[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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