Subversion Repositories slepc-dev

/*

    Folding spectral transformation, applies (A + sigma I)^2 as operator, or

    inv(B)(A + sigma I)^2 for generalized problems

*/

#include "src/st/stimpl.h"          /*I "slepcst.h" I*/

typedef struct {

  PetscTruth  left;

  Vec         w2;

} ST_FOLD;

#undef __FUNCT__  

#define __FUNCT__ "STApply_Fold"

PetscErrorCode STApply_Fold(ST st,Vec x,Vec y)

{

  PetscErrorCode ierr;

  ST_FOLD        *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  if (st->B) {

    /* generalized eigenproblem: y = (B^-1 A + sI)^2 x */

    ierr = MatMult(st->A,x,st->w);CHKERRQ(ierr);

    ierr = STAssociatedKSPSolve(st,st->w,ctx->w2);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(ctx->w2,-st->sigma,x);CHKERRQ(ierr);

    }

    ierr = MatMult(st->A,ctx->w2,st->w);CHKERRQ(ierr);

    ierr = STAssociatedKSPSolve(st,st->w,y);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(y,-st->sigma,ctx->w2);CHKERRQ(ierr);

    }

  } else {

    /* standard eigenproblem: y = (A + sI)^2 x */

    ierr = MatMult(st->A,x,st->w);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(st->w,-st->sigma,x);CHKERRQ(ierr);

    }

    ierr = MatMult(st->A,st->w,y);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(y,-st->sigma,st->w);CHKERRQ(ierr);

    }

  }

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STApplyTranspose_Fold"

PetscErrorCode STApplyTranspose_Fold(ST st,Vec x,Vec y)

{

  PetscErrorCode ierr;

  ST_FOLD        *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  if (st->B) {

    /* generalized eigenproblem: y = (A^T B^-T + sI)^2 x */

    ierr = STAssociatedKSPSolveTranspose(st,x,st->w);CHKERRQ(ierr);

    ierr = MatMult(st->A,st->w,ctx->w2);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(ctx->w2,-st->sigma,x);CHKERRQ(ierr);

    }

    ierr = STAssociatedKSPSolveTranspose(st,ctx->w2,st->w);CHKERRQ(ierr);

    ierr = MatMult(st->A,st->w,y);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(y,-st->sigma,ctx->w2);CHKERRQ(ierr);

    }

  } else {

    /* standard eigenproblem: y = (A^T + sI)^2 x */

    ierr = MatMultTranspose(st->A,x,st->w);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(st->w,-st->sigma,x);CHKERRQ(ierr);

    }

    ierr = MatMultTranspose(st->A,st->w,y);CHKERRQ(ierr);

    if (st->sigma != 0.0) {

      ierr = VecAXPY(y,-st->sigma,st->w);CHKERRQ(ierr);

    }

  }

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STBackTransform_Fold"

PetscErrorCode STBackTransform_Fold(ST st,PetscScalar *eigr,PetscScalar *eigi)

{

  ST_FOLD *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  PetscValidScalarPointer(eigr,2);

  PetscValidScalarPointer(eigi,3);

#if !defined(PETSC_USE_COMPLEX)

  if (*eigi == 0) {

#endif

    if (ctx->left) *eigr = st->sigma - PetscSqrtScalar(*eigr);

    else *eigr = st->sigma + PetscSqrtScalar(*eigr);

#if !defined(PETSC_USE_COMPLEX)

  } else {

    PetscScalar r,x,y;

    r = PetscSqrtScalar(*eigr * *eigr + *eigi * *eigi);

    x = PetscSqrtScalar((r + *eigr) / 2);

    y = PetscSqrtScalar((r - *eigr) / 2);

    if (*eigi < 0) y = - y;

    if (ctx->left) {

      *eigr = st->sigma - x;

      *eigi = - y;

    } else {

      *eigr = st->sigma + x;

      *eigi = y;

    }

  }

#endif

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STSetUp_Fold"

PetscErrorCode STSetUp_Fold(ST st)

{

  PetscErrorCode ierr;

  ST_FOLD        *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  if (st->B) {

    ierr = KSPSetOperators(st->ksp,st->B,st->B,DIFFERENT_NONZERO_PATTERN);CHKERRQ(ierr);

    ierr = KSPSetUp(st->ksp);CHKERRQ(ierr);

    if (ctx->w2) { ierr = VecDestroy(ctx->w2);CHKERRQ(ierr); }

    ierr = MatGetVecs(st->B,&ctx->w2,PETSC_NULL);CHKERRQ(ierr);

  }

  PetscFunctionReturn(0);

}

EXTERN_C_BEGIN

#undef __FUNCT__  

#define __FUNCT__ "STFoldSetLeftSide_Fold"

PetscErrorCode STFoldSetLeftSide_Fold(ST st,PetscTruth left)

{

  ST_FOLD *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  ctx->left = left;

  PetscFunctionReturn(0);

}

EXTERN_C_END

#undef __FUNCT__  

#define __FUNCT__ "STFoldSetLeftSide"

/*@

   STFoldSetLeftSide - Sets a flag to compute eigenvalues on the left side of shift.

   Collective on ST

   Input Parameters:

+  st  - the spectral transformation context

-  left - if true compute eigenvalues on the left side

   Options Database Key:

.  -st_fold_leftside - Sets the value of the flag

   Level: intermediate

.seealso: STSetShift()

@*/

PetscErrorCode STFoldSetLeftSide(ST st,PetscTruth left)

{

  PetscErrorCode ierr, (*f)(ST,PetscTruth);

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  ierr = PetscObjectQueryFunction((PetscObject)st,"STFoldSetLeftSide_C",(void (**)(void))&f);CHKERRQ(ierr);

  if (f) {

    ierr = (*f)(st,left);CHKERRQ(ierr);

  }

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STView_Fold"

PetscErrorCode STView_Fold(ST st,PetscViewer viewer)

{

  PetscErrorCode ierr;

  ST_FOLD        *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  if (ctx->left) {

    ierr = PetscViewerASCIIPrintf(viewer,"  computing eigenvalues on left side of shift\n");CHKERRQ(ierr);

  }  

  if (st->B) {

    ierr = STView_Default(st,viewer);CHKERRQ(ierr);

  }

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STSetFromOptions_Fold"

PetscErrorCode STSetFromOptions_Fold(ST st)

{

  PetscErrorCode ierr;

  ST_FOLD      *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  ierr = PetscOptionsHead("ST Fold Options");CHKERRQ(ierr);

  ierr = PetscOptionsTruth("-st_fold_leftside","Compute eigenvalues on left side of shift","STFoldSetLeftSide",ctx->left,&ctx->left,PETSC_NULL); CHKERRQ(ierr);

  ierr = PetscOptionsTail();CHKERRQ(ierr);

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STDestroy_Fold"

PetscErrorCode STDestroy_Fold(ST st)

{

  PetscErrorCode ierr;

  ST_FOLD        *ctx = (ST_FOLD *) st->data;

  PetscFunctionBegin;

  if (ctx->w2) { ierr = VecDestroy(ctx->w2);CHKERRQ(ierr); }

  ierr = PetscFree(ctx);CHKERRQ(ierr);

  PetscFunctionReturn(0);

}

EXTERN_C_BEGIN

#undef __FUNCT__  

#define __FUNCT__ "STCreate_Fold"

PetscErrorCode STCreate_Fold(ST st)

{

  PetscErrorCode ierr;

  ST_FOLD        *ctx;

  PetscFunctionBegin;

  ierr = PetscNew(ST_FOLD,&ctx); CHKERRQ(ierr);

  PetscLogObjectMemory(st,sizeof(ST_FOLD));

  st->data                = (void *) ctx;

  st->ops->apply           = STApply_Fold;

  st->ops->getbilinearform = STGetBilinearForm_Default;

  st->ops->applytrans      = STApplyTranspose_Fold;

  st->ops->backtr          = STBackTransform_Fold;

  st->ops->setup           = STSetUp_Fold;

  st->ops->view            = STView_Fold;

  st->ops->setfromoptions  = STSetFromOptions_Fold;

  st->ops->destroy         = STDestroy_Fold;

  st->checknullspace       = 0;

  ctx->left            = PETSC_FALSE;

  ierr = PetscObjectComposeFunctionDynamic((PetscObject)st,"STFoldSetLeftSide_C","STFoldSetLeftSide_Fold",

                    STFoldSetLeftSide_Fold);CHKERRQ(ierr);

  PetscFunctionReturn(0);

}

EXTERN_C_END