在 C++ 测量函数的执行时间
问题说明
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.
正确答案
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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