如何使自己的定时器没有标准库？ [英] How can I make my own timer without standard library?

问题描述

是否有一些特定数量的迭代，我可以使用 for循环，以便它完全需要1秒的循环完全执行？例如下面的代码在我的机器上执行0.125s：

  #include< iostream> 
 #include< cmath> 
 
 using namespace std; 
 
 int main（）{
 long long a = 0; 
 
 for（a = 0; a< = pow（10,4）; a ++）;然而，一个< = 8 * pow（10,4）花费了0.206美元s。编译器是GCC 4.9.2。 IDE是代码块。
 
 
 
我的电脑的规格：操作系统：Windows 8.1 
  
解决方案
我根据收到的意见发布此问题的答案
 
 
 
不能制作计时器，因为：
 
 
 
 
 
时间迭代将采取是不可预测的，这不仅取决于使用的CPU，但是你需要考虑电源管理，调度程序。 （通过tux3）
 
 
 
必须使用实时操作系统来完成。非实时操作系统中有太多的抖动。 Windows可以决定调度其他进程一段时间，或使用CPU为例如。内核网络，磁盘I / O等，以抢占时序。 （By nos）
 
 
 
 
在托管环境中不能使用标准C ++来自己定时。计时器实质上是与OS调度程序通信的机制，并且一个需要针对其的平台特定OS服务。 （By Kerrek SB）
 
 
 
 
编译器会优化这样一个循环，并通过死代码消除（由πάνταῥεῖ和Jongware） > 
 
 
 
Is there some specific number of iterations, that I could make using a for loop, so that it exactly takes 1 second for the loop to be executed completely? For example the following code took 0.125s on my machine to execute:
#include <iostream>
#include <cmath>

using namespace  std;

int main(){
    long long a=0;

    for (a=0;a<=pow(10,4);a++);
}
Though, a <= 8*pow(10,4) took 0.206 s. Compiler is GCC 4.9.2. IDE is codeblocks.

My PC's Specs: OS: Windows 8.1
解决方案
I am posting  this answer to your question, as per the comments received.

It is not possible to make a timer because:


The time that an iteration will take is unpredictable, this depends not only on the CPU used, but you need to take into account power management, the scheduler. (By tux3)
one would have to use a real time OS to accomplish that. There's too much jitter in non realtime OSs. Windows could decide to schedule other processes for a while, or use the CPU for e.g. kernel networking, disk I/O etc. that preempts the timing. (By nos)
One can't "make own timer" in a hosted environment just in standard C++. A timer is essentially a mechanism to communicate with the OS scheduler, and one needs platform-specific OS services for that. (By Kerrek SB)
The compiler would optimize such a loop and will remove it through dead-code elimination (By  πάντα ῥεῖ and Jongware).


                        
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