static char help[] = "Demonstrates the DMLocalToLocal bug in PETSc 3.6.\n\n";

/*
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

  Contributed by Constantine Khroulev
*/

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

PetscErrorCode PrintVecWithGhosts(DM da, Vec v)
{
  PetscScalar **p;
  PetscInt      i, j;
  MPI_Comm      com;
  PetscMPIInt   rank;
  DMDALocalInfo info;

  com = PetscObjectComm((PetscObject)da);
  PetscCallMPI(MPI_Comm_rank(com, &rank));
  PetscCall(DMDAGetLocalInfo(da, &info));
  PetscCall(PetscSynchronizedPrintf(com, "begin rank %d portion (with ghosts, %" PetscInt_FMT " x %" PetscInt_FMT ")\n", rank, info.gxm, info.gym));
  PetscCall(DMDAVecGetArray(da, v, &p));
  for (i = info.gxs; i < info.gxs + info.gxm; i++) {
    for (j = info.gys; j < info.gys + info.gym; j++) PetscCall(PetscSynchronizedPrintf(com, "%g, ", (double)PetscRealPart(p[j][i])));
    PetscCall(PetscSynchronizedPrintf(com, "\n"));
  }
  PetscCall(DMDAVecRestoreArray(da, v, &p));
  PetscCall(PetscSynchronizedPrintf(com, "end rank %d portion\n", rank));
  PetscCall(PetscSynchronizedFlush(com, PETSC_STDOUT));
  return PETSC_SUCCESS;
}

/* Set a Vec v to value, but do not touch ghosts. */
PetscErrorCode VecSetOwned(DM da, Vec v, PetscScalar value)
{
  PetscScalar **p;
  PetscInt      i, j, xs, xm, ys, ym;

  PetscCall(DMDAGetCorners(da, &xs, &ys, 0, &xm, &ym, 0));
  PetscCall(DMDAVecGetArray(da, v, &p));
  for (i = xs; i < xs + xm; i++) {
    for (j = ys; j < ys + ym; j++) p[j][i] = value;
  }
  PetscCall(DMDAVecRestoreArray(da, v, &p));
  return PETSC_SUCCESS;
}

int main(int argc, char **argv)
{
  PetscInt        M = 4, N = 3;
  DM              da;
  Vec             local;
  PetscScalar     value = 0.0;
  DMBoundaryType  bx = DM_BOUNDARY_PERIODIC, by = DM_BOUNDARY_PERIODIC;
  DMDAStencilType stype = DMDA_STENCIL_BOX;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCall(DMDACreate2d(PETSC_COMM_WORLD, bx, by, stype, M, N, PETSC_DECIDE, PETSC_DECIDE, 1, 1, NULL, NULL, &da));
  PetscCall(DMSetFromOptions(da));
  PetscCall(DMSetUp(da));
  PetscCall(DMCreateLocalVector(da, &local));

  PetscCall(VecSet(local, value));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "\nAfter setting all values to %d:\n", (int)PetscRealPart(value)));
  PetscCall(PrintVecWithGhosts(da, local));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "done\n"));

  value += 1.0;
  /* set values owned by a process, leaving ghosts alone */
  PetscCall(VecSetOwned(da, local, value));

  /* print after re-setting interior values again */
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "\nAfter setting interior values to %d:\n", (int)PetscRealPart(value)));
  PetscCall(PrintVecWithGhosts(da, local));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "done\n"));

  /* communicate ghosts */
  PetscCall(DMLocalToLocalBegin(da, local, INSERT_VALUES, local));
  PetscCall(DMLocalToLocalEnd(da, local, INSERT_VALUES, local));

  /* print again */
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "\nAfter local-to-local communication:\n"));
  PetscCall(PrintVecWithGhosts(da, local));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD, "done\n"));

  /* Free memory */
  PetscCall(VecDestroy(&local));
  PetscCall(DMDestroy(&da));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      nsize: 2

TEST*/