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Subject: [boost] [RegEx] Performance degradation since 1.36
From: Dave Vest (davevest_at_[hidden])
Date: 2009-10-26 05:08:49

I've just downloaded boost 1.40, compiled the libraries, and re-compiled our
application. Part of our application uses regular expressions extensively to
search through source code and the performance appears to be up to 5 x
slower in release mode than with the 1.36 libraries.


Boost source (no modifications) compiled with Visual Studio 2008 on Win 7.

(Note: 1.36 was compiled with VS 2008 on Win Vista.)


bjam debug release --with-thread --with-regex --with-date_time link=static




Regex creation:


boost::regex::flag_type flags = boost::regex::perl | boost::regex::optimize
| boost::regex::icase);

boost::regex * pengine = new boost::regex(strSampleExpression, flags);




Regex use:


boost::regex_iterator<char const*> itMatch(pszStr, pszStr + nStrLen,

boost::regex_iterator<char const*> itEnd;

if ( itMatch != itEnd )






A simple for(int i=0;i<100000;++i) loop test shows huge differences.


Any ideas why 1.40 is so much slower? Some change in default traits or some
documentation note I've missed?

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