cosine_similarity.hpp

Go to the documentation of this file.

/*
Copyright© 2014 Akihiro Nishimura

This software is released under the MIT License.
http://opensource.org/licenses/mit-license.php
*/

#ifndef SIG_UTIL_COSINE_SIMILARITY_HPP
#define SIG_UTIL_COSINE_SIMILARITY_HPP

#include <numeric>
#include "norm.hpp"
#include "comparable_check.hpp"

namespace sig
{

struct CosineSimilarity
{
    template<class C1, class C2>
    double operator()(C1 const& vec1, C2 const& vec2) const
    {
        using T = typename std::common_type<typename impl::container_traits<C1>::value_type, typename impl::container_traits<C2>::value_type>::type;

        assert(is_comparable(vec1, vec2, impl::NumericVectorTag()));

        return std::inner_product(std::begin(vec1), std::end(vec1), std::begin(vec2), static_cast<T>(0)) / (norm_L2(vec1) * norm_L2(vec2));
    }
};


const CosineSimilarity cosine_similarity;

}
#endif