Actual source code: bcgs.c
petsc-3.15.0 2021-03-30
2: #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h>
4: PetscErrorCode KSPSetFromOptions_BCGS(PetscOptionItems *PetscOptionsObject,KSP ksp)
5: {
9: PetscOptionsHead(PetscOptionsObject,"KSP BCGS Options");
10: PetscOptionsTail();
11: return(0);
12: }
14: PetscErrorCode KSPSetUp_BCGS(KSP ksp)
15: {
19: KSPSetWorkVecs(ksp,6);
20: return(0);
21: }
23: PetscErrorCode KSPSolve_BCGS(KSP ksp)
24: {
26: PetscInt i;
27: PetscScalar rho,rhoold,alpha,beta,omega,omegaold,d1;
28: Vec X,B,V,P,R,RP,T,S;
29: PetscReal dp = 0.0,d2;
30: KSP_BCGS *bcgs = (KSP_BCGS*)ksp->data;
33: X = ksp->vec_sol;
34: B = ksp->vec_rhs;
35: R = ksp->work[0];
36: RP = ksp->work[1];
37: V = ksp->work[2];
38: T = ksp->work[3];
39: S = ksp->work[4];
40: P = ksp->work[5];
42: /* Compute initial preconditioned residual */
43: KSPInitialResidual(ksp,X,V,T,R,B);
45: /* with right preconditioning need to save initial guess to add to final solution */
46: if (ksp->pc_side == PC_RIGHT && !ksp->guess_zero) {
47: if (!bcgs->guess) {
48: VecDuplicate(X,&bcgs->guess);
49: }
50: VecCopy(X,bcgs->guess);
51: VecSet(X,0.0);
52: }
54: /* Test for nothing to do */
55: if (ksp->normtype != KSP_NORM_NONE) {
56: VecNorm(R,NORM_2,&dp);
57: KSPCheckNorm(ksp,dp);
58: }
59: PetscObjectSAWsTakeAccess((PetscObject)ksp);
60: ksp->its = 0;
61: ksp->rnorm = dp;
62: PetscObjectSAWsGrantAccess((PetscObject)ksp);
63: KSPLogResidualHistory(ksp,dp);
64: KSPMonitor(ksp,0,dp);
65: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
66: if (ksp->reason) {
67: if (bcgs->guess) {
68: VecAXPY(X,1.0,bcgs->guess);
69: }
70: return(0);
71: }
73: /* Make the initial Rp == R */
74: VecCopy(R,RP);
76: rhoold = 1.0;
77: alpha = 1.0;
78: omegaold = 1.0;
79: VecSet(P,0.0);
80: VecSet(V,0.0);
82: i=0;
83: do {
84: VecDot(R,RP,&rho); /* rho <- (r,rp) */
85: beta = (rho/rhoold) * (alpha/omegaold);
86: VecAXPBYPCZ(P,1.0,-omegaold*beta,beta,R,V); /* p <- r - omega * beta* v + beta * p */
87: KSP_PCApplyBAorAB(ksp,P,V,T); /* v <- K p */
88: VecDot(V,RP,&d1);
89: KSPCheckDot(ksp,d1);
90: if (d1 == 0.0) {
91: if (ksp->errorifnotconverged) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"KSPSolve has not converged due to Nan or Inf inner product");
92: else {
93: ksp->reason = KSP_DIVERGED_NANORINF;
94: break;
95: }
96: }
97: alpha = rho / d1; /* a <- rho / (v,rp) */
98: VecWAXPY(S,-alpha,V,R); /* s <- r - a v */
99: KSP_PCApplyBAorAB(ksp,S,T,R); /* t <- K s */
100: VecDotNorm2(S,T,&d1,&d2);
101: if (d2 == 0.0) {
102: /* t is 0. if s is 0, then alpha v == r, and hence alpha p
103: may be our solution. Give it a try? */
104: VecDot(S,S,&d1);
105: if (d1 != 0.0) {
106: ksp->reason = KSP_DIVERGED_BREAKDOWN;
107: break;
108: }
109: VecAXPY(X,alpha,P); /* x <- x + a p */
110: PetscObjectSAWsTakeAccess((PetscObject)ksp);
111: ksp->its++;
112: ksp->rnorm = 0.0;
113: ksp->reason = KSP_CONVERGED_RTOL;
114: PetscObjectSAWsGrantAccess((PetscObject)ksp);
115: KSPLogResidualHistory(ksp,dp);
116: KSPMonitor(ksp,i+1,0.0);
117: break;
118: }
119: omega = d1 / d2; /* w <- (t's) / (t't) */
120: VecAXPBYPCZ(X,alpha,omega,1.0,P,S); /* x <- alpha * p + omega * s + x */
121: VecWAXPY(R,-omega,T,S); /* r <- s - w t */
122: if (ksp->normtype != KSP_NORM_NONE && ksp->chknorm < i+2) {
123: VecNorm(R,NORM_2,&dp);
124: KSPCheckNorm(ksp,dp);
125: }
127: rhoold = rho;
128: omegaold = omega;
130: PetscObjectSAWsTakeAccess((PetscObject)ksp);
131: ksp->its++;
132: ksp->rnorm = dp;
133: PetscObjectSAWsGrantAccess((PetscObject)ksp);
134: KSPLogResidualHistory(ksp,dp);
135: KSPMonitor(ksp,i+1,dp);
136: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
137: if (ksp->reason) break;
138: if (rho == 0.0) {
139: ksp->reason = KSP_DIVERGED_BREAKDOWN;
140: break;
141: }
142: i++;
143: } while (i<ksp->max_it);
145: if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;
147: KSPUnwindPreconditioner(ksp,X,T);
148: if (bcgs->guess) {
149: VecAXPY(X,1.0,bcgs->guess);
150: }
151: return(0);
152: }
154: PetscErrorCode KSPBuildSolution_BCGS(KSP ksp,Vec v,Vec *V)
155: {
157: KSP_BCGS *bcgs = (KSP_BCGS*)ksp->data;
160: if (ksp->pc_side == PC_RIGHT) {
161: if (v) {
162: KSP_PCApply(ksp,ksp->vec_sol,v);
163: if (bcgs->guess) {
164: VecAXPY(v,1.0,bcgs->guess);
165: }
166: *V = v;
167: } else SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Not working with right preconditioner");
168: } else {
169: if (v) {
170: VecCopy(ksp->vec_sol,v); *V = v;
171: } else *V = ksp->vec_sol;
172: }
173: return(0);
174: }
176: PetscErrorCode KSPReset_BCGS(KSP ksp)
177: {
178: KSP_BCGS *cg = (KSP_BCGS*)ksp->data;
182: VecDestroy(&cg->guess);
183: return(0);
184: }
186: PetscErrorCode KSPDestroy_BCGS(KSP ksp)
187: {
191: KSPReset_BCGS(ksp);
192: KSPDestroyDefault(ksp);
193: return(0);
194: }
196: /*MC
197: KSPBCGS - Implements the BiCGStab (Stabilized version of BiConjugate Gradient) method.
199: Options Database Keys:
200: . see KSPSolve()
202: Level: beginner
204: Notes:
205: See KSPBCGSL for additional stabilization
206: Supports left and right preconditioning but not symmetric
208: References:
209: . 1. - van der Vorst, SIAM J. Sci. Stat. Comput., 1992.
211: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG, KSPBCGSL, KSPFBICG, KSPSetPCSide()
212: M*/
213: PETSC_EXTERN PetscErrorCode KSPCreate_BCGS(KSP ksp)
214: {
216: KSP_BCGS *bcgs;
219: PetscNewLog(ksp,&bcgs);
221: ksp->data = bcgs;
222: ksp->ops->setup = KSPSetUp_BCGS;
223: ksp->ops->solve = KSPSolve_BCGS;
224: ksp->ops->destroy = KSPDestroy_BCGS;
225: ksp->ops->reset = KSPReset_BCGS;
226: ksp->ops->buildsolution = KSPBuildSolution_BCGS;
227: ksp->ops->buildresidual = KSPBuildResidualDefault;
228: ksp->ops->setfromoptions = KSPSetFromOptions_BCGS;
230: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
231: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
232: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,1);
233: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);
234: return(0);
235: }