[C/C++] Timer

• Timer

最近在做一些效能的測試需要用到比較精準的Timer，分別查了一下給Windows和Linux平台的寫法。

For Linux:

在Linux裡，則是使用timeval來計算時間，理論上精準到micro second


#include <stdio.h>
#include <sys/time.h>

int main()
{
int i;
struct timeval t1, t2;
double elapsedTime;

gettimeofday(&t1, NULL);
gettimeofday(&t2, NULL);

elapsedTime = (t2.tv_sec - t1.tv_sec) * 1000.0;
elapsedTime += (t2.tv_usec - t1.tv_usec) / 1000.0;
printf("%.3f ms\n",elapsedTime);
return 0;
}



For Windows:

Windows部份使用了QueryPerformanceFrequency()這個指令，理論上是精準到跟時脈值一樣。


#include <stdio.h>
#include <windows.h>
int main()
{
LARGE_INTEGER frequency;
LARGE_INTEGER t1, t2;
double elapsedTime;

QueryPerformanceFrequency(&frequency);

QueryPerformanceCounter(&t1);
QueryPerformanceCounter(&t2);

elapsedTime = (t2.QuadPart - t1.QuadPart) * 1000.0 / frequency.QuadPart;
printf("%.3f ms\n", elapsedTime);
return 0;
}