#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);

     MPI_Gather(&rank, 1, MPI_INT, gatherLoc.data(), 1, MPI_INT, 
                     0, MPI_COMM_WORLD);

     if(rank == 0) {
        for(int i = 0; i < gatherLoc.size(); ++i) {
           cout << i << " holds " << gatherLoc[i] << endl;
        }
     }

     MPI_Allgather(&rank, 1, MPI_INT, gatherLoc.data(), 1, MPI_INT, 
         MPI_COMM_WORLD);

     if(rank == 0) {
         for(int i =0; i < gatherLoc.size(); ++i) {
            cout << rank << " has " << gatherLoc[i] << " at " << i << endl; 
         }
     }
     
     MPI_Finalize();
     return 0;
}