time

Hi

How can i find out the time taken to run each iteration in the program below?

Code:

#include <stdio.h>
#include <time.h>

#include <iostream>
#include <iomanip>

using namespace std;

int main ()
{
  int n, x = 0;

  for (n = 1000; n > 0; n--)
  {

    x = n + x;
   // print time taken 

  }
  
  cout << x << endl;

  return 0;
}

Shuo

See the How to Time your Application FAQ.

I tried running the programs. it keeps giving 0.000000 seconds when i waited for a couple of seconds.

If you are using ints, that is to be expected. Are you using ints or doubles? Let's see your code.

It looks like there's a bug in that code.

This:

Code:

printf ( "The interval was: %f seconds\n",
    (double)( end - start ) / (double)CLOCKS_PER_SEC );

Should probably be this:

Code:

printf ( "The interval was: %lf seconds\n",
    (double)( end - start ) / (double)CLOCKS_PER_SEC );

Code:

#include <stdio.h> 
#include <time.h> 

int main ( void )
{
  clock_t start, end;

  /* Start the timer */
  start = clock();

  printf ( "Please wait a few moments and hit return\n" );
  getchar();

  /* End the timer */
  end = clock();

  /* Print out the difference */
  printf ( "The interval was: %f seconds\n",
	   (double)( end - start )/CLOCKS_PER_SEC );

  return 0;
}

Still gives the same answer.

Looking....

Yeah, printf ignores %lf and changes it to %f for you.

As for your code: it works fine here, compiling with (heaven help me) lcc-win32. I apparently waited 5.820000 seconds. I don't know what else to tell you.

Although that does remind me: your code is C, and definitely not C++. Be sure you're calling the appropriate compiler.

I get the 0.00000 answer too. Still researching. I'm on a mac.

Apparently, on Unix (FreeBSD), clock() returns CPU seconds, not elapsed seconds.

This is the code I used in one of my apps. It starts off with this at the front:

Code:

	// This is for elapsed time calculations. 
	char hours[3], minutes[3], seconds[3] ; 
	
	struct tm start_time ; 
	struct tm *the_time ;  
	time_t  stime, etime ; 
	
	double elapsed ; 
	int elap_hour, elap_min, elap_sec ; 
	
	time(&stime) ;  // Get start time in seconds since epoch 
	the_time = localtime(&stime) ; 
	
	// Save the Time of Day
	start_time.tm_hour = the_time->tm_hour ; 
	start_time.tm_min = the_time->tm_min ; 
	start_time.tm_sec = the_time->tm_sec ; 
	// End of elapsed time stuff, for now.

At the end, I do this:

Code:

		time(&etime) ; // Get end time in seconds since epoch 
		the_time = localtime(&etime) ; 
	
		sprintf(hours,   "%02d", the_time->tm_hour ) ; 
		sprintf(minutes, "%02d", the_time->tm_min  ) ; 
		sprintf(seconds, "%02d", the_time->tm_sec  ) ; 
	
		cout << "End Time:     " << hours << ":" << minutes << ":" << seconds << endl; 
	
		sprintf(hours,   "%02d", start_time.tm_hour ) ; 
		sprintf(minutes, "%02d", start_time.tm_min  ) ; 
		sprintf(seconds, "%02d", start_time.tm_sec  ) ; 
	
		cout << "Start Time:   " << hours << ":" << minutes << ":" << seconds << endl; 
	
		// Calculate the elapsed time 						   
		elapsed = difftime(etime, stime) ; 
		//printf("Elapsed time is %d %s.\n", (int) elapsed, ((int) elapsed == 1 ) ? "second" : "seconds"  ) ; 
		elap_hour = (int) (elapsed / (60*60)) ;   // hours  
		elap_min  = (int) (elapsed / 60) % 60  ;  // minutes 
		elap_sec  = (int) elapsed % (60) ;        // seconds 
	
		// printf("Elapsed (int) time is %10d\n" , (int) elapsed ) ; 
		printf("Elapsed Time: %02d:%02d:%02d\n", elap_hour, elap_min ,elap_sec ) ;

(Yes, I know it's ugly - but it works )