#include <stdio.h>
#include <mpi.h>

/* 
 * Sends 'n' messages between processes. When a process
 * receives a message it chooses a new destination at random.
 *
 * usage: random-mpi <n>
 */

main(int argc, char **argv)
{
    int n, i, data[1];
    int dest, size, rank;
    
    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD,&size);
    MPI_Comm_rank(MPI_COMM_WORLD,&rank);


    n = atoi(argv[1]);
  
    srandom(rank);
    
    /* Send 'n' startup messages. */
    if (rank < n) {
        while ((dest = (random()%size)) == rank);
        MPI_Send(data, 1, MPI_INT, dest, 0, MPI_COMM_WORLD);
    }
    
    while (1) {
        MPI_Recv(data, 1, MPI_INT, MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        
        /* Don't send to self. */
        while ((dest = (random()%size)) == rank);
        MPI_Send(data, 1, MPI_INT, dest, 0, MPI_COMM_WORLD);
    }
  
    MPI_Finalize();
}