Actual source code: cgs.c
2: /*
4: Note that for the complex numbers version, the VecDot() arguments
5: within the code MUST remain in the order given for correct computation
6: of inner products.
7: */
8: #include <petsc/private/kspimpl.h>
10: static PetscErrorCode KSPSetUp_CGS(KSP ksp)
11: {
12: KSPSetWorkVecs(ksp,7);
13: return 0;
14: }
16: static PetscErrorCode KSPSolve_CGS(KSP ksp)
17: {
18: PetscInt i;
19: PetscScalar rho,rhoold,a,s,b;
20: Vec X,B,V,P,R,RP,T,Q,U,AUQ;
21: PetscReal dp = 0.0;
22: PetscBool diagonalscale;
24: /* not sure what residual norm it does use, should use for right preconditioning */
26: PCGetDiagonalScale(ksp->pc,&diagonalscale);
29: X = ksp->vec_sol;
30: B = ksp->vec_rhs;
31: R = ksp->work[0];
32: RP = ksp->work[1];
33: V = ksp->work[2];
34: T = ksp->work[3];
35: Q = ksp->work[4];
36: P = ksp->work[5];
37: U = ksp->work[6];
38: AUQ = V;
40: /* Compute initial preconditioned residual */
41: KSPInitialResidual(ksp,X,V,T,R,B);
43: /* Test for nothing to do */
44: if (ksp->normtype != KSP_NORM_NONE) {
45: VecNorm(R,NORM_2,&dp);
46: KSPCheckNorm(ksp,dp);
47: if (ksp->normtype == KSP_NORM_NATURAL) dp *= dp;
48: } else dp = 0.0;
50: PetscObjectSAWsTakeAccess((PetscObject)ksp);
51: ksp->its = 0;
52: ksp->rnorm = dp;
53: PetscObjectSAWsGrantAccess((PetscObject)ksp);
54: KSPLogResidualHistory(ksp,dp);
55: KSPMonitor(ksp,0,dp);
56: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
57: if (ksp->reason) return 0;
59: /* Make the initial Rp == R */
60: VecCopy(R,RP);
61: /* added for Fidap */
62: /* Penalize Startup - Isaac Hasbani Trick for CGS
63: Since most initial conditions result in a mostly 0 residual,
64: we change all the 0 values in the vector RP to the maximum.
65: */
66: if (ksp->normtype == KSP_NORM_NATURAL) {
67: PetscReal vr0max;
68: PetscScalar *tmp_RP=NULL;
69: PetscInt numnp =0, *max_pos=NULL;
70: VecMax(RP, max_pos, &vr0max);
71: VecGetArray(RP, &tmp_RP);
72: VecGetLocalSize(RP, &numnp);
73: for (i=0; i<numnp; i++) {
74: if (tmp_RP[i] == 0.0) tmp_RP[i] = vr0max;
75: }
76: VecRestoreArray(RP, &tmp_RP);
77: }
78: /* end of addition for Fidap */
80: /* Set the initial conditions */
81: VecDot(R,RP,&rhoold); /* rhoold = (r,rp) */
82: VecCopy(R,U);
83: VecCopy(R,P);
84: KSP_PCApplyBAorAB(ksp,P,V,T);
86: i = 0;
87: do {
89: VecDot(V,RP,&s); /* s <- (v,rp) */
90: KSPCheckDot(ksp,s);
91: a = rhoold / s; /* a <- rho / s */
92: VecWAXPY(Q,-a,V,U); /* q <- u - a v */
93: VecWAXPY(T,1.0,U,Q); /* t <- u + q */
94: VecAXPY(X,a,T); /* x <- x + a (u + q) */
95: KSP_PCApplyBAorAB(ksp,T,AUQ,U);
96: VecAXPY(R,-a,AUQ); /* r <- r - a K (u + q) */
97: VecDot(R,RP,&rho); /* rho <- (r,rp) */
98: KSPCheckDot(ksp,rho);
99: if (ksp->normtype == KSP_NORM_NATURAL) {
100: dp = PetscAbsScalar(rho);
101: } else if (ksp->normtype != KSP_NORM_NONE) {
102: VecNorm(R,NORM_2,&dp);
103: KSPCheckNorm(ksp,dp);
104: } else dp = 0.0;
106: PetscObjectSAWsTakeAccess((PetscObject)ksp);
107: ksp->its++;
108: ksp->rnorm = dp;
109: PetscObjectSAWsGrantAccess((PetscObject)ksp);
110: KSPLogResidualHistory(ksp,dp);
111: KSPMonitor(ksp,i+1,dp);
112: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
113: if (ksp->reason) break;
115: b = rho / rhoold; /* b <- rho / rhoold */
116: VecWAXPY(U,b,Q,R); /* u <- r + b q */
117: VecAXPY(Q,b,P);
118: VecWAXPY(P,b,Q,U); /* p <- u + b(q + b p) */
119: KSP_PCApplyBAorAB(ksp,P,V,Q); /* v <- K p */
120: rhoold = rho;
121: i++;
122: } while (i<ksp->max_it);
123: if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;
125: KSPUnwindPreconditioner(ksp,X,T);
126: return 0;
127: }
129: /*MC
130: KSPCGS - This code implements the CGS (Conjugate Gradient Squared) method.
132: Options Database Keys:
133: see KSPSolve()
135: Level: beginner
137: References:
138: . * - Sonneveld, 1989.
140: Notes:
141: Does not require a symmetric matrix. Does not apply transpose of the matrix.
142: Supports left and right preconditioning, but not symmetric.
144: Developer Notes:
145: Has this weird support for doing the convergence test with the natural norm, I assume this works only with
146: no preconditioning and symmetric positive definite operator.
148: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS, KSPSetPCSide()
149: M*/
150: PETSC_EXTERN PetscErrorCode KSPCreate_CGS(KSP ksp)
151: {
152: ksp->data = (void*)0;
154: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
155: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
156: KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_LEFT,2);
157: KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_RIGHT,2);
158: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,1);
159: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);
161: ksp->ops->setup = KSPSetUp_CGS;
162: ksp->ops->solve = KSPSolve_CGS;
163: ksp->ops->destroy = KSPDestroyDefault;
164: ksp->ops->buildsolution = KSPBuildSolutionDefault;
165: ksp->ops->buildresidual = KSPBuildResidualDefault;
166: ksp->ops->setfromoptions = NULL;
167: ksp->ops->view = NULL;
168: return 0;
169: }