#include <iostream>
#include <vector>
#include <mpi.h>

using namespace std;

int main(int argc, char * argv[]) {

     MPI_Init(&argc, &argv);

     // Get the rank and size in the original communicator
     int rank, 
         size;

     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
     MPI_Comm_size(MPI_COMM_WORLD, &size);
     
     vector<int> gatherLoc(size);
     int sum{0};


     MPI_Reduce(&rank, &sum, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);

     if(rank == 0) {
        cout << "The sum is " << sum << endl;
        cout << endl << endl;
     }

     sum =0;

     MPI_Allreduce(&rank, &sum, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
     cout << "on " << rank << "  the sum is " << sum << endl;
     MPI_Finalize();
     return 0;
}