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30 
31 #ifndef OPENCV_FLANN_GROUND_TRUTH_H_
32 #define OPENCV_FLANN_GROUND_TRUTH_H_
33 
34 #include "dist.h"
35 #include "matrix.h"
36 
37 
38 namespace cvflann
39 {
40 
41 template <typename Distance>
42 void find_nearest(const Matrix<typename Distance::ElementType>& dataset, typename Distance::ElementType* query, int* matches, int nn,
43                   int skip = 0, Distance distance = Distance())
44 {
45     typedef typename Distance::ResultType DistanceType;
46     int n = nn + skip;
47 
48     std::vector<int> match(n);
49     std::vector<DistanceType> dists(n);
50 
51     dists[0] = distance(dataset[0], query, dataset.cols);
52     match[0] = 0;
53     int dcnt = 1;
54 
55     for (size_t i=1; i<dataset.rows; ++i) {
56         DistanceType tmp = distance(dataset[i], query, dataset.cols);
57 
58         if (dcnt<n) {
59             match[dcnt] = (int)i;
60             dists[dcnt++] = tmp;
61         }
62         else if (tmp < dists[dcnt-1]) {
63             dists[dcnt-1] = tmp;
64             match[dcnt-1] = (int)i;
65         }
66 
67         int j = dcnt-1;
68         // bubble up
69         while (j>=1 && dists[j]<dists[j-1]) {
70             std::swap(dists[j],dists[j-1]);
71             std::swap(match[j],match[j-1]);
72             j--;
73         }
74     }
75 
76     for (int i=0; i<nn; ++i) {
77         matches[i] = match[i+skip];
78     }
79 }
80 
81 
82 template <typename Distance>
83 void compute_ground_truth(const Matrix<typename Distance::ElementType>& dataset, const Matrix<typename Distance::ElementType>& testset, Matrix<int>& matches,
84                           int skip=0, Distance d = Distance())
85 {
86     for (size_t i=0; i<testset.rows; ++i) {
87         find_nearest<Distance>(dataset, testset[i], matches[i], (int)matches.cols, skip, d);
88     }
89 }
90 
91 
92 }
93 
94 #endif //OPENCV_FLANN_GROUND_TRUTH_H_
95