Bugs item #1115124, was opened at 2005-02-02 16:08 Message generated for change (Tracker Item Submitted) made by Item Submitter You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1115124&group_id=7586 Category: random Group: None Status: Open Resolution: None Priority: 5 Submitted By: Morgan (toth21) Assigned to: Jens Maurer (jmaurer) Summary: Diff in state of mersenne_twister gen between GCC3.41 & CW9 Initial Comment: I have found a bug with the mersenne_twister random number generator class, where results when calling for a random number vary between codewarrior 9.0 and gcc 3.4.1 with boost 1.31.0. A simple example is shown below: #include <boost/random/mersenne_twister.hpp> //for mt11213b typedef boost::mt11213b base_generator_type; class foo { public: foo(const base_generator_type gen):m_gen(gen) {} ~foo(void) {} rand_type operator() ( void ) { const float x = m_gen(); return x; } private: base_generator_type m_gen; } int main(void) { base_generator_type gen( (uint32_t) 2000); //seed is not important foo f(gen); cout << "Random result is " << f() << endl; } The resulting numbers will be different between codewarrior 9.0 running on windows (xp or 2000) and gcc 3.4.1 running on Suse linux 7.3.(Hope that is enough info). I tracked the cause of the bug down to class initialization. In the case of CW9.0, the compiler when constructing a foo, will use a mersenne_twister copy ctor when initializing m_gen, while in the case of gcc 3.4.1 it will choose the following in the .hpp file template<class Generator> explicit mersenne_twister(Generator & gen) { seed (gen); } therefore using the provided generator as a seed to the new generator rather than just copying its state, even though no template parameter is provided. Anyways I will leave it up to the more informed to decide which is more desirable/proper; however, this is a fairly nasty bug at the moment as you can not reproduce results between these two platforms when using this random number generator for your random numbers. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=107586&aid=1115124&group_id=7586 ------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl _______________________________________________ Boost-bugs mailing list Boost-bugs@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/boost-bugs