[C++]高精度代码运行时间（ QueryPerformanceCounter ）

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <WinBase.h>
#include <WinNT.h>

using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{
// 	DWORD start_time = GetTickCount();
// 	int k = 0;
// 	for ( int i=0;i<1000000;++i)
// 	{
// 		++k;
// 	}
// 	DWORD end_time=GetTickCount();
// 
// 	DWORD start_time1 = GetTickCount();
// 	int p = 0;
// 	for ( int i=0;i<1000000;i++)
// 	{
// 		p++;
// 	}
// 	DWORD end_time1=GetTickCount();
// 	cout<<"The (++k) run time is:"<<(end_time-start_time)<<"ms!"<<endl;//输出运行时间
// 	cout<<"The (p++) run time is:"<<(end_time1-start_time1)<<"ms!"<<endl;//输出运行时间

	LARGE_INTEGER litmp;
	LONGLONG QPart1, QPart2;
	LONGLONG QPart11, QPart12;

	double dfMinus, dfFreq, dfTim;
	double dfMinus1, dfTim1;
	int k = 0;

	QueryPerformanceFrequency(&litmp);//获取CPU时钟频率
	dfFreq = (double)litmp.QuadPart;

	//------------------
	QueryPerformanceCounter(&litmp);         //获取开始计数值
	QPart1 = litmp.QuadPart;

	k = 0;
	for ( int i=0;i<1000000;i++)
	{
		k++;
	}

	QueryPerformanceCounter(&litmp);        //获取结束计数值
	QPart2 = litmp.QuadPart;


	//------------------
	QueryPerformanceCounter(&litmp);         //获取开始计数值
	QPart11 = litmp.QuadPart;

	k = 0;
	for ( int i=0;i<1000000;i++)
	{
		++k;
	}

	QueryPerformanceCounter(&litmp);        //获取结束计数值
	QPart12 = litmp.QuadPart;

	dfMinus = (double)(QPart2-QPart1);
	dfTim = dfMinus/dfFreq;
	dfMinus1 = (double)(QPart12-QPart11);
	dfTim1 = dfMinus1/dfFreq;
	cout<<"The (k++) run time is:"<< dfTim <<"ms!"<<endl;//输出运行时间
	cout<<"The (++k) run time is:"<< dfTim1 <<"ms!"<<endl;//输出运行时间
	


	while (1)
	{
		if ( getchar() == 'a')
		{
			return 0;             //只有输入A才会返回、退出
		}
	}
	return 0;
}

---------------------------------------------------------------------------------------------------------------

#ifndef COUNTTIME1000 

#define COUNTTIME1000

//统计事件的类,用于多个线程当中会有风险

class CCountTime  
{

public:

	//构造函数
	CCountTime();

	//析构函数，虚函数
	virtual ~CCountTime();

	//开始统计
	void BeginCount();

	//结束统计,返回结果，毫秒,重新开始计时
	double EndCount(BOOL b_ReCount=FALSE);

	//时间统计参数

private:

	//64位整数
	LARGE_INTEGER litmp;
	
	//时钟频率
	double dfFreq;
	
	//用于获取两个时刻点的时间差,起始计时
	LONGLONG QPart1;

	//用于获取两个时刻点的时间差,终止计时
	LONGLONG QPart2;

	//返回的计时结果,单位微秒
	double dfMinus;

	//返回的计时结果,单位毫秒
	double dfTime;
	
};

#endif 

#include "stdafx.h"

#include "CountTime.h"


CCountTime::CCountTime()
{

	//获得计时器的时钟频率
	QueryPerformanceFrequency(&litmp);
	
	//时钟频率
	dfFreq = (double)litmp.QuadPart;


	//开始计时
	BeginCount();

}

CCountTime::~CCountTime()
{

	//不需要手动释放

}


void CCountTime::BeginCount()
{
	
	//获取高精度计时器的值
	QueryPerformanceCounter(&litmp);
	
	//开始计时
	QPart1 = litmp.QuadPart; 
}


double CCountTime::EndCount(BOOL b_ReCount)
{
	
	//获取高精度计时器的值
	QueryPerformanceCounter(&litmp);
	
	//终止计时
	QPart2 = litmp.QuadPart; 
	
	//计算计数器值
	dfMinus = (double)(QPart2 - QPart1);
	
	//获得对应时间，
	dfTime = dfMinus / dfFreq;

	//传入TRUE则重新计时
	if (b_ReCount)
	{

		//开始计时
	    QPart1 = litmp.QuadPart; 

	}
	

	//返回时间,单位毫秒 
	return dfTime*1000;
}