distances.hpp

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#ifndef KNNCOLLE_HNSW_DISTANCES_HPP
#define KNNCOLLE_HNSW_DISTANCES_HPP
 
#include <cmath>
#include <functional>
 
namespace knncolle_hnsw {
 
template<typename Dim_, typename InternalData_>
struct DistanceOptions {
    std::function<hnswlib::SpaceInterface<InternalData_>*(Dim_)> create;
 
    std::function<InternalData_(InternalData_)> normalize;
};
 
template<typename InternalData_>
class ManhattanDistance : public hnswlib::SpaceInterface<InternalData_> {
private:
    size_t my_data_size;
    size_t my_dim;
 
public:
    ManhattanDistance(size_t dim) : my_data_size(dim * sizeof(InternalData_)), my_dim(dim) {}
 
public:
    size_t get_data_size() {
        return my_data_size;
    }
 
    hnswlib::DISTFUNC<InternalData_> get_dist_func() {
        return L1;
    }
 
    void * get_dist_func_param() {
        return &my_dim;
    }
 
private:
    static InternalData_ L1(const void *pVect1v, const void *pVect2v, const void *qty_ptr) {
        const InternalData_* pVect1 = static_cast<const InternalData_*>(pVect1v);
        const InternalData_* pVect2 = static_cast<const InternalData_*>(pVect2v);
        size_t qty = *((size_t *) qty_ptr);
        InternalData_ res = 0;
        for (; qty > 0; --qty, ++pVect1, ++pVect2) {
            res += std::abs(*pVect1 - *pVect2);
        }
        return res;
    }
};
 
template<typename InternalData_>
class SquaredEuclideanDistance : public hnswlib::SpaceInterface<InternalData_> {
private:
    size_t my_data_size;
    size_t my_dim;
 
public:
    SquaredEuclideanDistance(size_t dim) : my_data_size(dim * sizeof(InternalData_)), my_dim(dim) {}
 
public:
    size_t get_data_size() {
        return my_data_size;
    }
 
    hnswlib::DISTFUNC<InternalData_> get_dist_func() {
        return L2;
    }
 
    void * get_dist_func_param() {
        return &my_dim;
    }
 
private:
    static InternalData_ L2(const void *pVect1v, const void *pVect2v, const void *qty_ptr) {
        const InternalData_* pVect1 = static_cast<const InternalData_*>(pVect1v);
        const InternalData_* pVect2 = static_cast<const InternalData_*>(pVect2v);
        size_t qty = *((size_t *) qty_ptr);
        InternalData_ res = 0;
        for (; qty > 0; --qty, ++pVect1, ++pVect2) {
            auto delta = *pVect1 - *pVect2;
            res += delta * delta;
        }
        return res;
    }
};
 
}
 
#endif