C++ 计算 代码运行时间的 几种方法

转自:http://blog.csdn.net/actionli/archive/2007/07/06/1681595.aspx

有许多专门的测试工具，测试的准确性很高，本文说的是一些简单的测试方法，这些方法多数是记录CPU的运行时间，没有考虑操作系统的分时复用，不过不太严格的情况都可一用。

1. #include <time.h>
long start=clock(),end(0);
//ToDo:process code
end=clock();
long result=(end-start)/1000

2. windows 平台
#include <windows.h>
double start=getticktime(),end(0);
//ToDo:process code
end=getticktime();
double result=end-start;

3.windows 平台
#include <windows.h>
LARGE_INTEGER frequency,start,end;
QueryPerformanceFrequency(&frequency);
QueryPerformanceCounter(&start);
//ToDO:process code
QueryPerformanceCounter(&end);
double d = (double)(end.QuadPart - start.QuadPart) / (double)frequency.QuadPart * 1000.0;

4.根据线程而来的
CThreadTime ElapsedTime;
ElapsedTime.BeginGetElapsedTime();

//TODO: Your performance code

int nThreadTine = ElapsedTime.EndGetElapsedTime();

该类的实现如下：
// This class is for getting the elapsed thread time of the CPU, the unit is ms
// the usage is:
//
// CThreadTime ElapsedTime;
// ElapsedTime.BeginGetElapsedTime();
// TODO: Your performance code
// int nThreadTine = ElapsedTime.EndGetElapsedTime();
//

#include <Windows.h>

class CThreadTime
{
public:
void BeginGetElapsedTime();
__int64 EndGetElapsedTime();

private:
__int64 FileTimeToQuadWord(PFILETIME pft);

private:
FILETIME ftKernelTimeStart;
FILETIME ftKernelTimeEnd;
FILETIME ftUserTimeStart;
FILETIME ftUserTimeEnd;
FILETIME ftDummy;
};

// Get the time elapsed since the thread start
inline void CThreadTime::BeginGetElapsedTime()
{
GetThreadTimes(GetCurrentThread(), &ftDummy, &ftDummy, &ftKernelTimeStart, &ftUserTimeStart);
}

// Calculate the time elapsed
inline __int64 CThreadTime::EndGetElapsedTime()
{
GetThreadTimes(GetCurrentThread(), &ftDummy, &ftDummy, &ftKernelTimeEnd, &ftUserTimeEnd);

__int64 qwKernelTimeElapsed = FileTimeToQuadWord(&ftKernelTimeEnd) - FileTimeToQuadWord(&ftKernelTimeStart);
__int64 qwUserTimeElapsed = FileTimeToQuadWord(&ftUserTimeEnd) - FileTimeToQuadWord(&ftUserTimeStart);

// Get total time duration by adding the kernel and user times.
// the default is 100ns, so we convert it to ms
return (qwKernelTimeElapsed + qwUserTimeElapsed) / 10000;
}

inline __int64 CThreadTime::FileTimeToQuadWord(PFILETIME pft)
{
return (Int64ShllMod32(pft->dwHighDateTime, 32) | pft->dwLowDateTime);
}