#include<assert.h>
#include<mpi.h>
#include<civl-mpi.cvh>
#include<stdio.h>
#pragma CIVL ACSL

$input int in;
$input int _mpi_nprocs = 2;
$assume(in > 0);
MPI_Comm comm = MPI_COMM_WORLD;
int rank;

/*@ 
  @   requires x > 0;
  @   ensures x == in;
  @ \mpi_collective(comm, BOTH):
  @   ensures x == in;
  @
 */
int gimmeOne(int x) 
{
  return 1 + x;
}

int main(int argc, char * argv[]) {
  int x;

  MPI_Init(&argc, &argv);
  MPI_Comm_rank(comm, &rank);
  if(rank == 1)
    MPI_Send(&rank, 1, MPI_INT, 0, 0, comm);
  x = gimmeOne(in);
  if(rank == 0)
    MPI_Recv(&x, 1, MPI_INT, 1, 0, comm, MPI_STATUS_IGNORE);
  MPI_Finalize();
}