Hi, I think this has been asked before, but since I am not aware of any answer, I would like to bring up the topic again: When using CppAD::AD<double> with boost ublas, certain compilation errors show up. I attach a small example (ublas_cppad.cpp) and the (start of the) error messages I get (compilation_errors.txt, produced with boost 1.59.0, g++ 4.9.3, CppAD-20151124). The problem is in matrix_assign.hpp; when changing template<class E1, class E2, class S> BOOST_UBLAS_INLINE bool equals (const matrix_expression<E1> &e1, const matrix_expression<E2> &e2, S epsilon, S min_norm) { return norm_inf (e1 - e2) < epsilon * std::max<S> (std::max<S> (norm_inf (e1), norm_inf (e2)), min_norm); } to template<class E1, class E2, class S> BOOST_UBLAS_INLINE bool equals (const matrix_expression<E1> &e1, const matrix_expression<E2> &e2, S epsilon, S min_norm) { S tmp = norm_inf (e1 - e2); return tmp < epsilon * std::max<S> (std::max<S> (norm_inf (e1), norm_inf (e2)), min_norm); } the example code compiles without errors. Can someone point out, how this should be fixed (either on boost or CppAD side)? In general, are there requirements for a type T to cooperate with ublas matrices one should be aware of? Thank you Peter