Date: 2015-10-02T22:21:33+00:00

Actual source code: bicg.c
petsc-3.6.2 2015-10-02
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      2: #include <petsc/private/kspimpl.h>

      6: PetscErrorCode KSPSetUp_BiCG(KSP ksp)
      7: {

     11:   /* check user parameters and functions */
     12:   if (ksp->pc_side == PC_RIGHT) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"no right preconditioning for KSPBiCG");
     13:   else if (ksp->pc_side == PC_SYMMETRIC) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"no symmetric preconditioning for KSPBiCG");
     14:   KSPSetWorkVecs(ksp,6);
     15:   return(0);
     16: }

     20: PetscErrorCode  KSPSolve_BiCG(KSP ksp)
     21: {
     23:   PetscInt       i;
     24:   PetscBool      diagonalscale;
     25:   PetscScalar    dpi,a=1.0,beta,betaold=1.0,b,ma;
     26:   PetscReal      dp;
     27:   Vec            X,B,Zl,Zr,Rl,Rr,Pl,Pr;
     28:   Mat            Amat,Pmat;

     31:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
     32:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);

     34:   X  = ksp->vec_sol;
     35:   B  = ksp->vec_rhs;
     36:   Rl = ksp->work[0];
     37:   Zl = ksp->work[1];
     38:   Pl = ksp->work[2];
     39:   Rr = ksp->work[3];
     40:   Zr = ksp->work[4];
     41:   Pr = ksp->work[5];

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

     45:   if (!ksp->guess_zero) {
     46:     KSP_MatMult(ksp,Amat,X,Rr);      /*   r <- b - Ax       */
     47:     VecAYPX(Rr,-1.0,B);
     48:   } else {
     49:     VecCopy(B,Rr);           /*     r <- b (x is 0) */
     50:   }
     51:   VecCopy(Rr,Rl);
     52:   KSP_PCApply(ksp,Rr,Zr);     /*     z <- Br         */
     53:   VecConjugate(Rl);
     54:   KSP_PCApplyTranspose(ksp,Rl,Zl);
     55:   VecConjugate(Rl);
     56:   VecConjugate(Zl);
     57:   if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
     58:     VecNorm(Zr,NORM_2,&dp);  /*    dp <- z'*z       */
     59:   } else {
     60:     VecNorm(Rr,NORM_2,&dp);  /*    dp <- r'*r       */
     61:   }
     62:   KSPMonitor(ksp,0,dp);
     63:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
     64:   ksp->its   = 0;
     65:   ksp->rnorm = dp;
     66:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
     67:   KSPLogResidualHistory(ksp,dp);
     68:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
     69:   if (ksp->reason) return(0);

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

    131: /*MC
    132:      KSPBICG - Implements the Biconjugate gradient method (similar to running the conjugate
    133:          gradient on the normal equations).

    135:    Options Database Keys:
    136: .   see KSPSolve()

    138:    Level: beginner

    140:    Notes: this method requires that one be apply to apply the transpose of the preconditioner and operator
    141:          as well as the operator and preconditioner.
    142:          Supports only left preconditioning

    144:          See KSPCGNE for code that EXACTLY runs the preconditioned conjugate gradient method on the
    145:          normal equations

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

    149: M*/
    152: PETSC_EXTERN PetscErrorCode KSPCreate_BiCG(KSP ksp)
    153: {

    157:   ksp->data = (void*)0;
    158:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
    159:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_LEFT,2);

    161:   ksp->ops->setup          = KSPSetUp_BiCG;
    162:   ksp->ops->solve          = KSPSolve_BiCG;
    163:   ksp->ops->destroy        = KSPDestroyDefault;
    164:   ksp->ops->view           = 0;
    165:   ksp->ops->setfromoptions = 0;
    166:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
    167:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
    168:   return(0);
    169: }