如何衡量在Linux / Windows的CPU时间和挂钟时间？ [英] How can I measure CPU time and wall clock time on both Linux/Windows?

问题描述

我的意思是：我怎么能测量时间我的CPU功能上执行，需要运行我的功能挂钟时间用在何处？ （IM感兴趣的Linux / Windows与x86和x86_64的）。看看我想做的事（IM使用C ++在这里，但我会preFER℃溶液）：

I mean: how can I measure time my CPU spent on function execution and wall clock time it takes to run my function? (Im interested in Linux/Windows and both x86 and x86_64). See what I want to do (Im using C++ here but I would prefer C solution):

int startcputime, endcputime, wcts, wcte;

startcputime = cputime();
function(args);
endcputime = cputime();

std::cout << "it took " << endcputime - startcputime << " s of CPU to execute this\n";

wcts = wallclocktime();
function(args);
wcte = wallclocktime();

std::cout << "it took " << wcte - wcts << " s of real time to execute this\n";

另一个重要的问题：就是这个类型的时间测量体系结构无关的或不

推荐答案

下面是一个复制粘贴的解决方案，以及在Windows和Linux可以作为C和C ++。

Here's a copy-paste solution that works on both Windows and Linux as well as C and C++.

正如评论中提到，有，这是否提振库。但是，如果你不能使用boost，这应该工作：

As mentioned in the comments, there's a boost library that does this. But if you can't use boost, this should work:

//  Windows
#ifdef _WIN32
#include <Windows.h>
double get_wall_time(){
    LARGE_INTEGER time,freq;
    if (!QueryPerformanceFrequency(&freq)){
        //  Handle error
        return 0;
    }
    if (!QueryPerformanceCounter(&time)){
        //  Handle error
        return 0;
    }
    return (double)time.QuadPart / freq.QuadPart;
}
double get_cpu_time(){
    FILETIME a,b,c,d;
    if (GetProcessTimes(GetCurrentProcess(),&a,&b,&c,&d) != 0){
        //  Returns total user time.
        //  Can be tweaked to include kernel times as well.
        return
            (double)(d.dwLowDateTime |
            ((unsigned long long)d.dwHighDateTime << 32)) * 0.0000001;
    }else{
        //  Handle error
        return 0;
    }
}

//  Posix/Linux
#else
#include <time.h>
#include <sys/time.h>
double get_wall_time(){
    struct timeval time;
    if (gettimeofday(&time,NULL)){
        //  Handle error
        return 0;
    }
    return (double)time.tv_sec + (double)time.tv_usec * .000001;
}
double get_cpu_time(){
    return (double)clock() / CLOCKS_PER_SEC;
}
#endif

有一堆方法来实现这些时钟。但这里是上面的代码片段使用：

There's a bunch of ways to implement these clocks. But here's what the above snippet uses:

对于Windows：

• 挂钟时间：<一href=\"http://msdn.microsoft.com/en-us/library/windows/desktop/aa373083%28v=vs.85%29.aspx\">Performance计数器


• CPU时间：<一href=\"http://msdn.microsoft.com/en-us/library/windows/desktop/ms683223%28v=vs.85%29.aspx\"><$c$c>GetProcessTimes()

对于Linux：

• 挂钟时间： 函数gettimeofday（）


• CPU时间： 时钟（）

这是一个小的演示：

#include <math.h>
#include <iostream>
using namespace std;

int main(){

    //  Start Timers
    double wall0 = get_wall_time();
    double cpu0  = get_cpu_time();

    //  Perform some computation.
    double sum = 0;
#pragma omp parallel for reduction(+ : sum)
    for (long long i = 1; i < 10000000000; i++){
        sum += log((double)i);
    }

    //  Stop timers
    double wall1 = get_wall_time();
    double cpu1  = get_cpu_time();

    cout << "Wall Time = " << wall1 - wall0 << endl;
    cout << "CPU Time  = " << cpu1  - cpu0  << endl;

    //  Prevent Code Elimination
    cout << endl;
    cout << "Sum = " << sum << endl;

}

输出（12个线程）：

Output (12 threads):

Wall Time = 15.7586
CPU Time  = 178.719

Sum = 2.20259e+011

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