Actual source code: bcgs.c
petsc-3.6.4 2016-04-12
2: #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h> /*I "petscksp.h" I*/
6: PetscErrorCode KSPSetFromOptions_BCGS(PetscOptions *PetscOptionsObject,KSP ksp)
7: {
11: PetscOptionsHead(PetscOptionsObject,"KSP BCGS Options");
12: PetscOptionsTail();
13: return(0);
14: }
18: PetscErrorCode KSPSetUp_BCGS(KSP ksp)
19: {
23: KSPSetWorkVecs(ksp,6);
24: return(0);
25: }
30: PetscErrorCode KSPSolve_BCGS(KSP ksp)
31: {
33: PetscInt i;
34: PetscScalar rho,rhoold,alpha,beta,omega,omegaold,d1;
35: Vec X,B,V,P,R,RP,T,S;
36: PetscReal dp = 0.0,d2;
37: KSP_BCGS *bcgs = (KSP_BCGS*)ksp->data;
40: X = ksp->vec_sol;
41: B = ksp->vec_rhs;
42: R = ksp->work[0];
43: RP = ksp->work[1];
44: V = ksp->work[2];
45: T = ksp->work[3];
46: S = ksp->work[4];
47: P = ksp->work[5];
49: /* Compute initial preconditioned residual */
50: KSPInitialResidual(ksp,X,V,T,R,B);
52: /* with right preconditioning need to save initial guess to add to final solution */
53: if (ksp->pc_side == PC_RIGHT && !ksp->guess_zero) {
54: if (!bcgs->guess) {
55: VecDuplicate(X,&bcgs->guess);
56: }
57: VecCopy(X,bcgs->guess);
58: VecSet(X,0.0);
59: }
61: /* Test for nothing to do */
62: if (ksp->normtype != KSP_NORM_NONE) {
63: VecNorm(R,NORM_2,&dp);
64: }
65: PetscObjectSAWsTakeAccess((PetscObject)ksp);
66: ksp->its = 0;
67: ksp->rnorm = dp;
68: PetscObjectSAWsGrantAccess((PetscObject)ksp);
69: KSPLogResidualHistory(ksp,dp);
70: KSPMonitor(ksp,0,dp);
71: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
72: if (ksp->reason) return(0);
74: /* Make the initial Rp == R */
75: VecCopy(R,RP);
77: rhoold = 1.0;
78: alpha = 1.0;
79: omegaold = 1.0;
80: VecSet(P,0.0);
81: VecSet(V,0.0);
83: i=0;
84: do {
85: VecDot(R,RP,&rho); /* rho <- (r,rp) */
86: beta = (rho/rhoold) * (alpha/omegaold);
87: VecAXPBYPCZ(P,1.0,-omegaold*beta,beta,R,V); /* p <- r - omega * beta* v + beta * p */
88: KSP_PCApplyBAorAB(ksp,P,V,T); /* v <- K p */
89: VecDot(V,RP,&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: }
126: rhoold = rho;
127: omegaold = omega;
129: PetscObjectSAWsTakeAccess((PetscObject)ksp);
130: ksp->its++;
131: ksp->rnorm = dp;
132: PetscObjectSAWsGrantAccess((PetscObject)ksp);
133: KSPLogResidualHistory(ksp,dp);
134: KSPMonitor(ksp,i+1,dp);
135: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
136: if (ksp->reason) break;
137: if (rho == 0.0) {
138: ksp->reason = KSP_DIVERGED_BREAKDOWN;
139: break;
140: }
141: i++;
142: } while (i<ksp->max_it);
144: if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;
146: KSPUnwindPreconditioner(ksp,X,T);
147: if (bcgs->guess) {
148: VecAXPY(X,1.0,bcgs->guess);
149: }
150: return(0);
151: }
155: PetscErrorCode KSPBuildSolution_BCGS(KSP ksp,Vec v,Vec *V)
156: {
158: KSP_BCGS *bcgs = (KSP_BCGS*)ksp->data;
161: if (ksp->pc_side == PC_RIGHT) {
162: if (v) {
163: KSP_PCApply(ksp,ksp->vec_sol,v);
164: if (bcgs->guess) {
165: VecAXPY(v,1.0,bcgs->guess);
166: }
167: *V = v;
168: } else SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Not working with right preconditioner");
169: } else {
170: if (v) {
171: VecCopy(ksp->vec_sol,v); *V = v;
172: } else *V = ksp->vec_sol;
173: }
174: return(0);
175: }
179: PetscErrorCode KSPReset_BCGS(KSP ksp)
180: {
181: KSP_BCGS *cg = (KSP_BCGS*)ksp->data;
185: VecDestroy(&cg->guess);
186: return(0);
187: }
191: PetscErrorCode KSPDestroy_BCGS(KSP ksp)
192: {
196: KSPReset_BCGS(ksp);
197: KSPDestroyDefault(ksp);
198: return(0);
199: }
201: /*MC
202: KSPBCGS - Implements the BiCGStab (Stabilized version of BiConjugate Gradient Squared) method.
204: Options Database Keys:
205: . see KSPSolve()
207: Level: beginner
209: Notes: See KSPBCGSL for additional stabilization
210: Supports left and right preconditioning but not symmetric
212: References: van der Vorst, SIAM J. Sci. Stat. Comput., 1992.
214: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG, KSPBCGSL, KSPFBICG, KSPSetPCSide()
215: M*/
218: PETSC_EXTERN PetscErrorCode KSPCreate_BCGS(KSP ksp)
219: {
221: KSP_BCGS *bcgs;
224: PetscNewLog(ksp,&bcgs);
226: ksp->data = bcgs;
227: ksp->ops->setup = KSPSetUp_BCGS;
228: ksp->ops->solve = KSPSolve_BCGS;
229: ksp->ops->destroy = KSPDestroy_BCGS;
230: ksp->ops->reset = KSPReset_BCGS;
231: ksp->ops->buildsolution = KSPBuildSolution_BCGS;
232: ksp->ops->buildresidual = KSPBuildResidualDefault;
233: ksp->ops->setfromoptions = KSPSetFromOptions_BCGS;
235: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
236: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
237: return(0);
238: }