ground_truth.h

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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 FLANN_GROUND_TRUTH_H_
#define FLANN_GROUND_TRUTH_H_
 
#include "FLANN/algorithms/dist.h"
#include "FLANN/util/matrix.h"
 
 
namespace flann
{
 
template <typename Distance>
void find_nearest(const Matrix<typename Distance::ElementType>& dataset, typename Distance::ElementType* query, size_t* matches, size_t nn,
                  size_t skip = 0, Distance distance = Distance())
{
    //typedef typename Distance::ElementType ElementType;
    typedef typename Distance::ResultType DistanceType;
    int n = nn + skip;
 
    int* match = new int[n];
    DistanceType* dists = new DistanceType[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] = i;
            dists[dcnt++] = tmp;
        }
        else if (tmp < dists[dcnt-1]) {
            dists[dcnt-1] = tmp;
            match[dcnt-1] = 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 (size_t i=0; i<nn; ++i) {
        matches[i] = match[i+skip];
    }
 
    delete[] match;
    delete[] dists;
}
 
 
template <typename Distance>
void compute_ground_truth(const Matrix<typename Distance::ElementType>& dataset, const Matrix<typename Distance::ElementType>& testset, Matrix<size_t>& matches,
                          int skip=0, Distance d = Distance())
{
    for (size_t i=0; i<testset.rows; ++i) {
        find_nearest<Distance>(dataset, testset[i], matches[i], matches.cols, skip, d);
    }
}
 
 
}
 
#endif //FLANN_GROUND_TRUTH_H_