Actual source code: bcgs.c

petsc-3.11.3 2019-06-26
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  2:  #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h>

  4: PetscErrorCode KSPSetFromOptions_BCGS(PetscOptionItems *PetscOptionsObject,KSP ksp)
  5: {

  9:   PetscOptionsHead(PetscOptionsObject,"KSP BCGS Options");
 10:   PetscOptionsTail();
 11:   return(0);
 12: }

 14: PetscErrorCode KSPSetUp_BCGS(KSP ksp)
 15: {

 19:   KSPSetWorkVecs(ksp,6);
 20:   return(0);
 21: }


 24: PetscErrorCode KSPSolve_BCGS(KSP ksp)
 25: {
 27:   PetscInt       i;
 28:   PetscScalar    rho,rhoold,alpha,beta,omega,omegaold,d1;
 29:   Vec            X,B,V,P,R,RP,T,S;
 30:   PetscReal      dp    = 0.0,d2;
 31:   KSP_BCGS       *bcgs = (KSP_BCGS*)ksp->data;

 34:   X  = ksp->vec_sol;
 35:   B  = ksp->vec_rhs;
 36:   R  = ksp->work[0];
 37:   RP = ksp->work[1];
 38:   V  = ksp->work[2];
 39:   T  = ksp->work[3];
 40:   S  = ksp->work[4];
 41:   P  = ksp->work[5];

 43:   /* Compute initial preconditioned residual */
 44:   KSPInitialResidual(ksp,X,V,T,R,B);

 46:   /* with right preconditioning need to save initial guess to add to final solution */
 47:   if (ksp->pc_side == PC_RIGHT && !ksp->guess_zero) {
 48:     if (!bcgs->guess) {
 49:       VecDuplicate(X,&bcgs->guess);
 50:     }
 51:     VecCopy(X,bcgs->guess);
 52:     VecSet(X,0.0);
 53:   }

 55:   /* Test for nothing to do */
 56:   if (ksp->normtype != KSP_NORM_NONE) {
 57:     VecNorm(R,NORM_2,&dp);
 58:     KSPCheckNorm(ksp,dp);
 59:   }
 60:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
 61:   ksp->its   = 0;
 62:   ksp->rnorm = dp;
 63:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
 64:   KSPLogResidualHistory(ksp,dp);
 65:   KSPMonitor(ksp,0,dp);
 66:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
 67:   if (ksp->reason) {
 68:     if (bcgs->guess) {
 69:       VecAXPY(X,1.0,bcgs->guess);
 70:     }
 71:     return(0);
 72:   }

 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:     KSPCheckDot(ksp,d1);
 91:     if (d1 == 0.0) {
 92:       if (ksp->errorifnotconverged) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"KSPSolve has not converged due to Nan or Inf inner product");
 93:       else {
 94:         ksp->reason = KSP_DIVERGED_NANORINF;
 95:         break;
 96:       }
 97:     }
 98:     alpha = rho / d1;                 /*   a <- rho / (v,rp)  */
 99:     VecWAXPY(S,-alpha,V,R);     /*   s <- r - a v       */
100:     KSP_PCApplyBAorAB(ksp,S,T,R); /*   t <- K s    */
101:     VecDotNorm2(S,T,&d1,&d2);
102:     if (d2 == 0.0) {
103:       /* t is 0.  if s is 0, then alpha v == r, and hence alpha p
104:          may be our solution.  Give it a try? */
105:       VecDot(S,S,&d1);
106:       if (d1 != 0.0) {
107:         ksp->reason = KSP_DIVERGED_BREAKDOWN;
108:         break;
109:       }
110:       VecAXPY(X,alpha,P);   /*   x <- x + a p       */
111:       PetscObjectSAWsTakeAccess((PetscObject)ksp);
112:       ksp->its++;
113:       ksp->rnorm  = 0.0;
114:       ksp->reason = KSP_CONVERGED_RTOL;
115:       PetscObjectSAWsGrantAccess((PetscObject)ksp);
116:       KSPLogResidualHistory(ksp,dp);
117:       KSPMonitor(ksp,i+1,0.0);
118:       break;
119:     }
120:     omega = d1 / d2;                               /*   w <- (t's) / (t't) */
121:     VecAXPBYPCZ(X,alpha,omega,1.0,P,S); /* x <- alpha * p + omega * s + x */
122:     VecWAXPY(R,-omega,T,S);     /*   r <- s - w t       */
123:     if (ksp->normtype != KSP_NORM_NONE && ksp->chknorm < i+2) {
124:       VecNorm(R,NORM_2,&dp);
125:       KSPCheckNorm(ksp,dp);
126:     }

128:     rhoold   = rho;
129:     omegaold = omega;

131:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
132:     ksp->its++;
133:     ksp->rnorm = dp;
134:     PetscObjectSAWsGrantAccess((PetscObject)ksp);
135:     KSPLogResidualHistory(ksp,dp);
136:     KSPMonitor(ksp,i+1,dp);
137:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
138:     if (ksp->reason) break;
139:     if (rho == 0.0) {
140:       ksp->reason = KSP_DIVERGED_BREAKDOWN;
141:       break;
142:     }
143:     i++;
144:   } while (i<ksp->max_it);

146:   if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;

148:   KSPUnwindPreconditioner(ksp,X,T);
149:   if (bcgs->guess) {
150:     VecAXPY(X,1.0,bcgs->guess);
151:   }
152:   return(0);
153: }

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: }

177: PetscErrorCode KSPReset_BCGS(KSP ksp)
178: {
179:   KSP_BCGS       *cg = (KSP_BCGS*)ksp->data;

183:   VecDestroy(&cg->guess);
184:   return(0);
185: }

187: PetscErrorCode KSPDestroy_BCGS(KSP ksp)
188: {

192:   KSPReset_BCGS(ksp);
193:   KSPDestroyDefault(ksp);
194:   return(0);
195: }

197: /*MC
198:      KSPBCGS - Implements the BiCGStab (Stabilized version of BiConjugate Gradient) method.

200:    Options Database Keys:
201: .   see KSPSolve()

203:    Level: beginner

205:    Notes:
206:     See KSPBCGSL for additional stabilization
207:           Supports left and right preconditioning but not symmetric

209:    References:
210: .    1. -   van der Vorst, SIAM J. Sci. Stat. Comput., 1992.

212: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG, KSPBCGSL, KSPFBICG, KSPSetPCSide()
213: M*/
214: PETSC_EXTERN PetscErrorCode KSPCreate_BCGS(KSP ksp)
215: {
217:   KSP_BCGS       *bcgs;

220:   PetscNewLog(ksp,&bcgs);

222:   ksp->data                = bcgs;
223:   ksp->ops->setup          = KSPSetUp_BCGS;
224:   ksp->ops->solve          = KSPSolve_BCGS;
225:   ksp->ops->destroy        = KSPDestroy_BCGS;
226:   ksp->ops->reset          = KSPReset_BCGS;
227:   ksp->ops->buildsolution  = KSPBuildSolution_BCGS;
228:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
229:   ksp->ops->setfromoptions = KSPSetFromOptions_BCGS;

231:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
232:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
233:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,1);
234:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);
235:   return(0);
236: }