static char help[] = "Tests VecView() contour plotting for 2d DMDAs.\n\n";

/*
  MATLAB must be installed to configure PETSc to have MATLAB engine.
Unless you have specific important reasons for using the MATLAB engine, we do not
recommend it. If you want to use MATLAB for visualization and maybe a little post processing
then you can use the socket viewer and send the data to MATLAB via that.

  VecView() on DMDA vectors first puts the Vec elements into global natural ordering before printing (or plotting)
them. In 2d 5 by 2 DMDA this means the numbering is

     5  6   7   8   9
     0  1   2   3   4

Now the default split across 2 processors with the DM  is (by rank)

    0  0   0  1   1
    0  0   0  1   1

So the global PETSc ordering is

    3  4  5   8  9
    0  1  2   6  7

Use the options
     -da_grid_x <nx> - number of grid points in x direction, if M < 0
     -da_grid_y <ny> - number of grid points in y direction, if N < 0
     -da_processors_x <MX> number of processors in x directio
     -da_processors_y <MY> number of processors in x direction
*/

#include <petscdm.h>
#include <petscdmda.h>

int main(int argc,char **argv)
{
  PetscMPIInt      rank;
  PetscInt         M = 10,N = 8;
  PetscErrorCode   ierr;
  PetscBool        flg = PETSC_FALSE;
  DM               da;
  PetscViewer      viewer;
  Vec              local,global;
  PetscScalar      value;
  DMBoundaryType   bx    = DM_BOUNDARY_NONE,by = DM_BOUNDARY_NONE;
  DMDAStencilType  stype = DMDA_STENCIL_BOX;
#if defined(PETSC_HAVE_MATLAB_ENGINE)
  PetscViewer      mviewer;
  PetscMPIInt      size;
#endif

  ierr = PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
  ierr = PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"",300,0,300,300,&viewer);CHKERRQ(ierr);
#if defined(PETSC_HAVE_MATLAB_ENGINE)
  ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRMPI(ierr);
  if (size == 1) {
    ierr = PetscViewerMatlabOpen(PETSC_COMM_WORLD,"tmp.mat",FILE_MODE_WRITE,&mviewer);CHKERRQ(ierr);
  }
#endif

  ierr = PetscOptionsGetBool(NULL,NULL,"-star_stencil",&flg,NULL);CHKERRQ(ierr);
  if (flg) stype = DMDA_STENCIL_STAR;

  /* Create distributed array and get vectors */
  ierr = DMDACreate2d(PETSC_COMM_WORLD,bx,by,stype,M,N,PETSC_DECIDE,PETSC_DECIDE,1,1,NULL,NULL,&da);CHKERRQ(ierr);
  ierr = DMSetFromOptions(da);CHKERRQ(ierr);
  ierr = DMSetUp(da);CHKERRQ(ierr);
  ierr = DMCreateGlobalVector(da,&global);CHKERRQ(ierr);
  ierr = DMCreateLocalVector(da,&local);CHKERRQ(ierr);

  value = -3.0;
  ierr  = VecSet(global,value);CHKERRQ(ierr);
  ierr  = DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);CHKERRQ(ierr);
  ierr  = DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);CHKERRQ(ierr);

  ierr  = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRMPI(ierr);
  value = rank+1;
  ierr  = VecScale(local,value);CHKERRQ(ierr);
  ierr  = DMLocalToGlobalBegin(da,local,ADD_VALUES,global);CHKERRQ(ierr);
  ierr  = DMLocalToGlobalEnd(da,local,ADD_VALUES,global);CHKERRQ(ierr);

  flg  = PETSC_FALSE;
  ierr = PetscOptionsGetBool(NULL,NULL, "-view_global", &flg,NULL);CHKERRQ(ierr);
  if (flg) { /* view global vector in natural ordering */
    ierr = VecView(global,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
  }
  ierr = DMView(da,viewer);CHKERRQ(ierr);
  ierr = VecView(global,viewer);CHKERRQ(ierr);
#if defined(PETSC_HAVE_MATLAB_ENGINE)
  if (size == 1) {
    ierr = DMView(da,mviewer);CHKERRQ(ierr);
    ierr = VecView(global,mviewer);CHKERRQ(ierr);
  }
#endif

  /* Free memory */
#if defined(PETSC_HAVE_MATLAB_ENGINE)
  if (size == 1) {
    ierr = PetscViewerDestroy(&mviewer);CHKERRQ(ierr);
  }
#endif
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
  ierr = VecDestroy(&local);CHKERRQ(ierr);
  ierr = VecDestroy(&global);CHKERRQ(ierr);
  ierr = DMDestroy(&da);CHKERRQ(ierr);
  ierr = PetscFinalize();
  return ierr;
}

/*TEST

   test:
      requires: x
      nsize: 2
      args: -nox

TEST*/