From: Noam Postavsky <npostavs@users.sourceforge.net>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: Emacs developers <emacs-devel@gnu.org>
Subject: Re: [Emacs-diffs] master c66aaa6: Recomplexify ‘delete-trailing-whitespace’ by treating \n as whitespace again
Date: Wed, 15 Mar 2017 13:05:59 -0400 [thread overview]
Message-ID: <CAM-tV-9W1xPcwBmTZ9JGbKRuL6AKXR5E7OaFayGx-OLtCU+hLQ@mail.gmail.com> (raw)
In-Reply-To: <jwvzigmzjcs.fsf-monnier+gmane.emacs.devel@gnu.org>
On Wed, Mar 15, 2017 at 10:50 AM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>>>> Recomplexify ‘delete-trailing-whitespace’ by treating \n as
>>>> whitespace again
>>>> Mostly reverts "Simplify ‘delete-trailing-whitespace’ by not treating
>>>> \n as whitespace" from 2016-07-04. Setting \n to non-whitespace
>>>> causes the regex engine to backtrack a lot when searching for
>>>> "\\s-+$" (Bug#26079).
>>> Why do we use syntax-tables?
>>> IOW why do we use \s- rather than something like [\s\t]?
>> No clue. But (re-search-forward "[\s\t]+$" nil t) is also slow.
>
> Slower than "\\s-+$"?
No, seems to be twice as fast actually (this is still horribly slow).
On the test file given in Bug#26079[1]
(benchmark 1 '(re-search-forward "[\s\t]+$" nil t)) ;=> Elapsed time: 9.944000s
(benchmark 1 '(save-excursion
(let ((end-marker nil))
(goto-char (point-min))
(with-syntax-table (make-syntax-table (syntax-table))
(modify-syntax-entry ?\f "_")
(modify-syntax-entry ?\n "_")
(re-search-forward "\\s-+$" end-marker t))))) ;=> Elapsed
time: 20.496000s
[1]: https://raw.githubusercontent.com/stakemori/e8theta_degree3/master/results/wt18_17_5/wt18_17_5.org
next prev parent reply other threads:[~2017-03-15 17:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170315023157.29463.36647@vcs0.savannah.gnu.org>
[not found] ` <20170315023159.30AA520CAB@vcs0.savannah.gnu.org>
2017-03-15 11:28 ` [Emacs-diffs] master c66aaa6: Recomplexify ‘delete-trailing-whitespace’ by treating \n as whitespace again Stefan Monnier
2017-03-15 12:09 ` Noam Postavsky
2017-03-15 14:50 ` Stefan Monnier
2017-03-15 17:05 ` Noam Postavsky [this message]
2017-03-15 20:26 ` Stefan Monnier
2017-03-16 0:18 ` Noam Postavsky
2017-03-16 2:52 ` Stefan Monnier
2017-03-16 3:04 ` Noam Postavsky
2017-03-16 3:08 ` Stefan Monnier
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