如何输出高精度时间差

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昨天看核心编程看到171页，看到了GetThreadTimes，结果按书上的源码运行无法获取时间向师傅求助，师傅告诉我

猪头三 22:25:44你看到的时间一样，是因为你的时间精度不够猪头三 22:25:56你应该要更加高精度的时间获取

于是搜到到这篇

http://zhidao.baidu.com/question/85502612.html#281447-qzone-1-49353-2b4b15c6dbd92b17940ffe005c9ace27请教VC++高手如何输出高精度时间差

文中高手回答到

晕了,想钱想疯了也就算了,百度的分数也嫌多嫌少的,开了眼了.楼主到MSDN里看下这两个函数:

BOOL QueryPerformanceFrequency(LARGE_INTEGER* lpFrequency);BOOL QueryPerformanceCounter(LARGE_INTEGER* lpPerformanceCount);

另外给你个实现类:

class CStopwatch {public:CStopwatch() { QueryPerformanceFrequency(&m_liPerfFreq); Start();}void Start() { QueryPerformanceCounter(&m_liPerfStart); }__int64 Now() const {LARGE_INTEGER liPerfNow;QueryPerformanceCounter(&liPerfNow);return (((liPerfNow.QuadPart - m_liPerfStart.QuadPart) * 1000) / m_liPerfFreq.QuadPart);}private:LARGE_INTEGER m_liPerfFreq;LARGE_INTEGER m_liPerfStart;};

在Now函数里，有个乘数是1000，目的是让Now返回的时间为毫秒。使用：

CStopwatch stopwatch;//do the work that would take long time;__int64 qwElapsedTime = stopwatch.Now();//qwElapsedTime indicates how long the work has spent;

注意，因为是高精度时间，因此，你要做的工作应该是短期内能完成的工作，时间太长，误差会特别大，因为线程有占用时间片的因素存在。

测试成功获取代码运行时间我的程序代码如下

#include <stdio.h>#include <tchar.h>#include <Windows.h>#include <Locale.h>class CStopwatch {public:CStopwatch() { QueryPerformanceFrequency(&m_liPerfFreq); Start(); }void Start() { QueryPerformanceCounter(&m_liPerfStart); }__int64 Now() const {LARGE_INTEGER liPerfNow;QueryPerformanceCounter(&liPerfNow);return (((liPerfNow.QuadPart - m_liPerfStart.QuadPart) * 1000) / m_liPerfFreq.QuadPart);}private:LARGE_INTEGER m_liPerfFreq;LARGE_INTEGER m_liPerfStart;};void PerformLongOperation();int _tmain(int argc, _TCHAR* argv[]){_wsetlocale(LC_ALL, L"chs"); //本地化PerformLongOperation();return 0;}void PerformLongOperation(){CStopwatch stopwatch;//执行运算代码Sleep(5000);__int64 qwElapsedTime = stopwatch.Now();_tprintf(TEXT("总执行时间%lld\n"),qwElapsedTime);}

这段高精度代码原来是核心编程里的，，，

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