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From: Felix Lee <flee@teleport.com>
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Subject: Re: Scoring is horribly slowed down by this entry. Why?
Date: Sat, 31 Jul 1999 16:12:31 -0700
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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\\) *$"
--