From: Felix Lee <flee@teleport.com>
Cc: ding@gnus.org
Subject: Re: Scoring is horribly slowed down by this entry. Why?
Date: Sat, 31 Jul 1999 16:12:31 -0700 [thread overview]
Message-ID: <199907312312.TAA07594@sclp3.sclp.com> (raw)
In-Reply-To: <87d7x8v3pn.fsf@cs.tu-berlin.de> on 01 Aug 1999 00:45:08 +0200.
Rui Zhu <sprache@iname.com>:
> ("\\([-_0-9A-Za-z]+\.\\)+\\(com\\|net\\) *$" -1000 nil r)
1. there are N possible starting points for the [...]+
pattern, and greedy-match semantics will have it doing N
attempts for each possible starting point. the (...)+
pattern around it forces each of these N attempts to be done
N times, so the best case performance is something like
O(N**3). this is going to be terrible, because N is pretty
large, since alphanumeric characters are common.
2. "\." should be "\\.". "\." == ".", which makes the
regexp behavior worse, since it will need to try matching
any character, not just alphanumerics, which makes N bigger,
sort of.
try using this instead:
"[-_0-9A-Za-z.]+\.\\(com\\|net\\) *$"
--
next prev parent reply other threads:[~1999-07-31 23:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-07-31 22:45 Rui Zhu
1999-07-31 23:12 ` Felix Lee [this message]
1999-07-31 23:28 ` Felix Lee
1999-08-02 23:36 ` Rui Zhu
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