为什么CLOCKS_PER_SEC不是每秒钟的实际时钟数？ [英] Why is CLOCKS_PER_SEC not the actual number of clocks per second?

问题描述

  #include< p>我已经写了这个简短的C ++程序来估计每秒的实际时钟节拍数。 iostream> 
 #include< time.h> 
 
 using namespace std; 
 
 int main（）{
 
 for（int i = 0; i <10; i ++）{
 
 int first_clock = clock ; 
 int first_time = time（NULL）; 
 
 while（time（NULL）< = first_time）{} 
 
 int second_time = time（NULL）; 
 int second_clock = clock（）; 
 
 cout<< 实际时钟每秒=< （second_clock  -  first_clock）/（second_time-first_time）< \\\
; 
 
 cout<< CLOCKS_PER_SEC =< CLOCKS_PER_SEC<< \\\
; 
 
} 
 
 return 0; 
 
} 
  

当我运行程序时，

 每秒实际时钟数= 199139 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 638164 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 610735 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 614835 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 642327 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 562068 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 605767 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 619543 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 650243 
 CLOCKS_PER_SEC = 1000000 
每秒实际时钟数= 639128 
 CLOCKS_PER_SEC = 1000000 
  

为什么CLOCKS_PER_SEC每秒钟的实际时钟滴答数不匹配？他们甚至不相等。这是怎么回事？

解决方案

clock 返回花费的时间 每秒总共有1,000,000个时钟滴答。 ^* 。您的程序似乎占用了其中的60％。

其他40％的用途。

sup> * _{好的，每秒都有虚拟 1,000,000个时钟滴答。实际数字是规范化的，因此您的程序可以感知到1,000,000个tick。}

I have just written this short C++ program to approximate the actual number of clock ticks per second.

#include <iostream>
#include <time.h>

using namespace std;

int main () {

    for(int i = 0; i < 10 ; i++) {

        int first_clock = clock();
        int first_time = time(NULL);

        while(time(NULL) <= first_time) {}

        int second_time = time(NULL);
        int second_clock = clock();

        cout << "Actual clocks per second = " << (second_clock - first_clock)/(second_time - first_time) << "\n";

        cout << "CLOCKS_PER_SEC = " << CLOCKS_PER_SEC << "\n";

    }

    return 0;

}

When I run the program, I get output that looks like this.

Actual clocks per second = 199139
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 638164
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 610735
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 614835
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 642327
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 562068
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 605767
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 619543
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 650243
CLOCKS_PER_SEC = 1000000
Actual clocks per second = 639128
CLOCKS_PER_SEC = 1000000

Why doesn't the actual number of clock ticks per second match up with CLOCKS_PER_SEC? They're not even approximately equal. What's going on here?

解决方案

clock returns the amount of time spent in your program. There are 1,000,000 clock ticks per second total^*. It appears that your program consumed 60% of them.

Something else used the other 40%.

^*_{Okay, there are virtually 1,000,000 clock ticks per second. The actual number is normalized so your program perceives 1,000,000 ticks.}

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