Hi Zhang, you wrote:

the following code generates a compile error raising from a macro in /ublas/traits.hpp: BOOST_STATIC_ASSERT ((boost::is_same::value));

Because I'm trying to prod on a vector of size_t and a matrix of unsigned char.

Because I want to save memory (the matrix is really huge) and I know the value in m will never exceed 255. The expression is ok to me (of course the result value is size_t). But the ASSERT prevent me from doing this.

Is there a workaround that permits me doing this kind of case without sacrificing the memory efficiency?

I'd try to add specializations of the form template<> struct promote_traits { typedef std::size_t promote_type; }; template<> struct promote_traits { typedef std::size_t promote_type; }; to the namespace boost::numeric::ublas. If there's enough interest we'll probaby have to extend promote_traits systematically one day.

Using size_t in the matrix will use three times more memory.

Looks like you're working on an interesting problem :-)

ublas::vector v1(5); matrix<unsigned char> m(5,5); prod(m,v1);

the same problem arises when I do prod(m,v2); here v2 is a vector<double>

The same solution should apply here. HTH, Joerg