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

Sun, 18/02/2007 - 20:47 — admin

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
QueryPerformanceCounter(&Counter);
// 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;
}
else
{
// 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.
Note: Most of the material in this article is taken from codeguru.com


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