static char help[] = "Tests application ordering.\n\n";

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

int main(int argc, char **argv)
{
  PetscMPIInt rank, size;
  PetscInt    n, *ispetsc, *isapp, start, N, i;
  AO          ao;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));
  PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
  n = rank + 2;
  PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));

  /* create the orderings */
  PetscCall(PetscMalloc2(n, &ispetsc, n, &isapp));

  PetscCallMPI(MPI_Scan(&n, &start, 1, MPIU_INT, MPI_SUM, PETSC_COMM_WORLD));
  PetscCallMPI(MPIU_Allreduce(&n, &N, 1, MPIU_INT, MPI_SUM, PETSC_COMM_WORLD));
  start -= n;

  for (i = 0; i < n; i++) {
    ispetsc[i] = start + i;
    isapp[i]   = N - start - i - 1;
  }

  /* create the application ordering */
  PetscCall(AOCreateBasic(PETSC_COMM_WORLD, n, isapp, ispetsc, &ao));
  PetscCall(AOView(ao, PETSC_VIEWER_STDOUT_WORLD));

  /* check the mapping */
  PetscCall(AOPetscToApplication(ao, n, ispetsc));
  for (i = 0; i < n; i++) {
    if (ispetsc[i] != isapp[i]) PetscCall(PetscPrintf(PETSC_COMM_WORLD, "[%d] Problem with mapping %" PetscInt_FMT " to %" PetscInt_FMT "\n", rank, i, ispetsc[i]));
  }
  PetscCall(PetscFree2(ispetsc, isapp));

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

/*TEST

   test:

   test:
      suffix: 2
      nsize: 2

   test:
      suffix: 3
      nsize: 3

TEST*/