精确计算程序运行的时间

#include <iostream.h>
#include <windows.h>

void main()
{

LARGE_INTEGER Freq;
LARGE_INTEGER Count1, Count2;
QueryPerformanceFrequency(&Freq);  //调用API函数,  这个API函数可是优先级0的函数啊.

QueryPerformanceCounter(&Count1);  //获取时间1

//测试程序;
Sleep(123);

QueryPerformanceCounter(&Count2);  //获取时间2

double d = (double)(Count2.QuadPart - Count1.QuadPart) / (double)Freq.QuadPart * 1000.0;

cout<<"count1 = "<<(double)Count1.QuadPart<<endl;
cout<<"count2 = "<<(double)Count2.QuadPart<<endl;

cout<<"run time is :"<<d<<" ms "<<endl;

cout<<"system timer frequence :"<<(double)Freq.QuadPart<<" Hz"<<endl;
}