Actual source code: ex35.c

  1: static char help[] = "Tests MatCreateSubMatrices().\n\n";

  3: #include <petscmat.h>

  5: int main(int argc, char **args)
  6: {
  7:   Mat         A, B, *Bsub;
  8:   PetscInt    i, j, m = 6, n = 6, N = 36, Ii, J;
  9:   PetscScalar v;
 10:   IS          isrow;

 12:   PetscFunctionBeginUser;
 13:   PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
 14:   PetscCall(MatCreateSeqAIJ(PETSC_COMM_WORLD, N, N, 5, NULL, &A));
 15:   for (i = 0; i < m; i++) {
 16:     for (j = 0; j < n; j++) {
 17:       v  = -1.0;
 18:       Ii = j + n * i;
 19:       if (i > 0) {
 20:         J = Ii - n;
 21:         PetscCall(MatSetValues(A, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 22:       }
 23:       if (i < m - 1) {
 24:         J = Ii + n;
 25:         PetscCall(MatSetValues(A, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 26:       }
 27:       if (j > 0) {
 28:         J = Ii - 1;
 29:         PetscCall(MatSetValues(A, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 30:       }
 31:       if (j < n - 1) {
 32:         J = Ii + 1;
 33:         PetscCall(MatSetValues(A, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 34:       }
 35:       v = 4.0;
 36:       PetscCall(MatSetValues(A, 1, &Ii, 1, &Ii, &v, INSERT_VALUES));
 37:     }
 38:   }
 39:   PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
 40:   PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
 41:   PetscCall(MatView(A, PETSC_VIEWER_STDOUT_SELF));

 43:   /* take the first diagonal block */
 44:   PetscCall(ISCreateStride(PETSC_COMM_WORLD, m, 0, 1, &isrow));
 45:   PetscCall(MatCreateSubMatrices(A, 1, &isrow, &isrow, MAT_INITIAL_MATRIX, &Bsub));
 46:   B = *Bsub;
 47:   PetscCall(ISDestroy(&isrow));
 48:   PetscCall(MatView(B, PETSC_VIEWER_STDOUT_SELF));
 49:   PetscCall(MatDestroySubMatrices(1, &Bsub));

 51:   /* take a strided block */
 52:   PetscCall(ISCreateStride(PETSC_COMM_WORLD, m, 0, 2, &isrow));
 53:   PetscCall(MatCreateSubMatrices(A, 1, &isrow, &isrow, MAT_INITIAL_MATRIX, &Bsub));
 54:   B = *Bsub;
 55:   PetscCall(ISDestroy(&isrow));
 56:   PetscCall(MatView(B, PETSC_VIEWER_STDOUT_SELF));
 57:   PetscCall(MatDestroySubMatrices(1, &Bsub));

 59:   /* take the last block */
 60:   PetscCall(ISCreateStride(PETSC_COMM_WORLD, m, N - m - 1, 1, &isrow));
 61:   PetscCall(MatCreateSubMatrices(A, 1, &isrow, &isrow, MAT_INITIAL_MATRIX, &Bsub));
 62:   B = *Bsub;
 63:   PetscCall(ISDestroy(&isrow));
 64:   PetscCall(MatView(B, PETSC_VIEWER_STDOUT_SELF));

 66:   PetscCall(MatDestroySubMatrices(1, &Bsub));
 67:   PetscCall(MatDestroy(&A));

 69:   PetscCall(PetscFinalize());
 70:   return 0;
 71: }

 73: /*TEST

 75:    test:

 77: TEST*/