xref: /petsc/src/dm/impls/da/dacreate.c (revision b412c318f95038d6b0c0d53c83ad7d4018d14d81)

#include <petsc-private/dmdaimpl.h>    /*I   "petscdmda.h"   I*/

#undef __FUNCT__
#define __FUNCT__ "DMSetFromOptions_DA"
PetscErrorCode  DMSetFromOptions_DA(DM da)
{
  PetscErrorCode ierr;
  DM_DA          *dd         = (DM_DA*)da->data;
  PetscInt       refine      = 0,maxnlevels = 100,*refx,*refy,*refz,n,i;
  PetscBool      negativeMNP = PETSC_FALSE,bM = PETSC_FALSE,bN = PETSC_FALSE, bP = PETSC_FALSE,flg;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(da,DM_CLASSID,1);

  if (dd->M < 0) {
    dd->M       = -dd->M;
    bM          = PETSC_TRUE;
    negativeMNP = PETSC_TRUE;
  }
  if (dd->dim > 1 && dd->N < 0) {
    dd->N       = -dd->N;
    bN          = PETSC_TRUE;
    negativeMNP = PETSC_TRUE;
  }
  if (dd->dim > 2 && dd->P < 0) {
    dd->P       = -dd->P;
    bP          = PETSC_TRUE;
    negativeMNP = PETSC_TRUE;
  }

  ierr = PetscOptionsHead("DMDA Options");CHKERRQ(ierr);
  if (bM) {ierr = PetscOptionsInt("-da_grid_x","Number of grid points in x direction","DMDASetSizes",dd->M,&dd->M,NULL);CHKERRQ(ierr);}
  if (bN) {ierr = PetscOptionsInt("-da_grid_y","Number of grid points in y direction","DMDASetSizes",dd->N,&dd->N,NULL);CHKERRQ(ierr);}
  if (bP) {ierr = PetscOptionsInt("-da_grid_z","Number of grid points in z direction","DMDASetSizes",dd->P,&dd->P,NULL);CHKERRQ(ierr);}

  ierr = PetscOptionsInt("-da_overlap","Decomposition overlap in all directions","DMDASetOverlap",dd->xol,&dd->xol,&flg);CHKERRQ(ierr);
  if (flg) {ierr = DMDASetOverlap(da,dd->xol,dd->xol,dd->xol);CHKERRQ(ierr);}
  ierr = PetscOptionsInt("-da_overlap_x","Decomposition overlap in x direction","DMDASetOverlap",dd->xol,&dd->xol,NULL);CHKERRQ(ierr);
  if (dd->dim > 1) {ierr = PetscOptionsInt("-da_overlap_y","Decomposition overlap in y direction","DMDASetOverlap",dd->yol,&dd->yol,NULL);CHKERRQ(ierr);}
  if (dd->dim > 2) {ierr = PetscOptionsInt("-da_overlap_z","Decomposition overlap in z direction","DMDASetOverlap",dd->zol,&dd->zol,NULL);CHKERRQ(ierr);}

  ierr = PetscOptionsInt("-da_local_subdomains","","DMDASetNumLocalSubdomains",dd->Nsub,&dd->Nsub,&flg);CHKERRQ(ierr);
  if (flg) {ierr = DMDASetNumLocalSubDomains(da,dd->Nsub);CHKERRQ(ierr);}

  /* Handle DMDA parallel distibution */
  ierr = PetscOptionsInt("-da_processors_x","Number of processors in x direction","DMDASetNumProcs",dd->m,&dd->m,NULL);CHKERRQ(ierr);
  if (dd->dim > 1) {ierr = PetscOptionsInt("-da_processors_y","Number of processors in y direction","DMDASetNumProcs",dd->n,&dd->n,NULL);CHKERRQ(ierr);}
  if (dd->dim > 2) {ierr = PetscOptionsInt("-da_processors_z","Number of processors in z direction","DMDASetNumProcs",dd->p,&dd->p,NULL);CHKERRQ(ierr);}
  /* Handle DMDA refinement */
  ierr = PetscOptionsInt("-da_refine_x","Refinement ratio in x direction","DMDASetRefinementFactor",dd->refine_x,&dd->refine_x,NULL);CHKERRQ(ierr);
  if (dd->dim > 1) {ierr = PetscOptionsInt("-da_refine_y","Refinement ratio in y direction","DMDASetRefinementFactor",dd->refine_y,&dd->refine_y,NULL);CHKERRQ(ierr);}
  if (dd->dim > 2) {ierr = PetscOptionsInt("-da_refine_z","Refinement ratio in z direction","DMDASetRefinementFactor",dd->refine_z,&dd->refine_z,NULL);CHKERRQ(ierr);}
  dd->coarsen_x = dd->refine_x; dd->coarsen_y = dd->refine_y; dd->coarsen_z = dd->refine_z;

  /* Get refinement factors, defaults taken from the coarse DMDA */
  ierr = PetscMalloc3(maxnlevels,PetscInt,&refx,maxnlevels,PetscInt,&refy,maxnlevels,PetscInt,&refz);CHKERRQ(ierr);
  ierr = DMDAGetRefinementFactor(da,&refx[0],&refy[0],&refz[0]);CHKERRQ(ierr);
  for (i=1; i<maxnlevels; i++) {
    refx[i] = refx[0];
    refy[i] = refy[0];
    refz[i] = refz[0];
  }
  n    = maxnlevels;
  ierr = PetscOptionsGetIntArray(((PetscObject)da)->prefix,"-da_refine_hierarchy_x",refx,&n,NULL);CHKERRQ(ierr);
  if (da->levelup - da->leveldown >= 0) dd->refine_x = refx[da->levelup - da->leveldown];
  if (da->levelup - da->leveldown >= 1) dd->coarsen_x = refx[da->levelup - da->leveldown - 1];
  if (dd->dim > 1) {
    n    = maxnlevels;
    ierr = PetscOptionsGetIntArray(((PetscObject)da)->prefix,"-da_refine_hierarchy_y",refy,&n,NULL);CHKERRQ(ierr);
    if (da->levelup - da->leveldown >= 0) dd->refine_y = refy[da->levelup - da->leveldown];
    if (da->levelup - da->leveldown >= 1) dd->coarsen_y = refy[da->levelup - da->leveldown - 1];
  }
  if (dd->dim > 2) {
    n    = maxnlevels;
    ierr = PetscOptionsGetIntArray(((PetscObject)da)->prefix,"-da_refine_hierarchy_z",refz,&n,NULL);CHKERRQ(ierr);
    if (da->levelup - da->leveldown >= 0) dd->refine_z = refz[da->levelup - da->leveldown];
    if (da->levelup - da->leveldown >= 1) dd->coarsen_z = refz[da->levelup - da->leveldown - 1];
  }

  if (negativeMNP) {ierr = PetscOptionsInt("-da_refine","Uniformly refine DA one or more times","None",refine,&refine,NULL);CHKERRQ(ierr);}
  ierr = PetscOptionsTail();CHKERRQ(ierr);

  while (refine--) {
    if (dd->bx == DMDA_BOUNDARY_PERIODIC || dd->interptype == DMDA_Q0) {
      dd->M = dd->refine_x*dd->M;
    } else {
      dd->M = 1 + dd->refine_x*(dd->M - 1);
    }
    if (dd->by == DMDA_BOUNDARY_PERIODIC || dd->interptype == DMDA_Q0) {
      dd->N = dd->refine_y*dd->N;
    } else {
      dd->N = 1 + dd->refine_y*(dd->N - 1);
    }
    if (dd->bz == DMDA_BOUNDARY_PERIODIC || dd->interptype == DMDA_Q0) {
      dd->P = dd->refine_z*dd->P;
    } else {
      dd->P = 1 + dd->refine_z*(dd->P - 1);
    }
    da->levelup++;
    if (da->levelup - da->leveldown >= 0) {
      dd->refine_x = refx[da->levelup - da->leveldown];
      dd->refine_y = refy[da->levelup - da->leveldown];
      dd->refine_z = refz[da->levelup - da->leveldown];
    }
    if (da->levelup - da->leveldown >= 1) {
      dd->coarsen_x = refx[da->levelup - da->leveldown - 1];
      dd->coarsen_y = refy[da->levelup - da->leveldown - 1];
      dd->coarsen_z = refz[da->levelup - da->leveldown - 1];
    }
  }
  ierr = PetscFree3(refx,refy,refz);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

extern PetscErrorCode  DMCreateGlobalVector_DA(DM,Vec*);
extern PetscErrorCode  DMCreateLocalVector_DA(DM,Vec*);
extern PetscErrorCode  DMGlobalToLocalBegin_DA(DM,Vec,InsertMode,Vec);
extern PetscErrorCode  DMGlobalToLocalEnd_DA(DM,Vec,InsertMode,Vec);
extern PetscErrorCode  DMLocalToGlobalBegin_DA(DM,Vec,InsertMode,Vec);
extern PetscErrorCode  DMLocalToGlobalEnd_DA(DM,Vec,InsertMode,Vec);
extern PetscErrorCode  DMLocalToLocalBegin_DA(DM,Vec,InsertMode,Vec);
extern PetscErrorCode  DMLocalToLocalEnd_DA(DM,Vec,InsertMode,Vec);
extern PetscErrorCode  DMCreateInterpolation_DA(DM,DM,Mat*,Vec*);
extern PetscErrorCode  DMCreateColoring_DA(DM,ISColoringType,ISColoring*);
extern PetscErrorCode  DMCreateMatrix_DA(DM,Mat*);
extern PetscErrorCode  DMCreateCoordinateDM_DA(DM,DM*);
extern PetscErrorCode  DMRefine_DA(DM,MPI_Comm,DM*);
extern PetscErrorCode  DMCoarsen_DA(DM,MPI_Comm,DM*);
extern PetscErrorCode  DMRefineHierarchy_DA(DM,PetscInt,DM[]);
extern PetscErrorCode  DMCoarsenHierarchy_DA(DM,PetscInt,DM[]);
extern PetscErrorCode  DMCreateInjection_DA(DM,DM,VecScatter*);
extern PetscErrorCode  DMCreateAggregates_DA(DM,DM,Mat*);
extern PetscErrorCode  DMView_DA(DM,PetscViewer);
extern PetscErrorCode  DMSetUp_DA(DM);
extern PetscErrorCode  DMDestroy_DA(DM);
extern PetscErrorCode  DMCreateDomainDecomposition_DA(DM,PetscInt*,char***,IS**,IS**,DM**);
extern PetscErrorCode  DMCreateDomainDecompositionScatters_DA(DM,PetscInt,DM*,VecScatter**,VecScatter**,VecScatter**);

#undef __FUNCT__
#define __FUNCT__ "DMLoad_DA"
PetscErrorCode DMLoad_DA(DM da,PetscViewer viewer)
{
  PetscErrorCode   ierr;
  PetscInt         dim,m,n,p,dof,swidth;
  DMDAStencilType  stencil;
  DMDABoundaryType bx,by,bz;
  PetscBool        coors;
  DM               dac;
  Vec              c;

  PetscFunctionBegin;
  ierr = PetscViewerBinaryRead(viewer,&dim,1,PETSC_INT);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&m,1,PETSC_INT);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&n,1,PETSC_INT);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&p,1,PETSC_INT);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&dof,1,PETSC_INT);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&swidth,1,PETSC_INT);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&bx,1,PETSC_ENUM);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&by,1,PETSC_ENUM);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&bz,1,PETSC_ENUM);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&stencil,1,PETSC_ENUM);CHKERRQ(ierr);

  ierr = DMDASetDim(da, dim);CHKERRQ(ierr);
  ierr = DMDASetSizes(da, m,n,p);CHKERRQ(ierr);
  ierr = DMDASetBoundaryType(da, bx, by, bz);CHKERRQ(ierr);
  ierr = DMDASetDof(da, dof);CHKERRQ(ierr);
  ierr = DMDASetStencilType(da, stencil);CHKERRQ(ierr);
  ierr = DMDASetStencilWidth(da, swidth);CHKERRQ(ierr);
  ierr = DMSetUp(da);CHKERRQ(ierr);
  ierr = PetscViewerBinaryRead(viewer,&coors,1,PETSC_ENUM);CHKERRQ(ierr);
  if (coors) {
    ierr = DMGetCoordinateDM(da,&dac);CHKERRQ(ierr);
    ierr = DMCreateGlobalVector(dac,&c);CHKERRQ(ierr);
    ierr = VecLoad(c,viewer);CHKERRQ(ierr);
    ierr = DMSetCoordinates(da,c);CHKERRQ(ierr);
    ierr = VecDestroy(&c);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMCreateSubDM_DA"
PetscErrorCode DMCreateSubDM_DA(DM dm, PetscInt numFields, PetscInt fields[], IS *is, DM *subdm)
{
  DM_DA         *da = (DM_DA*) dm->data;
  PetscSection   section;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  if (subdm) {
    ierr = DMClone(dm, subdm);CHKERRQ(ierr);
    ierr = DMDASetDof(*subdm, numFields);CHKERRQ(ierr);
  }
  ierr = DMGetDefaultSection(dm, &section);CHKERRQ(ierr);
  if (section) {
    ierr = DMCreateSubDM_Section_Private(dm, numFields, fields, is, subdm);CHKERRQ(ierr);
  } else {
    if (is) {
      PetscInt *indices, cnt = 0, dof = da->w, i, j;

      ierr = PetscMalloc(da->Nlocal*numFields/dof * sizeof(PetscInt), &indices);CHKERRQ(ierr);
      for (i = da->base/dof; i < (da->base+da->Nlocal)/dof; ++i) {
        for (j = 0; j < numFields; ++j) {
          indices[cnt++] = dof*i + fields[j];
        }
      }
      if (cnt != da->Nlocal*numFields/dof) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_PLIB, "Count %d does not equal expected value %d", cnt, da->Nlocal*numFields/dof);
      ierr = ISCreateGeneral(PetscObjectComm((PetscObject) dm), cnt, indices, PETSC_OWN_POINTER, is);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMCreateFieldDecomposition_DA"
PetscErrorCode DMCreateFieldDecomposition_DA(DM dm, PetscInt *len,char ***namelist, IS **islist, DM **dmlist)
{
  PetscInt       i;
  PetscErrorCode ierr;
  DM_DA          *dd = (DM_DA*)dm->data;
  PetscInt       dof = dd->w;

  PetscFunctionBegin;
  if (len) *len = dof;
  if (islist) {
    Vec      v;
    PetscInt rstart,n;

    ierr = DMGetGlobalVector(dm,&v);CHKERRQ(ierr);
    ierr = VecGetOwnershipRange(v,&rstart,NULL);CHKERRQ(ierr);
    ierr = VecGetLocalSize(v,&n);CHKERRQ(ierr);
    ierr = DMRestoreGlobalVector(dm,&v);CHKERRQ(ierr);
    ierr = PetscMalloc(dof*sizeof(IS),islist);CHKERRQ(ierr);
    for (i=0; i<dof; i++) {
      ierr = ISCreateStride(PetscObjectComm((PetscObject)dm),n/dof,rstart+i,dof,&(*islist)[i]);CHKERRQ(ierr);
    }
  }
  if (namelist) {
    ierr = PetscMalloc(dof*sizeof(const char*), namelist);CHKERRQ(ierr);
    if (dd->fieldname) {
      for (i=0; i<dof; i++) {
        ierr = PetscStrallocpy(dd->fieldname[i],&(*namelist)[i]);CHKERRQ(ierr);
      }
    } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Currently DMDA must have fieldnames");
  }
  if (dmlist) {
    DM da;

    ierr = DMDACreate(PetscObjectComm((PetscObject)dm), &da);CHKERRQ(ierr);
    ierr = DMDASetDim(da, dd->dim);CHKERRQ(ierr);
    ierr = DMDASetSizes(da, dd->M, dd->N, dd->P);CHKERRQ(ierr);
    ierr = DMDASetNumProcs(da, dd->m, dd->n, dd->p);CHKERRQ(ierr);
    ierr = DMDASetBoundaryType(da, dd->bx, dd->by, dd->bz);CHKERRQ(ierr);
    ierr = DMDASetDof(da, 1);CHKERRQ(ierr);
    ierr = DMDASetStencilType(da, dd->stencil_type);CHKERRQ(ierr);
    ierr = DMDASetStencilWidth(da, dd->s);CHKERRQ(ierr);
    ierr = DMSetUp(da);CHKERRQ(ierr);
    ierr = PetscMalloc(dof*sizeof(DM),dmlist);CHKERRQ(ierr);
    for (i=0; i<dof-1; i++) {ierr = PetscObjectReference((PetscObject)da);CHKERRQ(ierr);}
    for (i=0; i<dof; i++) (*dmlist)[i] = da;
  }
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMClone_DA"
PetscErrorCode DMClone_DA(DM dm, DM *newdm)
{
  DM_DA         *da = (DM_DA *) dm->data;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = DMSetType(*newdm, DMDA);CHKERRQ(ierr);
  ierr = DMDASetDim(*newdm, da->dim);CHKERRQ(ierr);
  ierr = DMDASetSizes(*newdm, da->M, da->N, da->P);CHKERRQ(ierr);
  ierr = DMDASetNumProcs(*newdm, da->m, da->n, da->p);CHKERRQ(ierr);
  ierr = DMDASetBoundaryType(*newdm, da->bx, da->by, da->bz);CHKERRQ(ierr);
  ierr = DMDASetDof(*newdm, da->w);CHKERRQ(ierr);
  ierr = DMDASetStencilType(*newdm, da->stencil_type);CHKERRQ(ierr);
  ierr = DMDASetStencilWidth(*newdm, da->s);CHKERRQ(ierr);
  ierr = DMDASetOwnershipRanges(*newdm, da->lx, da->ly, da->lz);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*MC
   DMDA = "da" - A DM object that is used to manage data for a structured grid in 1, 2, or 3 dimensions.
         In the global representation of the vector each process stores a non-overlapping rectangular (or slab in 3d) portion of the grid points.
         In the local representation these rectangular regions (slabs) are extended in all directions by a stencil width.

         The vectors can be thought of as either cell centered or vertex centered on the mesh. But some variables cannot be cell centered and others
         vertex centered.


  Level: intermediate

.seealso: DMType, DMCOMPOSITE, DMDACreate(), DMCreate(), DMSetType()
M*/


#undef __FUNCT__
#define __FUNCT__ "DMCreate_DA"
PETSC_EXTERN PetscErrorCode DMCreate_DA(DM da)
{
  PetscErrorCode ierr;
  DM_DA          *dd;

  PetscFunctionBegin;
  PetscValidPointer(da,1);
  ierr     = PetscNewLog(da,DM_DA,&dd);CHKERRQ(ierr);
  da->data = dd;

  dd->dim        = -1;
  dd->interptype = DMDA_Q1;
  dd->refine_x   = 2;
  dd->refine_y   = 2;
  dd->refine_z   = 2;
  dd->coarsen_x  = 2;
  dd->coarsen_y  = 2;
  dd->coarsen_z  = 2;
  dd->fieldname  = NULL;
  dd->nlocal     = -1;
  dd->Nlocal     = -1;
  dd->M          = -1;
  dd->N          = -1;
  dd->P          = -1;
  dd->m          = -1;
  dd->n          = -1;
  dd->p          = -1;
  dd->w          = -1;
  dd->s          = -1;

  dd->xs = -1; dd->xe = -1; dd->ys = -1; dd->ye = -1; dd->zs = -1; dd->ze = -1;
  dd->Xs = -1; dd->Xe = -1; dd->Ys = -1; dd->Ye = -1; dd->Zs = -1; dd->Ze = -1;

  dd->Nsub            = 1;
  dd->xol             = 0;
  dd->yol             = 0;
  dd->zol             = 0;
  dd->xo              = 0;
  dd->yo              = 0;
  dd->zo              = 0;
  dd->Mo              = -1;
  dd->No              = -1;
  dd->Po              = -1;

  dd->gtol         = NULL;
  dd->ltog         = NULL;
  dd->ltol         = NULL;
  dd->ao           = NULL;
  dd->base         = -1;
  dd->bx           = DMDA_BOUNDARY_NONE;
  dd->by           = DMDA_BOUNDARY_NONE;
  dd->bz           = DMDA_BOUNDARY_NONE;
  dd->stencil_type = DMDA_STENCIL_BOX;
  dd->interptype   = DMDA_Q1;
  dd->idx          = NULL;
  dd->Nl           = -1;
  dd->lx           = NULL;
  dd->ly           = NULL;
  dd->lz           = NULL;

  dd->elementtype = DMDA_ELEMENT_Q1;

  ierr = PetscStrallocpy(VECSTANDARD,(char**)&da->vectype);CHKERRQ(ierr);

  da->ops->globaltolocalbegin          = DMGlobalToLocalBegin_DA;
  da->ops->globaltolocalend            = DMGlobalToLocalEnd_DA;
  da->ops->localtoglobalbegin          = DMLocalToGlobalBegin_DA;
  da->ops->localtoglobalend            = DMLocalToGlobalEnd_DA;
  da->ops->localtolocalbegin           = DMLocalToLocalBegin_DA;
  da->ops->localtolocalend             = DMLocalToLocalEnd_DA;
  da->ops->createglobalvector          = DMCreateGlobalVector_DA;
  da->ops->createlocalvector           = DMCreateLocalVector_DA;
  da->ops->createinterpolation         = DMCreateInterpolation_DA;
  da->ops->getcoloring                 = DMCreateColoring_DA;
  da->ops->creatematrix                = DMCreateMatrix_DA;
  da->ops->refine                      = DMRefine_DA;
  da->ops->coarsen                     = DMCoarsen_DA;
  da->ops->refinehierarchy             = DMRefineHierarchy_DA;
  da->ops->coarsenhierarchy            = DMCoarsenHierarchy_DA;
  da->ops->getinjection                = DMCreateInjection_DA;
  da->ops->getaggregates               = DMCreateAggregates_DA;
  da->ops->destroy                     = DMDestroy_DA;
  da->ops->view                        = 0;
  da->ops->setfromoptions              = DMSetFromOptions_DA;
  da->ops->setup                       = DMSetUp_DA;
  da->ops->clone                       = DMClone_DA;
  da->ops->load                        = DMLoad_DA;
  da->ops->createcoordinatedm          = DMCreateCoordinateDM_DA;
  da->ops->createsubdm                 = DMCreateSubDM_DA;
  da->ops->createfielddecomposition    = DMCreateFieldDecomposition_DA;
  da->ops->createdomaindecomposition   = DMCreateDomainDecomposition_DA;
  da->ops->createddscatters            = DMCreateDomainDecompositionScatters_DA;
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMDACreate"
/*@
  DMDACreate - Creates a DMDA object.

  Collective on MPI_Comm

  Input Parameter:
. comm - The communicator for the DMDA object

  Output Parameter:
. da  - The DMDA object

  Level: advanced

  Developers Note: Since there exists DMDACreate1/2/3d() should this routine even exist?

.keywords: DMDA, create
.seealso:  DMDASetSizes(), DMDADuplicate(),  DMDACreate1d(), DMDACreate2d(), DMDACreate3d()
@*/
PetscErrorCode  DMDACreate(MPI_Comm comm, DM *da)
{
  PetscErrorCode ierr;

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