問題描述

我想了解某個(gè)函數(shù)在我的 C++ 程序中在 Linux 上執(zhí)行所需的時(shí)間.之后，我想做一個(gè)速度比較.我看到了幾個(gè)時(shí)間函數(shù)，但最終從 boost 得到了這個(gè).時(shí)間:

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

現(xiàn)在，我不清楚是否使用上述功能，我是否會(huì)獲得 CPU 在該功能上花費(fèi)的唯一時(shí)間?

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.任何人都可以幫助我如何使用上述功能嗎?

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:現(xiàn)在，我正在使用 std::chrono::system_clock::now() 以秒為單位獲取時(shí)間，但是由于每次 CPU 負(fù)載不同，這會(huì)給我不同的結(jié)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.

推薦答案

它是 C++11 中非常易于使用的方法.您必須使用 標(biāo)頭中的 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.

像這樣使用它:

#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;
}

這將測(cè)量函數(shù)long_operation的持續(xù)時(shí)間.

This will measure the duration of the function long_operation.

可能的輸出:

150ms
150.068ms

工作示例:https://godbolt.org/z/oe5cMd

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