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/*

    The ST (spectral transformation) interface routines related to the

    KSP object associated to it.

*/

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

#undef __FUNCT__  

#define __FUNCT__ "STAssociatedKSPSolve"

/*

   STAssociatedKSPSolve - Solves the linear system of equations associated

   to the spectral transformation.

   Input Parameters:

.  st - the spectral transformation context

.  b  - right hand side vector

   Output  Parameter:

.  x - computed solution

*/

PetscErrorCode STAssociatedKSPSolve(ST st,Vec b,Vec x)

{

  PetscErrorCode ierr;

  PetscInt       its;

  KSPConvergedReason reason;

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  PetscValidHeaderSpecific(b,VEC_COOKIE,2);

  PetscValidHeaderSpecific(x,VEC_COOKIE,3);

  if (!st->ksp) { SETERRQ(PETSC_ERR_SUP,"ST has no associated KSP"); }

  ierr = KSPSolve(st->ksp,b,x);CHKERRQ(ierr);

  ierr = KSPGetConvergedReason(st->ksp,&reason);CHKERRQ(ierr);

  if (reason<0) { SETERRQ1(0,"Warning: KSP did not converge (%d)",reason); }

  ierr = KSPGetIterationNumber(st->ksp,&its);CHKERRQ(ierr);  

  st->lineariterations += its;

  PetscLogInfo((st,"ST: linear solve iterations=%d\n",its));

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STAssociatedKSPSolveTranspose"

/*

   STAssociatedKSPSolveTranspose - Solves the transpose of the linear

   system of equations associated to the spectral transformation.

   Input Parameters:

.  st - the spectral transformation context

.  b  - right hand side vector

   Output  Parameter:

.  x - computed solution

*/

PetscErrorCode STAssociatedKSPSolveTranspose(ST st,Vec b,Vec x)

{

  PetscErrorCode ierr;

  PetscInt       its;

  KSPConvergedReason reason;

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  PetscValidHeaderSpecific(b,VEC_COOKIE,2);

  PetscValidHeaderSpecific(x,VEC_COOKIE,3);

  if (!st->ksp) { SETERRQ(PETSC_ERR_SUP,"ST has no associated KSP"); }

  ierr = KSPSolveTranspose(st->ksp,b,x);CHKERRQ(ierr);

  ierr = KSPGetConvergedReason(st->ksp,&reason);CHKERRQ(ierr);

  if (reason<0) { SETERRQ1(0,"Warning: KSP did not converge (%d)",reason); }

  ierr = KSPGetIterationNumber(st->ksp,&its);CHKERRQ(ierr);  

  st->lineariterations += its;

  PetscLogInfo((st,"ST: linear solve iterations=%d\n",its));

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STSetKSP"

/*@

   STSetKSP - Sets the KSP object associated with the spectral

   transformation.

   Not collective

   Input Parameters:

+  st   - the spectral transformation context

-  ksp  - the linear system context

   Level: advanced

@*/

PetscErrorCode STSetKSP(ST st,KSP ksp)

{

  PetscErrorCode ierr;

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  PetscValidHeaderSpecific(ksp,KSP_COOKIE,2);

  PetscCheckSameComm(st,1,ksp,2);

  if (st->ksp) {

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

  }

  st->ksp = ksp;

  ierr = PetscObjectReference((PetscObject)st->ksp);CHKERRQ(ierr);

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STGetKSP"

/*@

   STGetKSP - Gets the KSP object associated with the spectral

   transformation.

   Not collective

   Input Parameter:

.  st - the spectral transformation context

   Output Parameter:

.  ksp  - the linear system context

   Notes:

   On output, the value of ksp can be PETSC_NULL if the combination of

   eigenproblem type and selected transformation does not require to

   solve a linear system of equations.

   Level: intermediate

@*/

PetscErrorCode STGetKSP(ST st,KSP* ksp)

{

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  if (!st->type_name) { SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"Must call STSetType first"); }

  if (ksp)  *ksp = st->ksp;

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STGetNumberLinearIterations"

/*@

   STGetNumberLinearIterations - Gets the total number of linear iterations

   used by the ST object.

   Not Collective

   Input Parameter:

.  st - the spectral transformation context

   Output Parameter:

.  lits - number of linear iterations

   Level: intermediate

.seealso: STResetNumberLinearIterations()

@*/

PetscErrorCode STGetNumberLinearIterations(ST st,int* lits)

{

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  PetscValidIntPointer(lits,2);

  *lits = st->lineariterations;

  PetscFunctionReturn(0);

}

#undef __FUNCT__  

#define __FUNCT__ "STResetNumberLinearIterations"

/*@

   STResetNumberLinearIterations - Resets the counter for total number of

   linear iterations used by the ST object.

   Collective on ST

   Input Parameter:

.  st - the spectral transformation context

   Level: intermediate

.seealso: STGetNumberLinearIterations()

@*/

PetscErrorCode STResetNumberLinearIterations(ST st)

{

  PetscFunctionBegin;

  PetscValidHeaderSpecific(st,ST_COOKIE,1);

  st->lineariterations = 0;

  PetscFunctionReturn(0);

}

#undef __FUNCT__

#define __FUNCT__ "STCheckNullSpace_Default"

PetscErrorCode STCheckNullSpace_Default(ST st,int n,Vec* V)

{

  PetscErrorCode ierr;

  int            i,c;

  PetscReal      norm;

  Vec            *T,w;

  Mat            A;

  PC             pc;

  MatNullSpace   nullsp;

  PetscFunctionBegin;

  ierr = PetscMalloc(n*sizeof(Vec),&T);CHKERRQ(ierr);

  ierr = KSPGetPC(st->ksp,&pc);CHKERRQ(ierr);

  ierr = PCGetOperators(pc,&A,PETSC_NULL,PETSC_NULL);CHKERRQ(ierr);

  ierr = MatGetVecs(A,PETSC_NULL,&w);CHKERRQ(ierr);

  c = 0;

  for (i=0;i<n;i++) {

    ierr = MatMult(A,V[i],w);CHKERRQ(ierr);

    ierr = VecNorm(w,NORM_2,&norm);CHKERRQ(ierr);

    if (norm < 1e-8) {

      PetscLogInfo((st,"STCheckNullSpace: vector %i norm=%g\n",i,norm));

      T[c] = V[i];

      c++;

    }

  }

  ierr = VecDestroy(w);CHKERRQ(ierr);

  if (c>0) {

    ierr = MatNullSpaceCreate(st->comm,PETSC_FALSE,c,T,&nullsp);CHKERRQ(ierr);

    ierr = KSPSetNullSpace(st->ksp,nullsp);CHKERRQ(ierr);

    ierr = MatNullSpaceDestroy(nullsp);CHKERRQ(ierr);

  }

  ierr = PetscFree(T);CHKERRQ(ierr);

  PetscFunctionReturn(0);

}

#undef __FUNCT__

#define __FUNCT__ "STCheckNullSpace"

/*@C

   STCheckNullSpace - Given a set of vectors, this function test each of

   them to be a nullspace vector of the coefficient matrix of the associated

   KSP object. All these nullspace vectors are passed to the KSP object.

   Collective on ST

   Input Parameters:

+  st - the spectral transformation context

.  n  - number of vectors

-  V  - vectors to be checked

   Note:

   This function allows to handle singular pencils and to solve some problems

   in which the nullspace is important (see the users guide for details).

   Level: developer

.seealso: EPSAttachDeflationSpace()

@*/

PetscErrorCode STCheckNullSpace(ST st,int n,Vec* V)

{

  PetscErrorCode ierr;

  PetscFunctionBegin;

  if (n>0 && st->checknullspace) {

    ierr = (*st->checknullspace)(st,n,V);CHKERRQ(ierr);

  }

  PetscFunctionReturn(0);

}