Actual source code: ex12.c
1: /*
2: Simple example to show how PETSc programs can be run from MATLAB.
3: See ex12.m.
4: */
6: static char help[] = "Solves the one dimensional heat equation.\n\n";
8: #include <petscdm.h>
9: #include <petscdmda.h>
11: int main(int argc, char **argv)
12: {
13: PetscMPIInt rank, size;
14: PetscInt M = 14, time_steps = 20, w = 1, s = 1, localsize, j, i, mybase, myend, globalsize;
15: DM da;
16: Vec global, local;
17: PetscScalar *globalptr, *localptr;
18: PetscReal h, k;
20: PetscFunctionBeginUser;
21: PetscCall(PetscInitialize(&argc, &argv, NULL, help));
22: PetscCall(PetscOptionsGetInt(NULL, NULL, "-M", &M, NULL));
23: PetscCall(PetscOptionsGetInt(NULL, NULL, "-time", &time_steps, NULL));
25: /* Set up the array */
26: PetscCall(DMDACreate1d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, M, w, s, NULL, &da));
27: PetscCall(DMSetFromOptions(da));
28: PetscCall(DMSetUp(da));
29: PetscCall(DMCreateGlobalVector(da, &global));
30: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
31: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
33: /* Make copy of local array for doing updates */
34: PetscCall(DMCreateLocalVector(da, &local));
36: /* determine starting point of each processor */
37: PetscCall(VecGetOwnershipRange(global, &mybase, &myend));
39: /* Initialize the Array */
40: PetscCall(VecGetLocalSize(global, &globalsize));
41: PetscCall(VecGetArray(global, &globalptr));
43: for (i = 0; i < globalsize; i++) {
44: j = i + mybase;
46: globalptr[i] = PetscSinReal((PETSC_PI * j * 6) / ((PetscReal)M) + 1.2 * PetscSinReal((PETSC_PI * j * 2) / ((PetscReal)M))) * 4 + 4;
47: }
49: PetscCall(VecRestoreArray(global, &localptr));
51: /* Assign Parameters */
52: h = 1.0 / M;
53: k = h * h / 2.2;
54: PetscCall(VecGetLocalSize(local, &localsize));
56: for (j = 0; j < time_steps; j++) {
57: /* Global to Local */
58: PetscCall(DMGlobalToLocalBegin(da, global, INSERT_VALUES, local));
59: PetscCall(DMGlobalToLocalEnd(da, global, INSERT_VALUES, local));
61: /*Extract local array */
62: PetscCall(VecGetArray(local, &localptr));
63: PetscCall(VecGetArray(global, &globalptr));
65: /* Update Locally - Make array of new values */
66: /* Note: I don't do anything for the first and last entry */
67: for (i = 1; i < localsize - 1; i++) globalptr[i - 1] = localptr[i] + (k / (h * h)) * (localptr[i + 1] - 2.0 * localptr[i] + localptr[i - 1]);
69: PetscCall(VecRestoreArray(global, &globalptr));
70: PetscCall(VecRestoreArray(local, &localptr));
72: /* View Wave */
73: /* Set Up Display to Show Heat Graph */
74: #if defined(PETSC_USE_SOCKET_VIEWER)
75: PetscCall(VecView(global, PETSC_VIEWER_SOCKET_WORLD));
76: #endif
77: }
79: PetscCall(VecDestroy(&local));
80: PetscCall(VecDestroy(&global));
81: PetscCall(DMDestroy(&da));
82: PetscCall(PetscFinalize());
83: return 0;
84: }