/* greetings.cpp -- greetings program
 *
 * Send a message from all processes with rank != 0 to process 0.
 *    Process 0 prints the messages received.
 *
 * Input: none.
 * Output: contents of messages received by process 0.
 *
 * See Chapter 3, pp. 41 & ff in PPMPI.
 */
#include <iostream.h>
#include <stdio.h> //for the sprintf() function
#include <string.h>
#include <mpi++.h>

int main(int argc, char* argv[]) {
    int         my_rank;       /* rank of process      */
    int         p;             /* number of processes  */
    int         source;        /* rank of sender       */
    int         dest;          /* rank of receiver     */
    int         tag = 0;       /* tag for messages     */
    char        message[100];  /* storage for message  */
    MPI::Status  status;        /* return status for    */
                               /* receive              */

    /* Start up MPI */
    MPI::Init(argc, argv);

    /* Find out process rank  */
    my_rank = MPI::COMM_WORLD.Get_rank();

    /* Find out number of processes */
    p = MPI::COMM_WORLD.Get_size();

    if (my_rank != 0) {
        /* Create message */
        sprintf(message, "Greetings from process %d!",
            my_rank);
        dest = 0;
        /* Use strlen+1 so that '\0' gets transmitted */
        MPI::COMM_WORLD.Send(message, strlen(message)+1, MPI::CHAR, 
            dest, tag);
    } else { /* my_rank == 0 */
        for (source = 1; source < p; source++) {
            MPI::COMM_WORLD.Recv(message, 100, MPI::CHAR, source, tag, 
                status);
            cout << message << endl;
        }
    }

    /* Shut down MPI */
    MPI::Finalize();
} /* main */