Example of using MPI Split

main.cpp

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


using namespace std;


int main(int argc, char *argv[]) {
  MPI::Init_thread(MPI_THREAD_FUNNELED);

  MPI::Intracomm comm = MPI_COMM_WORLD;

  int rank = comm.Get_rank();
  int size = comm.Get_size();

  int myColor = rank % 3;


  MPI::Intracomm comm2 = comm.Split(myColor, rank);


  comm2.Bcast(&rank, 1, MPI::INT, 0);

  cout << "My root is " << rank << ", my local rank is " << comm2.Get_rank() << " and my global rank is " << comm.Get_rank() << endl;


  MPI_Finalize();

}