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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