转自http://blog.csdn.net/ap1005834/article/details/53419647
一、前言
这里记下从网上找到的一些自己比较常用的C++计时代码
二、Linux下精确至毫秒
#include <sys/time.h>
#include <iostream>
#include <time.h>
double get_wall_time()
{
struct timeval time ;
if (gettimeofday(&time,NULL)){
return 0;
}
return (double)time.tv_sec + (double)time.tv_usec * .000001;
}
int main()
{
unsigned int t = 0;
double start_time = get_wall_time()
while(t++<10e+6);
double end_time = get_wall_time()
std::cout<<"循环耗时为:"<<end_time-start_time<<"ms";
return 0;
}
三、Windows下精确至毫秒
#include <windows.h>
#include <iostream>
int main()
{
DWORD start, stop;
unsigned int t = 0;
start = GetTickCount();
while (t++ < 10e+6);
stop = GetTickCount();
printf("time: %lld ms\n", stop - start);
return 0;
}
试验中，发现貌似getTickCount函数会有10几毫秒的误差，囧。。。
四、Windows下精确至微秒
//MyTimer.h//
#ifndef __MyTimer_H__
#define __MyTimer_H__
#include <windows.h>
class MyTimer
{
private:
int _freq;
LARGE_INTEGER _begin;
LARGE_INTEGER _end;
public:
long costTime; // 花费的时间(精确到微秒)
public:
MyTimer()
{
LARGE_INTEGER tmp;
QueryPerformanceFrequency(&tmp);//QueryPerformanceFrequency()作用：返回硬件支持的高精度计数器的频率。
_freq = tmp.QuadPart;
costTime = 0;
}
void Start() // 开始计时
{
QueryPerformanceCounter(&_begin);//获得初始值
}
void End() // 结束计时
{
QueryPerformanceCounter(&_end);//获得终止值
costTime = (long)((_end.QuadPart - _begin.QuadPart) * 1000000 / _freq);
}
void Reset() // 计时清0
{
costTime = 0;
}
};
#endif
//main.cpp
#include "MyTimer.h"
#include <iostream>
int main()
{
MyTimer timer;
unsigned int t = 0;
timer.Start();
while (t++ < 10e+5);
timer.End();
std::cout << "耗时为：" << timer.costTime << "us";
return 0 ;
}