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

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

/*@C
   DMDAGetGhostCorners - Returns the global (x,y,z) indices of the lower left
   corner and size of the local region, including ghost points.

   Not Collective

   Input Parameter:
.  da - the distributed array

   Output Parameters:
+  x - the corner index for the first dimension
.  y - the corner index for the second dimension (only used in 2D and 3D problems)
.  z - the corner index for the third dimension (only used in 3D problems)
.  m - the width in the first dimension
.  n - the width in the second dimension (only used in 2D and 3D problems)
-  p - the width in the third dimension (only used in 3D problems)

   Level: beginner

   Note:
   The corner information is independent of the number of degrees of
   freedom per node set with the `DMDACreateXX()` routine. Thus the x, y, z, and
   m, n, p can be thought of as coordinates on a logical grid, where each
   grid point has (potentially) several degrees of freedom.
   Any of y, z, n, and p can be passed in as NULL if not needed.

.seealso: `DM`, `DMDA`, `DMDAGetCorners()`, `DMDACreate1d()`, `DMDACreate2d()`, `DMDACreate3d()`, `DMDAGetOwnershipRanges()`, `DMStagGetGhostCorners()`
@*/
PetscErrorCode DMDAGetGhostCorners(DM da, PetscInt *x, PetscInt *y, PetscInt *z, PetscInt *m, PetscInt *n, PetscInt *p)
{
  PetscInt w;
  DM_DA   *dd = (DM_DA *)da->data;

  PetscFunctionBegin;
  PetscValidHeaderSpecificType(da, DM_CLASSID, 1, DMDA);
  /* since the xs, xe ... have all been multiplied by the number of degrees
     of freedom per cell, w = dd->w, we divide that out before returning.*/
  w = dd->w;
  if (x) *x = dd->Xs / w + dd->xo;
  if (y) *y = dd->Ys + dd->yo;
  if (z) *z = dd->Zs + dd->zo;
  if (m) *m = (dd->Xe - dd->Xs) / w;
  if (n) *n = (dd->Ye - dd->Ys);
  if (p) *p = (dd->Ze - dd->Zs);
  PetscFunctionReturn(0);
}