C ++ While loop, usleep () / sleep (), how not to use 90% of the processor? (Ubuntu 12.04)

Question

Suppose I have C ++ code like

#include "myheaderfiles.h"
//..some stuff
//...some more stuff
int main()
{
   double milliseconds;
   int seconds;
   int minutes;
   int timelimit=2;
   ...
   ...
   //...code here that increments 
   //.....milliseconds,seconds, and minutes

   while(minutes <=timelimit)
   {
      //...do stuff
      if(milliseconds>500)
      {
         //...do stuff 
         //...every half second
      } //end if
   } //end while
}//end main

The program will work fine and does what it should do, but it will use 90% + of my processor.

I was asked to use usleep () in my while loop of 100 ms or so, since I really care about doing things every 500 ms anyway. Thus, it starts the processor when it is not needed.

So, I added it to my while loop so

   while(minutes <=timelimit)
   {
      //...do stuff
      if(milliseconds>500)
      {
         //...do stuff 
         //...every half second
      } //end if
      usleep(100000);
   } //end while

It compiles fine, but when I run it, the program will hang right at home and never return. I read somewhere that before calling usleep you need to flush all buffers, so I blushed all file streams and replicas, etc. Etc. Still out of luck.

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Answer 1

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Answer 2

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  #include <unistd.h>
  #include <iostream> 

  int main() {
    std::cout << "hello" << std::endl;

    int i = 0;
    while(i < 10) {
      ++i;
      usleep(100000);
      std::cout << "i = " << i << std::endl;                                                                                                                                        
    }
    std::cout << "bye" << std::endl;
    return 0;
  }

Answer 3

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#include <iostream>
#include <unistd.h>

using namespace std;

#define MILLISECOND 1000
#define SECOND 1000*MILLISECOND

int main(int argc, char *argv[]){
    int time = 20;
    int sec_counter = 0;
    do{     
        cout<<sec_counter<<" second"<<endl;
        usleep(SECOND);
        sec_counter++;
    } while(sec_counter<time+1);
    return 0;
}

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