Actual source code: daghost.c

petsc-3.5.1 2014-07-24
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  2: /*
  3:   Code for manipulating distributed regular arrays in parallel.
  4: */

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

 10: /*@
 11:    DMDAGetGhostCorners - Returns the global (x,y,z) indices of the lower left
 12:    corner of the local region, including ghost points.

 14:    Not Collective

 16:    Input Parameter:
 17: .  da - the distributed array

 19:    Output Parameters:
 20: +  x,y,z - the corner indices (where y and z are optional; these are used
 21:            for 2D and 3D problems)
 22: -  m,n,p - widths in the corresponding directions (where n and p are optional;
 23:            these are used for 2D and 3D problems)

 25:    Level: beginner

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

 34: .keywords: distributed array, get, ghost, corners, nodes, local indices

 36: .seealso: DMDAGetCorners(), DMDACreate1d(), DMDACreate2d(), DMDACreate3d(), DMDAGetOwnershipRanges()

 38: @*/
 39: PetscErrorCode  DMDAGetGhostCorners(DM da,PetscInt *x,PetscInt *y,PetscInt *z,PetscInt *m,PetscInt *n,PetscInt *p)
 40: {
 41:   PetscInt w;
 42:   DM_DA    *dd = (DM_DA*)da->data;

 46:   /* since the xs, xe ... have all been multiplied by the number of degrees
 47:      of freedom per cell, w = dd->w, we divide that out before returning.*/
 48:   w = dd->w;
 49:   if (x) *x = dd->Xs/w + dd->xo; if (m) *m = (dd->Xe - dd->Xs)/w;
 50:   if (y) *y = dd->Ys   + dd->yo; if (n) *n = (dd->Ye - dd->Ys);
 51:   if (z) *z = dd->Zs   + dd->zo; if (p) *p = (dd->Ze - dd->Zs);
 52:   return(0);
 53: }