Berkeley

/*
 ============================================================================
 Name        : Berkeley.c
 Author      :
 Version     :
 Copyright   : Your copyright notice
 Description : Hello MPI World in C
 ============================================================================
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.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 */
    MPI_Status status ;   /* return status for receive */

    /* start up MPI */

    MPI_Init(&argc, &argv);

    /* find out process rank */
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    /* find out number of processes */
    MPI_Comm_size(MPI_COMM_WORLD, &p);

    source = 0;
    int difference[p];
    time_t t;
    srand(time(NULL) + my_rank);

    if (my_rank != 0) {
        time_t seconds;
        int diff = rand() % 2000 - 1000;
        seconds = time (NULL);
        seconds -= diff;
        printf("Process - %d\tTime - %ld \n", my_rank, seconds);
        difference[my_rank] = 0;
        MPI_Send(&seconds, 1, MPI_LONG, source, tag, MPI_COMM_WORLD);

        MPI_Barrier(MPI_COMM_WORLD);

        int adjust;
        MPI_Recv(&adjust, 1, MPI_INT, source, tag, MPI_COMM_WORLD, &status);

        printf("%d must adjust time with %d\n", my_rank, adjust);
    } else {
        time_t seconds;
        seconds = time (NULL);
        printf("master time %d\n", seconds);
        long int sec;
        int k;
        for(k = 0; k < p; k++) {
            if(k != source) {
                MPI_Recv(&sec, 1, MPI_LONG, k, tag, MPI_COMM_WORLD, &status);
                int diff = sec - seconds;
                difference[my_rank] = diff;
                printf("Process %d has difference of %d \n", k, diff);
            }
        }

        MPI_Barrier(MPI_COMM_WORLD);

        srand(time(NULL) + my_rank);
        int masterRand = rand() % 1000;
        time_t newTime = time(NULL) + masterRand;
        int masterDiff = newTime - seconds;
        printf("master difference %d\n", masterDiff);

        for(k = 0; k < p; k++) {
            if(k != source) {
                int adjust = difference[k] * (-1) + masterDiff;
                MPI_Send(&adjust, 1, MPI_INT, k, tag, MPI_COMM_WORLD);
            }
        }
    }

    MPI_Finalize();
    return 0;
}