Actual source code: bcgs.c
2: #include src/ksp/ksp/kspimpl.h
6: static PetscErrorCode KSPSetUp_BCGS(KSP ksp)
7: {
11: if (ksp->pc_side == PC_SYMMETRIC) {
12: SETERRQ(PETSC_ERR_SUP,"no symmetric preconditioning for KSPBCGS");
13: }
14: KSPDefaultGetWork(ksp,6);
15: return(0);
16: }
20: static PetscErrorCode KSPSolve_BCGS(KSP ksp)
21: {
23: PetscInt i;
24: PetscScalar rho,rhoold,alpha,beta,omega,omegaold,d1,d2,zero = 0.0,tmp;
25: Vec X,B,V,P,R,RP,T,S;
26: PetscReal dp = 0.0;
30: X = ksp->vec_sol;
31: B = ksp->vec_rhs;
32: R = ksp->work[0];
33: RP = ksp->work[1];
34: V = ksp->work[2];
35: T = ksp->work[3];
36: S = ksp->work[4];
37: P = ksp->work[5];
39: /* Compute initial preconditioned residual */
40: KSPInitialResidual(ksp,X,V,T,R,B);
42: /* Test for nothing to do */
43: if (ksp->normtype != KSP_NO_NORM) {
44: VecNorm(R,NORM_2,&dp);
45: }
46: PetscObjectTakeAccess(ksp);
47: ksp->its = 0;
48: ksp->rnorm = dp;
49: PetscObjectGrantAccess(ksp);
50: KSPLogResidualHistory(ksp,dp);
51: KSPMonitor(ksp,0,dp);
52: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
53: if (ksp->reason) return(0);
55: /* Make the initial Rp == R */
56: VecCopy(R,RP);
58: rhoold = 1.0;
59: alpha = 1.0;
60: omegaold = 1.0;
61: VecSet(&zero,P);
62: VecSet(&zero,V);
64: i=0;
65: do {
66: VecDot(R,RP,&rho); /* rho <- (r,rp) */
67: if (rho == 0.0) {
68: ksp->reason = KSP_DIVERGED_BREAKDOWN;
69: break;
70: }
71: beta = (rho/rhoold) * (alpha/omegaold);
72: tmp = -omegaold; VecAXPY(&tmp,V,P); /* p <- p - w v */
73: VecAYPX(&beta,R,P); /* p <- r + p beta */
74: KSP_PCApplyBAorAB(ksp,P,V,T); /* v <- K p */
75: VecDot(V,RP,&d1);
76: alpha = rho / d1; tmp = -alpha; /* a <- rho / (v,rp) */
77: VecWAXPY(&tmp,V,R,S); /* s <- r - a v */
78: KSP_PCApplyBAorAB(ksp,S,T,R);/* t <- K s */
79: VecDot(S,T,&d1);
80: VecDot(T,T,&d2);
81: if (d2 == 0.0) {
82: /* t is 0. if s is 0, then alpha v == r, and hence alpha p
83: may be our solution. Give it a try? */
84: VecDot(S,S,&d1);
85: if (d1 == 0.0) {
86: ksp->reason = KSP_DIVERGED_BREAKDOWN;
87: break;
88: }
89: VecAXPY(&alpha,P,X); /* x <- x + a p */
90: PetscObjectTakeAccess(ksp);
91: ksp->its++;
92: ksp->rnorm = 0.0;
93: ksp->reason = KSP_CONVERGED_RTOL;
94: PetscObjectGrantAccess(ksp);
95: KSPLogResidualHistory(ksp,dp);
96: KSPMonitor(ksp,i+1,0.0);
97: break;
98: }
99: omega = d1 / d2; /* w <- (t's) / (t't) */
100: VecAXPY(&alpha,P,X); /* x <- x + a p */
101: VecAXPY(&omega,S,X); /* x <- x + w s */
102: tmp = -omega;
103: VecWAXPY(&tmp,T,S,R); /* r <- s - w t */
104: if (ksp->normtype != KSP_NO_NORM) {
105: VecNorm(R,NORM_2,&dp);
106: }
108: rhoold = rho;
109: omegaold = omega;
111: PetscObjectTakeAccess(ksp);
112: ksp->its++;
113: ksp->rnorm = dp;
114: PetscObjectGrantAccess(ksp);
115: KSPLogResidualHistory(ksp,dp);
116: KSPMonitor(ksp,i+1,dp);
117: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
118: if (ksp->reason) break;
119: i++;
120: } while (i<ksp->max_it);
122: if (i >= ksp->max_it) {
123: ksp->reason = KSP_DIVERGED_ITS;
124: }
126: KSPUnwindPreconditioner(ksp,X,T);
127: return(0);
128: }
130: /*MC
131: KSPBCGS - Implements the BiCGStab (Stabilized version of BiConjugate Gradient Squared) method.
133: Options Database Keys:
134: . see KSPSolve()
136: Level: beginner
138: Notes: Reference: van der Vorst, SIAM J. Sci. Stat. Comput., 1992.
140: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG
141: M*/
145: PetscErrorCode KSPCreate_BCGS(KSP ksp)
146: {
148: ksp->data = (void*)0;
149: ksp->pc_side = PC_LEFT;
150: ksp->ops->setup = KSPSetUp_BCGS;
151: ksp->ops->solve = KSPSolve_BCGS;
152: ksp->ops->destroy = KSPDefaultDestroy;
153: ksp->ops->buildsolution = KSPDefaultBuildSolution;
154: ksp->ops->buildresidual = KSPDefaultBuildResidual;
155: ksp->ops->setfromoptions = 0;
156: ksp->ops->view = 0;
157: return(0);
158: }