C++ 计算 代码运行时间的 几种方法

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);

}