This patch improves performance for input string which doesn't match
even the first part of a pattern. Although there is no less effective
for grep as it uses a superset of DFA, gawk speeds up about 40%.
$ time -p env LC_ALL=ja_JP.eucJP ./gawk '/k/ { print }' ../k
(before)
real 2.85 user 2.79 sys 0.05
(after)
real 1.70 user 1.64 sys 0.06
I think that this improvement should have been performed in bug#17576.
From 2cf24a4e084c873f7ae3f184251b8dca1a55e851 Mon Sep 17 00:00:00 2001
From: Norihiro Tanaka <nori...@kcn.ne.jp>
Date: Mon, 20 Oct 2014 23:20:15 +0900
Subject: [PATCH] dfa: improvement for checking of multibyte character boundary
When found newline, we can skip check of a multibyte character boundary
before the character, as we assume newline as a single byte character.
by that.
The improvement speeds up about 40% for input string which doesn't match
even the first part of a pattern.
* src/dfa.c (skip_remains_mb): If an input character is newline, skip
checking for multibyte character boundary until there.
---
src/dfa.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/src/dfa.c b/src/dfa.c
index 58a4b83..b9f065f 100644
--- a/src/dfa.c
+++ b/src/dfa.c
@@ -3252,6 +3252,8 @@ skip_remains_mb (struct dfa *d, unsigned char const *p,
unsigned char const *mbp, char const *end)
{
wint_t wc;
+ if (*p == eolbyte)
+ return p;
while (mbp < p)
mbp += mbs_to_wchar (&wc, (char const *) mbp,
end - (char const *) mbp, d);
--
2.1.1
