[Haskell-cafe] Re: Computer time, independent of date

[Cetin Sert]

Here's a basic draft project for clock_gettime(CLOCK_MONOTONIC, ...)
http://sert.homedns.org/hs/mnsec/
http://sert.homedns.org/hs/mnsec/dist/mnsec-1.0.0.tar.gz

It could be extended to cover other clock types than just monotonic.

Regards,
CS

2009/1/9 John Goerzen <jgoerzen at complete.org>

> Steve Schafer wrote:
> > On Fri, 09 Jan 2009 11:01:18 -0200, you wrote:
> >
> >> I'm writing a program that will read medical signs
> >>from many patients. It's important to have a precise
> >> measure of the time interval between some signs, and
> >> that can't depend on adjustments of time. (Supose
> >> my software is running midnight at the end of a year
> >> with leap seconds. I would get wrong time intervals.)
> >
> > If you really need that level of accuracy, there is nothing available on
> > an off-the-shelf machine that will do the job. You need an independent
> > timekeeping source of some kind, one that is not subject to the vagaries
>
> I'm not sure that the original question implied *that* level of need.
>
> Linux has High-Resolution Timers (HRTs) that may be appropriate.  See
> the manpage for clock_gettime(), which defines these HRTs:
>
>       CLOCK_REALTIME
>              System-wide real-time clock.  Setting this clock requires
> appropriate privi-
>              leges.
>
>       CLOCK_MONOTONIC
>              Clock  that  cannot be set and represents monotonic time
> since some unspeci-
>              fied starting point.
>
>       CLOCK_PROCESS_CPUTIME_ID
>              High-resolution per-process timer from the CPU.
>
>       CLOCK_THREAD_CPUTIME_ID
>              Thread-specific CPU-time clock.
>
> CLOCK_MONOTONIC, in particular, looks suitable.  Using it could be a
> matter of just a few quick likes in FFI.
>
> I don't know if Windows has similar features.
>
> -- John
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