#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>

#define N 16

int main(int argc, char** argv) {
    int rank, size, i;
    int* data;

    /* initialize MPI */
    MPI_Init(&argc, &argv);

    /* get the rank (process id) and size (number of processes) */
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    /* have process 0 read in the data */
    if (rank == 0) {
        printf("Enter %d values: ", N);
        fflush(stdout);
        
        data = malloc(N * sizeof(int));
        for (i = 0 ; i < N; i++) {
            scanf("%d", data + i);
        }
    }

    /* our portion of the data */
    int portion[N / size];

    /* now scatter the characters to all processes*/
    MPI_Scatter(data, N / size, MPI_INT,
            portion, N / size, MPI_INT, 0, MPI_COMM_WORLD);

    /* have each process square its data */
    for (i = 0; i < (N / size); i++) {
        portion[i] *= portion[i];
    }

    /* gather the data back up in process 0 */
    MPI_Gather(portion, N / size, MPI_INT,
            data, N / size, MPI_INT, 0, MPI_COMM_WORLD);

    /* have process 0 print the results */
    if (rank == 0) {
        printf("Results: ");
        for (i = 0; i < N; i++) {
            printf("%d ", data[i]);
        }
        printf("\n");
    }

    /* quit MPI */
    MPI_Finalize();
    return 0;
}