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

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

    // Get the total number of processes and the rank of this process
    int world_rank, world_size;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);

    // Ensure the total number of processes is divisible by 4
    if (world_size % 4 != 0) {
        fprintf(stderr, "World size must be a multiple of 4\n");
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    // Calculate the color for MPI_Comm_split. This will be used to divide processes into groups
    int color = world_rank / 4;

    // Split the world communicator into smaller communicators, one for each group of 4 processes
    MPI_Comm new_comm;
    MPI_Comm_split(MPI_COMM_WORLD, color, world_rank, &new_comm);

    // Get the new rank and the size of the new group
    int new_rank, new_size;
    MPI_Comm_rank(new_comm, &new_rank);
    MPI_Comm_size(new_comm, &new_size);

    // Ring communication within the new group
    int token;
    if (new_rank == 0) {
        token = world_rank;
        MPI_Send(&token, 1, MPI_INT, (new_rank + 1) % new_size, 0, new_comm);
        MPI_Recv(&token, 1, MPI_INT, new_size - 1, 0, new_comm, MPI_STATUS_IGNORE);
    } else {
        MPI_Recv(&token, 1, MPI_INT, new_rank - 1, 0, new_comm, MPI_STATUS_IGNORE);
        MPI_Send(&token, 1, MPI_INT, (new_rank + 1) % new_size, 0, new_comm);
    }

    // Each process prints its old and new rank, and the size of the new group, along with the token received
    printf("Old Rank: %d, New Rank: %d, Size of New Group: %d, Received Token: %d\n", world_rank, new_rank, new_size, token);

    // Finalize the new communicator
    MPI_Comm_free(&new_comm);

    // Finalize the MPI environment
    MPI_Finalize();
}