C++计时器

/Windows系统下可以用 time()，clock()，timeGetTime()，GetTickCount()，QueryPerformanceCounter()来对一段程序代码进行计时
#include <stdio.h>
#include <windows.h>
#include <time.h>                   //time_t time()  clock_t clock()
#include <Mmsystem.h>               //timeGetTime()
#pragma comment(lib, "Winmm.lib")   //timeGetTime()
//使用方法：将Sleep()函数换成需要测试运行时间的函数即可。
int main()
{   //用time()来计时，以秒为单位
time_t timeBegin, timeEnd;
timeBegin = time(NULL);
Sleep(1000);
timeEnd = time(NULL);
printf("%d\n", timeEnd - timeBegin);

//用clock()来计时，以毫秒为单位
clock_t  clockBegin, clockEnd;
clockBegin = clock();
Sleep(800);
clockEnd = clock();
printf("%d\n", clockEnd - clockBegin);

//用timeGetTime()来计时，以毫秒为单位
DWORD  dwBegin, dwEnd;
dwBegin = timeGetTime();
Sleep(800);
dwEnd = timeGetTime();
printf("%d\n", dwEnd - dwBegin);

//用GetTickCount()来计时，以毫秒为单位
DWORD  dwGTCBegin, dwGTCEnd;
dwGTCBegin = GetTickCount();
Sleep(800);
dwGTCEnd = GetTickCount();
printf("%d\n", dwGTCEnd - dwGTCBegin);

//用QueryPerformanceCounter()来计时，以微秒为单位
LARGE_INTEGER  large_interger;
double dff;
__int64  c1, c2;
QueryPerformanceFrequency(&large_interger);
dff = large_interger.QuadPart;
QueryPerformanceCounter(&large_interger);
c1 = large_interger.QuadPart;
Sleep(800);
QueryPerformanceCounter(&large_interger);
c2 = large_interger.QuadPart;
printf("本机高精度计时器频率%lf\n", dff);
printf("第一次计时器值%I64d\n第二次计时器值%I64d\n计时器差%I64d\n", c1, c2, c2 - c1);
printf("计时%lf毫秒\n\n", (c2 - c1) * 1000 / dff);
return 0;
}