clock（）函数总是返回0 [英] clock() function always returning 0

问题描述

可能重复：

函数只返回一个零值。

Possible Duplicate:
The C clock() function just returns a zero

我运行下面的代码来测试clock（）函数的工作。我在ubuntu 12.04上工作。

I ran the following code to test the working of clock() function. I work on ubuntu 12.04.

#include <stdio.h>
#include <time.h>
#include <iostream>
using namespace std;


double diffclock(clock_t clock1,clock_t clock2)
{
double diffticks=clock1-clock2;
double diffms=(diffticks*10)/CLOCKS_PER_SEC;
return diffms;
}

int main()
{
string name;
int i;
clock_t begin=clock();
cout << "Hi what is your name? ";
getline(cin, name);
clock_t end=clock();
cout << "Time elapsed: " << double(diffclock(end,begin)) << " ms"<< endl;
return 0;
}

但是无论我写多少时间写我的名字，

But no matter how much time i take to write my name, the time elapsed is always shown as 0ms.

你能告诉我这是什么问题吗？

Can you tell me what is the problem?

推荐答案

clock（）返回从程序启动开始执行的刻度数 USED 。没有必要（在这个特定的）例子中得到 clock_t begin 值。

clock() returns the number of ticks USED SINCE THE PROGRAM STARTED executing. There is no need (in this specific) example to get the clock_t begin value.

尝试打印出 begin 和 end 值，看看它们是什么。

Try printing out both the begin and end values and see what they are. They're likely both 0 or close to 0 as waiting for user input doesn't use CPU time.

不管怎样，我推荐的时间（）函数，因为您不需要 精确度。
http://www.cplusplus.com/reference/clibrary/ctime/time/

Either way, I recommend the time() function as you don't need tick precision. http://www.cplusplus.com/reference/clibrary/ctime/time/

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