Fast hash function for `std::vector`

I implemented this solution for getting an hash value from vector<T>:

namespace std
{
    template<typename T>
    struct hash<vector<T>>
    {
        typedef vector<T> argument_type;
        typedef std::size_t result_type;
        result_type operator()(argument_type const& in) const
        {
            size_t size = in.size();
            size_t seed = 0;
            for (size_t i = 0; i < size; i++)
                //Combine the hash of the current vector with the hashes of the previous ones
                hash_combine(seed, in[i]);
            return seed;
        }
    };
}

//using boost::hash_combine
template <class T>
inline void hash_combine(std::size_t& seed, T const& v)
{
    seed ^= std::hash<T>()(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}

But this solution doesn't scale at all: with a vector<double> of 10 millions elements it's gonna take more than 2.5 s (according to VS).

Does exists a fast hash function for this scenario?

Notice that creating an hash value from the vector reference is not a feasible solution, since the related unordred_map will be used in different runs and in addition two vector<double> with the same content but different addresses will be mapped differently (undesired behavior for this application).