在 C++ 中测量函数的执行时间

问题描述

我想了解某个函数在我的 C++ 程序中在 Linux 上执行所需的时间.之后，我想做一个速度比较.我看到了几个时间函数，但最终从 boost 得到了这个.时间:

I want to find out how much time a certain function takes in my C++ program to execute on Linux. Afterwards, I want to make a speed comparison . I saw several time function but ended up with this from boost. Chrono:

process_user_cpu_clock, captures user-CPU time spent by the current process

现在，我不清楚是否使用上述功能，我是否会获得 CPU 在该功能上花费的唯一时间?

Now, I am not clear if I use the above function, will I get the only time which CPU spent on that function?

其次，我找不到任何使用上述功能的示例.任何人都可以帮助我如何使用上述功能吗?

Secondly, I could not find any example of using the above function. Can any one please help me how to use the above function?

PS:现在，我正在使用 std::chrono::system_clock::now() 以秒为单位获取时间，但是由于每次 CPU 负载不同，这会给我不同的结果.

P.S: Right now , I am using std::chrono::system_clock::now() to get time in seconds but this gives me different results due to different CPU load every time.

推荐答案

它是 C++11 中非常易于使用的方法.您必须使用 标头中的 std::chrono::high_resolution_clock.

It is a very easy-to-use method in C++11. You have to use std::chrono::high_resolution_clock from <chrono> header.

像这样使用它:

#include <chrono>

/* Only needed for the sake of this example. */
#include <iostream>
#include <thread>
    
void long_operation()
{
    /* Simulating a long, heavy operation. */

    using namespace std::chrono_literals;
    std::this_thread::sleep_for(150ms);
}

int main()
{
    using std::chrono::high_resolution_clock;
    using std::chrono::duration_cast;
    using std::chrono::duration;
    using std::chrono::milliseconds;

    auto t1 = high_resolution_clock::now();
    long_operation();
    auto t2 = high_resolution_clock::now();

    /* Getting number of milliseconds as an integer. */
    auto ms_int = duration_cast<milliseconds>(t2 - t1);

    /* Getting number of milliseconds as a double. */
    duration<double, std::milli> ms_double = t2 - t1;

    std::cout << ms_int.count() << "ms
";
    std::cout << ms_double.count() << "ms";
    return 0;
}

这将测量函数long_operation的持续时间.

This will measure the duration of the function long_operation.

可能的输出:

150ms
150.068ms

工作示例:https://godbolt.org/z/oe5cMd

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