xref: /petsc/src/dm/impls/shell/dmshell.c (revision b00a91154f763f12aa55f3d53a3f2776f15f49e3)

#include <petscdmshell.h>       /*I    "petscdmshell.h"  I*/
#include <petscmat.h>
#include <petsc-private/dmimpl.h>

typedef struct  {
  Vec        Xglobal;
  Vec        Xlocal;
  Mat        A;
  VecScatter gtol;
  VecScatter ltog;
  VecScatter ltol;
} DM_Shell;

#undef __FUNCT__
#define __FUNCT__ "DMGlobalToLocalBeginDefaultShell"
/*@
   DMGlobalToLocalBeginDefaultShell - Uses the GlobalToLocal VecScatter context set by the user to begin a global to local scatter
   Collective

   Input Arguments:
+  dm - shell DM
.  g - global vector
.  mode - InsertMode
-  l - local vector

   Level: advanced

   Note:  This is not normally called directly by user code, generally user code calls DMGlobalToLocalBegin() and DMGlobalToLocalEnd(). If the user provides their own custom routines to DMShellSetLocalToGlobal() then those routines might have reason to call this function.

.seealso: DMGlobalToLocalEndDefaultShell()
@*/
PetscErrorCode DMGlobalToLocalBeginDefaultShell(DM dm,Vec g,InsertMode mode,Vec l)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
  if (!shell->gtol) SETERRQ(((PetscObject)dm)->comm,PETSC_ERR_ARG_WRONGSTATE, "Cannot be used without first setting the scatter context via DMShellSetGlobalToLocalVecScatter()");
  ierr = VecScatterBegin(shell->gtol,g,l,mode,SCATTER_FORWARD);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMGlobalToLocalEndDefaultShell"
/*@
   DMGlobalToLocalEndDefaultShell - Uses the GlobalToLocal VecScatter context set by the user to end a global to local scatter
   Collective

   Input Arguments:
+  dm - shell DM
.  g - global vector
.  mode - InsertMode
-  l - local vector

   Level: advanced

.seealso: DMGlobalToLocalBeginDefaultShell()
@*/
PetscErrorCode DMGlobalToLocalEndDefaultShell(DM dm,Vec g,InsertMode mode,Vec l)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
   if (!shell->gtol) SETERRQ(((PetscObject)dm)->comm,PETSC_ERR_ARG_WRONGSTATE, "Cannot be used without first setting the scatter context via DMShellSetGlobalToLocalVecScatter()");
  ierr = VecScatterEnd(shell->gtol,g,l,mode,SCATTER_FORWARD);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMLocalToGlobalBeginDefaultShell"
/*@
   DMLocalToGlobalBeginDefaultShell - Uses the LocalToGlobal VecScatter context set by the user to begin a local to global scatter
   Collective

   Input Arguments:
+  dm - shell DM
.  l - local vector
.  mode - InsertMode
-  g - global vector

   Level: advanced

   Note:  This is not normally called directly by user code, generally user code calls DMLocalToGlobalBegin() and DMLocalToGlobalEnd(). If the user provides their own custom routines to DMShellSetLocalToGlobal() then those routines might have reason to call this function.

.seealso: DMLocalToGlobalEndDefaultShell()
@*/
PetscErrorCode DMLocalToGlobalBeginDefaultShell(DM dm,Vec l,InsertMode mode,Vec g)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
  if (!shell->ltog) SETERRQ(((PetscObject)dm)->comm,PETSC_ERR_ARG_WRONGSTATE, "Cannot be used without first setting the scatter context via DMShellSetLocalToGlobalVecScatter()");
  ierr = VecScatterBegin(shell->ltog,l,g,mode,SCATTER_FORWARD);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMLocalToGlobalEndDefaultShell"
/*@
   DMLocalToGlobalEndDefaultShell - Uses the LocalToGlobal VecScatter context set by the user to end a local to global scatter
   Collective

   Input Arguments:
+  dm - shell DM
.  l - local vector
.  mode - InsertMode
-  g - global vector

   Level: advanced

.seealso: DMLocalToGlobalBeginDefaultShell()
@*/
PetscErrorCode DMLocalToGlobalEndDefaultShell(DM dm,Vec l,InsertMode mode,Vec g)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
   if (!shell->ltog) SETERRQ(((PetscObject)dm)->comm,PETSC_ERR_ARG_WRONGSTATE, "Cannot be used without first setting the scatter context via DMShellSetLocalToGlobalVecScatter()");
  ierr = VecScatterEnd(shell->ltog,l,g,mode,SCATTER_FORWARD);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMLocalToLocalBeginDefaultShell"
/*@
   DMLocalToLocalBeginDefaultShell - Uses the LocalToLocal VecScatter context set by the user to begin a local to local scatter
   Collective

   Input Arguments:
+  dm - shell DM
.  g - the original local vector
-  mode - InsertMode

   Output Parameter:
.  l  - the local vector with correct ghost values

   Level: advanced

   Note:  This is not normally called directly by user code, generally user code calls DMLocalToLocalBegin() and DMLocalToLocalEnd(). If the user provides their own custom routines to DMShellSetLocalToLocal() then those routines might have reason to call this function.

.seealso: DMLocalToLocalEndDefaultShell()
@*/
PetscErrorCode DMLocalToLocalBeginDefaultShell(DM dm,Vec g,InsertMode mode,Vec l)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
  if (!shell->ltol) SETERRQ(((PetscObject)dm)->comm,PETSC_ERR_ARG_WRONGSTATE, "Cannot be used without first setting the scatter context via DMShellSetLocalToLocalVecScatter()");
  ierr = VecScatterBegin(shell->ltol,g,l,mode,SCATTER_FORWARD);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMLocalToLocalEndDefaultShell"
/*@
   DMLocalToLocalEndDefaultShell - Uses the LocalToLocal VecScatter context set by the user to end a local to local scatter
   Collective

   Input Arguments:
+  dm - shell DM
.  g - the original local vector
-  mode - InsertMode

   Output Parameter:
.  l  - the local vector with correct ghost values

   Level: advanced

.seealso: DMLocalToLocalBeginDefaultShell()
@*/
PetscErrorCode DMLocalToLocalEndDefaultShell(DM dm,Vec g,InsertMode mode,Vec l)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
   if (!shell->ltol) SETERRQ(((PetscObject)dm)->comm,PETSC_ERR_ARG_WRONGSTATE, "Cannot be used without first setting the scatter context via DMShellSetGlobalToLocalVecScatter()");
  ierr = VecScatterEnd(shell->ltol,g,l,mode,SCATTER_FORWARD);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMCreateMatrix_Shell"
static PetscErrorCode DMCreateMatrix_Shell(DM dm,Mat *J)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;
  Mat            A;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidPointer(J,3);
  if (!shell->A) {
    if (shell->Xglobal) {
      PetscInt m,M;
      ierr = PetscInfo(dm,"Naively creating matrix using global vector distribution without preallocation");CHKERRQ(ierr);
      ierr = VecGetSize(shell->Xglobal,&M);CHKERRQ(ierr);
      ierr = VecGetLocalSize(shell->Xglobal,&m);CHKERRQ(ierr);
      ierr = MatCreate(PetscObjectComm((PetscObject)dm),&shell->A);CHKERRQ(ierr);
      ierr = MatSetSizes(shell->A,m,m,M,M);CHKERRQ(ierr);
      ierr = MatSetType(shell->A,dm->mattype);CHKERRQ(ierr);
      ierr = MatSetUp(shell->A);CHKERRQ(ierr);
    } else SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_USER,"Must call DMShellSetMatrix(), DMShellSetCreateMatrix(), or provide a vector");
  }
  A = shell->A;
  /* the check below is tacky and incomplete */
  if (dm->mattype) {
    PetscBool flg,aij,seqaij,mpiaij;
    ierr = PetscObjectTypeCompare((PetscObject)A,dm->mattype,&flg);CHKERRQ(ierr);
    ierr = PetscObjectTypeCompare((PetscObject)A,MATSEQAIJ,&seqaij);CHKERRQ(ierr);
    ierr = PetscObjectTypeCompare((PetscObject)A,MATMPIAIJ,&mpiaij);CHKERRQ(ierr);
    ierr = PetscStrcmp(dm->mattype,MATAIJ,&aij);CHKERRQ(ierr);
    if (!flg) {
      if (!(aij && (seqaij || mpiaij))) SETERRQ2(PetscObjectComm((PetscObject)dm),PETSC_ERR_ARG_NOTSAMETYPE,"Requested matrix of type %s, but only %s available",dm->mattype,((PetscObject)A)->type_name);
    }
  }
  if (((PetscObject)A)->refct < 2) { /* We have an exclusive reference so we can give it out */
    ierr = PetscObjectReference((PetscObject)A);CHKERRQ(ierr);
    ierr = MatZeroEntries(A);CHKERRQ(ierr);
    *J   = A;
  } else {                      /* Need to create a copy, could use MAT_SHARE_NONZERO_PATTERN in most cases */
    ierr = MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,J);CHKERRQ(ierr);
    ierr = MatZeroEntries(*J);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMCreateGlobalVector_Shell"
PetscErrorCode DMCreateGlobalVector_Shell(DM dm,Vec *gvec)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;
  Vec            X;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidPointer(gvec,2);
  *gvec = 0;
  X     = shell->Xglobal;
  if (!X) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_USER,"Must call DMShellSetGlobalVector() or DMShellSetCreateGlobalVector()");
  if (((PetscObject)X)->refct < 2) { /* We have an exclusive reference so we can give it out */
    ierr  = PetscObjectReference((PetscObject)X);CHKERRQ(ierr);
    ierr  = VecZeroEntries(X);CHKERRQ(ierr);
    *gvec = X;
  } else {                      /* Need to create a copy, could use MAT_SHARE_NONZERO_PATTERN in most cases */
    ierr = VecDuplicate(X,gvec);CHKERRQ(ierr);
    ierr = VecZeroEntries(*gvec);CHKERRQ(ierr);
  }
  ierr = VecSetDM(*gvec,dm);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMCreateLocalVector_Shell"
PetscErrorCode DMCreateLocalVector_Shell(DM dm,Vec *gvec)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;
  Vec            X;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidPointer(gvec,2);
  *gvec = 0;
  X     = shell->Xlocal;
  if (!X) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_USER,"Must call DMShellSetLocalVector() or DMShellSetCreateLocalVector()");
  if (((PetscObject)X)->refct < 2) { /* We have an exclusive reference so we can give it out */
    ierr  = PetscObjectReference((PetscObject)X);CHKERRQ(ierr);
    ierr  = VecZeroEntries(X);CHKERRQ(ierr);
    *gvec = X;
  } else {                      /* Need to create a copy, could use MAT_SHARE_NONZERO_PATTERN in most cases */
    ierr = VecDuplicate(X,gvec);CHKERRQ(ierr);
    ierr = VecZeroEntries(*gvec);CHKERRQ(ierr);
  }
  ierr = VecSetDM(*gvec,dm);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetMatrix"
/*@
   DMShellSetMatrix - sets a template matrix associated with the DMShell

   Collective

   Input Arguments:
+  dm - shell DM
-  J - template matrix

   Level: advanced

.seealso: DMCreateMatrix(), DMShellSetCreateMatrix()
@*/
PetscErrorCode DMShellSetMatrix(DM dm,Mat J)
{
  DM_Shell       *shell = (DM_Shell*)dm->data;
  PetscErrorCode ierr;
  PetscBool      isshell;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidHeaderSpecific(J,MAT_CLASSID,2);
  ierr = PetscObjectTypeCompare((PetscObject)dm,DMSHELL,&isshell);CHKERRQ(ierr);
  if (!isshell) PetscFunctionReturn(0);
  ierr     = PetscObjectReference((PetscObject)J);CHKERRQ(ierr);
  ierr     = MatDestroy(&shell->A);CHKERRQ(ierr);
  shell->A = J;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetCreateMatrix"
/*@C
   DMShellSetCreateMatrix - sets the routine to create a matrix associated with the shell DM

   Logically Collective on DM

   Input Arguments:
+  dm - the shell DM
-  func - the function to create a matrix

   Level: advanced

.seealso: DMCreateMatrix(), DMShellSetMatrix()
@*/
PetscErrorCode DMShellSetCreateMatrix(DM dm,PetscErrorCode (*func)(DM,Mat*))
{

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  dm->ops->creatematrix = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetGlobalVector"
/*@
   DMShellSetGlobalVector - sets a template global vector associated with the DMShell

   Logically Collective on DM

   Input Arguments:
+  dm - shell DM
-  X - template vector

   Level: advanced

.seealso: DMCreateGlobalVector(), DMShellSetMatrix(), DMShellSetCreateGlobalVector()
@*/
PetscErrorCode DMShellSetGlobalVector(DM dm,Vec X)
{
  DM_Shell       *shell = (DM_Shell*)dm->data;
  PetscErrorCode ierr;
  PetscBool      isshell;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidHeaderSpecific(X,VEC_CLASSID,2);
  ierr = PetscObjectTypeCompare((PetscObject)dm,DMSHELL,&isshell);CHKERRQ(ierr);
  if (!isshell) PetscFunctionReturn(0);
  ierr           = PetscObjectReference((PetscObject)X);CHKERRQ(ierr);
  ierr           = VecDestroy(&shell->Xglobal);CHKERRQ(ierr);
  shell->Xglobal = X;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetCreateGlobalVector"
/*@C
   DMShellSetCreateGlobalVector - sets the routine to create a global vector associated with the shell DM

   Logically Collective

   Input Arguments:
+  dm - the shell DM
-  func - the creation routine

   Level: advanced

.seealso: DMShellSetGlobalVector(), DMShellSetCreateMatrix()
@*/
PetscErrorCode DMShellSetCreateGlobalVector(DM dm,PetscErrorCode (*func)(DM,Vec*))
{

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  dm->ops->createglobalvector = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetLocalVector"
/*@
   DMShellSetLocalVector - sets a template local vector associated with the DMShell

   Logically Collective on DM

   Input Arguments:
+  dm - shell DM
-  X - template vector

   Level: advanced

.seealso: DMCreateLocalVector(), DMShellSetMatrix(), DMShellSetCreateLocalVector()
@*/
PetscErrorCode DMShellSetLocalVector(DM dm,Vec X)
{
  DM_Shell       *shell = (DM_Shell*)dm->data;
  PetscErrorCode ierr;
  PetscBool      isshell;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidHeaderSpecific(X,VEC_CLASSID,2);
  ierr = PetscObjectTypeCompare((PetscObject)dm,DMSHELL,&isshell);CHKERRQ(ierr);
  if (!isshell) PetscFunctionReturn(0);
  ierr = PetscObjectReference((PetscObject)X);CHKERRQ(ierr);
  ierr = VecDestroy(&shell->Xlocal);CHKERRQ(ierr);
  shell->Xlocal = X;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetCreateLocalVector"
/*@C
   DMShellSetCreateLocalVector - sets the routine to create a local vector associated with the shell DM

   Logically Collective

   Input Arguments:
+  dm - the shell DM
-  func - the creation routine

   Level: advanced

.seealso: DMShellSetLocalVector(), DMShellSetCreateMatrix()
@*/
PetscErrorCode DMShellSetCreateLocalVector(DM dm,PetscErrorCode (*func)(DM,Vec*))
{

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  dm->ops->createlocalvector = func;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetGlobalToLocal"
/*@C
   DMShellSetGlobalToLocal - Sets the routines used to perform a global to local scatter

   Logically Collective on DM

   Input Arguments
+  dm - the shell DM
.  begin - the routine that begins the global to local scatter
-  end - the routine that ends the global to local scatter

   Notes: If these functions are not provided but DMShellSetGlobalToLocalVecScatter() is called then
   DMGlobalToLocalBeginDefaultShell()/DMGlobalToLocalEndDefaultShell() are used to to perform the transfers

   Level: advanced

.seealso: DMShellSetLocalToGlobal(), DMGlobalToLocalBeginDefaultShell(), DMGlobalToLocalEndDefaultShell()
@*/
PetscErrorCode DMShellSetGlobalToLocal(DM dm,PetscErrorCode (*begin)(DM,Vec,InsertMode,Vec),PetscErrorCode (*end)(DM,Vec,InsertMode,Vec)) {
  PetscFunctionBegin;
  dm->ops->globaltolocalbegin = begin;
  dm->ops->globaltolocalend = end;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetLocalToGlobal"
/*@C
   DMShellSetLocalToGlobal - Sets the routines used to perform a local to global scatter

   Logically Collective on DM

   Input Arguments
+  dm - the shell DM
.  begin - the routine that begins the local to global scatter
-  end - the routine that ends the local to global scatter

   Notes: If these functions are not provided but DMShellSetLocalToGlobalVecScatter() is called then
   DMLocalToGlobalBeginDefaultShell()/DMLocalToGlobalEndDefaultShell() are used to to perform the transfers

   Level: advanced

.seealso: DMShellSetGlobalToLocal()
@*/
PetscErrorCode DMShellSetLocalToGlobal(DM dm,PetscErrorCode (*begin)(DM,Vec,InsertMode,Vec),PetscErrorCode (*end)(DM,Vec,InsertMode,Vec)) {
  PetscFunctionBegin;
  dm->ops->localtoglobalbegin = begin;
  dm->ops->localtoglobalend = end;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetLocalToLocal"
/*@C
   DMShellSetLocalToLocal - Sets the routines used to perform a local to local scatter

   Logically Collective on DM

   Input Arguments
+  dm - the shell DM
.  begin - the routine that begins the local to local scatter
-  end - the routine that ends the local to local scatter

   Notes: If these functions are not provided but DMShellSetLocalToLocalVecScatter() is called then
   DMLocalToLocalBeginDefaultShell()/DMLocalToLocalEndDefaultShell() are used to to perform the transfers

   Level: advanced

.seealso: DMShellSetGlobalToLocal(), DMLocalToLocalBeginDefaultShell(), DMLocalToLocalEndDefaultShell()
@*/
PetscErrorCode DMShellSetLocalToLocal(DM dm,PetscErrorCode (*begin)(DM,Vec,InsertMode,Vec),PetscErrorCode (*end)(DM,Vec,InsertMode,Vec)) {
  PetscFunctionBegin;
  dm->ops->localtolocalbegin = begin;
  dm->ops->localtolocalend = end;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetGlobalToLocalVecScatter"
/*@
   DMShellSetGlobalToLocalVecScatter - Sets a VecScatter context for global to local communication

   Logically Collective on DM

   Input Arguments
+  dm - the shell DM
-  gtol - the global to local VecScatter context

   Level: advanced

.seealso: DMShellSetGlobalToLocal(), DMGlobalToLocalBeginDefaultShell(), DMGlobalToLocalEndDefaultShell()
@*/
PetscErrorCode DMShellSetGlobalToLocalVecScatter(DM dm, VecScatter gtol)
{
  DM_Shell       *shell = (DM_Shell*)dm->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectReference((PetscObject)gtol);CHKERRQ(ierr);
  /* Call VecScatterDestroy() to avoid a memory leak in case of re-setting. */
  ierr = VecScatterDestroy(&shell->gtol);CHKERRQ(ierr);
  shell->gtol = gtol;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetLocalToGlobalVecScatter"
/*@
   DMShellSetLocalToGlobalVecScatter - Sets a VecScatter context for local to global communication

   Logically Collective on DM

   Input Arguments
+  dm - the shell DM
-  ltog - the local to global VecScatter context

   Level: advanced

.seealso: DMShellSetLocalToGlobal(), DMLocalToGlobalBeginDefaultShell(), DMLocalToGlobalEndDefaultShell()
@*/
PetscErrorCode DMShellSetLocalToGlobalVecScatter(DM dm, VecScatter ltog)
{
  DM_Shell       *shell = (DM_Shell*)dm->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectReference((PetscObject)ltog);CHKERRQ(ierr);
  /* Call VecScatterDestroy() to avoid a memory leak in case of re-setting. */
  ierr = VecScatterDestroy(&shell->ltog);CHKERRQ(ierr);
  shell->ltog = ltog;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellSetLocalToLocalVecScatter"
/*@
   DMShellSetLocalToLocalVecScatter - Sets a VecScatter context for local to local communication

   Logically Collective on DM

   Input Arguments
+  dm - the shell DM
-  ltol - the local to local VecScatter context

   Level: advanced

.seealso: DMShellSetLocalToLocal(), DMLocalToLocalBeginDefaultShell(), DMLocalToLocalEndDefaultShell()
@*/
PetscErrorCode DMShellSetLocalToLocalVecScatter(DM dm, VecScatter ltol)
{
  DM_Shell       *shell = (DM_Shell*)dm->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectReference((PetscObject)ltol);CHKERRQ(ierr);
  /* Call VecScatterDestroy() to avoid a memory leak in case of re-setting. */
  ierr = VecScatterDestroy(&shell->ltol);CHKERRQ(ierr);
  shell->ltol = ltol;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMDestroy_Shell"
static PetscErrorCode DMDestroy_Shell(DM dm)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
  ierr = MatDestroy(&shell->A);CHKERRQ(ierr);
  ierr = VecDestroy(&shell->Xglobal);CHKERRQ(ierr);
  ierr = VecDestroy(&shell->Xlocal);CHKERRQ(ierr);
  ierr = VecScatterDestroy(&shell->gtol);CHKERRQ(ierr);
  ierr = VecScatterDestroy(&shell->ltog);CHKERRQ(ierr);
  /* This was originally freed in DMDestroy(), but that prevents reference counting of backend objects */
  ierr = PetscFree(shell);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMView_Shell"
static PetscErrorCode DMView_Shell(DM dm,PetscViewer v)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
  ierr = VecView(shell->Xglobal,v);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMLoad_Shell"
static PetscErrorCode DMLoad_Shell(DM dm,PetscViewer v)
{
  PetscErrorCode ierr;
  DM_Shell       *shell = (DM_Shell*)dm->data;

  PetscFunctionBegin;
  ierr = VecCreate(PetscObjectComm((PetscObject)dm),&shell->Xglobal);CHKERRQ(ierr);
  ierr = VecLoad(shell->Xglobal,v);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMCreate_Shell"
PETSC_EXTERN PetscErrorCode DMCreate_Shell(DM dm)
{
  PetscErrorCode ierr;
  DM_Shell       *shell;

  PetscFunctionBegin;
  ierr     = PetscNewLog(dm,&shell);CHKERRQ(ierr);
  dm->data = shell;

  ierr = PetscObjectChangeTypeName((PetscObject)dm,DMSHELL);CHKERRQ(ierr);

  dm->ops->destroy            = DMDestroy_Shell;
  dm->ops->createglobalvector = DMCreateGlobalVector_Shell;
  dm->ops->createlocalvector  = DMCreateLocalVector_Shell;
  dm->ops->creatematrix       = DMCreateMatrix_Shell;
  dm->ops->view               = DMView_Shell;
  dm->ops->load               = DMLoad_Shell;
  dm->ops->globaltolocalbegin = DMGlobalToLocalBeginDefaultShell;
  dm->ops->globaltolocalend   = DMGlobalToLocalEndDefaultShell;
  dm->ops->localtoglobalbegin = DMLocalToGlobalBeginDefaultShell;
  dm->ops->localtoglobalend   = DMLocalToGlobalEndDefaultShell;
  dm->ops->localtolocalbegin  = DMLocalToLocalBeginDefaultShell;
  dm->ops->localtolocalend    = DMLocalToLocalEndDefaultShell;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMShellCreate"
/*@
    DMShellCreate - Creates a shell DM object, used to manage user-defined problem data

    Collective on MPI_Comm

    Input Parameter:
.   comm - the processors that will share the global vector

    Output Parameters:
.   shell - the shell DM

    Level: advanced

.seealso DMDestroy(), DMCreateGlobalVector(), DMCreateLocalVector()
@*/
PetscErrorCode  DMShellCreate(MPI_Comm comm,DM *dm)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidPointer(dm,2);
  ierr = DMCreate(comm,dm);CHKERRQ(ierr);
  ierr = DMSetType(*dm,DMSHELL);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}