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bug#19173: [PATCH] dfa: speed-up for long pattern


From: Jim Meyering
Subject: bug#19173: [PATCH] dfa: speed-up for long pattern
Date: Sat, 18 Jul 2015 11:44:28 -0700

On Sat, Jul 4, 2015 at 8:40 PM, Jim Meyering <address@hidden> wrote:
> On Mon, Nov 24, 2014 at 5:15 PM, Norihiro Tanaka <address@hidden> wrote:
...
> Thank you for that patch.
> I have rebased it and made some small improvements:
> I combined an if+do loop into a single for-loop and moved
> some declarations "down". I constructed a reproducer that
> does not require two large inputs to demonstrate the
> performance improvement.
>
> I've also begun to reword the commit log, but am out of time
> for this evening, so will post this here, for now.
>
> I am still trying to convince myself that this is a strict
> improvement, i.e., that the O(N^2) strstr calls avoided
> by this change served no purpose.

I have pushed that.
I have also pushed a test (attached) for this performance fix in
a separate commit. As with most performance-measuring tests,
it may be fragile, especially when many tests are run in parallel,
but it passes for me on a few different systems.

Attachment: 0001-tests-add-a-test-for-the-performance-fix.patch
Description: Text Data


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