如何获得在C ++中运行函数所花费的时间

问题描述

我通过谷歌搜索尝试了一些代码:

I tried some codes by googling :

clock_t start, end;
start = clock();
//CODES GOES HERE
end = clock();
std::cout << end - start <<"\n";
std::cout << (double) (end-start)/ CLOCKS_PER_SEC;

但即使

std::cout << (double) (end-start)/ (CLOCKS_PER_SEC/1000.0 );

不知道为什么，但是当我在Java中得到类似的内容时:getCurrentTimeMillis()可以很好地工作.我希望它显示毫秒数，因为计算机可以这么快地进行计算.

Don't know why but when I get the similar in Java : getCurrentTimeMillis() it works well. I want it to show the milliseconds as maybe the computer compute so fast.

推荐答案

我认为不能保证clock具有足够高的分辨率来分析您的功能.如果您想知道一个函数执行的速度，您应该将其运行数千次而不是一次，测量总耗时并取平均值.

I don't think it's guaranteed that clock has a high enough resolution to profile your function. If you want to know how fast a function executes, you should run it maybe a few thousands times instead of once, measure the total time it takes and take the average.

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