C/C++中计算程序运行时间-优快云博客

http://blog.youkuaiyun.com/trustbo/article/details/10582287

以前经常听人提起如何计算程序运行时间，给出一系列函数，当时没有注意，随便选了clock()最简单的方式进行计算。等到真正需要检测程序性能提升了多少，才发现这里面有很多要注意的地方。

最常用的的方式：

#include

time_t start = clock();

time_t end = clock();

printf("the running time is : %f\n", double(end -begin)/CLOCKS_PER_SEC);

clock()计算的是CPU执行耗时，注意是CPU！如果有多个核并行，最后的结果是每个CPU上运算时间的总和！想要精确到毫秒，可以double(end -begin)*1000/CLOCKS_PER_SEC

一般来说，只要求精确到秒的话，time是很好使的

#include<stdio.h>
#include<time.h>
intmain(){
time_tt_start,t_end;
t_start=time(NULL);
sleep(3000);
t_end=time(NULL);
printf("time: %.0f s\n",difftime(t_end,t_start));
return0;
}

如果要让程序休眠3秒，Windows使用Sleep(3000)，Linux使用sleep(3)，即Windows的Sleep接口的参数的单位是毫秒，Linux的sleep接口的参数的单位是秒。

如果需要精确到毫秒，以上程序就发挥不了作用，如果在Java要达到这要求就很简单了，代码如下所示：

下载:<a target="_blank" href="http://blog.jeoygin.org/wp-content/plugins/coolcode/coolcode.php?p=814&download=Time.java" style="color:rgb(62,115,160)">Time.java</a>

 
   public<wbr></wbr>class<wbr></wbr>Time<wbr></wbr>{ 
 <wbr><wbr><wbr></wbr></wbr></wbr>public<wbr></wbr>static<wbr></wbr>void<wbr></wbr>main(String[]<wbr></wbr>args)<wbr></wbr>{ 
 <wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr>try<wbr></wbr>{ 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>long<wbr></wbr>startTime<wbr>=<wbr></wbr></wbr>System.currentTimeMillis(); 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>Thread.sleep(3000); 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>long<wbr></wbr>endTime<wbr>=<wbr></wbr></wbr>System.currentTimeMillis(); 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>System.out.println("time:<wbr></wbr>"<wbr>+<wbr></wbr></wbr>(endTime<wbr>-<wbr></wbr></wbr>startTime)<wbr>+<wbr></wbr></wbr>"<wbr>ms</wbr>"); 
 <wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr>}<wbr></wbr>catch<wbr></wbr>(InterruptedException<wbr></wbr>e)<wbr></wbr>{ 
 <wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>e.printStackTrace(); 
 <wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr>} 
 <wbr><wbr><wbr></wbr></wbr></wbr>} 
 } 
 
 

通过Google找了一些资料后，发现C语言里没有标准的接口可以获得精确到毫秒的时间，都会调用到与操作系统相关的API，下面会分别介绍在Linux和Windows系统下的多种实现方法，希望对大家有帮助。

Linux系统

使用gettimeofday接口：

下载:<a target="_blank" href="http://blog.jeoygin.org/wp-content/plugins/coolcode/coolcode.php?p=814&download=gettimeofday.c" style="color:rgb(62,115,160)">gettimeofday.c</a>

 
   #include<wbr></wbr><</span>stdio.h> 
 #include<wbr></wbr><</span>sys/time.h> 
 <wbr></wbr> 
 int<wbr></wbr>main()<wbr></wbr>{ 
 <wbr><wbr><wbr></wbr></wbr></wbr>struct<wbr></wbr>timeval<wbr></wbr>start,<wbr></wbr>end; 
 <wbr><wbr><wbr></wbr></wbr></wbr>gettimeofday(<wbr>&amp;</wbr>start,<wbr></wbr>NULL<wbr></wbr>); 
 <wbr><wbr><wbr></wbr></wbr></wbr>sleep(3); 
 <wbr><wbr><wbr></wbr></wbr></wbr>gettimeofday(<wbr>&amp;</wbr>end,<wbr></wbr>NULL<wbr></wbr>); 
 <wbr><wbr><wbr></wbr></wbr></wbr>int<wbr></wbr>timeuse<wbr>=<wbr></wbr></wbr>1000000<wbr>*<wbr></wbr></wbr>(<wbr></wbr>end.tv_sec<wbr>-<wbr></wbr></wbr>start.tv_sec<wbr></wbr>)<wbr>+<wbr></wbr></wbr>end.tv_usec<wbr>-</wbr>start.tv_usec; 
 <wbr><wbr><wbr></wbr></wbr></wbr>printf("time: %d us\n",<wbr></wbr>timeuse); 
 <wbr><wbr><wbr></wbr></wbr></wbr>return<wbr></wbr>0; 
 } 
 
 

gettimeofday能得到微秒数，比毫秒还要更精确。

使用ftime接口：

下载:<a target="_blank" href="http://blog.jeoygin.org/wp-content/plugins/coolcode/coolcode.php?p=814&download=ftime.c" style="color:rgb(62,115,160)">ftime.c</a>

 
   #include<wbr></wbr><</span>stdio.h> 
 #include<wbr></wbr><</span>sys/timeb.h> 
 <wbr></wbr> 
 long<wbr></wbr>long<wbr></wbr>getSystemTime()<wbr></wbr>{ 
 <wbr><wbr><wbr></wbr></wbr></wbr>struct<wbr></wbr>timeb<wbr></wbr>t; 
 <wbr><wbr><wbr></wbr></wbr></wbr>ftime(&t); 
 <wbr><wbr><wbr></wbr></wbr></wbr>return<wbr></wbr>1000<wbr>*<wbr></wbr></wbr>t.time<wbr>+<wbr></wbr></wbr>t.millitm; 
 } 
 <wbr></wbr> 
 int<wbr></wbr>main()<wbr></wbr>{ 
 <wbr><wbr><wbr></wbr></wbr></wbr>long<wbr></wbr>long<wbr></wbr>start=getSystemTime(); 
 <wbr><wbr><wbr></wbr></wbr></wbr>sleep(3); 
 <wbr><wbr><wbr></wbr></wbr></wbr>long<wbr></wbr>long<wbr></wbr>end=getSystemTime(); 
 <wbr></wbr> 
 <wbr><wbr><wbr></wbr></wbr></wbr>printf("time: %lld ms\n",<wbr></wbr>end-start); 
 <wbr><wbr><wbr></wbr></wbr></wbr>return<wbr></wbr>0; 
 } 
 
 

Windows系统

使用GetTickCount接口：

下载:<a target="_blank" href="http://blog.jeoygin.org/wp-content/plugins/coolcode/coolcode.php?p=814&download=GetTickCount.c" style="color:rgb(62,115,160)">GetTickCount.c</a>

 
   #include<wbr></wbr><</span>windows.h> 
 #include<wbr></wbr><</span>stdio.h> 
 <wbr></wbr> 
 int<wbr></wbr>main()<wbr></wbr>{ 
 <wbr><wbr><wbr></wbr></wbr></wbr>DWORD<wbr></wbr>start,<wbr></wbr>stop; 
 <wbr><wbr><wbr></wbr></wbr></wbr>start<wbr>=<wbr></wbr></wbr>GetTickCount(); 
 <wbr><wbr><wbr></wbr></wbr></wbr>Sleep(3000); 
 <wbr><wbr><wbr></wbr></wbr></wbr>stop<wbr>=<wbr></wbr></wbr>GetTickCount(); 
 <wbr><wbr><wbr></wbr></wbr></wbr>printf("time: %lld ms\n",<wbr></wbr>stop<wbr>-<wbr></wbr></wbr>start); 
 <wbr><wbr><wbr></wbr></wbr></wbr>return<wbr></wbr>0; 
 } 
 
 

Windows系统下有些编译器使用printf输出64位整数参数要使用%I64d，比如VC。

使用QueryPerformanceX接口：

下载:<a target="_blank" href="http://blog.jeoygin.org/wp-content/plugins/coolcode/coolcode.php?p=814&download=QueryPerformance.c" style="color:rgb(62,115,160)">QueryPerformance.c</a>

 
   #include<wbr></wbr><</span>windows.h> 
 #include<wbr></wbr><</span>stdio.h> 
 <wbr></wbr> 
 int<wbr></wbr>main(){ 
 <wbr><wbr><wbr></wbr></wbr></wbr>LARGE_INTEGER<wbr></wbr>li; 
 <wbr><wbr><wbr></wbr></wbr></wbr>LONGLONG<wbr></wbr>start,<wbr></wbr>end,<wbr></wbr>freq; 
 <wbr><wbr><wbr></wbr></wbr></wbr>QueryPerformanceFrequenc<wbr>y</wbr>(&li); 
 <wbr><wbr><wbr></wbr></wbr></wbr>freq<wbr>=<wbr></wbr></wbr>li.QuadPart; 
 <wbr><wbr><wbr></wbr></wbr></wbr>QueryPerformanceCounter(&li); 
 <wbr><wbr><wbr></wbr></wbr></wbr>start<wbr>=<wbr></wbr></wbr>li.QuadPart; 
 <wbr><wbr><wbr></wbr></wbr></wbr>Sleep(3000); 
 <wbr><wbr><wbr></wbr></wbr></wbr>QueryPerformanceCounter(&li); 
 <wbr><wbr><wbr></wbr></wbr></wbr>end<wbr>=<wbr></wbr></wbr>li.QuadPart; 
 <wbr><wbr><wbr></wbr></wbr></wbr>int<wbr></wbr>useTime<wbr>=</wbr>(int)((end<wbr>-<wbr></wbr></wbr>start)<wbr>*<wbr></wbr></wbr>1000<wbr>/<wbr></wbr></wbr>freq); 
 <wbr><wbr><wbr></wbr></wbr></wbr>printf("time: %d ms\n",<wbr></wbr>useTime); 
 <wbr><wbr><wbr></wbr></wbr></wbr>return<wbr></wbr>0; 
 } 
 
 

使用GetSystemTime接口：

下载:<a target="_blank" href="http://blog.jeoygin.org/wp-content/plugins/coolcode/coolcode.php?p=814&download=GetSystemTime.c" style="color:rgb(62,115,160)">GetSystemTime.c</a>

 
   #include<wbr></wbr><</span>windows.h> 
 #include<wbr></wbr><</span>stdio.h> 
 <wbr></wbr> 
 int<wbr></wbr>main(){ 
 <wbr><wbr><wbr></wbr></wbr></wbr>SYSTEMTIME<wbr></wbr>currentTime; 
 <wbr><wbr><wbr></wbr></wbr></wbr>GetSystemTime(&currentTime); 
 <wbr><wbr><wbr></wbr></wbr></wbr>printf("time: %u/%u/%u %u:%u:%u:%u %d\n",<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr> 
 <wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>currentTime.wYear,currentTime.wMonth,currentTime.wDay, 
 <wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>currentTime.wHour,currentTime.wMinute,currentTime.wSecond, 
 <wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>currentTime.wMilliseconds,currentTime.wDayOfWeek); 
 <wbr><wbr><wbr></wbr></wbr></wbr>return<wbr></wbr>0; 
 } 
 
 