Actual source code: bcgs.c
1: #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h>
3: PetscErrorCode KSPSetFromOptions_BCGS(KSP ksp, PetscOptionItems *PetscOptionsObject)
4: {
5: PetscFunctionBegin;
6: PetscOptionsHeadBegin(PetscOptionsObject, "KSP BCGS Options");
7: PetscOptionsHeadEnd();
8: PetscFunctionReturn(PETSC_SUCCESS);
9: }
11: PetscErrorCode KSPSetUp_BCGS(KSP ksp)
12: {
13: PetscFunctionBegin;
14: PetscCall(KSPSetWorkVecs(ksp, 6));
15: PetscFunctionReturn(PETSC_SUCCESS);
16: }
18: PetscErrorCode KSPSolve_BCGS(KSP ksp)
19: {
20: PetscInt i;
21: PetscScalar rho, rhoold, alpha, beta, omega, omegaold, d1;
22: Vec X, B, V, P, R, RP, T, S;
23: PetscReal dp = 0.0, d2;
24: KSP_BCGS *bcgs = (KSP_BCGS *)ksp->data;
26: PetscFunctionBegin;
27: X = ksp->vec_sol;
28: B = ksp->vec_rhs;
29: R = ksp->work[0];
30: RP = ksp->work[1];
31: V = ksp->work[2];
32: T = ksp->work[3];
33: S = ksp->work[4];
34: P = ksp->work[5];
36: /* Compute initial preconditioned residual */
37: PetscCall(KSPInitialResidual(ksp, X, V, T, R, B));
39: /* with right preconditioning need to save initial guess to add to final solution */
40: if (ksp->pc_side == PC_RIGHT && !ksp->guess_zero) {
41: if (!bcgs->guess) PetscCall(VecDuplicate(X, &bcgs->guess));
42: PetscCall(VecCopy(X, bcgs->guess));
43: PetscCall(VecSet(X, 0.0));
44: }
46: /* Test for nothing to do */
47: if (ksp->normtype != KSP_NORM_NONE) {
48: PetscCall(VecNorm(R, NORM_2, &dp));
49: KSPCheckNorm(ksp, dp);
50: }
51: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)ksp));
52: ksp->its = 0;
53: ksp->rnorm = dp;
54: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)ksp));
55: PetscCall(KSPLogResidualHistory(ksp, dp));
56: PetscCall(KSPMonitor(ksp, 0, dp));
57: PetscCall((*ksp->converged)(ksp, 0, dp, &ksp->reason, ksp->cnvP));
58: if (ksp->reason) {
59: if (bcgs->guess) PetscCall(VecAXPY(X, 1.0, bcgs->guess));
60: PetscFunctionReturn(PETSC_SUCCESS);
61: }
63: /* Make the initial Rp == R */
64: PetscCall(VecCopy(R, RP));
66: rhoold = 1.0;
67: alpha = 1.0;
68: omegaold = 1.0;
69: PetscCall(VecSet(P, 0.0));
70: PetscCall(VecSet(V, 0.0));
72: i = 0;
73: do {
74: PetscCall(VecDot(R, RP, &rho)); /* rho <- (r,rp) */
75: beta = (rho / rhoold) * (alpha / omegaold);
76: PetscCall(VecAXPBYPCZ(P, 1.0, -omegaold * beta, beta, R, V)); /* p <- r - omega * beta* v + beta * p */
77: PetscCall(KSP_PCApplyBAorAB(ksp, P, V, T)); /* v <- K p */
78: PetscCall(VecDot(V, RP, &d1));
79: KSPCheckDot(ksp, d1);
80: if (d1 == 0.0) {
81: PetscCheck(!ksp->errorifnotconverged, PetscObjectComm((PetscObject)ksp), PETSC_ERR_NOT_CONVERGED, "KSPSolve breakdown due to zero inner product");
82: ksp->reason = KSP_DIVERGED_BREAKDOWN;
83: PetscCall(PetscInfo(ksp, "Breakdown due to zero inner product\n"));
84: break;
85: }
86: alpha = rho / d1; /* a <- rho / (v,rp) */
87: PetscCall(VecWAXPY(S, -alpha, V, R)); /* s <- r - a v */
88: PetscCall(KSP_PCApplyBAorAB(ksp, S, T, R)); /* t <- K s */
89: PetscCall(VecDotNorm2(S, T, &d1, &d2));
90: if (d2 == 0.0) {
91: /* t is 0. if s is 0, then alpha v == r, and hence alpha p
92: may be our solution. Give it a try? */
93: PetscCall(VecDot(S, S, &d1));
94: if (d1 != 0.0) {
95: PetscCheck(!ksp->errorifnotconverged, PetscObjectComm((PetscObject)ksp), PETSC_ERR_NOT_CONVERGED, "KSPSolve has failed due to singular preconditioned operator");
96: ksp->reason = KSP_DIVERGED_BREAKDOWN;
97: PetscCall(PetscInfo(ksp, "Failed due to singular preconditioned operator\n"));
98: break;
99: }
100: PetscCall(VecAXPY(X, alpha, P)); /* x <- x + a p */
101: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)ksp));
102: ksp->its++;
103: ksp->rnorm = 0.0;
104: ksp->reason = KSP_CONVERGED_RTOL;
105: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)ksp));
106: PetscCall(KSPLogResidualHistory(ksp, dp));
107: PetscCall(KSPMonitor(ksp, i + 1, 0.0));
108: break;
109: }
110: omega = d1 / d2; /* w <- (t's) / (t't) */
111: PetscCall(VecAXPBYPCZ(X, alpha, omega, 1.0, P, S)); /* x <- alpha * p + omega * s + x */
112: PetscCall(VecWAXPY(R, -omega, T, S)); /* r <- s - w t */
113: if (ksp->normtype != KSP_NORM_NONE && ksp->chknorm < i + 2) {
114: PetscCall(VecNorm(R, NORM_2, &dp));
115: KSPCheckNorm(ksp, dp);
116: }
118: rhoold = rho;
119: omegaold = omega;
121: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)ksp));
122: ksp->its++;
123: ksp->rnorm = dp;
124: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)ksp));
125: PetscCall(KSPLogResidualHistory(ksp, dp));
126: PetscCall(KSPMonitor(ksp, i + 1, dp));
127: PetscCall((*ksp->converged)(ksp, i + 1, dp, &ksp->reason, ksp->cnvP));
128: if (ksp->reason) break;
129: if (rho == 0.0) {
130: PetscCheck(!ksp->errorifnotconverged, PetscObjectComm((PetscObject)ksp), PETSC_ERR_NOT_CONVERGED, "KSPSolve breakdown due to zero inner product");
131: ksp->reason = KSP_DIVERGED_BREAKDOWN;
132: PetscCall(PetscInfo(ksp, "Breakdown due to zero rho inner product\n"));
133: break;
134: }
135: i++;
136: } while (i < ksp->max_it);
138: if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;
140: PetscCall(KSPUnwindPreconditioner(ksp, X, T));
141: if (bcgs->guess) PetscCall(VecAXPY(X, 1.0, bcgs->guess));
142: PetscFunctionReturn(PETSC_SUCCESS);
143: }
145: PetscErrorCode KSPBuildSolution_BCGS(KSP ksp, Vec v, Vec *V)
146: {
147: KSP_BCGS *bcgs = (KSP_BCGS *)ksp->data;
149: PetscFunctionBegin;
150: if (ksp->pc_side == PC_RIGHT) {
151: if (v) {
152: PetscCall(KSP_PCApply(ksp, ksp->vec_sol, v));
153: if (bcgs->guess) PetscCall(VecAXPY(v, 1.0, bcgs->guess));
154: *V = v;
155: } else SETERRQ(PetscObjectComm((PetscObject)ksp), PETSC_ERR_SUP, "Not working with right preconditioner");
156: } else {
157: if (v) {
158: PetscCall(VecCopy(ksp->vec_sol, v));
159: *V = v;
160: } else *V = ksp->vec_sol;
161: }
162: PetscFunctionReturn(PETSC_SUCCESS);
163: }
165: PetscErrorCode KSPReset_BCGS(KSP ksp)
166: {
167: KSP_BCGS *cg = (KSP_BCGS *)ksp->data;
169: PetscFunctionBegin;
170: PetscCall(VecDestroy(&cg->guess));
171: PetscFunctionReturn(PETSC_SUCCESS);
172: }
174: PetscErrorCode KSPDestroy_BCGS(KSP ksp)
175: {
176: PetscFunctionBegin;
177: PetscCall(KSPReset_BCGS(ksp));
178: PetscCall(KSPDestroyDefault(ksp));
179: PetscFunctionReturn(PETSC_SUCCESS);
180: }
182: /*MC
183: KSPBCGS - Implements the BiCGStab (Stabilized version of Biconjugate Gradient) method {cite}`vorst92`
185: Level: beginner
187: Notes:
188: Supports left and right preconditioning but not symmetric
190: See `KSPBCGSL` for additional stabilization
192: See `KSPFBCGS`, `KSPFBCGSR`, and `KSPPIPEBCGS` for flexible and pipelined versions of the algorithm
194: This method can be a good alternative to `KSPGMRES` in that it does not require explicitly storing the Krylov space as `KSPGMRES` requires
195: and there is no acceptable restart value that can be set with `KSPGMRESSetRestart()` that balances cost per iteration and convergence rates with `KSPGMRES`.
197: .seealso: [](ch_ksp), `KSPFBCGS`, `KSPFBCGSR`, `KSPPIPEBCGS`, `KSPBCGSL`, `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSP`, `KSPBICG`, `KSPBCGSL`, `KSPFBICG`, `KSPQMRCGS`, `KSPSetPCSide()`
198: M*/
199: PETSC_EXTERN PetscErrorCode KSPCreate_BCGS(KSP ksp)
200: {
201: KSP_BCGS *bcgs;
203: PetscFunctionBegin;
204: PetscCall(PetscNew(&bcgs));
206: ksp->data = bcgs;
207: ksp->ops->setup = KSPSetUp_BCGS;
208: ksp->ops->solve = KSPSolve_BCGS;
209: ksp->ops->destroy = KSPDestroy_BCGS;
210: ksp->ops->reset = KSPReset_BCGS;
211: ksp->ops->buildsolution = KSPBuildSolution_BCGS;
212: ksp->ops->buildresidual = KSPBuildResidualDefault;
213: ksp->ops->setfromoptions = KSPSetFromOptions_BCGS;
215: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_PRECONDITIONED, PC_LEFT, 3));
216: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_RIGHT, 2));
217: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_LEFT, 1));
218: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_RIGHT, 1));
219: PetscFunctionReturn(PETSC_SUCCESS);
220: }