Actual source code: cgs.c
petsc-3.10.5 2019-03-28
Report Typos and Errors

      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: {

     15:   KSPSetWorkVecs(ksp,7);
     16:   return(0);
     17: }

     19: static PetscErrorCode  KSPSolve_CGS(KSP ksp)
     20: {
     22:   PetscInt       i;
     23:   PetscScalar    rho,rhoold,a,s,b;
     24:   Vec            X,B,V,P,R,RP,T,Q,U,AUQ;
     25:   PetscReal      dp = 0.0;
     26:   PetscBool      diagonalscale;

     29:   /* not sure what residual norm it does use, should use for right preconditioning */

     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:   R   = ksp->work[0];
     37:   RP  = ksp->work[1];
     38:   V   = ksp->work[2];
     39:   T   = ksp->work[3];
     40:   Q   = ksp->work[4];
     41:   P   = ksp->work[5];
     42:   U   = ksp->work[6];
     43:   AUQ = V;

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

     48:   /* Test for nothing to do */
     49:   VecNorm(R,NORM_2,&dp);
     50:   if (ksp->normtype == KSP_NORM_NATURAL) dp *= dp;
     51:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
     52:   ksp->its   = 0;
     53:   ksp->rnorm = dp;
     54:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
     55:   KSPLogResidualHistory(ksp,dp);
     56:   KSPMonitor(ksp,0,dp);
     57:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
     58:   if (ksp->reason) return(0);

     60:   /* Make the initial Rp == R */
     61:   VecCopy(R,RP);
     62:   /*  added for Fidap */
     63:   /* Penalize Startup - Isaac Hasbani Trick for CGS
     64:      Since most initial conditions result in a mostly 0 residual,
     65:      we change all the 0 values in the vector RP to the maximum.
     66:   */
     67:   if (ksp->normtype == KSP_NORM_NATURAL) {
     68:     PetscReal   vr0max;
     69:     PetscScalar *tmp_RP=0;
     70:     PetscInt    numnp  =0, *max_pos=0;
     71:     VecMax(RP, max_pos, &vr0max);
     72:     VecGetArray(RP, &tmp_RP);
     73:     VecGetLocalSize(RP, &numnp);
     74:     for (i=0; i<numnp; i++) {
     75:       if (tmp_RP[i] == 0.0) tmp_RP[i] = vr0max;
     76:     }
     77:     VecRestoreArray(RP, &tmp_RP);
     78:   }
     79:   /*  end of addition for Fidap */

     81:   /* Set the initial conditions */
     82:   VecDot(R,RP,&rhoold);        /* rhoold = (r,rp)      */
     83:   VecCopy(R,U);
     84:   VecCopy(R,P);
     85:   KSP_PCApplyBAorAB(ksp,P,V,T);

     87:   i = 0;
     88:   do {

     90:     VecDot(V,RP,&s);           /* s <- (v,rp)          */
     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:     if (ksp->normtype == KSP_NORM_NATURAL) {
     99:       dp = PetscAbsScalar(rho);
    100:     } else {
    101:       VecNorm(R,NORM_2,&dp);
    102:     }

    104:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
    105:     ksp->its++;
    106:     ksp->rnorm = dp;
    107:     PetscObjectSAWsGrantAccess((PetscObject)ksp);
    108:     KSPLogResidualHistory(ksp,dp);
    109:     KSPMonitor(ksp,i+1,dp);
    110:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
    111:     if (ksp->reason) break;

    113:     b      = rho / rhoold;                           /* b <- rho / rhoold    */
    114:     VecWAXPY(U,b,Q,R);       /* u <- r + b q         */
    115:     VecAXPY(Q,b,P);
    116:     VecWAXPY(P,b,Q,U);       /* p <- u + b(q + b p)  */
    117:     KSP_PCApplyBAorAB(ksp,P,V,Q);    /* v <- K p    */
    118:     rhoold = rho;
    119:     i++;
    120:   } while (i<ksp->max_it);
    121:   if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;

    123:   KSPUnwindPreconditioner(ksp,X,T);
    124:   return(0);
    125: }

    127: /*MC
    128:      KSPCGS - This code implements the CGS (Conjugate Gradient Squared) method.

    130:    Options Database Keys:
    131: .   see KSPSolve()

    133:    Level: beginner

    135:    References:
    136: .     1. - Sonneveld, 1989.

    138:    Notes:
    139:     Does not require a symmetric matrix. Does not apply transpose of the matrix.
    140:         Supports left and right preconditioning, but not symmetric.

    142:    Developer Notes:
    143:     Has this weird support for doing the convergence test with the natural norm, I assume this works only with
    144:       no preconditioning and symmetric positive definite operator.

    146: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS, KSPSetPCSide()
    147: M*/
    148: PETSC_EXTERN PetscErrorCode KSPCreate_CGS(KSP ksp)
    149: {

    153:   ksp->data = (void*)0;

    155:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
    156:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
    157:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_LEFT,2);
    158:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_RIGHT,2);

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