Actual source code: ex35.c


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

  4: #include <petscmat.h>

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

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

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

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

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

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

 70:   PetscCall(PetscFinalize());
 71:   return 0;
 72: }

 74: /*TEST

 76:    test:

 78: TEST*/