static char help[] = "Test MatCreate() with MAT_STRUCTURE_ONLY .\n\n";

#include <petscmat.h>

int main(int argc, char **argv)
{
  Mat         mat;
  PetscInt    m = 7, n, i, j, rstart, rend;
  PetscMPIInt size;
  PetscScalar v;
  PetscBool   struct_only = PETSC_TRUE;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
  PetscCheck(size == 1, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "This is a uniprocessor example only!");

  PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD, PETSC_VIEWER_ASCII_COMMON));
  PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));
  PetscCall(PetscOptionsGetBool(NULL, NULL, "-struct_only", &struct_only, NULL));
  n = m;

  /* ------- Assemble matrix, test MatValid() --------- */
  PetscCall(MatCreate(PETSC_COMM_WORLD, &mat));
  PetscCall(MatSetSizes(mat, PETSC_DECIDE, PETSC_DECIDE, m, n));
  PetscCall(MatSetFromOptions(mat));
  if (struct_only) PetscCall(MatSetOption(mat, MAT_STRUCTURE_ONLY, PETSC_TRUE));
  PetscCall(MatSetUp(mat));
  PetscCall(MatGetOwnershipRange(mat, &rstart, &rend));
  for (i = rstart; i < rend; i++) {
    for (j = 0; j < n; j++) {
      v = 10.0 * i + j;
      PetscCall(MatSetValues(mat, 1, &i, 1, &j, &v, INSERT_VALUES));
    }
  }
  PetscCall(MatAssemblyBegin(mat, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(mat, MAT_FINAL_ASSEMBLY));
  PetscCall(MatView(mat, PETSC_VIEWER_STDOUT_WORLD));

  /* Free data structures */
  PetscCall(MatDestroy(&mat));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      output_file: output/ex107.out

   test:
      suffix: 2
      args: -mat_type baij -mat_block_size 2 -m 10

TEST*/