round_robin

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

int main(int argc, char** argv) {
    // Initialize the MPI environment
    MPI_Init(&argc, &argv);

    // Get the number of processes
    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);

    // Get the world_rank of the process
    int world_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

    MPI_Request request;
    MPI_Status st;
    int msg;

    if (world_rank == 0) {
        msg = 0;

        MPI_Send(&msg, 1, MPI_INT, world_size-1, 1, MPI_COMM_WORLD);
        printf("Process %d sends %d to proc %d\n", world_rank, msg, world_size - 1);

        MPI_Recv(&msg, 1, MPI_INT, world_rank+1, 1, MPI_COMM_WORLD, &st);
        printf("Process %d got %d from proc %d\n", world_rank, msg, world_size);

        msg++;
        MPI_Send(&msg, 1, MPI_INT, world_size - 1, 1, MPI_COMM_WORLD);
        printf("Process %d sends %d to proc %d\n", world_rank, msg, world_size - 1);

        MPI_Recv(&msg, 1, MPI_INT, world_rank + 1, 1, MPI_COMM_WORLD, &st);
        printf("Process %d got %d from proc %d\n", world_rank, msg, world_size);

    }
    if (world_rank > 0 && world_rank < (world_size - 1)) {
        MPI_Recv(&msg, 1, MPI_INT, world_rank + 1, 1, MPI_COMM_WORLD, &st);
        printf("Process %d got %d from proc %d\n", world_rank, msg, world_rank + 1);
        msg++;
        MPI_Send(&msg, 1, MPI_INT, world_rank - 1, 1, MPI_COMM_WORLD);
        printf("Process %d sends %d to proc %d\n", world_rank, msg, world_rank - 1);

        MPI_Recv(&msg, 1, MPI_INT, world_rank + 1, 1, MPI_COMM_WORLD, &st);
        printf("Process %d got %d from proc %d\n", world_rank, msg, world_rank + 1);
        msg++;
        MPI_Send(&msg, 1, MPI_INT, world_rank - 1, 1, MPI_COMM_WORLD);
        printf("Process %d sends %d to proc %d\n", world_rank, msg, world_rank - 1);
    }
    if (world_rank == world_size - 1) {
        MPI_Recv(&msg, 1, MPI_INT, 0, 1, MPI_COMM_WORLD, &st);

        printf("Process %d got %d from proc %d\n", world_rank, msg, 0);
        msg++;
        MPI_Send(&msg, 1, MPI_INT, world_rank - 1, 1, MPI_COMM_WORLD);
        printf("Process %d sends %d to proc %d\n", world_rank, msg, world_rank - 1);

        MPI_Recv(&msg, 1, MPI_INT, 0, 1, MPI_COMM_WORLD, &st);

        printf("Process %d got %d from proc %d\n", world_rank, msg, 0);
        msg++;
        MPI_Send(&msg, 1, MPI_INT, world_rank - 1, 1, MPI_COMM_WORLD);
        printf("Process %d sends %d to proc %d\n", world_rank, msg, world_rank - 1);
    }

    // Finalize the MPI environment.
    MPI_Finalize();
}