Date: 2021-02-01T14:41:51+00:00

Actual source code: shift.c
slepc-3.14.2 2021-02-01
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2020, 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 STBackTransform_Shift(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     18: {
     19:   PetscInt j;

     22:   for (j=0;j<n;j++) {
     23:     eigr[j] += st->sigma;
     24:   }
     25:   return(0);
     26: }

     28: PetscErrorCode STPostSolve_Shift(ST st)
     29: {

     33:   if (st->matmode == ST_MATMODE_INPLACE) {
     34:     if (st->nmat>1) {
     35:       MatAXPY(st->A[0],st->sigma,st->A[1],st->str);
     36:     } else {
     37:       MatShift(st->A[0],st->sigma);
     38:     }
     39:     st->Astate[0] = ((PetscObject)st->A[0])->state;
     40:     st->state   = ST_STATE_INITIAL;
     41:     st->opready = PETSC_FALSE;
     42:   }
     43:   return(0);
     44: }

     46: /*
     47:    Operator (shift):
     48:                Op               P         M
     49:    if nmat=1:  A-sI             NULL      A-sI
     50:    if nmat=2:  B^-1 (A-sB)      B         A-sB
     51: */
     52: PetscErrorCode STComputeOperator_Shift(ST st)
     53: {

     57:   st->usesksp = (st->nmat>1)? PETSC_TRUE: PETSC_FALSE;
     58:   PetscObjectReference((PetscObject)st->A[1]);
     59:   MatDestroy(&st->T[1]);
     60:   st->T[1] = st->A[1];
     61:   STMatMAXPY_Private(st,-st->sigma,0.0,0,NULL,PetscNot(st->state==ST_STATE_UPDATED),&st->T[0]);
     62:   if (st->nmat>1) { PetscObjectReference((PetscObject)st->T[1]); }
     63:   MatDestroy(&st->P);
     64:   st->P = (st->nmat>1)? st->T[1]: NULL;
     65:   st->M = st->T[0];
     66:   return(0);
     67: }

     69: PetscErrorCode STSetUp_Shift(ST st)
     70: {
     72:   PetscInt       k,nc,nmat=st->nmat;
     73:   PetscScalar    *coeffs=NULL;

     76:   if (nmat>1) {
     77:     STSetWorkVecs(st,1);
     78:   }
     79:   if (nmat>2) {  /* set-up matrices for polynomial eigenproblems */
     80:     if (st->transform) {
     81:       nc = (nmat*(nmat+1))/2;
     82:       PetscMalloc1(nc,&coeffs);
     83:       /* Compute coeffs */
     84:       STCoeffs_Monomial(st,coeffs);
     85:       /* T[n] = A_n */
     86:       k = nmat-1;
     87:       PetscObjectReference((PetscObject)st->A[k]);
     88:       MatDestroy(&st->T[k]);
     89:       st->T[k] = st->A[k];
     90:       for (k=0;k<nmat-1;k++) {
     91:         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]);
     92:       }
     93:       PetscFree(coeffs);
     94:       PetscObjectReference((PetscObject)st->T[nmat-1]);
     95:       MatDestroy(&st->P);
     96:       st->P = st->T[nmat-1];
     97:       if (!st->ksp) { STGetKSP(st,&st->ksp); }
     98:       STCheckFactorPackage(st);
     99:       KSPSetOperators(st->ksp,st->P,st->P);
    100:     } else {
    101:       for (k=0;k<nmat;k++) {
    102:         PetscObjectReference((PetscObject)st->A[k]);
    103:         MatDestroy(&st->T[k]);
    104:         st->T[k] = st->A[k];
    105:       }
    106:     }
    107:   }
    108:   if (st->P) {
    109:     KSPSetUp(st->ksp);
    110:   }
    111:   return(0);
    112: }

    114: PetscErrorCode STSetShift_Shift(ST st,PetscScalar newshift)
    115: {
    117:   PetscInt       k,nc,nmat=PetscMax(st->nmat,2);
    118:   PetscScalar    *coeffs=NULL;

    121:   if (st->transform) {
    122:     if (st->matmode == ST_MATMODE_COPY && nmat>2) {
    123:       nc = (nmat*(nmat+1))/2;
    124:       PetscMalloc1(nc,&coeffs);
    125:       /* Compute coeffs */
    126:       STCoeffs_Monomial(st,coeffs);
    127:     }
    128:     for (k=0;k<nmat-1;k++) {
    129:       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]);
    130:     }
    131:     if (st->matmode == ST_MATMODE_COPY && nmat>2) {
    132:       PetscFree(coeffs);
    133:     }
    134:     if (st->nmat<=2) st->M = st->T[0];
    135:   }
    136:   return(0);
    137: }

    139: SLEPC_EXTERN PetscErrorCode STCreate_Shift(ST st)
    140: {
    142:   st->usesksp = PETSC_TRUE;

    144:   st->ops->apply           = STApply_Generic;
    145:   st->ops->applytrans      = STApplyTranspose_Generic;
    146:   st->ops->backtransform   = STBackTransform_Shift;
    147:   st->ops->setshift        = STSetShift_Shift;
    148:   st->ops->getbilinearform = STGetBilinearForm_Default;
    149:   st->ops->setup           = STSetUp_Shift;
    150:   st->ops->computeoperator = STComputeOperator_Shift;
    151:   st->ops->postsolve       = STPostSolve_Shift;
    152:   st->ops->setdefaultksp   = STSetDefaultKSP_Default;
    153:   return(0);
    154: }