void gemv_impl(
matrix_expression<MatA, cpu_tag> const& A,
vector_expression<V, cpu_tag> const& x,
vector_expression<ResultV, cpu_tag>& result,
typename ResultV::value_type alpha,
unknown_orientation
) {
gemv_impl(A,x,result,alpha,row_major());
}
void gemv(
matrix_expression<M> const& A,
vector_expression<V> const& x,
vector_expression<ResultV>& result,
typename ResultV::value_type alpha,
boost::mpl::false_
) {
SIZE_CHECK(A().size1()==result().size());
SIZE_CHECK(A().size2()==x().size());
typedef typename M::orientation orientation;
gemv_impl(A, x, result, alpha, orientation());
}