xref: /petsc/src/mat/tests/ex21.c (revision 732aec7a18f2199fb53bb9a2f3aef439a834ce31)

static char help[] = "Tests converting a parallel AIJ formatted matrix to the parallel Row format.\n\
 This also tests MatGetRow() and MatRestoreRow() for the parallel case.\n\n";

#include <petscmat.h>

int main(int argc, char **args)
{
  Mat                C, A;
  PetscInt           i, j, m = 3, n = 2, Ii, J, rstart, rend, nz;
  PetscMPIInt        rank, size;
  const PetscInt    *idx;
  PetscScalar        v;
  const PetscScalar *values;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &args, NULL, help));
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
  n = 2 * size;

  /* 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(MatMPIAIJSetPreallocation(C, 5, NULL, 5, NULL));
  PetscCall(MatSeqAIJSetPreallocation(C, 5, NULL));
  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(MatGetOwnershipRange(C, &rstart, &rend));
  for (i = rstart; i < rend; i++) {
    PetscCall(MatGetRow(C, i, &nz, &idx, &values));
    PetscCall(PetscSynchronizedFPrintf(PETSC_COMM_WORLD, stdout, "[%d] get row %" PetscInt_FMT ": ", rank, i));
    for (j = 0; j < nz; j++) PetscCall(PetscSynchronizedFPrintf(PETSC_COMM_WORLD, stdout, "%" PetscInt_FMT " %g  ", idx[j], (double)PetscRealPart(values[j])));
    PetscCall(PetscSynchronizedFPrintf(PETSC_COMM_WORLD, stdout, "\n"));
    PetscCall(MatRestoreRow(C, i, &nz, &idx, &values));
  }
  PetscCall(PetscSynchronizedFlush(PETSC_COMM_WORLD, stdout));

  PetscCall(MatConvert(C, MATSAME, 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(MatView(A, PETSC_VIEWER_STDOUT_WORLD));

  PetscCall(MatDestroy(&A));
  PetscCall(MatDestroy(&C));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      args: -mat_type seqaij

TEST*/