Actual source code: cr.c

  1: #define PETSCKSP_DLL

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

  7: static PetscErrorCode KSPSetUp_CR(KSP ksp)
  8: {

 12:   if (ksp->pc_side == PC_RIGHT) {SETERRQ(PETSC_ERR_SUP,"no right preconditioning for KSPCR");}
 13:   else if (ksp->pc_side == PC_SYMMETRIC) {SETERRQ(PETSC_ERR_SUP,"no symmetric preconditioning for KSPCR");}
 14:   KSPDefaultGetWork(ksp,6);
 15:   return(0);
 16: }

 20: static PetscErrorCode  KSPSolve_CR(KSP ksp)
 21: {
 23:   PetscInt       i = 0;
 24:   MatStructure   pflag;
 25:   PetscReal      dp;
 26:   PetscScalar    ai, bi;
 27:   PetscScalar    apq,btop, bbot, mone = -1.0;
 28:   Vec            X,B,R,RT,P,AP,ART,Q;
 29:   Mat            Amat, Pmat;

 32:   X       = ksp->vec_sol;
 33:   B       = ksp->vec_rhs;
 34:   R       = ksp->work[0];
 35:   RT      = ksp->work[1];
 36:   P       = ksp->work[2];
 37:   AP      = ksp->work[3];
 38:   ART     = ksp->work[4];
 39:   Q       = ksp->work[5];

 41:   /* R is the true residual norm, RT is the preconditioned residual norm */
 42:   PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);
 43:   if (!ksp->guess_zero) {
 44:     KSP_MatMult(ksp,Amat,X,R);     /*   R <- A*X           */
 45:     VecAYPX(R,mone,B);            /*   R <- B-R == B-A*X  */
 46:   } else {
 47:     VecCopy(B,R);                  /*   R <- B (X is 0)    */
 48:   }
 49:   KSP_PCApply(ksp,R,P);     /*   P   <- B*R         */
 50:   KSP_MatMult(ksp,Amat,P,AP);      /*   AP  <- A*P         */
 51:   VecCopy(P,RT);                   /*   RT  <- P           */
 52:   VecCopy(AP,ART);                 /*   ART <- AP          */
 53:   VecDot(RT,ART,&btop);          /*   (RT,ART)           */
 54:   if (PetscAbsScalar(btop) < 0.0) {
 55:     ksp->reason = KSP_DIVERGED_INDEFINITE_MAT;
 56:     PetscLogInfo((ksp,"KSPSolve_CR:diverging due to indefinite or negative definite matrix\n"));
 57:     return(0);
 58:   }
 59: 
 60:   if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
 61:     VecNorm(RT,NORM_2,&dp);        /*   dp <- RT'*RT       */
 62:   } else if (ksp->normtype == KSP_UNPRECONDITIONED_NORM) {
 63:     VecNorm(R,NORM_2,&dp);         /*   dp <- R'*R         */
 64:   } else if (ksp->normtype == KSP_NATURAL_NORM) {
 65:     dp = sqrt(PetscAbsScalar(btop));                    /* dp = sqrt(R,AR)      */
 66:   }
 67:   ksp->its = 0;
 68:   KSPMonitor(ksp,0,dp);
 69:   PetscObjectTakeAccess(ksp);
 70:   ksp->rnorm              = dp;
 71:   PetscObjectGrantAccess(ksp);
 72:   KSPLogResidualHistory(ksp,dp);
 73:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
 74:   if (ksp->reason) return(0);

 76:   i = 0;
 77:   do {
 78:     KSP_PCApply(ksp,AP,Q);/*   Q <- B* AP          */

 80:     VecDot(AP,Q,&apq);
 81:     if (PetscAbsScalar(apq) <= 0.0) {
 82:       ksp->reason = KSP_DIVERGED_INDEFINITE_PC;
 83:       PetscLogInfo((ksp,"KSPSolve_CR:diverging due to indefinite or negative definite PC\n"));
 84:       break;
 85:     }
 86:     ai = btop/apq;                                      /* ai = (RT,ART)/(AP,Q)  */

 88:     VecAXPY(X,ai,P);            /*   X   <- X + ai*P     */
 89:     ai     = -ai;
 90:     VecAXPY(RT,ai,Q);           /*   RT  <- RT - ai*Q    */
 91:     KSP_MatMult(ksp,Amat,RT,ART);/*   ART <-   A*RT       */
 92:     bbot = btop;
 93:     VecDot(RT,ART,&btop);
 94:     if (PetscAbsScalar(btop) < 0.0) {
 95:       ksp->reason = KSP_DIVERGED_INDEFINITE_MAT;
 96:       PetscLogInfo((ksp,"KSPSolve_CR:diverging due to indefinite or negative definite matrix\n"));
 97:       break;
 98:     }

100:     if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
101:       VecNorm(RT,NORM_2,&dp);      /*   dp <- || RT ||      */
102:     } else if (ksp->normtype == KSP_NATURAL_NORM) {
103:       dp = sqrt(PetscAbsScalar(btop));                  /* dp = sqrt(R,AR)       */
104:     } else if (ksp->normtype == KSP_NO_NORM) {
105:       dp = 0.0;
106:     } else if (ksp->normtype == KSP_UNPRECONDITIONED_NORM) {
107:       VecAXPY(R,ai,AP);           /*   R   <- R - ai*AP    */
108:       VecNorm(R,NORM_2,&dp);       /*   dp <- R'*R          */
109:     } else {
110:       SETERRQ1(PETSC_ERR_SUP,"KSPNormType of %d not supported",(int)ksp->normtype);
111:     }

113:     PetscObjectTakeAccess(ksp);
114:     ksp->its++;
115:     ksp->rnorm = dp;
116:     PetscObjectGrantAccess(ksp);

118:     KSPLogResidualHistory(ksp,dp);
119:     KSPMonitor(ksp,i+1,dp);
120:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
121:     if (ksp->reason) break;

123:     bi = btop/bbot;
124:     VecAYPX(P,bi,RT);              /*   P <- RT + Bi P     */
125:     VecAYPX(AP,bi,ART);            /*   AP <- ART + Bi AP  */
126:     i++;
127:   } while (i<ksp->max_it);
128:   if (i >= ksp->max_it) {
129:     ksp->reason =  KSP_DIVERGED_ITS;
130:   }
131:   return(0);
132: }


135: /*MC
136:      KSPCR - This code implements the (preconditioned) conjugate residuals method

138:    Options Database Keys:
139: .   see KSPSolve()

141:    Level: beginner

143:    Notes: The operator and the preconditioner must be symmetric for this method. The 
144:           preconditioner must be POSITIVE-DEFINITE and the operator POSITIVE-SEMIDEFINITE

146: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPCG
147: M*/
151: PetscErrorCode PETSCKSP_DLLEXPORT KSPCreate_CR(KSP ksp)
152: {
154:   ksp->pc_side                   = PC_LEFT;
155:   ksp->ops->setup                = KSPSetUp_CR;
156:   ksp->ops->solve                = KSPSolve_CR;
157:   ksp->ops->destroy              = KSPDefaultDestroy;
158:   ksp->ops->buildsolution        = KSPDefaultBuildSolution;
159:   ksp->ops->buildresidual        = KSPDefaultBuildResidual;
160:   ksp->ops->setfromoptions       = 0;
161:   ksp->ops->view                 = 0;
162:   return(0);
163: }