static char help[] = "Demonstrates constructing an application ordering.\n\n";

#include <petscao.h>
#include <petscviewer.h>

int main(int argc, char **argv)
{
  PetscInt    n = 5;
  PetscMPIInt rank, size;
  IS          ispetsc, isapp;
  AO          ao;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));

  /* create the index sets */
  PetscCall(ISCreateStride(PETSC_COMM_WORLD, n, rank, size, &ispetsc));
  PetscCall(ISCreateStride(PETSC_COMM_WORLD, n, n * rank, 1, &isapp));

  /* create the application ordering */
  PetscCall(AOCreateBasicIS(isapp, ispetsc, &ao));

  PetscCall(AOView(ao, PETSC_VIEWER_STDOUT_WORLD));

  PetscCall(ISView(ispetsc, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(ISView(isapp, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(AOPetscToApplicationIS(ao, ispetsc));
  PetscCall(ISView(isapp, PETSC_VIEWER_STDOUT_WORLD));
  PetscCall(ISView(ispetsc, PETSC_VIEWER_STDOUT_WORLD));

  PetscCall(ISDestroy(&ispetsc));
  PetscCall(ISDestroy(&isapp));

  PetscCall(AODestroy(&ao));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:
      nsize: 2

TEST*/