在实际software开发工作中，我们经常会测试某个module或者function的执行效率。或者是某个算法的时间复杂度(虽然时间复杂度一定程度上依赖于机器性能，但在同一台computer上，经过算法优化，可以测试其复杂度)；这时候就需要精确获取时间，才可以准确的运行时间，下面的函数实现了精确计时，计时精度可以达到微秒级；可用于测试某个模块的效率！

//Purpose :this programme is designed for testing the performance of your code ,some function ect,

//it can show the time of spending on your running on it . it is  beneficial to improve your performance

//of code

// author :Jackery_shh

// data: July 8th  2015

#include

#include

#include

using namespace std;

#define  IN

#ifdef _DEBUG

#define _Trace_Size 500

inline void FileTrace(IN LPCTSTR szFormat, ...)

{

if (szFormat == NULL)

return;

TCHAR t_trace[_Trace_Size] = { _T('\0') };

va_list vl = NULL;

// 生成内容

va_start(vl, szFormat);

_vsntprintf_s(t_trace, _Trace_Size, _TRUNCATE, szFormat, vl);

va_end(vl);

OutputDebugString(t_trace);

}

#else

inline void FileTrace(IN LPCTSTR szFormat, ...){}

#endif

LARGE_INTEGER begin_time ,freq;

int main()

{

LARGE_INTEGER begin_time ,freq;

QueryPerformanceFrequency (&freq);

QueryPerformanceCounter (&begin_time);

//begin time

for (long test0=0;test0<5000000;test0++)

{

test0=test0+1;

}

LARGE_INTEGER end_time0;

QueryPerformanceCounter (&end_time0);

//after runnin the 'for' loop statement,the time is Time0

double Time0 = ((double) (end_time0.QuadPart - begin_time.QuadPart)*1000.0) / (double) (freq.QuadPart);

int test1=10000;

while (test1)

{

test1--;

}

LARGE_INTEGER end_time1;

QueryPerformanceCounter (&end_time1);

double Time1 = ((double) (end_time1.QuadPart - begin_time.QuadPart)*1000.0) / (double) (freq.QuadPart);

FileTrace(_T("*********************************************************************************\n"));

FileTrace(_T("Test result is as follow :\ntime: %I64x, %.3fms, %.3fms\n"), (ULONGLONG)0, Time0, Time1);

FileTrace(_T("*********************************************************************************\n"));

system("pause");

return 0;

}

将C语言梳理一下，分布在以下10个章节中：