impls/da/dalocal.c

/*
  Code for manipulating distributed regular arrays in parallel.
*/

#include <petsc/private/dmdaimpl.h>    /*I   "petscdmda.h"   I*/
#include <petscbt.h>
#include <petscsf.h>
#include <petscds.h>
#include <petscfe.h>

/*
   This allows the DMDA vectors to properly tell MATLAB their dimensions
*/
#if defined(PETSC_HAVE_MATLAB_ENGINE)
#include <engine.h>   /* MATLAB include file */
#include <mex.h>      /* MATLAB include file */
static PetscErrorCode  VecMatlabEnginePut_DA2d(PetscObject obj,void *mengine)
{
  PetscInt       n,m;
  Vec            vec = (Vec)obj;
  PetscScalar    *array;
  mxArray        *mat;
  DM             da;

  PetscFunctionBegin;
  PetscCall(VecGetDM(vec, &da));
  PetscCheck(da,PetscObjectComm((PetscObject)vec),PETSC_ERR_ARG_WRONGSTATE,"Vector not associated with a DMDA");
  PetscCall(DMDAGetGhostCorners(da,0,0,0,&m,&n,0));

  PetscCall(VecGetArray(vec,&array));
#if !defined(PETSC_USE_COMPLEX)
  mat = mxCreateDoubleMatrix(m,n,mxREAL);
#else
  mat = mxCreateDoubleMatrix(m,n,mxCOMPLEX);
#endif
  PetscCall(PetscArraycpy(mxGetPr(mat),array,n*m));
  PetscCall(PetscObjectName(obj));
  engPutVariable((Engine*)mengine,obj->name,mat);

  PetscCall(VecRestoreArray(vec,&array));
  PetscFunctionReturn(0);
}
#endif

PetscErrorCode  DMCreateLocalVector_DA(DM da,Vec *g)
{
  DM_DA          *dd = (DM_DA*)da->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(da,DM_CLASSID,1);
  PetscValidPointer(g,2);
  PetscCall(VecCreate(PETSC_COMM_SELF,g));
  PetscCall(VecSetSizes(*g,dd->nlocal,PETSC_DETERMINE));
  PetscCall(VecSetBlockSize(*g,dd->w));
  PetscCall(VecSetType(*g,da->vectype));
  if (dd->nlocal < da->bind_below) {
    PetscCall(VecSetBindingPropagates(*g,PETSC_TRUE));
    PetscCall(VecBindToCPU(*g,PETSC_TRUE));
  }
  PetscCall(VecSetDM(*g, da));
#if defined(PETSC_HAVE_MATLAB_ENGINE)
  if (dd->w == 1  && da->dim == 2) {
    PetscCall(PetscObjectComposeFunction((PetscObject)*g,"PetscMatlabEnginePut_C",VecMatlabEnginePut_DA2d));
  }
#endif
  PetscFunctionReturn(0);
}

/*@
  DMDAGetNumCells - Get the number of cells in the local piece of the DMDA. This includes ghost cells.

  Input Parameter:
. dm - The DM object

  Output Parameters:
+ numCellsX - The number of local cells in the x-direction
. numCellsY - The number of local cells in the y-direction
. numCellsZ - The number of local cells in the z-direction
- numCells - The number of local cells

  Level: developer

.seealso: `DMDAGetCellPoint()`
@*/
PetscErrorCode DMDAGetNumCells(DM dm, PetscInt *numCellsX, PetscInt *numCellsY, PetscInt *numCellsZ, PetscInt *numCells)
{
  DM_DA         *da  = (DM_DA*) dm->data;
  const PetscInt dim = dm->dim;
  const PetscInt mx  = (da->Xe - da->Xs)/da->w, my = da->Ye - da->Ys, mz = da->Ze - da->Zs;
  const PetscInt nC  = (mx)*(dim > 1 ? (my)*(dim > 2 ? (mz) : 1) : 1);

  PetscFunctionBegin;
  PetscValidHeaderSpecificType(dm, DM_CLASSID, 1,DMDA);
  if (numCellsX) {
    PetscValidIntPointer(numCellsX,2);
    *numCellsX = mx;
  }
  if (numCellsY) {
    PetscValidIntPointer(numCellsY,3);
    *numCellsY = my;
  }
  if (numCellsZ) {
    PetscValidIntPointer(numCellsZ,4);
    *numCellsZ = mz;
  }
  if (numCells) {
    PetscValidIntPointer(numCells,5);
    *numCells = nC;
  }
  PetscFunctionReturn(0);
}

/*@
  DMDAGetCellPoint - Get the DM point corresponding to the tuple (i, j, k) in the DMDA

  Input Parameters:
+ dm - The DM object
- i,j,k - The global indices for the cell

  Output Parameters:
. point - The local DM point

  Level: developer

.seealso: `DMDAGetNumCells()`
@*/
PetscErrorCode DMDAGetCellPoint(DM dm, PetscInt i, PetscInt j, PetscInt k, PetscInt *point)
{
  const PetscInt dim = dm->dim;
  DMDALocalInfo  info;

  PetscFunctionBegin;
  PetscValidHeaderSpecificType(dm, DM_CLASSID, 1,DMDA);
  PetscValidIntPointer(point,5);
  PetscCall(DMDAGetLocalInfo(dm, &info));
  if (dim > 0) PetscCheck(!(i < info.gxs) && !(i >= info.gxs+info.gxm),PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "X index %" PetscInt_FMT " not in [%" PetscInt_FMT ", %" PetscInt_FMT ")", i, info.gxs, info.gxs+info.gxm);
  if (dim > 1) PetscCheck(!(j < info.gys) && !(j >= info.gys+info.gym),PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Y index %" PetscInt_FMT " not in [%" PetscInt_FMT ", %" PetscInt_FMT ")", j, info.gys, info.gys+info.gym);
  if (dim > 2) PetscCheck(!(k < info.gzs) && !(k >= info.gzs+info.gzm),PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Z index %" PetscInt_FMT PetscInt_FMT " not in [%" PetscInt_FMT ", %" PetscInt_FMT ")", k, info.gzs, info.gzs+info.gzm);
  *point = i + (dim > 1 ? (j + (dim > 2 ? k*info.gym : 0))*info.gxm : 0);
  PetscFunctionReturn(0);
}

PetscErrorCode DMDAGetNumVertices(DM dm, PetscInt *numVerticesX, PetscInt *numVerticesY, PetscInt *numVerticesZ, PetscInt *numVertices)
{
  DM_DA          *da = (DM_DA*) dm->data;
  const PetscInt dim = dm->dim;
  const PetscInt mx  = (da->Xe - da->Xs)/da->w, my = da->Ye - da->Ys, mz = da->Ze - da->Zs;
  const PetscInt nVx = mx+1;
  const PetscInt nVy = dim > 1 ? (my+1) : 1;
  const PetscInt nVz = dim > 2 ? (mz+1) : 1;
  const PetscInt nV  = nVx*nVy*nVz;

  PetscFunctionBegin;
  if (numVerticesX) {
    PetscValidIntPointer(numVerticesX,2);
    *numVerticesX = nVx;
  }
  if (numVerticesY) {
    PetscValidIntPointer(numVerticesY,3);
    *numVerticesY = nVy;
  }
  if (numVerticesZ) {
    PetscValidIntPointer(numVerticesZ,4);
    *numVerticesZ = nVz;
  }
  if (numVertices) {
    PetscValidIntPointer(numVertices,5);
    *numVertices = nV;
  }
  PetscFunctionReturn(0);
}

PetscErrorCode DMDAGetNumFaces(DM dm, PetscInt *numXFacesX, PetscInt *numXFaces, PetscInt *numYFacesY, PetscInt *numYFaces, PetscInt *numZFacesZ, PetscInt *numZFaces)
{
  DM_DA          *da = (DM_DA*) dm->data;
  const PetscInt dim = dm->dim;
  const PetscInt mx  = (da->Xe - da->Xs)/da->w, my = da->Ye - da->Ys, mz = da->Ze - da->Zs;
  const PetscInt nxF = (dim > 1 ? (my)*(dim > 2 ? (mz) : 1) : 1);
  const PetscInt nXF = (mx+1)*nxF;
  const PetscInt nyF = mx*(dim > 2 ? mz : 1);
  const PetscInt nYF = dim > 1 ? (my+1)*nyF : 0;
  const PetscInt nzF = mx*(dim > 1 ? my : 0);
  const PetscInt nZF = dim > 2 ? (mz+1)*nzF : 0;

  PetscFunctionBegin;
  if (numXFacesX) {
    PetscValidIntPointer(numXFacesX,2);
    *numXFacesX = nxF;
  }
  if (numXFaces) {
    PetscValidIntPointer(numXFaces,3);
    *numXFaces = nXF;
  }
  if (numYFacesY) {
    PetscValidIntPointer(numYFacesY,4);
    *numYFacesY = nyF;
  }
  if (numYFaces) {
    PetscValidIntPointer(numYFaces,5);
    *numYFaces = nYF;
  }
  if (numZFacesZ) {
    PetscValidIntPointer(numZFacesZ,6);
    *numZFacesZ = nzF;
  }
  if (numZFaces) {
    PetscValidIntPointer(numZFaces,7);
    *numZFaces = nZF;
  }
  PetscFunctionReturn(0);
}

PetscErrorCode DMDAGetHeightStratum(DM dm, PetscInt height, PetscInt *pStart, PetscInt *pEnd)
{
  const PetscInt dim = dm->dim;
  PetscInt       nC, nV, nXF, nYF, nZF;

  PetscFunctionBegin;
  if (pStart) PetscValidIntPointer(pStart,3);
  if (pEnd)   PetscValidIntPointer(pEnd,4);
  PetscCall(DMDAGetNumCells(dm, NULL, NULL, NULL, &nC));
  PetscCall(DMDAGetNumVertices(dm, NULL, NULL, NULL, &nV));
  PetscCall(DMDAGetNumFaces(dm, NULL, &nXF, NULL, &nYF, NULL, &nZF));
  if (height == 0) {
    /* Cells */
    if (pStart) *pStart = 0;
    if (pEnd)   *pEnd   = nC;
  } else if (height == 1) {
    /* Faces */
    if (pStart) *pStart = nC+nV;
    if (pEnd)   *pEnd   = nC+nV+nXF+nYF+nZF;
  } else if (height == dim) {
    /* Vertices */
    if (pStart) *pStart = nC;
    if (pEnd)   *pEnd   = nC+nV;
  } else if (height < 0) {
    /* All points */
    if (pStart) *pStart = 0;
    if (pEnd)   *pEnd   = nC+nV+nXF+nYF+nZF;
  } else SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_OUTOFRANGE, "No points of height %" PetscInt_FMT " in the DA", height);
  PetscFunctionReturn(0);
}

PetscErrorCode DMDAGetDepthStratum(DM dm, PetscInt depth, PetscInt *pStart, PetscInt *pEnd)
{
  const PetscInt dim = dm->dim;
  PetscInt       nC, nV, nXF, nYF, nZF;

  PetscFunctionBegin;
  if (pStart) PetscValidIntPointer(pStart,3);
  if (pEnd)   PetscValidIntPointer(pEnd,4);
  PetscCall(DMDAGetNumCells(dm, NULL, NULL, NULL, &nC));
  PetscCall(DMDAGetNumVertices(dm, NULL, NULL, NULL, &nV));
  PetscCall(DMDAGetNumFaces(dm, NULL, &nXF, NULL, &nYF, NULL, &nZF));
  if (depth == dim) {
    /* Cells */
    if (pStart) *pStart = 0;
    if (pEnd)   *pEnd   = nC;
  } else if (depth == dim-1) {
    /* Faces */
    if (pStart) *pStart = nC+nV;
    if (pEnd)   *pEnd   = nC+nV+nXF+nYF+nZF;
  } else if (depth == 0) {
    /* Vertices */
    if (pStart) *pStart = nC;
    if (pEnd)   *pEnd   = nC+nV;
  } else if (depth < 0) {
    /* All points */
    if (pStart) *pStart = 0;
    if (pEnd)   *pEnd   = nC+nV+nXF+nYF+nZF;
  } else SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_OUTOFRANGE, "No points of depth %" PetscInt_FMT " in the DA", depth);
  PetscFunctionReturn(0);
}

PetscErrorCode DMDAGetConeSize(DM dm, PetscInt p, PetscInt *coneSize)
{
  const PetscInt dim = dm->dim;
  PetscInt       nC, nV, nXF, nYF, nZF;

  PetscFunctionBegin;
  *coneSize = 0;
  PetscCall(DMDAGetNumCells(dm, NULL, NULL, NULL, &nC));
  PetscCall(DMDAGetNumVertices(dm, NULL, NULL, NULL, &nV));
  PetscCall(DMDAGetNumFaces(dm, NULL, &nXF, NULL, &nYF, NULL, &nZF));
  switch (dim) {
  case 2:
    if (p >= 0) {
      if (p < nC) {
        *coneSize = 4;
      } else if (p < nC+nV) {
        *coneSize = 0;
      } else if (p < nC+nV+nXF+nYF+nZF) {
        *coneSize = 2;
      } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Point %" PetscInt_FMT " should be in [0, %" PetscInt_FMT ")", p, nC+nV+nXF+nYF+nZF);
    } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Negative point %" PetscInt_FMT " is invalid", p);
    break;
  case 3:
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Too lazy to do 3D");
  }
  PetscFunctionReturn(0);
}

PetscErrorCode DMDAGetCone(DM dm, PetscInt p, PetscInt *cone[])
{
  const PetscInt dim = dm->dim;
  PetscInt       nCx, nCy, nCz, nC, nVx, nVy, nVz, nV, nxF, nyF, nzF, nXF, nYF, nZF;

  PetscFunctionBegin;
  if (!cone) PetscCall(DMGetWorkArray(dm, 6, MPIU_INT, cone));
  PetscCall(DMDAGetNumCells(dm, &nCx, &nCy, &nCz, &nC));
  PetscCall(DMDAGetNumVertices(dm, &nVx, &nVy, &nVz, &nV));
  PetscCall(DMDAGetNumFaces(dm, &nxF, &nXF, &nyF, &nYF, &nzF, &nZF));
  switch (dim) {
  case 2:
    if (p >= 0) {
      if (p < nC) {
        const PetscInt cy = p / nCx;
        const PetscInt cx = p % nCx;

        (*cone)[0] = cy*nxF + cx + nC+nV;
        (*cone)[1] = cx*nyF + cy + nyF + nC+nV+nXF;
        (*cone)[2] = cy*nxF + cx + nxF + nC+nV;
        (*cone)[3] = cx*nyF + cy + nC+nV+nXF;
        SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Too lazy to do cell cones");
      } else if (p < nC+nV) {
      } else if (p < nC+nV+nXF) {
        const PetscInt fy = (p - nC+nV) / nxF;
        const PetscInt fx = (p - nC+nV) % nxF;

        (*cone)[0] = fy*nVx + fx + nC;
        (*cone)[1] = fy*nVx + fx + 1 + nC;
      } else if (p < nC+nV+nXF+nYF) {
        const PetscInt fx = (p - nC+nV+nXF) / nyF;
        const PetscInt fy = (p - nC+nV+nXF) % nyF;

        (*cone)[0] = fy*nVx + fx + nC;
        (*cone)[1] = fy*nVx + fx + nVx + nC;
      } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Point %" PetscInt_FMT " should be in [0, %" PetscInt_FMT ")", p, nC+nV+nXF+nYF+nZF);
    } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Negative point %" PetscInt_FMT " is invalid", p);
    break;
  case 3:
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Too lazy to do 3D");
  }
  PetscFunctionReturn(0);
}

PetscErrorCode DMDARestoreCone(DM dm, PetscInt p, PetscInt *cone[])
{
  PetscFunctionBegin;
  PetscCall(DMGetWorkArray(dm, 6, MPIU_INT, cone));
  PetscFunctionReturn(0);
}

PetscErrorCode DMDASetVertexCoordinates(DM dm, PetscReal xl, PetscReal xu, PetscReal yl, PetscReal yu, PetscReal zl, PetscReal zu)
{
  DM_DA         *da = (DM_DA *) dm->data;
  Vec            coordinates;
  PetscSection   section;
  PetscScalar   *coords;
  PetscReal      h[3];
  PetscInt       dim, size, M, N, P, nVx, nVy, nVz, nV, vStart, vEnd, v, i, j, k;

  PetscFunctionBegin;
  PetscValidHeaderSpecificType(dm, DM_CLASSID, 1,DMDA);
  PetscCall(DMDAGetInfo(dm, &dim, &M, &N, &P, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL));
  PetscCheck(dim <= 3,PetscObjectComm((PetscObject)dm),PETSC_ERR_PLIB,"The following code only works for dim <= 3");
  h[0] = (xu - xl)/M;
  h[1] = (yu - yl)/N;
  h[2] = (zu - zl)/P;
  PetscCall(DMDAGetDepthStratum(dm, 0, &vStart, &vEnd));
  PetscCall(DMDAGetNumVertices(dm, &nVx, &nVy, &nVz, &nV));
  PetscCall(PetscSectionCreate(PetscObjectComm((PetscObject) dm), &section));
  PetscCall(PetscSectionSetNumFields(section, 1));
  PetscCall(PetscSectionSetFieldComponents(section, 0, dim));
  PetscCall(PetscSectionSetChart(section, vStart, vEnd));
  for (v = vStart; v < vEnd; ++v) {
    PetscCall(PetscSectionSetDof(section, v, dim));
  }
  PetscCall(PetscSectionSetUp(section));
  PetscCall(PetscSectionGetStorageSize(section, &size));
  PetscCall(VecCreateSeq(PETSC_COMM_SELF, size, &coordinates));
  PetscCall(PetscObjectSetName((PetscObject)coordinates,"coordinates"));
  PetscCall(VecGetArray(coordinates, &coords));
  for (k = 0; k < nVz; ++k) {
    PetscInt ind[3], d, off;

    ind[0] = 0;
    ind[1] = 0;
    ind[2] = k + da->zs;
    for (j = 0; j < nVy; ++j) {
      ind[1] = j + da->ys;
      for (i = 0; i < nVx; ++i) {
        const PetscInt vertex = (k*nVy + j)*nVx + i + vStart;

        PetscCall(PetscSectionGetOffset(section, vertex, &off));
        ind[0] = i + da->xs;
        for (d = 0; d < dim; ++d) {
          coords[off+d] = h[d]*ind[d];
        }
      }
    }
  }
  PetscCall(VecRestoreArray(coordinates, &coords));
  PetscCall(DMSetCoordinateSection(dm, PETSC_DETERMINE, section));
  PetscCall(DMSetCoordinatesLocal(dm, coordinates));
  PetscCall(PetscSectionDestroy(&section));
  PetscCall(VecDestroy(&coordinates));
  PetscFunctionReturn(0);
}

/* ------------------------------------------------------------------- */

/*@C
     DMDAGetArray - Gets a work array for a DMDA

    Input Parameters:
+    da - information about my local patch
-    ghosted - do you want arrays for the ghosted or nonghosted patch

    Output Parameters:
.    vptr - array data structured

    Note:  The vector values are NOT initialized and may have garbage in them, so you may need
           to zero them.

  Level: advanced

.seealso: `DMDARestoreArray()`

@*/
PetscErrorCode  DMDAGetArray(DM da,PetscBool ghosted,void *vptr)
{
  PetscInt       j,i,xs,ys,xm,ym,zs,zm;
  char           *iarray_start;
  void           **iptr = (void**)vptr;
  DM_DA          *dd    = (DM_DA*)da->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecificType(da,DM_CLASSID,1,DMDA);
  if (ghosted) {
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (dd->arrayghostedin[i]) {
        *iptr                 = dd->arrayghostedin[i];
        iarray_start          = (char*)dd->startghostedin[i];
        dd->arrayghostedin[i] = NULL;
        dd->startghostedin[i] = NULL;

        goto done;
      }
    }
    xs = dd->Xs;
    ys = dd->Ys;
    zs = dd->Zs;
    xm = dd->Xe-dd->Xs;
    ym = dd->Ye-dd->Ys;
    zm = dd->Ze-dd->Zs;
  } else {
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (dd->arrayin[i]) {
        *iptr          = dd->arrayin[i];
        iarray_start   = (char*)dd->startin[i];
        dd->arrayin[i] = NULL;
        dd->startin[i] = NULL;

        goto done;
      }
    }
    xs = dd->xs;
    ys = dd->ys;
    zs = dd->zs;
    xm = dd->xe-dd->xs;
    ym = dd->ye-dd->ys;
    zm = dd->ze-dd->zs;
  }

  switch (da->dim) {
  case 1: {
    void *ptr;

    PetscCall(PetscMalloc(xm*sizeof(PetscScalar),&iarray_start));

    ptr   = (void*)(iarray_start - xs*sizeof(PetscScalar));
    *iptr = (void*)ptr;
    break;
  }
  case 2: {
    void **ptr;

    PetscCall(PetscMalloc((ym+1)*sizeof(void*)+xm*ym*sizeof(PetscScalar),&iarray_start));

    ptr = (void**)(iarray_start + xm*ym*sizeof(PetscScalar) - ys*sizeof(void*));
    for (j=ys; j<ys+ym; j++) ptr[j] = iarray_start + sizeof(PetscScalar)*(xm*(j-ys) - xs);
    *iptr = (void*)ptr;
    break;
  }
  case 3: {
    void ***ptr,**bptr;

    PetscCall(PetscMalloc((zm+1)*sizeof(void**)+(ym*zm+1)*sizeof(void*)+xm*ym*zm*sizeof(PetscScalar),&iarray_start));

    ptr  = (void***)(iarray_start + xm*ym*zm*sizeof(PetscScalar) - zs*sizeof(void*));
    bptr = (void**)(iarray_start + xm*ym*zm*sizeof(PetscScalar) + zm*sizeof(void**));
    for (i=zs; i<zs+zm; i++) ptr[i] = bptr + ((i-zs)*ym - ys);
    for (i=zs; i<zs+zm; i++) {
      for (j=ys; j<ys+ym; j++) {
        ptr[i][j] = iarray_start + sizeof(PetscScalar)*(xm*ym*(i-zs) + xm*(j-ys) - xs);
      }
    }
    *iptr = (void*)ptr;
    break;
  }
  default:
    SETERRQ(PetscObjectComm((PetscObject)da),PETSC_ERR_SUP,"Dimension %" PetscInt_FMT " not supported",da->dim);
  }

done:
  /* add arrays to the checked out list */
  if (ghosted) {
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (!dd->arrayghostedout[i]) {
        dd->arrayghostedout[i] = *iptr;
        dd->startghostedout[i] = iarray_start;
        break;
      }
    }
  } else {
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (!dd->arrayout[i]) {
        dd->arrayout[i] = *iptr;
        dd->startout[i] = iarray_start;
        break;
      }
    }
  }
  PetscFunctionReturn(0);
}

/*@C
     DMDARestoreArray - Restores an array of derivative types for a DMDA

    Input Parameters:
+    da - information about my local patch
.    ghosted - do you want arrays for the ghosted or nonghosted patch
-    vptr - array data structured

     Level: advanced

.seealso: `DMDAGetArray()`

@*/
PetscErrorCode  DMDARestoreArray(DM da,PetscBool ghosted,void *vptr)
{
  PetscInt i;
  void     **iptr = (void**)vptr,*iarray_start = NULL;
  DM_DA    *dd    = (DM_DA*)da->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecificType(da,DM_CLASSID,1,DMDA);
  if (ghosted) {
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (dd->arrayghostedout[i] == *iptr) {
        iarray_start           = dd->startghostedout[i];
        dd->arrayghostedout[i] = NULL;
        dd->startghostedout[i] = NULL;
        break;
      }
    }
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (!dd->arrayghostedin[i]) {
        dd->arrayghostedin[i] = *iptr;
        dd->startghostedin[i] = iarray_start;
        break;
      }
    }
  } else {
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (dd->arrayout[i] == *iptr) {
        iarray_start    = dd->startout[i];
        dd->arrayout[i] = NULL;
        dd->startout[i] = NULL;
        break;
      }
    }
    for (i=0; i<DMDA_MAX_WORK_ARRAYS; i++) {
      if (!dd->arrayin[i]) {
        dd->arrayin[i] = *iptr;
        dd->startin[i] = iarray_start;
        break;
      }
    }
  }
  PetscFunctionReturn(0);
}