source: CIVL/examples/mpi-pthread/mpi-pthreads.cvl

/* CIVL model of simple hybrid MPI+threads program.
 * The program has a defect.
 * Commnad line execution:
 *     civl verify -min mpi-pthreads.cvl
 */
#include<civlc.h>
#define TAG 0
#define NPROCS 2
#define NTHREADS 2

$gcomm gcomm = $gcomm_create($here, NPROCS);

void MPI_Process (int rank) {
  $comm comm = $comm_create($here, gcomm, rank);
  $proc threads[NTHREADS];
  
  void Thread(int tid) {
    int x = rank;
    $message in, out = $message_pack(rank, 1-rank, TAG, &x, sizeof(int));
    
    for (int j=0; j<2; j++) {
      if (rank == 1) {
        for (int i=0; i<2; i++) $comm_enqueue(comm, out);
        for (int i=0; i<2; i++) in = $comm_dequeue(comm, 1-rank, TAG);
      } else {
        for (int i=0; i<2; i++) in = $comm_dequeue(comm, 1-rank, TAG);
        for (int i=0; i<2; i++) $comm_enqueue(comm, out);
      }
    }
  }
  
  for (int i=0; i<NTHREADS; i++) threads[i] = $spawn Thread(i);
  for (int i=0; i<NTHREADS; i++) $wait(threads[i]);
  $comm_destroy(comm);
}

void main() {
  $proc procs[NPROCS];

  for (int i=0; i<NPROCS; i++) procs[i] = $spawn MPI_Process(i);
  for (int i=0; i<NPROCS; i++) $wait(procs[i]);
  $gcomm_destroy(gcomm);
}