Actual source code: bicg.c

  1: #define PETSCKSP_DLL

 3:  #include src/ksp/ksp/kspimpl.h

  7: PetscErrorCode KSPSetUp_BiCG(KSP ksp)
  8: {

 12:   /* check user parameters and functions */
 13:   if (ksp->pc_side == PC_RIGHT) {
 14:     SETERRQ(PETSC_ERR_SUP,"no right preconditioning for KSPBiCG");
 15:   } else if (ksp->pc_side == PC_SYMMETRIC) {
 16:     SETERRQ(PETSC_ERR_SUP,"no symmetric preconditioning for KSPBiCG");
 17:   }

 19:   /* get work vectors from user code */
 20:   KSPDefaultGetWork(ksp,6);
 21:   return(0);
 22: }

 26: PetscErrorCode  KSPSolve_BiCG(KSP ksp)
 27: {
 29:   PetscInt       i;
 30:   PetscTruth     diagonalscale;
 31:   PetscScalar    dpi,a=1.0,beta,betaold=1.0,b,ma;
 32:   PetscReal      dp;
 33:   Vec            X,B,Zl,Zr,Rl,Rr,Pl,Pr;
 34:   Mat            Amat,Pmat;
 35:   MatStructure   pflag;

 38:   PCDiagonalScale(ksp->pc,&diagonalscale);
 39:   if (diagonalscale) SETERRQ1(PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",ksp->type_name);

 41:   X       = ksp->vec_sol;
 42:   B       = ksp->vec_rhs;
 43:   Rl      = ksp->work[0];
 44:   Zl      = ksp->work[1];
 45:   Pl      = ksp->work[2];
 46:   Rr      = ksp->work[3];
 47:   Zr      = ksp->work[4];
 48:   Pr      = ksp->work[5];

 50:   PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);

 52:   if (!ksp->guess_zero) {
 53:     KSP_MatMult(ksp,Amat,X,Rr);      /*   r <- b - Ax       */
 54:     VecAYPX(Rr,-1.0,B);
 55:   } else {
 56:     VecCopy(B,Rr);           /*     r <- b (x is 0) */
 57:   }
 58:   VecCopy(Rr,Rl);
 59:   KSP_PCApply(ksp,Rr,Zr);     /*     z <- Br         */
 60:   VecConjugate(Rl);
 61:   KSP_PCApplyTranspose(ksp,Rl,Zl);
 62:   VecConjugate(Rl);
 63:   VecConjugate(Zl);
 64:   if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
 65:     VecNorm(Zr,NORM_2,&dp);  /*    dp <- z'*z       */
 66:   } else {
 67:     VecNorm(Rr,NORM_2,&dp);  /*    dp <- r'*r       */
 68:   }
 69:   KSPMonitor(ksp,0,dp);
 70:   PetscObjectTakeAccess(ksp);
 71:   ksp->its   = 0;
 72:   ksp->rnorm = dp;
 73:   PetscObjectGrantAccess(ksp);
 74:   KSPLogResidualHistory(ksp,dp);
 75:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
 76:   if (ksp->reason) return(0);

 78:   i = 0;
 79:   do {
 80:      VecDot(Zr,Rl,&beta);       /*     beta <- r'z     */
 81:      if (!i) {
 82:        if (beta == 0.0) {
 83:          ksp->reason = KSP_DIVERGED_BREAKDOWN_BICG;
 84:          return(0);
 85:        }
 86:        VecCopy(Zr,Pr);       /*     p <- z          */
 87:        VecCopy(Zl,Pl);
 88:      } else {
 89:        b = beta/betaold;
 90:        VecAYPX(Pr,b,Zr);  /*     p <- z + b* p   */
 91:        b = PetscConj(b);
 92:        VecAYPX(Pl,b,Zl);
 93:      }
 94:      betaold = beta;
 95:      KSP_MatMult(ksp,Amat,Pr,Zr);    /*     z <- Kp         */
 96:      VecConjugate(Pl);
 97:      KSP_MatMultTranspose(ksp,Amat,Pl,Zl);
 98:      VecConjugate(Pl);
 99:      VecConjugate(Zl);
100:      VecDot(Zr,Pl,&dpi);               /*     dpi <- z'p      */
101:      a = beta/dpi;                                 /*     a = beta/p'z    */
102:      VecAXPY(X,a,Pr);       /*     x <- x + ap     */
103:      ma = -a;
104:      VecAXPY(Rr,ma,Zr);CHKERRQ(ierr)
105:      ma = PetscConj(ma);
106:      VecAXPY(Rl,ma,Zl);
107:      if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
108:        KSP_PCApply(ksp,Rr,Zr);  /*     z <- Br         */
109:        VecConjugate(Rl);
110:        KSP_PCApplyTranspose(ksp,Rl,Zl);
111:        VecConjugate(Rl);
112:        VecConjugate(Zl);
113:        VecNorm(Zr,NORM_2,&dp);  /*    dp <- z'*z       */
114:      } else {
115:        VecNorm(Rr,NORM_2,&dp);  /*    dp <- r'*r       */
116:      }
117:      PetscObjectTakeAccess(ksp);
118:      ksp->its   = i+1;
119:      ksp->rnorm = dp;
120:      PetscObjectGrantAccess(ksp);
121:      KSPLogResidualHistory(ksp,dp);
122:      KSPMonitor(ksp,i+1,dp);
123:      (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
124:      if (ksp->reason) break;
125:      if (ksp->normtype == KSP_UNPRECONDITIONED_NORM) {
126:        KSP_PCApply(ksp,Rr,Zr);  /* z <- Br  */
127:        VecConjugate(Rl);
128:        KSP_PCApplyTranspose(ksp,Rl,Zl);
129:        VecConjugate(Rl);
130:        VecConjugate(Zl);
131:      }
132:      i++;
133:   } while (i<ksp->max_it);
134:   if (i >= ksp->max_it) {
135:     ksp->reason = KSP_DIVERGED_ITS;
136:   }
137:   return(0);
138: }

142: PetscErrorCode KSPDestroy_BiCG(KSP ksp)
143: {

147:   KSPDefaultFreeWork(ksp);
148:   return(0);
149: }

151: /*MC
152:      KSPBICG - Implements the Biconjugate gradient method (essentially running the conjugate
153:          gradient on the normal equations).

155:    Options Database Keys:
156: .   see KSPSolve()

158:    Level: beginner

160: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS

162: M*/
166: PetscErrorCode  KSPCreate_BiCG(KSP ksp)
167: {
169:   ksp->data                      = (void*)0;
170:   ksp->pc_side                   = PC_LEFT;
171:   ksp->ops->setup                = KSPSetUp_BiCG;
172:   ksp->ops->solve                = KSPSolve_BiCG;
173:   ksp->ops->destroy              = KSPDestroy_BiCG;
174:   ksp->ops->view                 = 0;
175:   ksp->ops->setfromoptions       = 0;
176:   ksp->ops->buildsolution        = KSPDefaultBuildSolution;
177:   ksp->ops->buildresidual        = KSPDefaultBuildResidual;

179:   return(0);
180: }