Date: 2013-09-02T10:06:07+00:00

Actual source code: shift.c

      1: /*
      2:     Shift spectral transformation, applies (A + sigma I) as operator, or
      3:     inv(B)(A + sigma B) for generalized problems

      5:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      6:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      7:    Copyright (c) 2002-2013, Universitat Politecnica de Valencia, Spain

      9:    This file is part of SLEPc.

     11:    SLEPc is free software: you can redistribute it and/or modify it under  the
     12:    terms of version 3 of the GNU Lesser General Public License as published by
     13:    the Free Software Foundation.

     15:    SLEPc  is  distributed in the hope that it will be useful, but WITHOUT  ANY
     16:    WARRANTY;  without even the implied warranty of MERCHANTABILITY or  FITNESS
     17:    FOR  A  PARTICULAR PURPOSE. See the GNU Lesser General Public  License  for
     18:    more details.

     20:    You  should have received a copy of the GNU Lesser General  Public  License
     21:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
     22:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     23: */

     25: #include <slepc-private/stimpl.h>          /*I "slepcst.h" I*/

     29: PetscErrorCode STApply_Shift(ST st,Vec x,Vec y)
     30: {

     34:   if (st->nmat>1) {
     35:     /* generalized eigenproblem: y = B^-1 (A + sB) x */
     36:     MatMult(st->T[0],x,st->w);
     37:     STMatSolve(st,1,st->w,y);
     38:   } else {
     39:     /* standard eigenproblem: y = (A + sI) x */
     40:     MatMult(st->T[0],x,y);
     41:   }
     42:   return(0);
     43: }

     47: PetscErrorCode STApplyTranspose_Shift(ST st,Vec x,Vec y)
     48: {

     52:   if (st->nmat>1) {
     53:     /* generalized eigenproblem: y = (A + sB)^T B^-T  x */
     54:     STMatSolveTranspose(st,1,x,st->w);
     55:     MatMultTranspose(st->T[0],st->w,y);
     56:   } else {
     57:     /* standard eigenproblem: y = (A^T + sI) x */
     58:     MatMultTranspose(st->T[0],x,y);
     59:   }
     60:   return(0);
     61: }

     65: PetscErrorCode STBackTransform_Shift(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     66: {
     67:   PetscInt j;

     70:   for (j=0;j<n;j++) {
     71:     eigr[j] -= st->sigma;
     72:   }
     73:   return(0);
     74: }

     78: PetscErrorCode STPostSolve_Shift(ST st)
     79: {
     81:   PetscScalar    s;

     84:   if (st->shift_matrix == ST_MATMODE_INPLACE) {
     85:     if (st->nmat>1) {
     86:       if (st->nmat==3) {
     87:         MatAXPY(st->A[0],-st->sigma*st->sigma,st->A[2],st->str);
     88:         MatAXPY(st->A[1],2.0*st->sigma,st->A[2],st->str);
     89:         s = st->sigma;
     90:       } else s = -st->sigma;
     91:       MatAXPY(st->A[0],s,st->A[1],st->str);
     92:     } else {
     93:       MatShift(st->A[0],st->sigma);
     94:     }
     95:     st->Astate[0] = ((PetscObject)st->A[0])->state;
     96:     st->setupcalled = 0;
     97:   }
     98:   return(0);
     99: }

    103: PetscErrorCode STSetUp_Shift(ST st)
    104: {

    108:   if (st->nmat<3) {
    109:     /* T[1] = B */
    110:     if (st->nmat>1) { PetscObjectReference((PetscObject)st->A[1]); }
    111:     st->T[1] = st->A[1];
    112:     /* T[0] = A+sigma*B  */
    113:     STMatGAXPY_Private(st,st->sigma,0.0,1,0,PETSC_TRUE);
    114:   } else {
    115:     /* T[2] = C */
    116:     PetscObjectReference((PetscObject)st->A[2]);
    117:     st->T[2] = st->A[2];
    118:     /* T[0] = A-sigma*B+sigma*sigma*C */
    119:     STMatGAXPY_Private(st,-st->sigma,0.0,2,0,PETSC_TRUE);
    120:     /* T[1] = B-2*sigma*C  */
    121:     STMatGAXPY_Private(st,-2.0*st->sigma,0.0,1,1,PETSC_TRUE);
    122:   }
    123:   if (st->nmat==2) {
    124:     if (!st->ksp) { STGetKSP(st,&st->ksp); }
    125:     KSPSetOperators(st->ksp,st->T[1],st->T[1],DIFFERENT_NONZERO_PATTERN);
    126:     KSPSetUp(st->ksp);
    127:     st->kspidx = 1;
    128:   }
    129:   return(0);
    130: }

    134: PetscErrorCode STSetShift_Shift(ST st,PetscScalar newshift)
    135: {
    137:   MatStructure   flg;

    140:   /* Nothing to be done if STSetUp has not been called yet */
    141:   if (!st->setupcalled) return(0);

    143:   if (st->nmat<3) {
    144:     STMatGAXPY_Private(st,newshift,st->sigma,1,0,PETSC_FALSE);
    145:   } else {
    146:     STMatGAXPY_Private(st,-newshift,-st->sigma,2,2,PETSC_FALSE);
    147:     STMatGAXPY_Private(st,-2.0*newshift,-2.0*st->sigma,1,1,PETSC_FALSE);
    148:   }

    150:   if (st->kspidx==0 || (st->nmat==3 && st->kspidx==1)) {  /* Update KSP operator */
    151:     /* Check if the new KSP matrix has the same zero structure */
    152:     if (st->nmat>1 && st->str == DIFFERENT_NONZERO_PATTERN && (st->sigma == 0.0 || newshift == 0.0)) flg = DIFFERENT_NONZERO_PATTERN;
    153:     else flg = SAME_NONZERO_PATTERN;
    154:     KSPSetOperators(st->ksp,st->T[st->kspidx],st->T[st->kspidx],flg);
    155:     KSPSetUp(st->ksp);
    156:   }
    157:   return(0);
    158: }

    162: PetscErrorCode STSetFromOptions_Shift(ST st)
    163: {
    165:   PC             pc;
    166:   PCType         pctype;
    167:   KSPType        ksptype;

    170:   if (!st->ksp) { STGetKSP(st,&st->ksp); }
    171:   KSPGetPC(st->ksp,&pc);
    172:   KSPGetType(st->ksp,&ksptype);
    173:   PCGetType(pc,&pctype);
    174:   if (!pctype && !ksptype) {
    175:     if (st->shift_matrix == ST_MATMODE_SHELL) {
    176:       /* in shell mode use GMRES with Jacobi as the default */
    177:       KSPSetType(st->ksp,KSPGMRES);
    178:       PCSetType(pc,PCJACOBI);
    179:     } else {
    180:       /* use direct solver as default */
    181:       KSPSetType(st->ksp,KSPPREONLY);
    182:       PCSetType(pc,PCREDUNDANT);
    183:     }
    184:   }
    185:   return(0);
    186: }

    190: PETSC_EXTERN PetscErrorCode STCreate_Shift(ST st)
    191: {
    193:   st->ops->apply           = STApply_Shift;
    194:   st->ops->getbilinearform = STGetBilinearForm_Default;
    195:   st->ops->applytrans      = STApplyTranspose_Shift;
    196:   st->ops->postsolve       = STPostSolve_Shift;
    197:   st->ops->backtransform   = STBackTransform_Shift;
    198:   st->ops->setfromoptions  = STSetFromOptions_Shift;
    199:   st->ops->setup           = STSetUp_Shift;
    200:   st->ops->setshift        = STSetShift_Shift;
    201:   return(0);
    202: }