Re: [boost] [Boost.Timer] Why timer doesn't have a specific windows version using QueryPerformanceCounter() and QueryPerformanceFrequency()?

Subject: Re: [boost] [Boost.Timer] Why timer doesn't have a specific windows version using QueryPerformanceCounter() and QueryPerformanceFrequency()?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-11-04 07:27:11

dlaugt_at_[hidden] wrote:
>
> Boost.Timer is based on the C function clock(). On windows,
> this function gives a precision of 1 millisecond only as
> CLOCKS_PER_SEC is equal to 1000.
>
> Why Boost.Timer doesn't use for windows
> QueryPerformanceCounter() and QueryPerformanceFrequency()?
> These functions give a precision around 2 microseconds.

>From the Boost.Timer documentation's Rationale section:

"There have been several requests for platform specific implementations to use supposedly high-performance timers from the operating system API.  John Maddock submitted an implementation using the Win32 API.  Tests showed that while the precision of these timers was high, the latency was sometimes very much higher than for the std::clock() function, and that is very bad.  Furthermore, results using the Win32 API were very dependent on both the compiler (Microsoft and Borland were tested) and the operating system version (Windows NT, Windows 95, etc.)  Thus the std::clock() function was much more reliable, and so was retained even on this platform with its own timer API."

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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