// forkadd.c
#include <stdio.h>
#include <stdlib.h>

#define N 1000000
int
main()
{
    int i, j;
    double *bigarray = malloc(N * sizeof(bigarray[0]));
    for (i = 0; i < N; i++)
        scanf("%lf", bigarray+i);
    
    double sum = 0.0;
    int children_done = 0;
    // distribute work across 10 child processes
    for (j = 0; j < 10; j++) {
        if (fork() == 0)  { 
            // child 'j' sums up interval [N*j/10, N*(j+1)/10]
            double childsum = 0.0;  // use separate variable for each child
            for (i = 0; i < N/10; i++)
                childsum += bigarray[j * N/10 + i];

            sum += childsum;        // add to total when done
            children_done += 1;
        }
    }

    // reap children before examining the result
    for (j = 0; j < 10; j++)
        wait(NULL);

    // double check that all children are done, output the result
    if (children_done == 10)
        printf("%lf\n", sum);
    return 0;
}