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    Join Date
    Feb 2000
    Indore, India

    Visual C++ Debugging: How do I evaluate the time difference between two events?

    Q: How do I evaluate the time difference between two events?

    A: Accurate time difference between events cannot be evaluated by clocking the time using 'CTime::GetCurrentTime()' or by using a timer. First method is limited in its accuracy to around a second and second method has limitations of lower priority.

    Here I present a function which returns the time elapsed from the last call. First call will always return a zero value. This uses the high-resolution performance counter. If it does not exist, each call will return zero.

    float TimeDiff()
      // Last counter reading
      static LARGE_INTEGER OldCounter = {0, 0};
      LARGE_INTEGER Counter, Frequency;
      if (QueryPerformanceFrequency(&Frequency))
        // Gets current counter reading
        // Calculates time difference (zero if called first time)
        float TimeDiff = OldCounter.LowPart ? (float) (Counter.LowPart - OldCounterLowPart) / Frequency.LowPart : 0;
        // Resets last counter reading
        OldCounter = Counter;
        // Returns time difference
        return TimeDiff;
        // No high resolution performance counter; returns zero
        return 0;
    Time difference is returned in seconds and the accuracy is determined by the high-resolution performance counter frequency.

    Last edited by Andreas Masur; April 2nd, 2006 at 04:25 PM.

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