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POC++ performance: lists and iterators
 

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    <p>I've got some inherited in-house C++ code, which when compiled with VC++ on Windows, runs an order of magnitude faster than when compiled with g++ on Linux (5 minutes vs. 2 hours). This remains the case both with and without the "normal" optimization flags, as well as over a few different versions of each compiler and respective platform, all on comparable hardware.</p> <p>Building a debug/profile version (-g -pg) on Linux with g++, I see the following three areas are consuming most of the time:</p> <pre><code>% cumulative self self total time seconds seconds calls Ks/call Ks/call name 31.95 955.93 955.93 3831474321 0.00 0.00 std::_List_const_iterator&lt;xxFile&gt;::operator!=(std::_List_const_iterator&lt;xxFile&gt; const&amp;) const 22.51 1629.64 673.71 3144944335 0.00 0.00 std::_List_const_iterator&lt;xxFile&gt;::operator++() 15.56 2095.29 465.65 686529986 0.00 0.00 std::iterator_traits&lt;std::_List_const_iterator&lt;dtFile&gt; &gt;::difference_type std::__distance&lt;std::_List_const_iterator&lt;xxFile&gt; &gt;(std::_List_const_iterator&lt;xxFile&gt;, std::_List_const_iterator&lt;xxFile&gt;, std::input_iterator_tag) </code></pre> <p>(The xxFile class consists of ints, floats, doubles, bools, and strings)</p> <p>My naive guesses are that there's something poorly coded which VC++ is compensating for or that the GNU STL may not be as optimized. I'm currently working on compiling the g++/Linux version with the Boost library, starting with assign/std/list.hpp and the boost::assign namespace.</p> <p>I'm unable to share the code, but does something obvious (besides my limited C++ experience) jump out as the cause, based on your experience?</p>
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    1. CODid you compile with `g++ -O2`? Did you use the latest GCC compiler (4.6.2)?
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    2. COYes, it does, though I'm unable to share the answer ;-)
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      1. USKerrek SB
    3. COI have tried -02 optimization and my latest attempt was with GCC 4.6.2 on Fedora 16 (as well as many past versions).
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