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Calculate time diff

Posted on 2002-06-20
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Last Modified: 2007-11-27
Hi,

My question is how can I write a function says like stop watch, time start, then stop, I want to get the time in mil seconds between that period.

thx
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Question by:PX
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Expert Comment

by:jkr
ID: 7096338
Use 'difftime()', e.g.

/* DIFFTIME.C: This program calculates the amount of time
 * needed to do a floating-point multiply 10 million times.
 */

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

void main( void )
{
   time_t   start, finish;
   long loop;
   double   result, elapsed_time;

   printf( "Multiplying 2 floating point numbers 10 million times...\n" );
   
   time( &start );
   for( loop = 0; loop < 10000000; loop++ )
      result = 3.63 * 5.27;
   time( &finish );

   elapsed_time = difftime( finish, start );
   printf( "\nProgram takes %6.0f seconds.\n", elapsed_time );
}


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LVL 86

Accepted Solution

by:
jkr earned 50 total points
ID: 7096340
Oops, I almost forgot about 'clock()':

/* CLOCK.C: This example prompts for how long
 * the program is to run and then continuously
 * displays the elapsed time for that period.
 */

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

void sleep( clock_t wait );

void main( void )
{
   long    i = 600000L;
   clock_t start, finish;
   double  duration;

   /* Delay for a specified time. */
   printf( "Delay for three seconds\n" );
   sleep( (clock_t)3 * CLOCKS_PER_SEC );
   printf( "Done!\n" );

   /* Measure the duration of an event. */
   printf( "Time to do %ld empty loops is ", i );
   start = clock();
   while( i-- )
      ;
   finish = clock();
   duration = (double)(finish - start) / CLOCKS_PER_SEC;
   printf( "%2.1f seconds\n", duration );
}

/* Pauses for a specified number of milliseconds. */
void sleep( clock_t wait )
{
   clock_t goal;
   goal = wait + clock();
   while( goal > clock() )
      ;
}


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Author Comment

by:PX
ID: 7098215
wonderful, quick response and exactly the answer as what I need, thx.
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