mpi_ping_pong.cpp

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

#define PING_PONG_LIMIT 10

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

  int ping_pong_count = 0;
  int partner_rank = (rank + 1) % 2;

  while (ping_pong_count < PING_PONG_LIMIT) {

    if (rank == ping_pong_count % 2) {
        // Increment the ping pong count before you send it
        ping_pong_count++;
        MPI_Send(&ping_pong_count, 1, MPI_INT, partner_rank, 0,
                 MPI_COMM_WORLD);
        printf("%d sent and incremented ping_pong_count "
               "%d to %d\n", rank, ping_pong_count,
               partner_rank);
    } 
    
    else {
        MPI_Recv(&ping_pong_count, 1, MPI_INT, partner_rank, 0,
                 MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        printf("%d received ping_pong_count %d from %d\n",
               rank, ping_pong_count, partner_rank);
    }

  }

}