C++高精度计时的几种方法总结(测试函数运行时间)

#include <time.h>　　　//引入头文件
void time1()
{
	clock_t start, end;
	start = clock();

	fun();  //需计时的函数

	end = clock();  
	cout << "elapsed time in clock = " << double(end - start) << "ms" << endl;  
}

#include <windows.h>　　　//引入头文件
void time2()
{
	DWORD t1, t2;
	t1 = GetTickCount();

	fun();  //需计时的函数

	t2 = GetTickCount();
	cout << "elapsed time in GetTickCount = " << double(t2 - t1) << "ms" << endl;
}

//QueryPerformanceCounter()是一个Windows API，所需头文件为<windows.h>
#include <windows.h>　　　//引入头文件
void time3()
{
	LARGE_INTEGER t1, t2, tc;
	QueryPerformanceFrequency(&tc);
	QueryPerformanceCounter(&t1);

	fun();  //需计时的函数

	QueryPerformanceCounter(&t2);
	double time = (double)(t2.QuadPart - t1.QuadPart) / (double)tc.QuadPart;
	cout << "elapsed time in QuadPart = " << time * 1000 << "ms" << endl;
}

#include <iostream>
#include <chrono>
void time4()
{
	// 计时开始时间点
	// chrone 中常用的时钟类:
	// 		- std::chrono::high_resolution_clock
	//   	- std::chrono::system_clock
	//      - std::chrono::steady_clock
	// 三种时钟类有一些区别，其中 high_resolution_clock 精度最高
	auto start = std::chrono::high_resolution_clock::now();

	// 要计时的代码段
	fun();  
	// 计时结束时间点
	auto end = std::chrono::high_resolution_clock::now();

	// 计算运行时间, 时间单位:
	//      - std::chrono::seconds
	//      - std::chrono::milliseconds
	//      - std::chrono::microseconds
	//      - std::chrono::nanoseconds
	auto duration = std::chrono::duration_cast<std::chrono::microseconds> (end - start);

	// 输出时间(给定时间单位)
	cout << "elapsed time in chrono = " << duration.count()/1000.0 << "ms" << endl;
} 

#include <iostream>
#include <chrono>
#include <thread>
#include <time.h>
#include <windows.h>

using namespace std;

void fun()
{
	// 睡眠100ms
	std::this_thread::sleep_for(std::chrono::milliseconds(100));
}
void compareTime()
{
	LARGE_INTEGER t1, t2, tc;
	QueryPerformanceFrequency(&tc);
	
	
	clock_t start, end;

	DWORD t11, t12;
	start = clock();
	t11 = GetTickCount();
	QueryPerformanceCounter(&t1);
	auto start1 = std::chrono::high_resolution_clock::now();

	fun();  //需计时的函数

	end = clock();
	t12 = GetTickCount();
	QueryPerformanceCounter(&t2);
	auto end1 = std::chrono::high_resolution_clock::now();
	double time = (double)(t2.QuadPart - t1.QuadPart) / (double)tc.QuadPart;
	auto duration = std::chrono::duration_cast<std::chrono::microseconds> (end1 - start1);

	cout << "elapsed time in clock = " << double(end - start) << "ms" << endl;
	cout << "elapsed time in GetTickCount = " << double(t12 - t11) << "ms" << endl;
	cout << "elapsed time in QuadPart = " << time * 1000 << "ms" << endl;
	cout << "elapsed time in chrono = " << duration.count() / 1000.0 << "ms" << endl;
}

//timeval结构定义为:
struct timeval{
long tv_sec; /*秒*/
long tv_usec; /*微秒*/
};
//timezone 结构定义为:
struct timezone{
int tz_minuteswest; /*和Greenwich 时间差了多少分钟*/
int tz_dsttime; /*日光节约时间的状态*/
};

#include <sys/time.h>　　　//引入头文件
int main()
{
    struct timeval t1,t2;
    double timeuse;
    gettimeofday(&t1,NULL);
 
    fun();
 
    gettimeofday(&t2,NULL);
    timeuse = (t2.tv_sec - t1.tv_sec) + (double)(t2.tv_usec - t1.tv_usec)/1000000.0;
 
    cout<<"time = "<<timeuse<<endl;  //输出时间（单位：ｓ）
}