, nrm0;
26: PetscBool bUpdateX;
27: PetscInt maxit;
28: PetscInt h, i, j, k, vi, ell;
29: PetscBLASInt ldMZ,bierr;
30: PetscScalar utb;
31: PetscReal max_s, pinv_tol;
35: /* set up temporary vectors */
36: vi = 0;
37: ell = bcgsl->ell;
38: bcgsl->vB = ksp->work[vi]; vi++;
39: bcgsl->vRt = ksp->work[vi]; vi++;
40: bcgsl->vTm = ksp->work[vi]; vi++;
41: bcgsl->vvR = ksp->work+vi; vi += ell+1;
42: bcgsl->vvU = ksp->work+vi; vi += ell+1;
43: bcgsl->vXr = ksp->work[vi]; vi++;
44: PetscBLASIntCast(ell+1,&ldMZ);
46: /* Prime the iterative solver */
47: KSPInitialResidual(ksp, VX, VTM, VB, VVR[0], ksp->vec_rhs);
48: VecNorm(VVR[0], NORM_2, &zeta0);
49: KSPCheckNorm(ksp,zeta0);
50: rnmax_computed = zeta0;
51: rnmax_true = zeta0;
53: (*ksp->converged)(ksp, 0, zeta0, &ksp->reason, ksp->cnvP);
54: if (ksp->reason) {
55: PetscObjectSAWsTakeAccess((PetscObject)ksp);
56: ksp->its = 0;
57: ksp->rnorm = zeta0;
58: PetscObjectSAWsGrantAccess((PetscObject)ksp);
59: return(0);
60: }
62: VecSet(VVU[0],0.0);
63: alpha = 0.;
64: rho0 = omega = 1;
66: if (bcgsl->delta>0.0) {
67: VecCopy(VX, VXR);
68: VecSet(VX,0.0);
69: VecCopy(VVR[0], VB);
70: } else {
71: VecCopy(ksp->vec_rhs, VB);
72: }
74: /* Life goes on */
75: VecCopy(VVR[0], VRT);
76: zeta = zeta0;
78: KSPGetTolerances(ksp, NULL, NULL, NULL, &maxit);
80: for (k=0; k<maxit; k += bcgsl->ell) {
81: ksp->its = k;
82: ksp->rnorm = zeta;
84: KSPLogResidualHistory(ksp, zeta);
85: KSPMonitor(ksp, ksp->its, zeta);
87: (*ksp->converged)(ksp, k, zeta, &ksp->reason, ksp->cnvP);
88: if (ksp->reason < 0) return(0);
89: else if (ksp->reason) break;
91: /* BiCG part */
92: rho0 = -omega*rho0;
93: nrm0 = zeta;
94: for (j=0; j<bcgsl->ell; j++) {
95: /* rho1 <- r_j' * r_tilde */
96: VecDot(VVR[j], VRT, &rho1);
97: KSPCheckDot(ksp,rho1);
98: if (rho1 == 0.0) {
99: ksp->reason = KSP_DIVERGED_BREAKDOWN_BICG;
100: return(0);
101: }
102: beta = alpha*(rho1/rho0);
103: rho0 = rho1;
104: for (i=0; i<=j; i++) {
105: /* u_i <- r_i - beta*u_i */
106: VecAYPX(VVU[i], -beta, VVR[i]);
107: }
108: /* u_{j+1} <- inv(K)*A*u_j */
109: KSP_PCApplyBAorAB(ksp, VVU[j], VVU[j+1], VTM);
111: VecDot(VVU[j+1], VRT, &sigma);
112: KSPCheckDot(ksp,sigma);
113: if (sigma == 0.0) {
114: ksp->reason = KSP_DIVERGED_BREAKDOWN_BICG;
115: return(0);
116: }
117: alpha = rho1/sigma;
119: /* x <- x + alpha*u_0 */
120: VecAXPY(VX, alpha, VVU[0]);
122: for (i=0; i<=j; i++) {
123: /* r_i <- r_i - alpha*u_{i+1} */
124: VecAXPY(VVR[i], -alpha, VVU[i+1]);
125: }
127: /* r_{j+1} <- inv(K)*A*r_j */
128: KSP_PCApplyBAorAB(ksp, VVR[j], VVR[j+1], VTM);
130: VecNorm(VVR[0], NORM_2, &nrm0);
131: KSPCheckNorm(ksp,nrm0);
132: if (bcgsl->delta>0.0) {
133: if (rnmax_computed<nrm0) rnmax_computed = nrm0;
134: if (rnmax_true<nrm0) rnmax_true = nrm0;
135: }
137: /* NEW: check for early exit */
138: (*ksp->converged)(ksp, k+j, nrm0, &ksp->reason, ksp->cnvP);
139: if (ksp->reason) {
140: PetscObjectSAWsTakeAccess((PetscObject)ksp);
142: ksp->its = k+j;
143: ksp->rnorm = nrm0;
145: PetscObjectSAWsGrantAccess((PetscObject)ksp);
146: if (ksp->reason < 0) return(0);
147: }
148: }
150: /* Polynomial part */
151: for (i = 0; i <= bcgsl->ell; ++i) {
152: VecMDot(VVR[i], i+1, VVR, &MZa[i*ldMZ]);
153: }
154: /* Symmetrize MZa */
155: for (i = 0; i <= bcgsl->ell; ++i) {
156: for (j = i+1; j <= bcgsl->ell; ++j) {
157: MZa[i*ldMZ+j] = MZa[j*ldMZ+i] = PetscConj(MZa[j*ldMZ+i]);
158: }
159: }
160: /* Copy MZa to MZb */
161: PetscArraycpy(MZb,MZa,ldMZ*ldMZ);
163: if (!bcgsl->bConvex || bcgsl->ell==1) {
164: PetscBLASInt ione = 1,bell;
165: PetscBLASIntCast(bcgsl->ell,&bell);
167: AY0c[0] = -1;
168: if (bcgsl->pinv) {
169: # if defined(PETSC_USE_COMPLEX)
170: PetscStackCallBLAS("LAPACKgesvd",LAPACKgesvd_("A","A",&bell,&bell,&MZa[1+ldMZ],&ldMZ,bcgsl->s,bcgsl->u,&bell,bcgsl->v,&bell,bcgsl->work,&bcgsl->lwork,bcgsl->realwork,&bierr));
171: # else
172: PetscStackCallBLAS("LAPACKgesvd",LAPACKgesvd_("A","A",&bell,&bell,&MZa[1+ldMZ],&ldMZ,bcgsl->s,bcgsl->u,&bell,bcgsl->v,&bell,bcgsl->work,&bcgsl->lwork,&bierr));
173: # endif
174: if (bierr!=0) {
175: ksp->reason = KSP_DIVERGED_BREAKDOWN;
176: return(0);
177: }
178: /* Apply pseudo-inverse */
179: max_s = bcgsl->s[0];
180: for (i=1; i<bell; i++) {
181: if (bcgsl->s[i] > max_s) {
182: max_s = bcgsl->s[i];
183: }
184: }
185: /* tolerance is hardwired to bell*max(s)*PETSC_MACHINE_EPSILON */
186: pinv_tol = bell*max_s*PETSC_MACHINE_EPSILON;
187: PetscArrayzero(&AY0c[1],bell);
188: for (i=0; i<bell; i++) {
189: if (bcgsl->s[i] >= pinv_tol) {
190: utb=0.;
191: for (j=0; j<bell; j++) {
192: utb += MZb[1+j]*bcgsl->u[i*bell+j];
193: }
195: for (j=0; j<bell; j++) {
196: AY0c[1+j] += utb/bcgsl->s[i]*bcgsl->v[j*bell+i];
197: }
198: }
199: }
200: } else {
201: PetscStackCallBLAS("LAPACKpotrf",LAPACKpotrf_("Lower", &bell, &MZa[1+ldMZ], &ldMZ, &bierr));
202: if (bierr!=0) {
203: ksp->reason = KSP_DIVERGED_BREAKDOWN;
204: return(0);
205: }
206: PetscArraycpy(&AY0c[1],&MZb[1],bcgsl->ell);
207: PetscStackCallBLAS("LAPACKpotrs",LAPACKpotrs_("Lower", &bell, &ione, &MZa[1+ldMZ], &ldMZ, &AY0c[1], &ldMZ, &bierr));
208: }
209: } else {
210: PetscBLASInt ione = 1;
211: PetscScalar aone = 1.0, azero = 0.0;
212: PetscBLASInt neqs;
213: PetscBLASIntCast(bcgsl->ell-1,&neqs);
215: PetscStackCallBLAS("LAPACKpotrf",LAPACKpotrf_("Lower", &neqs, &MZa[1+ldMZ], &ldMZ, &bierr));
216: if (bierr!=0) {
217: ksp->reason = KSP_DIVERGED_BREAKDOWN;
218: return(0);
219: }
220: PetscArraycpy(&AY0c[1],&MZb[1],bcgsl->ell-1);
221: PetscStackCallBLAS("LAPACKpotrs",LAPACKpotrs_("Lower", &neqs, &ione, &MZa[1+ldMZ], &ldMZ, &AY0c[1], &ldMZ, &bierr));
222: AY0c[0] = -1;
223: AY0c[bcgsl->ell] = 0.;
225: PetscArraycpy(&AYlc[1],&MZb[1+ldMZ*(bcgsl->ell)],bcgsl->ell-1);
226: PetscStackCallBLAS("LAPACKpotrs",LAPACKpotrs_("Lower", &neqs, &ione, &MZa[1+ldMZ], &ldMZ, &AYlc[1], &ldMZ, &bierr));
228: AYlc[0] = 0.;
229: AYlc[bcgsl->ell] = -1;
231: PetscStackCallBLAS("BLASgemv",BLASgemv_("NoTr", &ldMZ, &ldMZ, &aone, MZb, &ldMZ, AY0c, &ione, &azero, AYtc, &ione));
233: kappa0 = PetscRealPart(BLASdot_(&ldMZ, AY0c, &ione, AYtc, &ione));
235: /* round-off can cause negative kappa's */
236: if (kappa0<0) kappa0 = -kappa0;
237: kappa0 = PetscSqrtReal(kappa0);
239: kappaA = PetscRealPart(BLASdot_(&ldMZ, AYlc, &ione, AYtc, &ione));
241: PetscStackCallBLAS("BLASgemv",BLASgemv_("noTr", &ldMZ, &ldMZ, &aone, MZb, &ldMZ, AYlc, &ione, &azero, AYtc, &ione));
243: kappa1 = PetscRealPart(BLASdot_(&ldMZ, AYlc, &ione, AYtc, &ione));
245: if (kappa1<0) kappa1 = -kappa1;
246: kappa1 = PetscSqrtReal(kappa1);
248: if (kappa0!=0.0 && kappa1!=0.0) {
249: if (kappaA<0.7*kappa0*kappa1) {
250: ghat = (kappaA<0.0) ? -0.7*kappa0/kappa1 : 0.7*kappa0/kappa1;
251: } else {
252: ghat = kappaA/(kappa1*kappa1);
253: }
254: for (i=0; i<=bcgsl->ell; i++) {
255: AY0c[i] = AY0c[i] - ghat* AYlc[i];
256: }
257: }
258: }
260: omega = AY0c[bcgsl->ell];
261: for (h=bcgsl->ell; h>0 && omega==0.0; h--) omega = AY0c[h];
262: if (omega==0.0) {
263: ksp->reason = KSP_DIVERGED_BREAKDOWN;
264: return(0);
265: }
268: VecMAXPY(VX, bcgsl->ell,AY0c+1, VVR);
269: for (i=1; i<=bcgsl->ell; i++) AY0c[i] *= -1.0;
270: VecMAXPY(VVU[0], bcgsl->ell,AY0c+1, VVU+1);
271: VecMAXPY(VVR[0], bcgsl->ell,AY0c+1, VVR+1);
272: for (i=1; i<=bcgsl->ell; i++) AY0c[i] *= -1.0;
273: VecNorm(VVR[0], NORM_2, &zeta);
274: KSPCheckNorm(ksp,zeta);
276: /* Accurate Update */
277: if (bcgsl->delta>0.0) {
278: if (rnmax_computed<zeta) rnmax_computed = zeta;
279: if (rnmax_true<zeta) rnmax_true = zeta;
281: bUpdateX = (PetscBool) (zeta<bcgsl->delta*zeta0 && zeta0<=rnmax_computed);
282: if ((zeta<bcgsl->delta*rnmax_true && zeta0<=rnmax_true) || bUpdateX) {
283: /* r0 <- b-inv(K)*A*X */
284: KSP_PCApplyBAorAB(ksp, VX, VVR[0], VTM);
285: VecAYPX(VVR[0], -1.0, VB);
286: rnmax_true = zeta;
288: if (bUpdateX) {
289: VecAXPY(VXR,1.0,VX);
290: VecSet(VX,0.0);
291: VecCopy(VVR[0], VB);
292: rnmax_computed = zeta;
293: }
294: }
295: }
296: }
297: if (bcgsl->delta>0.0) {
298: VecAXPY(VX,1.0,VXR);
299: }
301: (*ksp->converged)(ksp, k, zeta, &ksp->reason, ksp->cnvP);
302: if (!ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
303: return(0);
304: }
306: /*@
307: KSPBCGSLSetXRes - Sets the parameter governing when
308: exact residuals will be used instead of computed residuals.
310: Logically Collective on ksp
312: Input Parameters:
313: + ksp - iterative context obtained from KSPCreate
314: - delta - computed residuals are used alone when delta is not positive
316: Options Database Keys:
318: . -ksp_bcgsl_xres delta
320: Level: intermediate
322: .seealso: KSPBCGSLSetEll(), KSPBCGSLSetPol(), KSP
323: @*/
324: PetscErrorCode KSPBCGSLSetXRes(KSP ksp, PetscReal delta)
325: {
326: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
331: if (ksp->setupstage) {
332: if ((delta<=0 && bcgsl->delta>0) || (delta>0 && bcgsl->delta<=0)) {
333: VecDestroyVecs(ksp->nwork,&ksp->work);
334: PetscFree5(AY0c,AYlc,AYtc,MZa,MZb);
335: PetscFree4(bcgsl->work,bcgsl->s,bcgsl->u,bcgsl->v);
336: ksp->setupstage = KSP_SETUP_NEW;
337: }
338: }
339: bcgsl->delta = delta;
340: return(0);
341: }
343: /*@
344: KSPBCGSLSetUsePseudoinverse - Use pseudoinverse (via SVD) to solve polynomial part of update
346: Logically Collective on ksp
348: Input Parameters:
349: + ksp - iterative context obtained from KSPCreate
350: - use_pinv - set to PETSC_TRUE when using pseudoinverse
352: Options Database Keys:
354: . -ksp_bcgsl_pinv - use pseudoinverse
356: Level: intermediate
358: .seealso: KSPBCGSLSetEll(), KSP
359: @*/
360: PetscErrorCode KSPBCGSLSetUsePseudoinverse(KSP ksp,PetscBool use_pinv)
361: {
362: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
365: bcgsl->pinv = use_pinv;
366: return(0);
367: }
369: /*@
370: KSPBCGSLSetPol - Sets the type of polynomial part will
371: be used in the BiCGSTab(L) solver.
373: Logically Collective on ksp
375: Input Parameters:
376: + ksp - iterative context obtained from KSPCreate
377: - uMROR - set to PETSC_TRUE when the polynomial is a convex combination of an MR and an OR step.
379: Options Database Keys:
381: + -ksp_bcgsl_cxpoly - use enhanced polynomial
382: - -ksp_bcgsl_mrpoly - use standard polynomial
384: Level: intermediate
386: .seealso: KSP, KSPBCGSL, KSPCreate(), KSPSetType()
387: @*/
388: PetscErrorCode KSPBCGSLSetPol(KSP ksp, PetscBool uMROR)
389: {
390: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
396: if (!ksp->setupstage) bcgsl->bConvex = uMROR;
397: else if (bcgsl->bConvex != uMROR) {
398: /* free the data structures,
399: then create them again
400: */
401: VecDestroyVecs(ksp->nwork,&ksp->work);
402: PetscFree5(AY0c,AYlc,AYtc,MZa,MZb);
403: PetscFree4(bcgsl->work,bcgsl->s,bcgsl->u,bcgsl->v);
405: bcgsl->bConvex = uMROR;
406: ksp->setupstage = KSP_SETUP_NEW;
407: }
408: return(0);
409: }
411: /*@
412: KSPBCGSLSetEll - Sets the number of search directions in BiCGStab(L).
414: Logically Collective on ksp
416: Input Parameters:
417: + ksp - iterative context obtained from KSPCreate
418: - ell - number of search directions
420: Options Database Keys:
422: . -ksp_bcgsl_ell ell
424: Level: intermediate
426: Notes:
427: For large ell it is common for the polynomial update problem to become singular (due to happy breakdown for smallish
428: test problems, but also for larger problems). Consequently, by default, the system is solved by pseudoinverse, which
429: allows the iteration to complete successfully. See KSPBCGSLSetUsePseudoinverse() to switch to a conventional solve.
431: .seealso: KSPBCGSLSetUsePseudoinverse(), KSP, KSPBCGSL
432: @*/
433: PetscErrorCode KSPBCGSLSetEll(KSP ksp, PetscInt ell)
434: {
435: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
439: if (ell < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE, "KSPBCGSLSetEll: second argument must be positive");
442: if (!ksp->setupstage) bcgsl->ell = ell;
443: else if (bcgsl->ell != ell) {
444: /* free the data structures, then create them again */
445: VecDestroyVecs(ksp->nwork,&ksp->work);
446: PetscFree5(AY0c,AYlc,AYtc,MZa,MZb);
447: PetscFree4(bcgsl->work,bcgsl->s,bcgsl->u,bcgsl->v);
449: bcgsl->ell = ell;
450: ksp->setupstage = KSP_SETUP_NEW;
451: }
452: return(0);
453: }
455: PetscErrorCode KSPView_BCGSL(KSP ksp, PetscViewer viewer)
456: {
457: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
459: PetscBool isascii;
462: PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii);
464: if (isascii) {
465: PetscViewerASCIIPrintf(viewer, " Ell = %D\n", bcgsl->ell);
466: PetscViewerASCIIPrintf(viewer, " Delta = %lg\n", bcgsl->delta);
467: }
468: return(0);
469: }
471: PetscErrorCode KSPSetFromOptions_BCGSL(PetscOptionItems *PetscOptionsObject,KSP ksp)
472: {
473: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
475: PetscInt this_ell;
476: PetscReal delta;
477: PetscBool flga = PETSC_FALSE, flg;
480: /* PetscOptionsBegin/End are called in KSPSetFromOptions. They
481: don't need to be called here.
482: */
483: PetscOptionsHead(PetscOptionsObject,"KSP BiCGStab(L) Options");
485: /* Set number of search directions */
486: PetscOptionsInt("-ksp_bcgsl_ell","Number of Krylov search directions","KSPBCGSLSetEll",bcgsl->ell,&this_ell,&flg);
487: if (flg) {
488: KSPBCGSLSetEll(ksp, this_ell);
489: }
491: /* Set polynomial type */
492: PetscOptionsBool("-ksp_bcgsl_cxpoly", "Polynomial part of BiCGStabL is MinRes + OR", "KSPBCGSLSetPol", flga,&flga,NULL);
493: if (flga) {
494: KSPBCGSLSetPol(ksp, PETSC_TRUE);
495: } else {
496: flg = PETSC_FALSE;
497: PetscOptionsBool("-ksp_bcgsl_mrpoly", "Polynomial part of BiCGStabL is MinRes", "KSPBCGSLSetPol", flg,&flg,NULL);
498: KSPBCGSLSetPol(ksp, PETSC_FALSE);
499: }
501: /* Will computed residual be refreshed? */
502: PetscOptionsReal("-ksp_bcgsl_xres", "Threshold used to decide when to refresh computed residuals", "KSPBCGSLSetXRes", bcgsl->delta, &delta, &flg);
503: if (flg) {
504: KSPBCGSLSetXRes(ksp, delta);
505: }
507: /* Use pseudoinverse? */
508: flg = bcgsl->pinv;
509: PetscOptionsBool("-ksp_bcgsl_pinv", "Polynomial correction via pseudoinverse", "KSPBCGSLSetUsePseudoinverse",flg,&flg,NULL);
510: KSPBCGSLSetUsePseudoinverse(ksp,flg);
511: PetscOptionsTail();
512: return(0);
513: }
515: PetscErrorCode KSPSetUp_BCGSL(KSP ksp)
516: {
517: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
518: PetscInt ell = bcgsl->ell,ldMZ = ell+1;
522: KSPSetWorkVecs(ksp, 6+2*ell);
523: PetscMalloc5(ldMZ,&AY0c,ldMZ,&AYlc,ldMZ,&AYtc,ldMZ*ldMZ,&MZa,ldMZ*ldMZ,&MZb);
524: PetscBLASIntCast(5*ell,&bcgsl->lwork);
525: PetscMalloc5(bcgsl->lwork,&bcgsl->work,ell,&bcgsl->s,ell*ell,&bcgsl->u,ell*ell,&bcgsl->v,5*ell,&bcgsl->realwork);
526: return(0);
527: }
529: PetscErrorCode KSPReset_BCGSL(KSP ksp)
530: {
531: KSP_BCGSL *bcgsl = (KSP_BCGSL*)ksp->data;
535: VecDestroyVecs(ksp->nwork,&ksp->work);
536: PetscFree5(AY0c,AYlc,AYtc,MZa,MZb);
537: PetscFree5(bcgsl->work,bcgsl->s,bcgsl->u,bcgsl->v,bcgsl->realwork);
538: return(0);
539: }
541: PetscErrorCode KSPDestroy_BCGSL(KSP ksp)
542: {
546: KSPReset_BCGSL(ksp);
547: KSPDestroyDefault(ksp);
548: return(0);
549: }
551: /*MC
552: KSPBCGSL - Implements a slight variant of the Enhanced
553: BiCGStab(L) algorithm in (3) and (2). The variation
554: concerns cases when either kappa0**2 or kappa1**2 is
555: negative due to round-off. Kappa0 has also been pulled
556: out of the denominator in the formula for ghat.
558: References:
559: + 1. - G.L.G. Sleijpen, H.A. van der Vorst, "An overview of
560: approaches for the stable computation of hybrid BiCG
561: methods", Applied Numerical Mathematics: Transactions
562: f IMACS, 19(3), 1996.
563: . 2. - G.L.G. Sleijpen, H.A. van der Vorst, D.R. Fokkema,
564: "BiCGStab(L) and other hybrid BiCG methods",
565: Numerical Algorithms, 7, 1994.
566: - 3. - D.R. Fokkema, "Enhanced implementation of BiCGStab(L)
567: for solving linear systems of equations", preprint
568: from www.citeseer.com.
570: Contributed by: Joel M. Malard, email jm.malard@pnl.gov
572: Options Database Keys:
573: + -ksp_bcgsl_ell <ell> Number of Krylov search directions, defaults to 2 -- KSPBCGSLSetEll()
574: . -ksp_bcgsl_cxpol - Use a convex function of the MinRes and OR polynomials after the BiCG step instead of default MinRes -- KSPBCGSLSetPol()
575: . -ksp_bcgsl_mrpoly - Use the default MinRes polynomial after the BiCG step -- KSPBCGSLSetPol()
576: . -ksp_bcgsl_xres <res> Threshold used to decide when to refresh computed residuals -- KSPBCGSLSetXRes()
577: - -ksp_bcgsl_pinv <true/false> - (de)activate use of pseudoinverse -- KSPBCGSLSetUsePseudoinverse()
579: Level: beginner
581: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPFGMRES, KSPBCGS, KSPSetPCSide(), KSPBCGSLSetEll(), KSPBCGSLSetXRes()
583: M*/
584: PETSC_EXTERN PetscErrorCode KSPCreate_BCGSL(KSP ksp)
585: {
587: KSP_BCGSL *bcgsl;
590: /* allocate BiCGStab(L) context */
591: PetscNewLog(ksp,&bcgsl);
592: ksp->data = (void*)bcgsl;
594: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
595: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
597: ksp->ops->setup = KSPSetUp_BCGSL;
598: ksp->ops->solve = KSPSolve_BCGSL;
599: ksp->ops->reset = KSPReset_BCGSL;
600: ksp->ops->destroy = KSPDestroy_BCGSL;
601: ksp->ops->buildsolution = KSPBuildSolutionDefault;
602: ksp->ops->buildresidual = KSPBuildResidualDefault;
603: ksp->ops->setfromoptions = KSPSetFromOptions_BCGSL;
604: ksp->ops->view = KSPView_BCGSL;
606: /* Let the user redefine the number of directions vectors */
607: bcgsl->ell = 2;
609: /*Choose between a single MR step or an averaged MR/OR */
610: bcgsl->bConvex = PETSC_FALSE;
612: bcgsl->pinv = PETSC_TRUE; /* Use the reliable method by default */
614: /* Set the threshold for when exact residuals will be used */
615: bcgsl->delta = 0.0;
616: return(0);
617: }