Measuring Time Using QueryPerformanceCounter() and QueryPerformanceFrequency()

Game Engine Foundation-Jamie King showing how to measure the high-performance CPU clock to gain a high granularity in game time measurement.

[ElectroLund]

Very helpful, thanks! Curiously, I'm getting better (faster) timing results using my platform's built-in timing functions to measure "Hello world" console writes. I didn't expect that.

[bgzdevtips]

Please someone correct me if I'm wrong but I think when Jamie said the delta.quad part equaled 1.433 megahertz he really meant it equaled 1.433 KILOhertz (1433, in dollars as Jamie says, is one thousand four hundred thirty three, so kilo means 1, 000). This would make more sense as that debug statement shouldn't have taken half the time of the original total clock frequency.

[mrGrad]

should i activate the HPET (high performance event timer) in bios and windows?

[deltakid]

2:17 lol!!! Yeah, Delta Airlines, good analogy

[bluehornet]

Very cool! So it took 0.00043434757 seconds to execute that qDebug() statement, is how I interpret that debugger result.So this is then about 434 microseconds? Is that your understanding too Jamie?

[mrrwsn]

why is my deltaseconds like 33000? Code is pretty much the same as yours.

[ryklin]

In Microsoft's documentation for QPC timers, it suggests we convert to the number of elapsed microseconds to guard against loss of precision as shown below. Any additional comments on this?

//
// We now have the elapsed number of ticks, along with the
// number of ticks-per-second. We use these values
// to convert to the number of elapsed microseconds.
// To guard against loss-of-precision, we convert
// to microseconds *before* dividing by ticks-per-second.
//

ElapsedMicroseconds.QuadPart *=
ElapsedMicroseconds.QuadPart /= Frequency.QuadPart;