DBSCANT.cc 6.04 KB
Newer Older
Jan Möbius's avatar
Jan Möbius committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145
/*===========================================================================*\
 *                                                                           *
 *                              OpenFlipper                                  *
 *           Copyright (c) 2001-2015, RWTH-Aachen University                 *
 *           Department of Computer Graphics and Multimedia                  *
 *                          All rights reserved.                             *
 *                            www.openflipper.org                            *
 *                                                                           *
 *---------------------------------------------------------------------------*
 * This file is part of OpenFlipper.                                         *
 *---------------------------------------------------------------------------*
 *                                                                           *
 * Redistribution and use in source and binary forms, with or without        *
 * modification, are permitted provided that the following conditions        *
 * are met:                                                                  *
 *                                                                           *
 * 1. Redistributions of source code must retain the above copyright notice, *
 *    this list of conditions and the following disclaimer.                  *
 *                                                                           *
 * 2. Redistributions in binary form must reproduce the above copyright      *
 *    notice, this list of conditions and the following disclaimer in the    *
 *    documentation and/or other materials provided with the distribution.   *
 *                                                                           *
 * 3. Neither the name of the copyright holder nor the names of its          *
 *    contributors may be used to endorse or promote products derived from   *
 *    this software without specific prior written permission.               *
 *                                                                           *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS       *
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED *
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A           *
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER *
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,  *
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,       *
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR        *
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF    *
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING      *
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS        *
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.              *
 *                                                                           *
\*===========================================================================*/

/*
 * DBSCAN.cc
 *
 *  Created on: May 18, 2012
 *      Author: ebke
 */

#include <queue>

namespace ACG {
namespace Algorithm {

namespace _DBSCAN_PRIVATE {

template<typename VALUE_TYPE>
class constant_1 {
    public:
        inline double operator()(VALUE_TYPE it) const {
            return 1.0;
        }
};

template<typename INPUT_ITERATOR, typename WEIGHT_FUNC>
inline double neighborhoodWeight(INPUT_ITERATOR first, const INPUT_ITERATOR last, WEIGHT_FUNC &weight_func) {
    double result = 0;
    for (; first != last; ++first)
        result += weight_func(**first);
    return result;
}

/*
 * Private functions.
 */
template<typename INPUT_ITERATOR, typename DISTANCE_FUNC, typename OUTPUT_ITERATOR>
inline
void region_query(INPUT_ITERATOR first, const INPUT_ITERATOR last, const INPUT_ITERATOR center,
                  DISTANCE_FUNC &distance_func, OUTPUT_ITERATOR result, const double epsilon) {

    for (; first != last; ++first) {
        if (center == first) continue;
        if (distance_func(*center, *first) <= epsilon) {
            *result++ = first;
        }
    }
}


template<typename INPUT_ITERATOR, typename DISTANCE_FUNC, typename WEIGHT_FUNC>
inline
void expand_cluster(INPUT_ITERATOR first, const INPUT_ITERATOR last, const INPUT_ITERATOR center,
                    DISTANCE_FUNC &distance_func, const double epsilon, const double n_min,
                    std::vector<int> &id_cache, const int current_cluster_id, WEIGHT_FUNC &weight_func) {


    std::queue<INPUT_ITERATOR> bfq;
    bfq.push(center);

    id_cache[std::distance(first, center)] = current_cluster_id;

    std::vector<INPUT_ITERATOR> neighborhood; neighborhood.reserve(std::distance(first, last));

    while (!bfq.empty()) {

        INPUT_ITERATOR current_element = bfq.front();
        bfq.pop();

        /*
         * Precondition: id_cache[current_idx] > 0
         */

        neighborhood.clear();
        region_query(first, last, current_element, distance_func, std::back_inserter(neighborhood), epsilon);

        /*
         * If the current element is not inside a dense area,
         * we don't use it as a seed to expand the cluster.
         */
        if (neighborhoodWeight(neighborhood.begin(), neighborhood.end(), weight_func) < n_min)
            continue;

        /*
         * Push yet unvisited elements onto the queue.
         */
        for (typename std::vector<INPUT_ITERATOR>::iterator it = neighborhood.begin(), it_end = neighborhood.end();
                it != it_end; ++it) {
            const size_t neighbor_idx = std::distance(first, *it);
            /*
             * Is the element classified as non-noise, yet?
             */
            if (id_cache[neighbor_idx] <= 0) {
                /*
                 * Classify it and use it as a seed.
                 */
                id_cache[neighbor_idx] = current_cluster_id;
                bfq.push(*it);
            }
        }
    }
}

} /* namespace _DBSCAN_PRIVATE */

} /* namespace Algorithm */
} /* namespace ACG */