GNU bug report logs - #24161
[PATCH 2/2] sed: speed up matching by reguler expression with dfa matcher

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From: Jim Meyering <jim <at> meyering.net>
To: Assaf Gordon <assafgordon <at> gmail.com>
Cc: Norihiro Tanaka <noritnk <at> kcn.ne.jp>, 24161 <at> debbugs.gnu.org
Subject: bug#24161: [PATCH 2/2] sed: speed up matching by reguler expression with dfa matcher
Date: Fri, 5 Aug 2016 08:11:35 -0700

On Fri, Aug 5, 2016 at 7:51 AM, Assaf Gordon <assafgordon <at> gmail.com> wrote:
> Hello Norihiro,
>
> On 08/05/2016 10:03 AM, Norihiro Tanaka wrote:
>>
>> We can speeds up sed by using dfa matcher brought from grep.  gawk users
>> it, sed does not uses it yet.  It will speed up matching for typical
>> cases.
>
> [...]
>>
>> I believe that this patch can greatly improve performance of matching by
>> sed, however I worry about the maintenance as updates for dfa is always
>> done in grep.
>
> Nice improvement, thank you for the patch!

Nice one, indeed.
I hope to review it by this weekend.

> I wonder, if this code is used by multiple gnu projects, wouldn't it be
> better to include it in gnulib (instead of duplicating the code) ?

Yes. However, I'm happy to move dfa.[ch] into gnulib after this patch lands.

> I also see from a cursory look that the test coverage is low (which is
> expected: sed currently use the native regex code and does not test
> specifically for it). I'm happy to try and add more tests, but it'll take a
> bit of time.

Eventually, we'll want dfa's tests to reside in gnulib.

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