循环展开c++

#pragma UNROLL 4

被用来做循环展开，下面是一个实例：

#include "time.h"
#include 
#include
#include
using namespace std;

int main()
{
    clock_t start_time, end_time;
    start_time = clock();   //获取开始执行时间

#pragma unroll 1000

    for (int i = 0; i < 2147483640; i++)
    {
        i++;
    }

    end_time = clock();     //获取结束时间
    double Times = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("%f seconds\n", Times);

    return 0;
}