并行化数组的初始化

Question

下面的代码是用C语言编写的。我能够并行计算数组和。

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>

int array_size;
int num_threads;
int step;
int midsum_padding;
int* array;
int* midsum;

void* sum_thread (void * arg);

int main (int argc, char** argv) {

    if(argc != 4) {
      printf("Need 3 arguments\n");
      return 0;
    }
    array_size = atoi(argv[1]);
    num_threads = atoi(argv[2]);
    midsum_padding = atoi(argv[3]);

    int i = 0;
    int final_sum = 0;
    struct timeval start, end;
    double elapsed;

    pthread_t *tid = malloc(num_threads*sizeof(pthread_t));
    int *idx = malloc(num_threads*sizeof(int));

    array = malloc(array_size*sizeof(int));
    midsum = malloc(num_threads*midsum_padding*sizeof(int));
    step = array_size/num_threads;

    for(i=0; i < array_size; i++) {
        array[i] = 5;
    }

    gettimeofday(&start,NULL);

    for(i=0; i < num_threads; i++) {
        idx[i] = i;
        midsum[i * midsum_padding] = 0;
        pthread_create(&tid[i], NULL, sum_thread, &idx[i]);
    }

    for(i=0; i < num_threads; i++) {
        pthread_join(tid[i], NULL);
        final_sum += midsum[i * midsum_padding];
    }
    gettimeofday(&end, NULL);

    elapsed = ((double)end.tv_sec    + 0.000001*(double)end.tv_usec)-
               ((double)start.tv_sec + 0.000001*(double)start.tv_usec);

    printf("%lf\n", elapsed);

    return 0;
}

void *sum_thread (void* arg) {
    int *val = arg;
    int idx = *val;
    int i = 0;
    for (i = idx * step; i < (idx + 1) * step; i++) {
        midsum[idx * midsum_padding] += array[i];
    }
}

但是如何更改数组初始化代码以使其也可以并行化？也就是说，每个线程也应该进行一些数组初始化。