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Re: Time resolution in Emacs argument optional ones
From: |
Paul Eggert |
Subject: |
Re: Time resolution in Emacs argument optional ones |
Date: |
Fri, 22 Apr 2022 14:52:47 -0700 |
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Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 |
On 4/22/22 12:35, Eli Zaretskii wrote:
to do such comparisons correctly we need to
have each time object state its resolution, otherwise you will never
know how to compare them.
Yes, quite true.
That resolution cannot be possibly determined by
measuring the system clock resolution, because doing that will at best
provide the figure for one class of time objects.
Also quite right. Emacs needs to determine the timestamp for each class
of objects as best it can.
the current implementation of measuring that resolution
fails miserably on MS-Windows, producing a very incorrect value.)
It's a correct value for what it's measuring, which is (roughly) the
number of digits needed to express each timestamp precisely. It's not
correct for a different measure, namely the timestamp resolution, which
it sounds like is what you'd prefer. As I mentioned in
<https://bugs.gnu.org/54764#111> it shouldn't be hard to support this
other measure, and I can look into doing that.
What is the plan for other kinds of time objects? For example, how
would we determine the resolution of file times
We could do what Coreutils does, in commands like 'cp -u' that sample
timestamps in each file system to determine resolution. This approach
works well enough in practice. There are Gnulib library functions to
deal with this sort of thing; it's not a new problem.
as your examples show, that kind of timestamp is the one that needs
resolution information much less than the other ones.
I don't see how the examples show that.
Please don't be obsessed with MS-Windows.
There's no obsession here on my part. MS-Windows appears to be the only
platform where current-time generates such low-resolution timestamps, or
generates syncopated timestamps, and that's why discussion has naturally
centered on that platform.
examples you gave deal with
file timestamps, and you explained that we do risk losing information
there.
Yes, and Emacs currently loses all information about file timestamp
resolution, on all platforms. It would be better for Emacs to report as
much of that information as it easily can. This could be done by using
the Gnulib library functions suggested above. Reporting this information
is better than losing it.
even if we consider the (contrived) example with 'date'
important for some reason, the result will be incorrect there for a
couple of milliseconds, and thereafter will become correct, and who's
to know, or care, that it was incorrect for those 2 milliseconds?
Yes, most users don't notice timestamps being a little off. And these
users surely won't care whether we improve the timestamps to be more
accurate. But that doesn't mean that it's a bad idea to improve
timestamp quality.
- Re: Time resolution in Emacs argument optional ones, (continued)
- Re: Time resolution in Emacs argument optional ones, Corwin Brust, 2022/04/22
- Re: Time resolution in Emacs argument optional ones, Paul Eggert, 2022/04/22
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/23
- Re: Time resolution in Emacs, Paul Eggert, 2022/04/23
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/24
- Re: Time resolution in Emacs, Max Nikulin, 2022/04/24
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/24
- Re: Time resolution in Emacs, Paul Eggert, 2022/04/25
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/25
Re: Time resolution in Emacs argument optional ones, Eli Zaretskii, 2022/04/22
- Re: Time resolution in Emacs argument optional ones,
Paul Eggert <=
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/23
- Time resolution in Emacs, Paul Eggert, 2022/04/25
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/25
- Re: Time resolution in Emacs, Paul Eggert, 2022/04/25
- Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/25
Re: Time resolution in Emacs, Max Nikulin, 2022/04/25
Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/25
Re: Time resolution in Emacs, Paul Eggert, 2022/04/25
Re: Time resolution in Emacs, Max Nikulin, 2022/04/29
Re: Time resolution in Emacs, Eli Zaretskii, 2022/04/29