Re: [Boost-bugs] [Boost C++ Libraries] #3513: regex_match very slow example

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3513: regex_match very slow example
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-10-30 15:36:57


#3513: regex_match very slow example
------------------------------------------------------------+---------------
  Reporter: Fernando Pelliccioni <fpelliccioni@…> | Owner: eric_niebler
      Type: Support Requests | Status: closed
 Milestone: Boost 1.41.0 | Component: xpressive
   Version: Boost 1.40.0 | Severity: Problem
Resolution: invalid | Keywords:
------------------------------------------------------------+---------------
Changes (by eric_niebler):

  * status: new => closed
  * resolution: => invalid

Comment:

 Your dynamic regex is slow because you are needlessly using nested
 quantifiers in two places. The regex begins and ends with
 "(?:.*\\r?\\n)*". This case is explicitly called out in xpressive's docs
 as a common pitfall. Please read this:

 http://www.boost.org/doc/libs/1_40_0/doc/html/xpressive/user_s_guide.html#boost_xpressive.user_s_guide.tips_n_tricks.beware_nested_quantifiers

 Your static regex does not use nested quantifiers. That explains the
 difference.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3513#comment:1>
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