Re: Optimizing for speed (QueryPerformanceCounter)

David Honig (honig@otc.net)
Wed, 18 Feb 1998 10:09:40 -0800

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At 12:39 AM 2/19/98 +1000, Eric Young wrote:
>
>On Tue, 17 Feb 1998, Chuck McManis wrote:
>> VC++5 on a Win95 platform and what I'd like is something like :
>>
>> long long t1, t2;
>> t1 = snap_time(); /* time in nSecs */
>> ... do something ...
>> t2 = snap_time();
>> printf("This run took %ld nS\n", (long)(t2 - t1));
>>
>
>Timing of this type of thing can be done at a cycle level via the following
>function

I have used this with the Win32 API in with MS VisC++ 4.2:

#define BIGMEASURE 1000000
#include <windows.h>

    LARGE_INTEGER ticks1,
      ticks2,
      tickfreq;
    int duration;
    float realtime,
      hertz;

    QueryPerformanceFrequency( &tickfreq );
       printf( "Ticks are %d %d per sec\n", tickfreq.HighPart,
tickfreq.LowPart );
       hertz = 1.0 / tickfreq.LowPart;

                   
        QueryPerformanceCounter( &ticks1 );
                // work
        QueryPerformanceCounter( &ticks2 );

        duration = ticks2.LowPart - ticks1.LowPart;
        realtime = duration * hertz;

        // i = number of bytes processed
        printf( "For %6d byte sample: %6d ticks %6f seconds %6e by/sec\n",
i, duration, realtime, i/realtime );

------------------------------------------------------------
      David Honig Orbit Technology
     honig@otc.net Intaanetto Jigyoubu

        Has Nike hired Monica to endorse kneepads yet?

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