Actual source code: bcgs.c
petsc-3.7.5 2017-01-01
2: #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h> /*I "petscksp.h" I*/
6: PetscErrorCode KSPSetFromOptions_BCGS(PetscOptionItems *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) {
73: if (bcgs->guess) {
74: VecAXPY(X,1.0,bcgs->guess);
75: }
76: return(0);
77: }
79: /* Make the initial Rp == R */
80: VecCopy(R,RP);
82: rhoold = 1.0;
83: alpha = 1.0;
84: omegaold = 1.0;
85: VecSet(P,0.0);
86: VecSet(V,0.0);
88: i=0;
89: do {
90: VecDot(R,RP,&rho); /* rho <- (r,rp) */
91: beta = (rho/rhoold) * (alpha/omegaold);
92: VecAXPBYPCZ(P,1.0,-omegaold*beta,beta,R,V); /* p <- r - omega * beta* v + beta * p */
93: KSP_PCApplyBAorAB(ksp,P,V,T); /* v <- K p */
94: VecDot(V,RP,&d1);
95: if (d1 == 0.0) {
96: if (ksp->errorifnotconverged) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"KSPSolve has not converged due to Nan or Inf inner product");
97: else {
98: ksp->reason = KSP_DIVERGED_NANORINF;
99: break;
100: }
101: }
102: alpha = rho / d1; /* a <- rho / (v,rp) */
103: VecWAXPY(S,-alpha,V,R); /* s <- r - a v */
104: KSP_PCApplyBAorAB(ksp,S,T,R); /* t <- K s */
105: VecDotNorm2(S,T,&d1,&d2);
106: if (d2 == 0.0) {
107: /* t is 0. if s is 0, then alpha v == r, and hence alpha p
108: may be our solution. Give it a try? */
109: VecDot(S,S,&d1);
110: if (d1 != 0.0) {
111: ksp->reason = KSP_DIVERGED_BREAKDOWN;
112: break;
113: }
114: VecAXPY(X,alpha,P); /* x <- x + a p */
115: PetscObjectSAWsTakeAccess((PetscObject)ksp);
116: ksp->its++;
117: ksp->rnorm = 0.0;
118: ksp->reason = KSP_CONVERGED_RTOL;
119: PetscObjectSAWsGrantAccess((PetscObject)ksp);
120: KSPLogResidualHistory(ksp,dp);
121: KSPMonitor(ksp,i+1,0.0);
122: break;
123: }
124: omega = d1 / d2; /* w <- (t's) / (t't) */
125: VecAXPBYPCZ(X,alpha,omega,1.0,P,S); /* x <- alpha * p + omega * s + x */
126: VecWAXPY(R,-omega,T,S); /* r <- s - w t */
127: if (ksp->normtype != KSP_NORM_NONE && ksp->chknorm < i+2) {
128: VecNorm(R,NORM_2,&dp);
129: }
131: rhoold = rho;
132: omegaold = omega;
134: PetscObjectSAWsTakeAccess((PetscObject)ksp);
135: ksp->its++;
136: ksp->rnorm = dp;
137: PetscObjectSAWsGrantAccess((PetscObject)ksp);
138: KSPLogResidualHistory(ksp,dp);
139: KSPMonitor(ksp,i+1,dp);
140: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
141: if (ksp->reason) break;
142: if (rho == 0.0) {
143: ksp->reason = KSP_DIVERGED_BREAKDOWN;
144: break;
145: }
146: i++;
147: } while (i<ksp->max_it);
149: if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;
151: KSPUnwindPreconditioner(ksp,X,T);
152: if (bcgs->guess) {
153: VecAXPY(X,1.0,bcgs->guess);
154: }
155: return(0);
156: }
160: PetscErrorCode KSPBuildSolution_BCGS(KSP ksp,Vec v,Vec *V)
161: {
163: KSP_BCGS *bcgs = (KSP_BCGS*)ksp->data;
166: if (ksp->pc_side == PC_RIGHT) {
167: if (v) {
168: KSP_PCApply(ksp,ksp->vec_sol,v);
169: if (bcgs->guess) {
170: VecAXPY(v,1.0,bcgs->guess);
171: }
172: *V = v;
173: } else SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Not working with right preconditioner");
174: } else {
175: if (v) {
176: VecCopy(ksp->vec_sol,v); *V = v;
177: } else *V = ksp->vec_sol;
178: }
179: return(0);
180: }
184: PetscErrorCode KSPReset_BCGS(KSP ksp)
185: {
186: KSP_BCGS *cg = (KSP_BCGS*)ksp->data;
190: VecDestroy(&cg->guess);
191: return(0);
192: }
196: PetscErrorCode KSPDestroy_BCGS(KSP ksp)
197: {
201: KSPReset_BCGS(ksp);
202: KSPDestroyDefault(ksp);
203: return(0);
204: }
206: /*MC
207: KSPBCGS - Implements the BiCGStab (Stabilized version of BiConjugate Gradient) method.
209: Options Database Keys:
210: . see KSPSolve()
212: Level: beginner
214: Notes: See KSPBCGSL for additional stabilization
215: Supports left and right preconditioning but not symmetric
217: References:
218: . 1. - van der Vorst, SIAM J. Sci. Stat. Comput., 1992.
220: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG, KSPBCGSL, KSPFBICG, KSPSetPCSide()
221: M*/
224: PETSC_EXTERN PetscErrorCode KSPCreate_BCGS(KSP ksp)
225: {
227: KSP_BCGS *bcgs;
230: PetscNewLog(ksp,&bcgs);
232: ksp->data = bcgs;
233: ksp->ops->setup = KSPSetUp_BCGS;
234: ksp->ops->solve = KSPSolve_BCGS;
235: ksp->ops->destroy = KSPDestroy_BCGS;
236: ksp->ops->reset = KSPReset_BCGS;
237: ksp->ops->buildsolution = KSPBuildSolution_BCGS;
238: ksp->ops->buildresidual = KSPBuildResidualDefault;
239: ksp->ops->setfromoptions = KSPSetFromOptions_BCGS;
241: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
242: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
243: return(0);
244: }