[Openmcl-devel] CCL 1.9 release candidate available

R. Matthew Emerson rme at clozure.com
Wed Feb 6 22:08:56 UTC 2013


On Feb 6, 2013, at 4:24 PM, Alexander Repenning <Alexander.Repenning at colorado.edu> wrote:

> 
> On Feb 6, 2013, at 1:48 PM, R. Matthew Emerson wrote:
> 
>> 
>> On Feb 6, 2013, at 3:36 PM, Alexander Repenning <alexander.repenning at Colorado.EDU> wrote:
>> 
>>> from the release notes:
>>> 
>>>> access to high-resolution clock
>>>> 
>>>> CCL:CURRENT-TIME-IN-NANOSECONDS returns the number of elapsed nanoseconds since some arbitrary point in time (likely system boot.)
>>>> 
>>> 
>>> This sounds very useful. What is the approximate resolution of this function on Windows, i.e., what kind of Windows timer function is this based on?
>> 
>> Pressing M-. on current-time-in-nanoseconds leads me to its definition in ccl:lib;time.lisp.  On Windows, that function uses #_GetSystemTimeAsFileTime.
> 
> 
> I was afraid of that because on most Windows systems, certainly XP, that would suggest a 15ms resolution which is rather disappointing. 

If you know of a Windows function that that would provide superior results, I'd love to hear about it.

QueryPerformanceCounter() is not a good solution.  It requires a lot of effort to compensate for its limitations.   See, for example, https://bugzilla.mozilla.org/show_bug.cgi?id=676349




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