Actual source code: ex8.c

  1: static char help[] = "Tests automatic allocation of matrix storage space.\n\n";

  3: #include <petscmat.h>

  5: int main(int argc, char **args)
  6: {
  7:   Mat         C;
  8:   PetscInt    i, j, m = 3, n = 3, Ii, J;
  9:   PetscScalar v;
 10:   MatInfo     info;

 12:   PetscFunctionBeginUser;
 13:   PetscCall(PetscInitialize(&argc, &args, NULL, help));
 14:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));
 15:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));

 17:   /* create the matrix for the five point stencil, YET AGAIN */
 18:   PetscCall(MatCreate(PETSC_COMM_SELF, &C));
 19:   PetscCall(MatSetSizes(C, PETSC_DECIDE, PETSC_DECIDE, m * n, m * n));
 20:   PetscCall(MatSetFromOptions(C));
 21:   PetscCall(MatSetUp(C));
 22:   for (i = 0; i < m; i++) {
 23:     for (j = 0; j < n; j++) {
 24:       v  = -1.0;
 25:       Ii = j + n * i;
 26:       if (i > 0) {
 27:         J = Ii - n;
 28:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 29:       }
 30:       if (i < m - 1) {
 31:         J = Ii + n;
 32:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 33:       }
 34:       if (j > 0) {
 35:         J = Ii - 1;
 36:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 37:       }
 38:       if (j < n - 1) {
 39:         J = Ii + 1;
 40:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 41:       }
 42:       v = 4.0;
 43:       PetscCall(MatSetValues(C, 1, &Ii, 1, &Ii, &v, INSERT_VALUES));
 44:     }
 45:   }
 46:   PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
 47:   PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
 48:   PetscCall(MatView(C, PETSC_VIEWER_STDOUT_SELF));

 50:   PetscCall(MatGetInfo(C, MAT_LOCAL, &info));
 51:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "matrix nonzeros = %" PetscInt_FMT ", allocated nonzeros = %" PetscInt_FMT "\n", (PetscInt)info.nz_used, (PetscInt)info.nz_allocated));

 53:   PetscCall(MatDestroy(&C));
 54:   PetscCall(PetscFinalize());
 55:   return 0;
 56: }

 58: /*TEST

 60:    test:

 62: TEST*/