#include <stdio.h>
#include <string.h>
#include <mpi.h>  // provides MPI macros and functions


int main (int argc, char *argv[])
{
    int my_rank;
    int P;
    int dest;
    int source;
    int tag=50;
    char hostname[256];
    MPI_Status status;

    MPI_Init(&argc,&argv);  // begin of every MPI program
    
    MPI_Comm_size(MPI_COMM_WORLD,&P);        // number of processes
    MPI_Comm_rank(MPI_COMM_WORLD,&my_rank);  // my process number

    gethostname(hostname,255);
    
    // number of current process always between 0 and P-1
    if (my_rank!=0) 
    {
        dest = 0;
        MPI_Send(hostname,strlen(hostname)+1,MPI_CHAR, // Send data
                 dest,tag,MPI_COMM_WORLD);             // (blocking)
    }
    else 
    {
        for (source=1; source<P; source++)
        {
            MPI_Recv(hostname,256,MPI_CHAR,source,tag, // Receive data
                     MPI_COMM_WORLD,&status);          // (blocking)
            std::cout << "Reveived a message from process " << P
                      << " on machine " << hostname;
        }
    }

    MPI_Finalize();  // end of every MPI program

    return 0;
}