/*
   file: nblock.c
   compile: cc nblock.c -lmpi
   run: mpirun -np 2 ./a.out

   rank = 0 : value = 3 
   rank = 0 : value = 3 
   rank = 1 : value = 1 
   rank = 1 : value = 3 
*/

#include "mpi.h" 
main( argc, argv ) 
int argc; 
char **argv; 
{ 

    int myrank; 
    int other;
    MPI_Status status; 
    MPI_Request   send_request;
    MPI_Request   recv_request;

    int a[20] = {3,2,3};
    int b[20] = {1,2,1};

    MPI_Init( &argc, &argv ); 
    MPI_Comm_rank( MPI_COMM_WORLD, &myrank ); 

    if (myrank == 0){
      other = 1;
    }else {
      other = 0;
    }

    MPI_Isend(a, 1, MPI_INT, other, 0, MPI_COMM_WORLD, &send_request);
    MPI_Irecv(b, 1, MPI_INT, other, 0, MPI_COMM_WORLD, &send_request);
    MPI_Isend(b, 1, MPI_INT, other, 0, MPI_COMM_WORLD, &send_request);
    MPI_Irecv(a, 1, MPI_INT, other, 0, MPI_COMM_WORLD, &send_request);

    MPI_Wait(&send_request, &status);
    MPI_Wait(&recv_request, &status);

    printf("rank = %d : value = %d \n", myrank, a[0]);
    printf("rank = %d : value = %d \n", myrank, b[0]);

    MPI_Finalize(); 
  }