Calculate Execution Time?

This is a discussion on Calculate Execution Time? within the C Programming forums, part of the General Programming Boards category; How to calculate Execution time in milliseconds? if i use time() function i can get the result only in seconds ...

  1. #1
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    Calculate Execution Time?

    How to calculate Execution time in milliseconds?
    if i use time() function i can get the result only in seconds .
    What about clock function ? How to print the difference using clock_t variable?

    ts=clock();
    quicksort(x,0,size-1);
    printf("Time elapsed: %f\n", ((double)clock() - ts) / CLOCKS_PER_SEC);

    its only resulting in Seconds .
    Last edited by infantheartlyje; 10-14-2011 at 12:57 AM.

  2. #2
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    If you're on Windows...
    Code:
    #include <windows.h>
    #include <stdio.h>
    
    int main(void)
      { long long int Elapsed;
         
        Elapsed = GetTickCount();
    
    
         // do something really long here...
    
    
        printf("That took %lld milliseconds", GetTickCount() - Elapsed);
    
        return 0;
    }
    Now if you're not on Windows...
    Code:
    // ?????

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    Quote Originally Posted by CommonTater View Post
    Now if you're not on Windows...
    Yes. Its not windows programming. Any way thank you.

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    How about telling us what it is (reducing the space to 1), rather than what it isn't (which merely reduces N to N-1).
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    Quote Originally Posted by infantheartlyje View Post
    Yes. Its not windows programming. Any way thank you.
    On all *nix systems, you can use gettimeofday();
    With that you can get to upto nanoseconds accuracy.
    Manasij Mukherjee | gcc-4.8.2 @Arch Linux
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    1.None of the other participants are fast and steady.
    2.The fast and unsteady suddenly falls asleep while running !



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    Do you want the wall-clock time or the actual time that the processor is running your code?

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    Quote Originally Posted by manasij7479 View Post
    On all *nix systems, you can use gettimeofday();
    With that you can get to upto nanoseconds accuracy.
    Very helpful. Thanks a lot !!!

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    Quote Originally Posted by iceaway View Post
    Do you want the wall-clock time or the actual time that the processor is running your code?
    Actual time that the processor is running.

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    Quote Originally Posted by infantheartlyje View Post
    Actual time that the processor is running.
    Then you should probably use clock() instead of gettimeofday().

    Code:
    clock_t t0, t1, elapsed;
    t0 = clock();
    /* Call function */
    t1 = clock();
    elapsed = 1000 * (t1 - t0) / (CLOCKS_PER_SEC);
    printf("Avg elapsed time: %ld ms\n\n", elapsed);
    Last edited by iceaway; 10-14-2011 at 02:15 AM.

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    Quote Originally Posted by iceaway View Post
    Then you should probably use clock() instead of gettimeofday().
    But by using this clock() function i couldn't get the milliseconds ?

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    Quote Originally Posted by infantheartlyje View Post
    But by using this clock() function i couldn't get the milliseconds ?
    If you read the man page I linked to, you would see that dividing the return value from clock() with CLOCKS_PER_SEC gives you the result in seconds. Hence, if you multiply (t1 - t0) by 1000 before you divide by CLOCKS_PER_SEC you get the result in milliseconds. Or you can divide (t1 - t0) by (CLOCKS_PER_SEC/1000) if you expect very long times which could cause wraparounds.

    Also read the "Conforming to" and see if any of that applies to you.

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    This is what I've used:
    Code:
    //add:
    #include <time.h>
    
    //and in your program:
    clock_t start, stop;
    
    start = clock();
    //rest of the program here
    
    stop = clock();
     printf("\n         Elapsed Time:     %.3lf seconds\n", (double)(stop-start)/CLOCKS_PER_SEC);
    Works in Windows with Pelles C. Standard C though.

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