TheRock/rocm-systems/projects/rocprofiler-systems/examples/mpi/send-recv.c

// Author: Wes Kendall
// Copyright 2011 www.mpitutorial.com
// This code is provided freely with the tutorials on mpitutorial.com. Feel
// free to modify it for your own use. Any distribution of the code must
// either provide a link to www.mpitutorial.com or keep this header intact.
//
// Ping pong example with MPI_Send and MPI_Recv. Two processes ping pong a
// number back and forth, incrementing it until it reaches a given value.
//
#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char** argv)
{
    const int PING_PONG_LIMIT = 10;

    // Initialize the MPI environment
    MPI_Init(NULL, NULL);
    // Find out rank, size
    int world_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);

    // We are assuming 2 processes for this task
    if(world_size != 2)
    {
        fprintf(stderr, "World size must be two for %s, not %i\n", argv[0], world_size);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    int ping_pong_count = 0;
    int partner_rank    = (world_rank + 1) % 2;
    while(ping_pong_count < PING_PONG_LIMIT)
    {
        if(world_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", world_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", world_rank,
                   ping_pong_count, partner_rank);
        }
    }
    MPI_Finalize();
}