代码

#include <time.h>
#include <stdio.h>
#define N 1048576
int arr[N*2];
int arr2[N*2];
int main() {
    int i, j, k, s, t;
    volatile int w;
    for (i=0; i<10; ++i) {
        for (j=0; j<N; ++j) {
            arr2[j*2]=arr[j]=rand(), arr2[j*2+1]=arr[j+N]=rand();
        }
        asm("":::"memory");

        s=0;
        t=clock();
        for (j=0; j<N; ++j) {
            if (s<arr[j])s+=arr[j+N];
        }
        w = s;
        printf("%12d<%08X>", clock()-t, s);

        s=0;
        t=clock();
        for (j=0; j<N; ++j) {
            if (s<arr2[j*2])s+=arr2[j*2+1];
        }
        w = s;
        printf("%12d<%08X>", clock()-t, s);
    }
}

评测结果