Hi, I've written a little Meta Template Program which should calculate the first 3 perfect numbers. ( range 1 - 500 ) The code is compilable if you use the range 1 - 30 really fast and works correctly. But I've tried to compile the code but I can't get it finished. Someone tried it on a Machine with 40 GB RAM and it now compiles for more than 12 hours and uses more than 7.1 GB RAM ( the compilation ) I've tried it by myself with g++ 3.4.x and g++ 4.0.x and with VC++ 7.1 The code works on all tested compilers if the range would be 1 - 30 but If the range is 1 - 500 VC++ says: d:\boost\vc71\include\boost-1_33_1\boost\mpl\aux_\preprocessed\plain\apply_wrap.hpp(48): fatal error C1204: compiler limit: internal structure overflow. ( This seems to be a known bug in VC++ http://support.microsoft.com/default.aspx?scid=kb;en-us;883655 ) and g++ compiles and compiles and uses more and more RAM. Is the code really so evil slow or is it a compiler Bug in g++? Maybe anyone has an answer. BR evilissimo #include <boost/mpl/long.hpp> #include <boost/mpl/range_c.hpp> #include <boost/mpl/vector_c.hpp> #include <boost/mpl/arithmetic.hpp> #include <boost/mpl/accumulate.hpp> #include <boost/mpl/back_inserter.hpp> #include <boost/mpl/equal.hpp> #include <boost/mpl/copy_if.hpp> #include <boost/mpl/at.hpp> #include <boost/mpl/size.hpp> #include <iostream> namespace mpl = boost::mpl; template < typename Sum , typename Div , typename Num > struct perf_num_plus_if : mpl::if_< mpl::equal_to< mpl::modulus< Num,Div > , mpl::long_<0> >, typename mpl::plus<Sum,Div>::type, Sum >::type {}; template< typename Num > struct perf_num_impl : mpl::accumulate< mpl::range_c< long, 1, Num::value/2+1 >, mpl::long_<0>, perf_num_plus_if< mpl::_, mpl::_, Num > >::type {}; template< long Start , long End > struct perfect_number : mpl::copy_if< mpl::range_c<long,Start,End>, mpl::equal_to< mpl::_1 , perf_num_impl<mpl::_1> >, mpl::back_inserter< mpl::vector_c<long> > >::type {}; template< typename Seq , size_t Pos , size_t Max > struct Output { Output() { std::cout << mpl::at_c<Seq, Pos >::type::value << std::endl; Output< Seq , Pos+1 , Max >(); } }; template< typename Seq , size_t N > struct Output< Seq , N , N > { Output(){} }; int main() { typedef perfect_number< 1 , 500 > vec; Output< vec , 0 , mpl::size< vec >::value >(); }