Actual source code: ex8.c


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

  4: #include <petscmat.h>

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

 13:   PetscFunctionBeginUser;
 14:   PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
 15:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));
 16:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));

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

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

 54:   PetscCall(MatDestroy(&C));
 55:   PetscCall(PetscFinalize());
 56:   return 0;
 57: }

 59: /*TEST

 61:    test:

 63: TEST*/