Hi! This error occurs in DEBUG mode only. No testcase yet, but you probably have an idea anyway? regards, Markus [..snipped ...]\boost_1_35_0\boost\numeric\ublas\traits.hpp(97) : error C2784: 'boost::numeric::interval<T,Policies> boost::numeric::sqrt(const boost::numeric::interval<T,Policies> &)' : could not deduce template argument for 'const boost::numeric::interval<T,Policies> &' from 'const double' [..snipped...]\boost_1_35_0\boost\numeric\interval\arith2.hpp(198): see declaration of 'boost::numeric::sqrt' [..snipped...]\boost_1_35_0\boost\numeric\ublas\traits.hpp(93) : while compiling class template member function 'double boost::numeric::ublas::scalar_traits<T>::type_sqrt(const double &)' with [ T=double ] [..snipped...]\boost_1_35_0\boost\numeric\ublas\traits.hpp(151) : see reference to class template instantiation 'boost::numeric::ublas::scalar_traits<T>' being compiled with [ T=double ] [..snipped ...]\boost_1_35_0\boost\numeric\ublas\traits.hpp(97) : fatal error C1903: unable to recover from previous error(s); stopping compilation