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Re: [Grep-devel] [PATCH] dfa: fix performance bug that recomputes trans
From: |
Jim Meyering |
Subject: |
Re: [Grep-devel] [PATCH] dfa: fix performance bug that recomputes trans |
Date: |
Fri, 9 Dec 2016 16:08:52 -0800 |
On Fri, Dec 9, 2016 at 3:11 PM, Paul Eggert <address@hidden> wrote:
> * lib/dfa.c (build_state): Fix performance bug introduced in Nov
> 25 on-demand changes. The bug caused build_state to reset all
> d->trans elements to -2 even when d->trans was already non-null.
> Use C99 style decls after statements in this function.
> ---
> ChangeLog | 6 ++++++
> lib/dfa.c | 46 ++++++++++++++++++++--------------------------
> 2 files changed, 26 insertions(+), 26 deletions(-)
>
> diff --git a/ChangeLog b/ChangeLog
> index fd3e9d8..a05fa6b 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,5 +1,11 @@
> 2016-12-09 Paul Eggert <address@hidden>
>
> + dfa: fix performance bug that recomputes trans
> + * lib/dfa.c (build_state): Fix performance bug introduced in Nov
> + 25 on-demand changes. The bug caused build_state to reset all
> + d->trans elements to -2 even when d->trans was already non-null.
> + Use C99 style decls after statements in this function.
Thank you for both of those changes. In the future, please keep
semantics-changing diffs separate from those like the
declaration-moving one that is nominally in the NSC
(no-semantic-change) category.
Do you have an example (preferably pathological) that demonstrates a
significant performance difference? If so, I'd like to mention this in
grep's NEWS file.