Date: 2021-03-03T22:27:23+00:00

Actual source code: cgs.c
petsc-3.14.5 2021-03-03
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:   if (ksp->normtype != KSP_NORM_NONE) {
     50:     VecNorm(R,NORM_2,&dp);
     51:     KSPCheckNorm(ksp,dp);
     52:     if (ksp->normtype == KSP_NORM_NATURAL) dp *= dp;
     53:   } else dp = 0.0;

     55:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
     56:   ksp->its   = 0;
     57:   ksp->rnorm = dp;
     58:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
     59:   KSPLogResidualHistory(ksp,dp);
     60:   KSPMonitor(ksp,0,dp);
     61:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
     62:   if (ksp->reason) return(0);

     64:   /* Make the initial Rp == R */
     65:   VecCopy(R,RP);
     66:   /*  added for Fidap */
     67:   /* Penalize Startup - Isaac Hasbani Trick for CGS
     68:      Since most initial conditions result in a mostly 0 residual,
     69:      we change all the 0 values in the vector RP to the maximum.
     70:   */
     71:   if (ksp->normtype == KSP_NORM_NATURAL) {
     72:     PetscReal   vr0max;
     73:     PetscScalar *tmp_RP=NULL;
     74:     PetscInt    numnp  =0, *max_pos=NULL;
     75:     VecMax(RP, max_pos, &vr0max);
     76:     VecGetArray(RP, &tmp_RP);
     77:     VecGetLocalSize(RP, &numnp);
     78:     for (i=0; i<numnp; i++) {
     79:       if (tmp_RP[i] == 0.0) tmp_RP[i] = vr0max;
     80:     }
     81:     VecRestoreArray(RP, &tmp_RP);
     82:   }
     83:   /*  end of addition for Fidap */

     85:   /* Set the initial conditions */
     86:   VecDot(R,RP,&rhoold);        /* rhoold = (r,rp)      */
     87:   VecCopy(R,U);
     88:   VecCopy(R,P);
     89:   KSP_PCApplyBAorAB(ksp,P,V,T);

     91:   i = 0;
     92:   do {

     94:     VecDot(V,RP,&s);           /* s <- (v,rp)          */
     95:     KSPCheckDot(ksp,s);
     96:     a    = rhoold / s;                               /* a <- rho / s         */
     97:     VecWAXPY(Q,-a,V,U);      /* q <- u - a v         */
     98:     VecWAXPY(T,1.0,U,Q);      /* t <- u + q           */
     99:     VecAXPY(X,a,T);           /* x <- x + a (u + q)   */
    100:     KSP_PCApplyBAorAB(ksp,T,AUQ,U);
    101:     VecAXPY(R,-a,AUQ);       /* r <- r - a K (u + q) */
    102:     VecDot(R,RP,&rho);         /* rho <- (r,rp)        */
    103:     KSPCheckDot(ksp,rho);
    104:     if (ksp->normtype == KSP_NORM_NATURAL) {
    105:       dp = PetscAbsScalar(rho);
    106:     } else if (ksp->normtype != KSP_NORM_NONE) {
    107:       VecNorm(R,NORM_2,&dp);
    108:       KSPCheckNorm(ksp,dp);
    109:     } else dp = 0.0;

    111:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
    112:     ksp->its++;
    113:     ksp->rnorm = dp;
    114:     PetscObjectSAWsGrantAccess((PetscObject)ksp);
    115:     KSPLogResidualHistory(ksp,dp);
    116:     KSPMonitor(ksp,i+1,dp);
    117:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
    118:     if (ksp->reason) break;

    120:     b      = rho / rhoold;                           /* b <- rho / rhoold    */
    121:     VecWAXPY(U,b,Q,R);       /* u <- r + b q         */
    122:     VecAXPY(Q,b,P);
    123:     VecWAXPY(P,b,Q,U);       /* p <- u + b(q + b p)  */
    124:     KSP_PCApplyBAorAB(ksp,P,V,Q);    /* v <- K p    */
    125:     rhoold = rho;
    126:     i++;
    127:   } while (i<ksp->max_it);
    128:   if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;

    130:   KSPUnwindPreconditioner(ksp,X,T);
    131:   return(0);
    132: }

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

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

    140:    Level: beginner

    142:    References:
    143: .     1. - Sonneveld, 1989.

    145:    Notes:
    146:     Does not require a symmetric matrix. Does not apply transpose of the matrix.
    147:         Supports left and right preconditioning, but not symmetric.

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

    153: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS, KSPSetPCSide()
    154: M*/
    155: PETSC_EXTERN PetscErrorCode KSPCreate_CGS(KSP ksp)
    156: {

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

    162:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
    163:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
    164:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_LEFT,2);
    165:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_RIGHT,2);
    166:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,1);
    167:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);

    169:   ksp->ops->setup          = KSPSetUp_CGS;
    170:   ksp->ops->solve          = KSPSolve_CGS;
    171:   ksp->ops->destroy        = KSPDestroyDefault;
    172:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
    173:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
    174:   ksp->ops->setfromoptions = NULL;
    175:   ksp->ops->view           = NULL;
    176:   return(0);
    177: }