#include <stdio.h>
#include <time.h>
#include <string.h>

#include "mpi.h"

int main (int argc, char* argv[])
{ /* main */
    const int  maximum_message_length = 100;
    const int  master_rank            =   0;
    char       message[maximum_message_length+1];
    MPI_Status status;      /* Info about receive status  */

    int        my_rank;     /* This process ID            */
    int        num_procs;   /* Number of processes in run */
    int        source;      /* Process ID to receive from */

    int        loop_source;   /*just an iterator*/
    int        destination; /* Process ID to send to      */
    int        tag = 0;     /* Message ID                 */

    int        mpi_error;   /* Error code for MPI calls   */
    int        icount   ;
    char  processor_name[MPI_MAX_PROCESSOR_NAME];
    int  name_length;
    int  got_message[20],received;  //used as a boolean

    mpi_error =MPI_Init(&argc, &argv);//will not deal with mpi_error except last one.
    mpi_error =MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
    mpi_error =MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
    if (my_rank != master_rank) {
        mpi_error=MPI_Get_processor_name(processor_name,&name_length); 
        sprintf(message, "Greetings from process #%d running on %s\n", my_rank, processor_name);
        destination = master_rank;
        mpi_error =MPI_Send(message, strlen(message) + 1, MPI_CHAR,destination, tag, MPI_COMM_WORLD);
    } /* if (my_rank != master_rank) */
    else {
        for (loop_source=1;loop_source < num_procs; loop_source++) {
            got_message[loop_source]=0;
        }
        loop_source = 1; 
        while (1) {
            for (source = 1; source < num_procs;source++) {
                if (!(got_message[source]==1)) {
                    MPI_Iprobe(source,tag,MPI_COMM_WORLD,&received,&status);
                    if (received) {
                        got_message[source]=1;
                        MPI_Recv(message, maximum_message_length + 1, MPI_CHAR, source, tag, MPI_COMM_WORLD, &status);
                        printf( "%s  \n", message);
                        loop_source++;
                    }//received

                }
            }//for source
            if (loop_source==num_procs)break;
        }//while
    }//if-else
    mpi_error = MPI_Finalize();
    if (MPI_SUCCESS!=mpi_error)
          return mpi_error;
    else

          return 0;
    
} /* main */


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