CODEWITHSUNDEEP
c++windows
stack356
stack356

Reputation: 170

C++ QueryPerformanceCounter more accurate than sleep?

I found an example of QueryPerformanceCounter,

http://advancedcppwithexamples.blogspot.com/2009/08/measuring-elapsed-time-in-c-using_21.html

The example measures a sleep of 100ms with QueryPerformanceCounter which reports only 79ms.

Is there a reason sleep is so inaccurate?

Upvotes: 0

Views: 1512

Answers (1)

Mark Ransom
Mark Ransom

Reputation: 308138

sleep is inaccurate for two reasons: it's based on a very slow clock, and it relies on the OS to resume execution at the end of the period.

The performance counter is actually built into the CPU so it's as accurate as the clock signal that runs the chip. It isn't affected by the OS or tasks whatsoever.

Upvotes: 3

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