xref: /petsc/src/mat/tests/ex20.c (revision 732aec7a18f2199fb53bb9a2f3aef439a834ce31)

static char help[] = "Tests converting a matrix to another format with MatConvert().\n\n";

#include <petscmat.h>

int main(int argc, char **args)
{
  Mat         C, A;
  PetscInt    i, j, m = 5, n = 4, Ii, J;
  PetscMPIInt rank, size;
  PetscScalar v;
  char        mtype[256];

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

  /* This example does not work correctly for np > 2 */
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
  PetscCheck(size <= 2, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "Use np <= 2");

  /* Create the matrix for the five point stencil, YET AGAIN */
  PetscCall(MatCreate(PETSC_COMM_WORLD, &C));
  PetscCall(MatSetSizes(C, PETSC_DECIDE, PETSC_DECIDE, m * n, m * n));
  PetscCall(MatSetFromOptions(C));
  PetscCall(MatSetUp(C));
  for (i = 0; i < m; i++) {
    for (j = 2 * rank; j < 2 * rank + 2; j++) {
      v  = -1.0;
      Ii = j + n * i;
      if (i > 0) {
        J = Ii - n;
        PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
      }
      if (i < m - 1) {
        J = Ii + n;
        PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
      }
      if (j > 0) {
        J = Ii - 1;
        PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
      }
      if (j < n - 1) {
        J = Ii + 1;
        PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
      }
      v = 4.0;
      PetscCall(MatSetValues(C, 1, &Ii, 1, &Ii, &v, INSERT_VALUES));
    }
  }

  PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
  PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD, PETSC_VIEWER_ASCII_INFO));
  PetscCall(MatView(C, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(MatView(C, PETSC_VIEWER_STDOUT_WORLD));

  PetscCall(PetscStrncpy(mtype, MATSAME, sizeof(mtype)));
  PetscCall(PetscOptionsGetString(NULL, NULL, "-conv_mat_type", mtype, sizeof(mtype), NULL));
  PetscCall(MatConvert(C, mtype, MAT_INITIAL_MATRIX, &A));
  PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD, PETSC_VIEWER_ASCII_INFO));
  PetscCall(MatView(A, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD, PETSC_VIEWER_ASCII_IMPL));
  PetscCall(MatView(A, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));

  /* Free data structures */
  PetscCall(MatDestroy(&A));
  PetscCall(MatDestroy(&C));

  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      args: -conv_mat_type seqaij

TEST*/