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

int main(int argc, char **argv)
{
    MPI::Init(argc, argv);

    // get the number of processes, and the id of this process
    int rank = MPI::COMM_WORLD.Get_rank();
    int nprocs = MPI::COMM_WORLD.Get_size();

    // we want to perform 1000 iterations in total. Work out the 
    // number of iterations to perform per process...
    int count = 1000 / nprocs;

    // we use the rank of this process to work out which
    // iterations to perform.
    int start = rank * count;
    int stop = start + count;

    // now perform the loop
    int nloops = 0;

    for (int i=start; i<stop; ++i)
    {
        ++nloops;
    }

    std::cout << "Process " << rank << " performed " << nloops 
              << " iterations of the loop.\n";

    if (rank != 0)
    {
        // if we are not the master process (rank 0) then we need to
        // tell that process how many iterations we performed
        MPI::COMM_WORLD.Send( &nloops, 1, MPI_INT, 0, 0 );
    }
    else
    {
        // if we are the master process, then we need to wait to be
        // told how many iterations were performed by each other
        // process
        int total_nloops = nloops;

        for (int i=1; i<nprocs; ++i)
        {
            MPI::COMM_WORLD.Recv( &nloops, 1, MPI_INT, i, 0 );

            total_nloops += nloops;
        }

        // ok - are there any more loops to run?
        nloops = 0;

        for (int i=total_nloops; i<1000; ++i)
        {
            ++nloops;
        }

        std::cout << "Process 0 performed the remaining " << nloops
                  << " iterations of the loop\n";
    }

    MPI::Finalize();

    return 0;
}