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
  4: */
 5:  #include src/st/stimpl.h

  9: PetscErrorCode STApply_Shift(ST st,Vec x,Vec y)
 10: {

 14:   if (st->B) {
 15:     /* generalized eigenproblem: y = (B^-1 A + sI) x */
 16:     MatMult(st->A,x,st->w);
 17:     STAssociatedKSPSolve(st,st->w,y);
 18:   }
 19:   else {
 20:     /* standard eigenproblem: y = (A + sI) x */
 21:     MatMult(st->A,x,y);
 22:   }
 23:   if (st->sigma != 0.0) {
 24:     VecAXPY(y,st->sigma,x);
 25:   }
 26:   return(0);
 27: }

 31: PetscErrorCode STApplyTranspose_Shift(ST st,Vec x,Vec y)
 32: {

 36:   if (st->B) {
 37:     /* generalized eigenproblem: y = (A^T B^-T + sI) x */
 38:     STAssociatedKSPSolveTranspose(st,x,st->w);
 39:     MatMultTranspose(st->A,st->w,y);
 40:   }
 41:   else {
 42:     /* standard eigenproblem: y = (A^T + sI) x */
 43:     MatMultTranspose(st->A,x,y);
 44:   }
 45:   if (st->sigma != 0.0) {
 46:     VecAXPY(y,st->sigma,x);
 47:   }
 48:   return(0);
 49: }

 53: PetscErrorCode STApplyB_Shift(ST st,Vec x,Vec y)
 54: {

 58:   VecCopy( x, y );
 59:   return(0);
 60: }

 64: PetscErrorCode STBackTransform_Shift(ST st,PetscScalar *eigr,PetscScalar *eigi)
 65: {
 67:   if (eigr) *eigr -= st->sigma;
 68:   return(0);
 69: }

 73: PetscErrorCode STSetUp_Shift(ST st)
 74: {

 78:   if (st->B) {
 79:     KSPSetOperators(st->ksp,st->B,st->B,DIFFERENT_NONZERO_PATTERN);
 80:     KSPSetUp(st->ksp);
 81:   }
 82:   return(0);
 83: }

 87: PetscErrorCode STView_Shift(ST st,PetscViewer viewer)
 88: {

 92:   if (st->B) {
 93:     STView_Default(st,viewer);
 94:   }
 95:   return(0);
 96: }

101: PetscErrorCode STCreate_Shift(ST st)
102: {
104:   st->ops->apply       = STApply_Shift;
105:   st->ops->applyB      = STApplyB_Shift;
106:   st->ops->applynoB    = STApply_Shift;
107:   st->ops->applytrans  = STApplyTranspose_Shift;
108:   st->ops->backtr      = STBackTransform_Shift;
109:   st->ops->setup       = STSetUp_Shift;
110:   st->ops->view        = STView_Shift;
111:   st->checknullspace   = 0;
112:   return(0);
113: }