Actual source code: shift.c
slepc-3.10.1 2018-10-23
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2018, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.
      7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: */
     10: /*
     11:    Shift spectral transformation, applies (A + sigma I) as operator, or
     12:    inv(B)(A + sigma B) for generalized problems
     13: */

     15: #include <slepc/private/stimpl.h>

     17: PetscErrorCode STApply_Shift(ST st,Vec x,Vec y)
     18: {

     22:   if (st->nmat>1) {
     23:     /* generalized eigenproblem: y = B^-1 (A - sB) x */
     24:     MatMult(st->T[0],x,st->work[0]);
     25:     STMatSolve(st,st->work[0],y);
     26:   } else {
     27:     /* standard eigenproblem: y = (A - sI) x */
     28:     MatMult(st->T[0],x,y);
     29:   }
     30:   return(0);
     31: }

     33: PetscErrorCode STApplyTranspose_Shift(ST st,Vec x,Vec y)
     34: {

     38:   if (st->nmat>1) {
     39:     /* generalized eigenproblem: y = (A - sB)^T B^-T  x */
     40:     STMatSolveTranspose(st,x,st->work[0]);
     41:     MatMultTranspose(st->T[0],st->work[0],y);
     42:   } else {
     43:     /* standard eigenproblem: y = (A^T - sI) x */
     44:     MatMultTranspose(st->T[0],x,y);
     45:   }
     46:   return(0);
     47: }

     49: PetscErrorCode STBackTransform_Shift(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     50: {
     51:   PetscInt j;

     54:   for (j=0;j<n;j++) {
     55:     eigr[j] += st->sigma;
     56:   }
     57:   return(0);
     58: }

     60: PetscErrorCode STPostSolve_Shift(ST st)
     61: {

     65:   if (st->shift_matrix == ST_MATMODE_INPLACE) {
     66:     if (st->nmat>1) {
     67:       MatAXPY(st->A[0],st->sigma,st->A[1],st->str);
     68:     } else {
     69:       MatShift(st->A[0],st->sigma);
     70:     }
     71:     st->Astate[0] = ((PetscObject)st->A[0])->state;
     72:     st->state = ST_STATE_INITIAL;
     73:   }
     74:   return(0);
     75: }

     77: PetscErrorCode STSetUp_Shift(ST st)
     78: {
     80:   PetscInt       k,nc,nmat=PetscMax(st->nmat,2);
     81:   PetscScalar    *coeffs=NULL;

     84:   if (st->nmat>1) {
     85:     STSetWorkVecs(st,1);
     86:   }
     87:   if (nmat<3 || st->transform) {
     88:     if (nmat>2) {
     89:       nc = (nmat*(nmat+1))/2;
     90:       PetscMalloc1(nc,&coeffs);
     91:       /* Compute coeffs */
     92:       STCoeffs_Monomial(st,coeffs);
     93:     }
     94:     /* T[n] = A_n */
     95:     k = nmat-1;
     96:     PetscObjectReference((PetscObject)st->A[k]);
     97:     MatDestroy(&st->T[k]);
     98:     st->T[k] = st->A[k];
     99:     for (k=0;k<nmat-1;k++) {
    100:       STMatMAXPY_Private(st,nmat>2?st->sigma:-st->sigma,0.0,k,coeffs?coeffs+((nmat-k)*(nmat-k-1))/2:NULL,PetscNot(st->state==ST_STATE_UPDATED),&st->T[k]);
    101:     }
    102:      if (nmat>2) { PetscFree(coeffs); }
    103:   } else {
    104:     for (k=0;k<nmat;k++) {
    105:       PetscObjectReference((PetscObject)st->A[k]);
    106:       MatDestroy(&st->T[k]);
    107:       st->T[k] = st->A[k];
    108:     }
    109:   }
    110:   if (nmat>=2 && st->transform) {
    111:     PetscObjectReference((PetscObject)st->T[nmat-1]);
    112:     MatDestroy(&st->P);
    113:     st->P = st->T[nmat-1];
    114:   }
    115:   if (st->P) {
    116:     if (!st->ksp) { STGetKSP(st,&st->ksp); }
    117:     STCheckFactorPackage(st);
    118:     KSPSetOperators(st->ksp,st->P,st->P);
    119:     KSPSetUp(st->ksp);
    120:   }
    121:   return(0);
    122: }

    124: PetscErrorCode STSetShift_Shift(ST st,PetscScalar newshift)
    125: {
    127:   PetscInt       k,nc,nmat=PetscMax(st->nmat,2);
    128:   PetscScalar    *coeffs=NULL;

    131:   if (st->transform) {
    132:     if (st->shift_matrix == ST_MATMODE_COPY && nmat>2) {
    133:       nc = (nmat*(nmat+1))/2;
    134:       PetscMalloc1(nc,&coeffs);
    135:       /* Compute coeffs */
    136:       STCoeffs_Monomial(st,coeffs);
    137:     }
    138:     for (k=0;k<nmat-1;k++) {
    139:       STMatMAXPY_Private(st,nmat>2?newshift:-newshift,nmat>2?st->sigma:-st->sigma,k,coeffs?coeffs+((nmat-k)*(nmat-k-1))/2:NULL,PETSC_FALSE,&st->T[k]);
    140:     }
    141:     if (st->shift_matrix == ST_MATMODE_COPY && nmat>2) {
    142:         PetscFree(coeffs);
    143:     }
    144:   }
    145:   return(0);
    146: }

    148: PETSC_EXTERN PetscErrorCode STCreate_Shift(ST st)
    149: {
    151:   st->ops->apply           = STApply_Shift;
    152:   st->ops->getbilinearform = STGetBilinearForm_Default;
    153:   st->ops->applytrans      = STApplyTranspose_Shift;
    154:   st->ops->postsolve       = STPostSolve_Shift;
    155:   st->ops->backtransform   = STBackTransform_Shift;
    156:   st->ops->setup           = STSetUp_Shift;
    157:   st->ops->setshift        = STSetShift_Shift;
    158:   st->ops->setdefaultksp   = STSetDefaultKSP_Default;
    159:   return(0);
    160: }