T operator()( const vex::multivector<T, N> &x ) const {
        auto max = detail::vexcl_reductor<T>(x.queue_list());

        // Reducing a multivector results in std::array<T, N>:
        auto m = max( fabs(x) );

        // We will need to reduce it even further:
        return *std::max_element(m.begin(), m.end());
    }
 static void resize( vex::multivector< T , N , own > &x1 , const vex::multivector< T , N , own > &x2 )
 {
     x1.resize( x2.queue_list() , x2.size() );
 }