Actual source code: daghost.c

1: /*
2: Code for manipulating distributed regular arrays in parallel.
3: */
5: #include <petsc/private/dmdaimpl.h>
7: /*@C
8: DMDAGetGhostCorners - Returns the global (`i`,`j`,`k`) indices of the lower left
9: corner and size of the local region, including ghost points.
11: Not Collective
13: Input Parameter:
14: . da - the `DMDA`
16: Output Parameters:
17: + x - the corner index for the first dimension
18: . y - the corner index for the second dimension (only used in 2D and 3D problems)
19: . z - the corner index for the third dimension (only used in 3D problems)
20: . m - the width in the first dimension
21: . n - the width in the second dimension (only used in 2D and 3D problems)
22: - p - the width in the third dimension (only used in 3D problems)
24: Level: beginner
26: Notes:
27: Any of `y`, `z`, `n`, and `p` can be passed in as `NULL` if not needed.
29: The corner information is independent of the number of degrees of
30: freedom per node set with the `DMDACreateXX()` routine. Thus the `x`, `y`, and `z`
31: can be thought of as the lower left coordinates of the patch of values on process on a logical grid and `m`, `n`, and `p` as the
32: extent of the patch. Where
33: grid point has (potentially) several degrees of freedom.
35: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAGetCorners()`, `DMDACreate1d()`, `DMDACreate2d()`, `DMDACreate3d()`, `DMDAGetOwnershipRanges()`, `DMStagGetGhostCorners()`, `DMSTAG`
36: @*/
37: **PetscErrorCode DMDAGetGhostCorners(DM da, PetscInt *x, PetscInt *y, PetscInt *z, PetscInt *m, PetscInt *n, PetscInt *p)**
38: {
39: PetscInt w;
40: DM_DA *dd = (DM_DA *)da->data;
42: PetscFunctionBegin;
44: /* since the xs, xe ... have all been multiplied by the number of degrees
45: of freedom per cell, w = dd->w, we divide that out before returning.*/
46: w = dd->w;
47: if (x) *x = dd->Xs / w + dd->xo;
48: if (y) *y = dd->Ys + dd->yo;
49: if (z) *z = dd->Zs + dd->zo;
50: if (m) *m = (dd->Xe - dd->Xs) / w;
51: if (n) *n = (dd->Ye - dd->Ys);
52: if (p) *p = (dd->Ze - dd->Zs);
53: PetscFunctionReturn(PETSC_SUCCESS);
54: }