C++获取程序执行时间的五个方法对比
五种获取C/C++程序执行时间的方法对比如下：
核心函数 头文件 函数库 精度 准确度
QueryPerformanceCounter windows.h API us 非常准确
GetTickTount windows.h API ms 准确
clock time.h C函数 ms 较准确
time time.h C函数 s 很准确
ftime sys/timeb.h C函数 ms 较准确
在windows平台下建议使用GetTickCount，当对精度和准确度要求高可以用QueryPerformanceCounter，Linux平台下建议使用ftime，
本程序均在windows平台下运行，五种获取程序执行时间的代码如下：
#include <iostream>
#include <fstream>
#include <ctime>
#include <windows.h>
#include <tchar.h>
#include <sys/timeb.h>
#include <time.h>
#include <cmath>
#include <stdio.h>
using namespace std;
/**************************获取系统时间*************************/
void MyGetSystemTime()
{
SYSTEMTIME currentTime;
GetSystemTime(¤tTime);
printf("time: %u/%u/%u %u:%u:%u:%u %d\n",
currentTime.wYear,currentTime.wMonth,currentTime.wDay,
currentTime.wHour,currentTime.wMinute,currentTime.wSecond,
currentTime.wMilliseconds,currentTime.wDayOfWeek);
}
/****************自己实现的定时器，要比Sleep准确****************/
void MySleep(DWORD dwMilliseconds)
{
LARGE_INTEGER litmp;
LONGLONG QPart1;
QueryPerformanceCounter(&litmp);
QPart1 = litmp.QuadPart;//获得初始值
LONGLONG QPart2;
double dfMinus, dfFreq, dfTim;
QueryPerformanceFrequency(&litmp);
dfFreq = (double)litmp.QuadPart;//获得计数器的时钟频率
do
{
QueryPerformanceCounter(&litmp);
QPart2 = litmp.QuadPart;//获得中止值
dfMinus = (double)(QPart2-QPart1);
dfTim = dfMinus / dfFreq * 1000;//获得对应的时间值，单位为毫秒
}while(dfTim < dwMilliseconds);
}
int main()
{
/**************QueryPerformanceCounter(),windows.h,API,us****************///精度最高
LARGE_INTEGER nFreq;
LARGE_INTEGER nBeginTime;
LARGE_INTEGER nEndTime;
double time;
QueryPerformanceFrequency(&nFreq);
QueryPerformanceCounter(&nBeginTime);
Sleep(1000);
QueryPerformanceCounter(&nEndTime);
time=(double)(nEndTime.QuadPart-nBeginTime.QuadPart)/(double)nFreq.QuadPart;
printf("%f\n",time);
/**************GetTickCount(),windows.h,API,ms****************///首选
DWORD start, end;
start = GetTickCount();
MySleep(1000);
end = GetTickCount();
printf("time: %d ms\n", end - start);
/**************clock(),time.h,C函数,ms,不太准****************/
clock_t start, end;
start = clock();
Sleep(1000);
end = clock();
printf("time: %d ms\n", end - start);
/**************time(),time.h,C函数,s****************/
time_t start, end;
start = time(NULL);
Sleep(1000);
end = time(NULL);
printf("time: %d ms\n", end - start);
/**************ftime(),sys/timeb.h,C函数,ms,不太准****************/
struct timeb startTime , endTime;
ftime(&startTime);
Sleep(1000);
ftime(&endTime);
printf("time: %d ms\n", (endTime.time-startTime.time)*1000 + (endTime.millitm - startTime.millitm));
return 0;
}
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