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 * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
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#ifndef OPENCV_FLANN_GROUND_TRUTH_H_
#define OPENCV_FLANN_GROUND_TRUTH_H_

//! @cond IGNORED

#include "dist.h"
#include "matrix.h"


namespace cvflann
{

template <typename Distance>
void find_nearest(const Matrix<typename Distance::ElementType>& dataset, typename Distance::ElementType* query, int* matches, int nn,
                  int skip = 0, Distance distance = Distance())
{
    typedef typename Distance::ResultType DistanceType;
    int n = nn + skip;

    std::vector<int> match(n);
    std::vector<DistanceType> dists(n);

    dists[0] = distance(dataset[0], query, dataset.cols);
    match[0] = 0;
    int dcnt = 1;

    for (size_t i = 1; i < dataset.rows; ++i) {
        DistanceType tmp = distance(dataset[i], query, dataset.cols);

        if (dcnt < n) {
            match[dcnt] = (int)i;
            dists[dcnt++] = tmp;
        }
        else if (tmp < dists[dcnt - 1]) {
            dists[dcnt - 1] = tmp;
            match[dcnt - 1] = (int)i;
        }

        int j = dcnt - 1;
        // bubble up
        while (j >= 1 && dists[j] < dists[j - 1]) {
            std::swap(dists[j], dists[j - 1]);
            std::swap(match[j], match[j - 1]);
            j--;
        }
    }

    for (int i = 0; i < nn; ++i) {
        matches[i] = match[i + skip];
    }
}


template <typename Distance>
void compute_ground_truth(const Matrix<typename Distance::ElementType>& dataset, const Matrix<typename Distance::ElementType>& testset, Matrix<int>& matches,
                          int skip = 0, Distance d = Distance())
{
    for (size_t i = 0; i < testset.rows; ++i) {
        find_nearest<Distance>(dataset, testset[i], matches[i], (int)matches.cols, skip, d);
    }
}


}

//! @endcond

#endif //OPENCV_FLANN_GROUND_TRUTH_H_