source: CIVL/mods/dev.civl.com/examples/concurrency/ring1.cvl@ cb4d4f4

#include <civlc.cvh>
/* Create nprocs processes.  Have them exchange data in a cycle.
 * Commandline example:
 *     civl verify -inputNPROCS=3 ring.cvl -simplify=false
 */
#include<comm.cvh>
#include "mp_root.cvh"

void MPI_Process (int rank) {
  #include "mp_proc.cvh"
  $comm comm = $comm_create($here, COMM_WORLD, rank);
  double x=rank, y;
  
  sendrecv(&x, 1, (rank+1)%NPROCS, 0, &y, 1, (rank+NPROCS-1)%NPROCS, 0, comm);
  $assert(y==(rank+NPROCS-1)%NPROCS);
  $comm_destroy(comm);
}