Charles Karney wrote:
I haven't delved into the code to see where all these problems arise.
interestingly, just two days ago I received similar report regarding "bad" distribution of uniform_int . Here is test program (comparing number of random results in top and bottom 10% of range): #include <iostream> #include <boost/random/mersenne_twister.hpp> #include <boost/random/uniform_int.hpp> #include <boost/random/variate_generator.hpp> int main() { boost::mt19937 rng; boost::variate_generator<boost::mt19937&, boost::uniform_int<> > gen(rng, boost::uniform_int<>(0,100000000)); for (int i = 0; i < 20; ++i) { int small = 0, large = 0; for (int j = 0; j < 100000; ++j) { int x = gen(); if (x < 10000000) ++small; else if (x >= 100000000 - 10000000) ++large; } std::cout << small << " " << large << std::endl; } } and output: 10320 9631 10200 9862 10128 9904 10204 9924 10247 9839 10225 9839 10062 9890 10159 9635 10160 9748 10256 9703 10157 9883 10352 9830 10258 9791 10152 9866 10251 9564 10197 9887 10444 9743 10223 10036 10455 10010 10270 9882 author of this test (and original report) successfully used Mersenne Twister generator in his own project - with much better peformance and distribution. B.