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| <h2>Regular Expression Performance Comparison</h2> |
| <p> |
| The following tables provide comparisons between the following regular |
| expression libraries:</p> |
| <p><a href="http://research.microsoft.com/projects/greta">GRETA</a>.</p> |
| <p><a href="http://www.boost.org/">The Boost regex library</a>.</p> |
| <p><a href="http://arglist.com/regex/">Henry Spencer's regular expression library</a> |
| - this is provided for comparison as a typical non-backtracking implementation.</p> |
| <P>Philip Hazel's <A href="http://www.pcre.org">PCRE</A> library.</P> |
| <H3>Details</H3> |
| <P>Machine: Intel Pentium 4 2.8GHz PC.</P> |
| <P>Compiler: %compiler%.</P> |
| <P>C++ Standard Library: %library%.</P> |
| <P>OS: %os%.</P> |
| <P>Boost version: %boost%.</P> |
| <P>PCRE version: %pcre%.</P> |
| <P> |
| As ever care should be taken in interpreting the results, only sensible regular |
| expressions (rather than pathological cases) are given, most are taken from the |
| Boost regex examples, or from the <a href="http://www.regxlib.com/">Library of |
| Regular Expressions</a>. In addition, some variation in the relative |
| performance of these libraries can be expected on other machines - as memory |
| access and processor caching effects can be quite large for most finite state |
| machine algorithms.</P> |
| <H3>Averages</H3> |
| <P>The following are the average relative scores for all the tests: the perfect |
| regular expression library would score 1, in practice anything less than 2 |
| is pretty good.</P> |
| <P>%averages%</P> |
| <h3>Comparison 1: Long Search</h3> |
| <p>For each of the following regular expressions the time taken to find all |
| occurrences of the expression within a long English language text was measured |
| (<a href="http://www.gutenberg.org/files/3200/old/mtent12.zip">mtent12.txt</a> |
| from <a href="http://promo.net/pg/">Project Gutenberg</a>, 19Mb). </p> |
| <P>%long_twain_search%</P> |
| <h3>Comparison 2: Medium Sized Search</h3> |
| <p>For each of the following regular expressions the time taken to find all |
| occurrences of the expression within a medium sized English language text was |
| measured (the first 50K from mtent12.txt - up to the end of Chapter 1). </p> |
| <P>%short_twain_search%</P> |
| <H3>Comparison 3: C++ Code Search</H3> |
| <P>For each of the following regular expressions the time taken to find all |
| occurrences of the expression within the C++ source file <A href="../../../boost/crc.hpp"> |
| boost/crc.hpp</A> was measured. </P> |
| <P>%code_search%</P> |
| <H3> |
| <H3>Comparison 4: HTML Document Search</H3> |
| </H3> |
| <P>For each of the following regular expressions the time taken to find all |
| occurrences of the expression within the html file <A href="../../libraries.htm">libs/libraries.htm</A> |
| was measured. </P> |
| <P>%html_search%</P> |
| <H3>Comparison 3: Simple Matches</H3> |
| <p> |
| For each of the following regular expressions the time taken to match against |
| the text indicated was measured. </p> |
| <P>%short_matches%</P> |
| <hr> |
| <p><i>© Copyright John Maddock 2003</i></p> |
| <p><i>Use, modification and distribution are subject to the Boost Software License, |
| Version 1.0. (See accompanying file <a href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> |
| or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p> |
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