1 | /* -*- mode: C++; indent-tabs-mode: nil; -*- |
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2 | * |
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3 | * This file is a part of LEMON, a generic C++ optimization library. |
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4 | * |
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5 | * Copyright (C) 2003-2010 |
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6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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8 | * |
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9 | * Permission to use, modify and distribute this software is granted |
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10 | * provided that this copyright notice appears in all copies. For |
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11 | * precise terms see the accompanying LICENSE file. |
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12 | * |
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13 | * This software is provided "AS IS" with no warranty of any kind, |
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14 | * express or implied, and with no claim as to its suitability for any |
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15 | * purpose. |
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16 | * |
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17 | */ |
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18 | |
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19 | #ifndef LEMON_FRACTIONAL_MATCHING_H |
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20 | #define LEMON_FRACTIONAL_MATCHING_H |
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21 | |
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22 | #include <vector> |
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23 | #include <queue> |
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24 | #include <set> |
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25 | #include <limits> |
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26 | |
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27 | #include <lemon/core.h> |
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28 | #include <lemon/unionfind.h> |
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29 | #include <lemon/bin_heap.h> |
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30 | #include <lemon/maps.h> |
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31 | #include <lemon/assert.h> |
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32 | #include <lemon/elevator.h> |
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33 | |
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34 | ///\ingroup matching |
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35 | ///\file |
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36 | ///\brief Fractional matching algorithms in general graphs. |
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37 | |
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38 | namespace lemon { |
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39 | |
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40 | /// \brief Default traits class of MaxFractionalMatching class. |
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41 | /// |
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42 | /// Default traits class of MaxFractionalMatching class. |
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43 | /// \tparam GR Graph type. |
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44 | template <typename GR> |
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45 | struct MaxFractionalMatchingDefaultTraits { |
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46 | |
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47 | /// \brief The type of the graph the algorithm runs on. |
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48 | typedef GR Graph; |
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49 | |
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50 | /// \brief The type of the map that stores the matching. |
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51 | /// |
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52 | /// The type of the map that stores the matching arcs. |
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53 | /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
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54 | typedef typename Graph::template NodeMap<typename GR::Arc> MatchingMap; |
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55 | |
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56 | /// \brief Instantiates a MatchingMap. |
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57 | /// |
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58 | /// This function instantiates a \ref MatchingMap. |
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59 | /// \param graph The graph for which we would like to define |
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60 | /// the matching map. |
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61 | static MatchingMap* createMatchingMap(const Graph& graph) { |
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62 | return new MatchingMap(graph); |
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63 | } |
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64 | |
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65 | /// \brief The elevator type used by MaxFractionalMatching algorithm. |
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66 | /// |
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67 | /// The elevator type used by MaxFractionalMatching algorithm. |
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68 | /// |
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69 | /// \sa Elevator |
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70 | /// \sa LinkedElevator |
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71 | typedef LinkedElevator<Graph, typename Graph::Node> Elevator; |
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72 | |
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73 | /// \brief Instantiates an Elevator. |
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74 | /// |
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75 | /// This function instantiates an \ref Elevator. |
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76 | /// \param graph The graph for which we would like to define |
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77 | /// the elevator. |
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78 | /// \param max_level The maximum level of the elevator. |
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79 | static Elevator* createElevator(const Graph& graph, int max_level) { |
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80 | return new Elevator(graph, max_level); |
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81 | } |
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82 | }; |
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83 | |
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84 | /// \ingroup matching |
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85 | /// |
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86 | /// \brief Max cardinality fractional matching |
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87 | /// |
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88 | /// This class provides an implementation of fractional matching |
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89 | /// algorithm based on push-relabel principle. |
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90 | /// |
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91 | /// The maximum cardinality fractional matching is a relaxation of the |
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92 | /// maximum cardinality matching problem where the odd set constraints |
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93 | /// are omitted. |
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94 | /// It can be formulated with the following linear program. |
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95 | /// \f[ \sum_{e \in \delta(u)}x_e \le 1 \quad \forall u\in V\f] |
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96 | /// \f[x_e \ge 0\quad \forall e\in E\f] |
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97 | /// \f[\max \sum_{e\in E}x_e\f] |
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98 | /// where \f$\delta(X)\f$ is the set of edges incident to a node in |
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99 | /// \f$X\f$. The result can be represented as the union of a |
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100 | /// matching with one value edges and a set of odd length cycles |
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101 | /// with half value edges. |
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102 | /// |
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103 | /// The algorithm calculates an optimal fractional matching and a |
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104 | /// barrier. The number of adjacents of any node set minus the size |
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105 | /// of node set is a lower bound on the uncovered nodes in the |
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106 | /// graph. For maximum matching a barrier is computed which |
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107 | /// maximizes this difference. |
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108 | /// |
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109 | /// The algorithm can be executed with the run() function. After it |
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110 | /// the matching (the primal solution) and the barrier (the dual |
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111 | /// solution) can be obtained using the query functions. |
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112 | /// |
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113 | /// The primal solution is multiplied by |
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114 | /// \ref MaxFractionalMatching::primalScale "2". |
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115 | /// |
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116 | /// \tparam GR The undirected graph type the algorithm runs on. |
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117 | #ifdef DOXYGEN |
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118 | template <typename GR, typename TR> |
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119 | #else |
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120 | template <typename GR, |
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121 | typename TR = MaxFractionalMatchingDefaultTraits<GR> > |
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122 | #endif |
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123 | class MaxFractionalMatching { |
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124 | public: |
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125 | |
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126 | /// \brief The \ref MaxFractionalMatchingDefaultTraits "traits |
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127 | /// class" of the algorithm. |
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128 | typedef TR Traits; |
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129 | /// The type of the graph the algorithm runs on. |
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130 | typedef typename TR::Graph Graph; |
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131 | /// The type of the matching map. |
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132 | typedef typename TR::MatchingMap MatchingMap; |
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133 | /// The type of the elevator. |
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134 | typedef typename TR::Elevator Elevator; |
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135 | |
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136 | /// \brief Scaling factor for primal solution |
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137 | /// |
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138 | /// Scaling factor for primal solution. |
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139 | static const int primalScale = 2; |
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140 | |
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141 | private: |
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142 | |
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143 | const Graph &_graph; |
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144 | int _node_num; |
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145 | bool _allow_loops; |
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146 | int _empty_level; |
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147 | |
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148 | TEMPLATE_GRAPH_TYPEDEFS(Graph); |
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149 | |
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150 | bool _local_matching; |
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151 | MatchingMap *_matching; |
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152 | |
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153 | bool _local_level; |
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154 | Elevator *_level; |
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155 | |
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156 | typedef typename Graph::template NodeMap<int> InDegMap; |
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157 | InDegMap *_indeg; |
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158 | |
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159 | void createStructures() { |
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160 | _node_num = countNodes(_graph); |
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161 | |
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162 | if (!_matching) { |
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163 | _local_matching = true; |
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164 | _matching = Traits::createMatchingMap(_graph); |
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165 | } |
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166 | if (!_level) { |
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167 | _local_level = true; |
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168 | _level = Traits::createElevator(_graph, _node_num); |
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169 | } |
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170 | if (!_indeg) { |
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171 | _indeg = new InDegMap(_graph); |
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172 | } |
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173 | } |
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174 | |
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175 | void destroyStructures() { |
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176 | if (_local_matching) { |
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177 | delete _matching; |
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178 | } |
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179 | if (_local_level) { |
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180 | delete _level; |
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181 | } |
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182 | if (_indeg) { |
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183 | delete _indeg; |
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184 | } |
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185 | } |
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186 | |
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187 | void postprocessing() { |
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188 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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189 | if ((*_indeg)[n] != 0) continue; |
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190 | _indeg->set(n, -1); |
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191 | Node u = n; |
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192 | while ((*_matching)[u] != INVALID) { |
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193 | Node v = _graph.target((*_matching)[u]); |
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194 | _indeg->set(v, -1); |
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195 | Arc a = _graph.oppositeArc((*_matching)[u]); |
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196 | u = _graph.target((*_matching)[v]); |
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197 | _indeg->set(u, -1); |
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198 | _matching->set(v, a); |
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199 | } |
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200 | } |
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201 | |
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202 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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203 | if ((*_indeg)[n] != 1) continue; |
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204 | _indeg->set(n, -1); |
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205 | |
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206 | int num = 1; |
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207 | Node u = _graph.target((*_matching)[n]); |
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208 | while (u != n) { |
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209 | _indeg->set(u, -1); |
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210 | u = _graph.target((*_matching)[u]); |
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211 | ++num; |
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212 | } |
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213 | if (num % 2 == 0 && num > 2) { |
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214 | Arc prev = _graph.oppositeArc((*_matching)[n]); |
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215 | Node v = _graph.target((*_matching)[n]); |
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216 | u = _graph.target((*_matching)[v]); |
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217 | _matching->set(v, prev); |
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218 | while (u != n) { |
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219 | prev = _graph.oppositeArc((*_matching)[u]); |
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220 | v = _graph.target((*_matching)[u]); |
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221 | u = _graph.target((*_matching)[v]); |
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222 | _matching->set(v, prev); |
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223 | } |
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224 | } |
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225 | } |
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226 | } |
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227 | |
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228 | public: |
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229 | |
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230 | typedef MaxFractionalMatching Create; |
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231 | |
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232 | ///\name Named Template Parameters |
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233 | |
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234 | ///@{ |
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235 | |
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236 | template <typename T> |
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237 | struct SetMatchingMapTraits : public Traits { |
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238 | typedef T MatchingMap; |
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239 | static MatchingMap *createMatchingMap(const Graph&) { |
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240 | LEMON_ASSERT(false, "MatchingMap is not initialized"); |
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241 | return 0; // ignore warnings |
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242 | } |
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243 | }; |
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244 | |
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245 | /// \brief \ref named-templ-param "Named parameter" for setting |
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246 | /// MatchingMap type |
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247 | /// |
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248 | /// \ref named-templ-param "Named parameter" for setting MatchingMap |
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249 | /// type. |
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250 | template <typename T> |
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251 | struct SetMatchingMap |
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252 | : public MaxFractionalMatching<Graph, SetMatchingMapTraits<T> > { |
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253 | typedef MaxFractionalMatching<Graph, SetMatchingMapTraits<T> > Create; |
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254 | }; |
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255 | |
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256 | template <typename T> |
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257 | struct SetElevatorTraits : public Traits { |
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258 | typedef T Elevator; |
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259 | static Elevator *createElevator(const Graph&, int) { |
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260 | LEMON_ASSERT(false, "Elevator is not initialized"); |
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261 | return 0; // ignore warnings |
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262 | } |
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263 | }; |
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264 | |
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265 | /// \brief \ref named-templ-param "Named parameter" for setting |
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266 | /// Elevator type |
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267 | /// |
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268 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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269 | /// type. If this named parameter is used, then an external |
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270 | /// elevator object must be passed to the algorithm using the |
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271 | /// \ref elevator(Elevator&) "elevator()" function before calling |
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272 | /// \ref run() or \ref init(). |
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273 | /// \sa SetStandardElevator |
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274 | template <typename T> |
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275 | struct SetElevator |
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276 | : public MaxFractionalMatching<Graph, SetElevatorTraits<T> > { |
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277 | typedef MaxFractionalMatching<Graph, SetElevatorTraits<T> > Create; |
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278 | }; |
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279 | |
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280 | template <typename T> |
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281 | struct SetStandardElevatorTraits : public Traits { |
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282 | typedef T Elevator; |
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283 | static Elevator *createElevator(const Graph& graph, int max_level) { |
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284 | return new Elevator(graph, max_level); |
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285 | } |
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286 | }; |
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287 | |
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288 | /// \brief \ref named-templ-param "Named parameter" for setting |
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289 | /// Elevator type with automatic allocation |
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290 | /// |
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291 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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292 | /// type with automatic allocation. |
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293 | /// The Elevator should have standard constructor interface to be |
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294 | /// able to automatically created by the algorithm (i.e. the |
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295 | /// graph and the maximum level should be passed to it). |
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296 | /// However an external elevator object could also be passed to the |
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297 | /// algorithm with the \ref elevator(Elevator&) "elevator()" function |
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298 | /// before calling \ref run() or \ref init(). |
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299 | /// \sa SetElevator |
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300 | template <typename T> |
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301 | struct SetStandardElevator |
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302 | : public MaxFractionalMatching<Graph, SetStandardElevatorTraits<T> > { |
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303 | typedef MaxFractionalMatching<Graph, |
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304 | SetStandardElevatorTraits<T> > Create; |
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305 | }; |
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306 | |
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307 | /// @} |
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308 | |
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309 | protected: |
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310 | |
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311 | MaxFractionalMatching() {} |
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312 | |
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313 | public: |
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314 | |
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315 | /// \brief Constructor |
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316 | /// |
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317 | /// Constructor. |
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318 | /// |
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319 | MaxFractionalMatching(const Graph &graph, bool allow_loops = true) |
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320 | : _graph(graph), _allow_loops(allow_loops), |
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321 | _local_matching(false), _matching(0), |
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322 | _local_level(false), _level(0), _indeg(0) |
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323 | {} |
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324 | |
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325 | ~MaxFractionalMatching() { |
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326 | destroyStructures(); |
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327 | } |
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328 | |
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329 | /// \brief Sets the matching map. |
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330 | /// |
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331 | /// Sets the matching map. |
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332 | /// If you don't use this function before calling \ref run() or |
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333 | /// \ref init(), an instance will be allocated automatically. |
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334 | /// The destructor deallocates this automatically allocated map, |
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335 | /// of course. |
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336 | /// \return <tt>(*this)</tt> |
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337 | MaxFractionalMatching& matchingMap(MatchingMap& map) { |
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338 | if (_local_matching) { |
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339 | delete _matching; |
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340 | _local_matching = false; |
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341 | } |
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342 | _matching = ↦ |
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343 | return *this; |
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344 | } |
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345 | |
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346 | /// \brief Sets the elevator used by algorithm. |
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347 | /// |
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348 | /// Sets the elevator used by algorithm. |
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349 | /// If you don't use this function before calling \ref run() or |
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350 | /// \ref init(), an instance will be allocated automatically. |
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351 | /// The destructor deallocates this automatically allocated elevator, |
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352 | /// of course. |
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353 | /// \return <tt>(*this)</tt> |
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354 | MaxFractionalMatching& elevator(Elevator& elevator) { |
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355 | if (_local_level) { |
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356 | delete _level; |
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357 | _local_level = false; |
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358 | } |
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359 | _level = &elevator; |
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360 | return *this; |
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361 | } |
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362 | |
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363 | /// \brief Returns a const reference to the elevator. |
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364 | /// |
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365 | /// Returns a const reference to the elevator. |
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366 | /// |
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367 | /// \pre Either \ref run() or \ref init() must be called before |
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368 | /// using this function. |
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369 | const Elevator& elevator() const { |
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370 | return *_level; |
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371 | } |
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372 | |
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373 | /// \name Execution control |
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374 | /// The simplest way to execute the algorithm is to use one of the |
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375 | /// member functions called \c run(). \n |
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376 | /// If you need more control on the execution, first |
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377 | /// you must call \ref init() and then one variant of the start() |
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378 | /// member. |
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379 | |
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380 | /// @{ |
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381 | |
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382 | /// \brief Initializes the internal data structures. |
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383 | /// |
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384 | /// Initializes the internal data structures and sets the initial |
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385 | /// matching. |
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386 | void init() { |
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387 | createStructures(); |
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388 | |
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389 | _level->initStart(); |
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390 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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391 | _indeg->set(n, 0); |
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392 | _matching->set(n, INVALID); |
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393 | _level->initAddItem(n); |
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394 | } |
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395 | _level->initFinish(); |
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396 | |
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397 | _empty_level = _node_num; |
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398 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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399 | for (OutArcIt a(_graph, n); a != INVALID; ++a) { |
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400 | if (_graph.target(a) == n && !_allow_loops) continue; |
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401 | _matching->set(n, a); |
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402 | Node v = _graph.target((*_matching)[n]); |
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403 | _indeg->set(v, (*_indeg)[v] + 1); |
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404 | break; |
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405 | } |
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406 | } |
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407 | |
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408 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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409 | if ((*_indeg)[n] == 0) { |
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410 | _level->activate(n); |
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411 | } |
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412 | } |
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413 | } |
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414 | |
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415 | /// \brief Starts the algorithm and computes a fractional matching |
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416 | /// |
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417 | /// The algorithm computes a maximum fractional matching. |
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418 | /// |
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419 | /// \param postprocess The algorithm computes first a matching |
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420 | /// which is a union of a matching with one value edges, cycles |
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421 | /// with half value edges and even length paths with half value |
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422 | /// edges. If the parameter is true, then after the push-relabel |
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423 | /// algorithm it postprocesses the matching to contain only |
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424 | /// matching edges and half value odd cycles. |
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425 | void start(bool postprocess = true) { |
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426 | Node n; |
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427 | while ((n = _level->highestActive()) != INVALID) { |
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428 | int level = _level->highestActiveLevel(); |
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429 | int new_level = _level->maxLevel(); |
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430 | for (InArcIt a(_graph, n); a != INVALID; ++a) { |
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431 | Node u = _graph.source(a); |
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432 | if (n == u && !_allow_loops) continue; |
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433 | Node v = _graph.target((*_matching)[u]); |
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434 | if ((*_level)[v] < level) { |
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435 | _indeg->set(v, (*_indeg)[v] - 1); |
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436 | if ((*_indeg)[v] == 0) { |
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437 | _level->activate(v); |
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438 | } |
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439 | _matching->set(u, a); |
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440 | _indeg->set(n, (*_indeg)[n] + 1); |
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441 | _level->deactivate(n); |
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442 | goto no_more_push; |
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443 | } else if (new_level > (*_level)[v]) { |
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444 | new_level = (*_level)[v]; |
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445 | } |
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446 | } |
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447 | |
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448 | if (new_level + 1 < _level->maxLevel()) { |
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449 | _level->liftHighestActive(new_level + 1); |
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450 | } else { |
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451 | _level->liftHighestActiveToTop(); |
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452 | } |
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453 | if (_level->emptyLevel(level)) { |
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454 | _level->liftToTop(level); |
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455 | } |
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456 | no_more_push: |
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457 | ; |
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458 | } |
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459 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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460 | if ((*_matching)[n] == INVALID) continue; |
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461 | Node u = _graph.target((*_matching)[n]); |
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462 | if ((*_indeg)[u] > 1) { |
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463 | _indeg->set(u, (*_indeg)[u] - 1); |
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464 | _matching->set(n, INVALID); |
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465 | } |
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466 | } |
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467 | if (postprocess) { |
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468 | postprocessing(); |
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469 | } |
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470 | } |
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471 | |
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472 | /// \brief Starts the algorithm and computes a perfect fractional |
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473 | /// matching |
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474 | /// |
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475 | /// The algorithm computes a perfect fractional matching. If it |
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476 | /// does not exists, then the algorithm returns false and the |
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477 | /// matching is undefined and the barrier. |
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478 | /// |
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479 | /// \param postprocess The algorithm computes first a matching |
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480 | /// which is a union of a matching with one value edges, cycles |
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481 | /// with half value edges and even length paths with half value |
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482 | /// edges. If the parameter is true, then after the push-relabel |
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483 | /// algorithm it postprocesses the matching to contain only |
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484 | /// matching edges and half value odd cycles. |
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485 | bool startPerfect(bool postprocess = true) { |
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486 | Node n; |
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487 | while ((n = _level->highestActive()) != INVALID) { |
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488 | int level = _level->highestActiveLevel(); |
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489 | int new_level = _level->maxLevel(); |
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490 | for (InArcIt a(_graph, n); a != INVALID; ++a) { |
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491 | Node u = _graph.source(a); |
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492 | if (n == u && !_allow_loops) continue; |
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493 | Node v = _graph.target((*_matching)[u]); |
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494 | if ((*_level)[v] < level) { |
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495 | _indeg->set(v, (*_indeg)[v] - 1); |
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496 | if ((*_indeg)[v] == 0) { |
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497 | _level->activate(v); |
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498 | } |
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499 | _matching->set(u, a); |
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500 | _indeg->set(n, (*_indeg)[n] + 1); |
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501 | _level->deactivate(n); |
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502 | goto no_more_push; |
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503 | } else if (new_level > (*_level)[v]) { |
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504 | new_level = (*_level)[v]; |
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505 | } |
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506 | } |
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507 | |
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508 | if (new_level + 1 < _level->maxLevel()) { |
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509 | _level->liftHighestActive(new_level + 1); |
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510 | } else { |
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511 | _level->liftHighestActiveToTop(); |
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512 | _empty_level = _level->maxLevel() - 1; |
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513 | return false; |
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514 | } |
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515 | if (_level->emptyLevel(level)) { |
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516 | _level->liftToTop(level); |
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517 | _empty_level = level; |
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518 | return false; |
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519 | } |
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520 | no_more_push: |
---|
521 | ; |
---|
522 | } |
---|
523 | if (postprocess) { |
---|
524 | postprocessing(); |
---|
525 | } |
---|
526 | return true; |
---|
527 | } |
---|
528 | |
---|
529 | /// \brief Runs the algorithm |
---|
530 | /// |
---|
531 | /// Just a shortcut for the next code: |
---|
532 | ///\code |
---|
533 | /// init(); |
---|
534 | /// start(); |
---|
535 | ///\endcode |
---|
536 | void run(bool postprocess = true) { |
---|
537 | init(); |
---|
538 | start(postprocess); |
---|
539 | } |
---|
540 | |
---|
541 | /// \brief Runs the algorithm to find a perfect fractional matching |
---|
542 | /// |
---|
543 | /// Just a shortcut for the next code: |
---|
544 | ///\code |
---|
545 | /// init(); |
---|
546 | /// startPerfect(); |
---|
547 | ///\endcode |
---|
548 | bool runPerfect(bool postprocess = true) { |
---|
549 | init(); |
---|
550 | return startPerfect(postprocess); |
---|
551 | } |
---|
552 | |
---|
553 | ///@} |
---|
554 | |
---|
555 | /// \name Query Functions |
---|
556 | /// The result of the %Matching algorithm can be obtained using these |
---|
557 | /// functions.\n |
---|
558 | /// Before the use of these functions, |
---|
559 | /// either run() or start() must be called. |
---|
560 | ///@{ |
---|
561 | |
---|
562 | |
---|
563 | /// \brief Return the number of covered nodes in the matching. |
---|
564 | /// |
---|
565 | /// This function returns the number of covered nodes in the matching. |
---|
566 | /// |
---|
567 | /// \pre Either run() or start() must be called before using this function. |
---|
568 | int matchingSize() const { |
---|
569 | int num = 0; |
---|
570 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
571 | if ((*_matching)[n] != INVALID) { |
---|
572 | ++num; |
---|
573 | } |
---|
574 | } |
---|
575 | return num; |
---|
576 | } |
---|
577 | |
---|
578 | /// \brief Returns a const reference to the matching map. |
---|
579 | /// |
---|
580 | /// Returns a const reference to the node map storing the found |
---|
581 | /// fractional matching. This method can be called after |
---|
582 | /// running the algorithm. |
---|
583 | /// |
---|
584 | /// \pre Either \ref run() or \ref init() must be called before |
---|
585 | /// using this function. |
---|
586 | const MatchingMap& matchingMap() const { |
---|
587 | return *_matching; |
---|
588 | } |
---|
589 | |
---|
590 | /// \brief Return \c true if the given edge is in the matching. |
---|
591 | /// |
---|
592 | /// This function returns \c true if the given edge is in the |
---|
593 | /// found matching. The result is scaled by \ref primalScale |
---|
594 | /// "primal scale". |
---|
595 | /// |
---|
596 | /// \pre Either run() or start() must be called before using this function. |
---|
597 | int matching(const Edge& edge) const { |
---|
598 | return (edge == (*_matching)[_graph.u(edge)] ? 1 : 0) + |
---|
599 | (edge == (*_matching)[_graph.v(edge)] ? 1 : 0); |
---|
600 | } |
---|
601 | |
---|
602 | /// \brief Return the fractional matching arc (or edge) incident |
---|
603 | /// to the given node. |
---|
604 | /// |
---|
605 | /// This function returns one of the fractional matching arc (or |
---|
606 | /// edge) incident to the given node in the found matching or \c |
---|
607 | /// INVALID if the node is not covered by the matching or if the |
---|
608 | /// node is on an odd length cycle then it is the successor edge |
---|
609 | /// on the cycle. |
---|
610 | /// |
---|
611 | /// \pre Either run() or start() must be called before using this function. |
---|
612 | Arc matching(const Node& node) const { |
---|
613 | return (*_matching)[node]; |
---|
614 | } |
---|
615 | |
---|
616 | /// \brief Returns true if the node is in the barrier |
---|
617 | /// |
---|
618 | /// The barrier is a subset of the nodes. If the nodes in the |
---|
619 | /// barrier have less adjacent nodes than the size of the barrier, |
---|
620 | /// then at least as much nodes cannot be covered as the |
---|
621 | /// difference of the two subsets. |
---|
622 | bool barrier(const Node& node) const { |
---|
623 | return (*_level)[node] >= _empty_level; |
---|
624 | } |
---|
625 | |
---|
626 | /// @} |
---|
627 | |
---|
628 | }; |
---|
629 | |
---|
630 | /// \ingroup matching |
---|
631 | /// |
---|
632 | /// \brief Weighted fractional matching in general graphs |
---|
633 | /// |
---|
634 | /// This class provides an efficient implementation of fractional |
---|
635 | /// matching algorithm. The implementation uses priority queues and |
---|
636 | /// provides \f$O(nm\log n)\f$ time complexity. |
---|
637 | /// |
---|
638 | /// The maximum weighted fractional matching is a relaxation of the |
---|
639 | /// maximum weighted matching problem where the odd set constraints |
---|
640 | /// are omitted. |
---|
641 | /// It can be formulated with the following linear program. |
---|
642 | /// \f[ \sum_{e \in \delta(u)}x_e \le 1 \quad \forall u\in V\f] |
---|
643 | /// \f[x_e \ge 0\quad \forall e\in E\f] |
---|
644 | /// \f[\max \sum_{e\in E}x_ew_e\f] |
---|
645 | /// where \f$\delta(X)\f$ is the set of edges incident to a node in |
---|
646 | /// \f$X\f$. The result must be the union of a matching with one |
---|
647 | /// value edges and a set of odd length cycles with half value edges. |
---|
648 | /// |
---|
649 | /// The algorithm calculates an optimal fractional matching and a |
---|
650 | /// proof of the optimality. The solution of the dual problem can be |
---|
651 | /// used to check the result of the algorithm. The dual linear |
---|
652 | /// problem is the following. |
---|
653 | /// \f[ y_u + y_v \ge w_{uv} \quad \forall uv\in E\f] |
---|
654 | /// \f[y_u \ge 0 \quad \forall u \in V\f] |
---|
655 | /// \f[\min \sum_{u \in V}y_u \f] |
---|
656 | /// |
---|
657 | /// The algorithm can be executed with the run() function. |
---|
658 | /// After it the matching (the primal solution) and the dual solution |
---|
659 | /// can be obtained using the query functions. |
---|
660 | /// |
---|
661 | /// The primal solution is multiplied by |
---|
662 | /// \ref MaxWeightedFractionalMatching::primalScale "2". |
---|
663 | /// If the value type is integer, then the dual |
---|
664 | /// solution is scaled by |
---|
665 | /// \ref MaxWeightedFractionalMatching::dualScale "4". |
---|
666 | /// |
---|
667 | /// \tparam GR The undirected graph type the algorithm runs on. |
---|
668 | /// \tparam WM The type edge weight map. The default type is |
---|
669 | /// \ref concepts::Graph::EdgeMap "GR::EdgeMap<int>". |
---|
670 | #ifdef DOXYGEN |
---|
671 | template <typename GR, typename WM> |
---|
672 | #else |
---|
673 | template <typename GR, |
---|
674 | typename WM = typename GR::template EdgeMap<int> > |
---|
675 | #endif |
---|
676 | class MaxWeightedFractionalMatching { |
---|
677 | public: |
---|
678 | |
---|
679 | /// The graph type of the algorithm |
---|
680 | typedef GR Graph; |
---|
681 | /// The type of the edge weight map |
---|
682 | typedef WM WeightMap; |
---|
683 | /// The value type of the edge weights |
---|
684 | typedef typename WeightMap::Value Value; |
---|
685 | |
---|
686 | /// The type of the matching map |
---|
687 | typedef typename Graph::template NodeMap<typename Graph::Arc> |
---|
688 | MatchingMap; |
---|
689 | |
---|
690 | /// \brief Scaling factor for primal solution |
---|
691 | /// |
---|
692 | /// Scaling factor for primal solution. |
---|
693 | static const int primalScale = 2; |
---|
694 | |
---|
695 | /// \brief Scaling factor for dual solution |
---|
696 | /// |
---|
697 | /// Scaling factor for dual solution. It is equal to 4 or 1 |
---|
698 | /// according to the value type. |
---|
699 | static const int dualScale = |
---|
700 | std::numeric_limits<Value>::is_integer ? 4 : 1; |
---|
701 | |
---|
702 | private: |
---|
703 | |
---|
704 | TEMPLATE_GRAPH_TYPEDEFS(Graph); |
---|
705 | |
---|
706 | typedef typename Graph::template NodeMap<Value> NodePotential; |
---|
707 | |
---|
708 | const Graph& _graph; |
---|
709 | const WeightMap& _weight; |
---|
710 | |
---|
711 | MatchingMap* _matching; |
---|
712 | NodePotential* _node_potential; |
---|
713 | |
---|
714 | int _node_num; |
---|
715 | bool _allow_loops; |
---|
716 | |
---|
717 | enum Status { |
---|
718 | EVEN = -1, MATCHED = 0, ODD = 1 |
---|
719 | }; |
---|
720 | |
---|
721 | typedef typename Graph::template NodeMap<Status> StatusMap; |
---|
722 | StatusMap* _status; |
---|
723 | |
---|
724 | typedef typename Graph::template NodeMap<Arc> PredMap; |
---|
725 | PredMap* _pred; |
---|
726 | |
---|
727 | typedef ExtendFindEnum<IntNodeMap> TreeSet; |
---|
728 | |
---|
729 | IntNodeMap *_tree_set_index; |
---|
730 | TreeSet *_tree_set; |
---|
731 | |
---|
732 | IntNodeMap *_delta1_index; |
---|
733 | BinHeap<Value, IntNodeMap> *_delta1; |
---|
734 | |
---|
735 | IntNodeMap *_delta2_index; |
---|
736 | BinHeap<Value, IntNodeMap> *_delta2; |
---|
737 | |
---|
738 | IntEdgeMap *_delta3_index; |
---|
739 | BinHeap<Value, IntEdgeMap> *_delta3; |
---|
740 | |
---|
741 | Value _delta_sum; |
---|
742 | |
---|
743 | void createStructures() { |
---|
744 | _node_num = countNodes(_graph); |
---|
745 | |
---|
746 | if (!_matching) { |
---|
747 | _matching = new MatchingMap(_graph); |
---|
748 | } |
---|
749 | if (!_node_potential) { |
---|
750 | _node_potential = new NodePotential(_graph); |
---|
751 | } |
---|
752 | if (!_status) { |
---|
753 | _status = new StatusMap(_graph); |
---|
754 | } |
---|
755 | if (!_pred) { |
---|
756 | _pred = new PredMap(_graph); |
---|
757 | } |
---|
758 | if (!_tree_set) { |
---|
759 | _tree_set_index = new IntNodeMap(_graph); |
---|
760 | _tree_set = new TreeSet(*_tree_set_index); |
---|
761 | } |
---|
762 | if (!_delta1) { |
---|
763 | _delta1_index = new IntNodeMap(_graph); |
---|
764 | _delta1 = new BinHeap<Value, IntNodeMap>(*_delta1_index); |
---|
765 | } |
---|
766 | if (!_delta2) { |
---|
767 | _delta2_index = new IntNodeMap(_graph); |
---|
768 | _delta2 = new BinHeap<Value, IntNodeMap>(*_delta2_index); |
---|
769 | } |
---|
770 | if (!_delta3) { |
---|
771 | _delta3_index = new IntEdgeMap(_graph); |
---|
772 | _delta3 = new BinHeap<Value, IntEdgeMap>(*_delta3_index); |
---|
773 | } |
---|
774 | } |
---|
775 | |
---|
776 | void destroyStructures() { |
---|
777 | if (_matching) { |
---|
778 | delete _matching; |
---|
779 | } |
---|
780 | if (_node_potential) { |
---|
781 | delete _node_potential; |
---|
782 | } |
---|
783 | if (_status) { |
---|
784 | delete _status; |
---|
785 | } |
---|
786 | if (_pred) { |
---|
787 | delete _pred; |
---|
788 | } |
---|
789 | if (_tree_set) { |
---|
790 | delete _tree_set_index; |
---|
791 | delete _tree_set; |
---|
792 | } |
---|
793 | if (_delta1) { |
---|
794 | delete _delta1_index; |
---|
795 | delete _delta1; |
---|
796 | } |
---|
797 | if (_delta2) { |
---|
798 | delete _delta2_index; |
---|
799 | delete _delta2; |
---|
800 | } |
---|
801 | if (_delta3) { |
---|
802 | delete _delta3_index; |
---|
803 | delete _delta3; |
---|
804 | } |
---|
805 | } |
---|
806 | |
---|
807 | void matchedToEven(Node node, int tree) { |
---|
808 | _tree_set->insert(node, tree); |
---|
809 | _node_potential->set(node, (*_node_potential)[node] + _delta_sum); |
---|
810 | _delta1->push(node, (*_node_potential)[node]); |
---|
811 | |
---|
812 | if (_delta2->state(node) == _delta2->IN_HEAP) { |
---|
813 | _delta2->erase(node); |
---|
814 | } |
---|
815 | |
---|
816 | for (InArcIt a(_graph, node); a != INVALID; ++a) { |
---|
817 | Node v = _graph.source(a); |
---|
818 | Value rw = (*_node_potential)[node] + (*_node_potential)[v] - |
---|
819 | dualScale * _weight[a]; |
---|
820 | if (node == v) { |
---|
821 | if (_allow_loops && _graph.direction(a)) { |
---|
822 | _delta3->push(a, rw / 2); |
---|
823 | } |
---|
824 | } else if ((*_status)[v] == EVEN) { |
---|
825 | _delta3->push(a, rw / 2); |
---|
826 | } else if ((*_status)[v] == MATCHED) { |
---|
827 | if (_delta2->state(v) != _delta2->IN_HEAP) { |
---|
828 | _pred->set(v, a); |
---|
829 | _delta2->push(v, rw); |
---|
830 | } else if ((*_delta2)[v] > rw) { |
---|
831 | _pred->set(v, a); |
---|
832 | _delta2->decrease(v, rw); |
---|
833 | } |
---|
834 | } |
---|
835 | } |
---|
836 | } |
---|
837 | |
---|
838 | void matchedToOdd(Node node, int tree) { |
---|
839 | _tree_set->insert(node, tree); |
---|
840 | _node_potential->set(node, (*_node_potential)[node] - _delta_sum); |
---|
841 | |
---|
842 | if (_delta2->state(node) == _delta2->IN_HEAP) { |
---|
843 | _delta2->erase(node); |
---|
844 | } |
---|
845 | } |
---|
846 | |
---|
847 | void evenToMatched(Node node, int tree) { |
---|
848 | _delta1->erase(node); |
---|
849 | _node_potential->set(node, (*_node_potential)[node] - _delta_sum); |
---|
850 | Arc min = INVALID; |
---|
851 | Value minrw = std::numeric_limits<Value>::max(); |
---|
852 | for (InArcIt a(_graph, node); a != INVALID; ++a) { |
---|
853 | Node v = _graph.source(a); |
---|
854 | Value rw = (*_node_potential)[node] + (*_node_potential)[v] - |
---|
855 | dualScale * _weight[a]; |
---|
856 | |
---|
857 | if (node == v) { |
---|
858 | if (_allow_loops && _graph.direction(a)) { |
---|
859 | _delta3->erase(a); |
---|
860 | } |
---|
861 | } else if ((*_status)[v] == EVEN) { |
---|
862 | _delta3->erase(a); |
---|
863 | if (minrw > rw) { |
---|
864 | min = _graph.oppositeArc(a); |
---|
865 | minrw = rw; |
---|
866 | } |
---|
867 | } else if ((*_status)[v] == MATCHED) { |
---|
868 | if ((*_pred)[v] == a) { |
---|
869 | Arc mina = INVALID; |
---|
870 | Value minrwa = std::numeric_limits<Value>::max(); |
---|
871 | for (OutArcIt aa(_graph, v); aa != INVALID; ++aa) { |
---|
872 | Node va = _graph.target(aa); |
---|
873 | if ((*_status)[va] != EVEN || |
---|
874 | _tree_set->find(va) == tree) continue; |
---|
875 | Value rwa = (*_node_potential)[v] + (*_node_potential)[va] - |
---|
876 | dualScale * _weight[aa]; |
---|
877 | if (minrwa > rwa) { |
---|
878 | minrwa = rwa; |
---|
879 | mina = aa; |
---|
880 | } |
---|
881 | } |
---|
882 | if (mina != INVALID) { |
---|
883 | _pred->set(v, mina); |
---|
884 | _delta2->increase(v, minrwa); |
---|
885 | } else { |
---|
886 | _pred->set(v, INVALID); |
---|
887 | _delta2->erase(v); |
---|
888 | } |
---|
889 | } |
---|
890 | } |
---|
891 | } |
---|
892 | if (min != INVALID) { |
---|
893 | _pred->set(node, min); |
---|
894 | _delta2->push(node, minrw); |
---|
895 | } else { |
---|
896 | _pred->set(node, INVALID); |
---|
897 | } |
---|
898 | } |
---|
899 | |
---|
900 | void oddToMatched(Node node) { |
---|
901 | _node_potential->set(node, (*_node_potential)[node] + _delta_sum); |
---|
902 | Arc min = INVALID; |
---|
903 | Value minrw = std::numeric_limits<Value>::max(); |
---|
904 | for (InArcIt a(_graph, node); a != INVALID; ++a) { |
---|
905 | Node v = _graph.source(a); |
---|
906 | if ((*_status)[v] != EVEN) continue; |
---|
907 | Value rw = (*_node_potential)[node] + (*_node_potential)[v] - |
---|
908 | dualScale * _weight[a]; |
---|
909 | |
---|
910 | if (minrw > rw) { |
---|
911 | min = _graph.oppositeArc(a); |
---|
912 | minrw = rw; |
---|
913 | } |
---|
914 | } |
---|
915 | if (min != INVALID) { |
---|
916 | _pred->set(node, min); |
---|
917 | _delta2->push(node, minrw); |
---|
918 | } else { |
---|
919 | _pred->set(node, INVALID); |
---|
920 | } |
---|
921 | } |
---|
922 | |
---|
923 | void alternatePath(Node even, int tree) { |
---|
924 | Node odd; |
---|
925 | |
---|
926 | _status->set(even, MATCHED); |
---|
927 | evenToMatched(even, tree); |
---|
928 | |
---|
929 | Arc prev = (*_matching)[even]; |
---|
930 | while (prev != INVALID) { |
---|
931 | odd = _graph.target(prev); |
---|
932 | even = _graph.target((*_pred)[odd]); |
---|
933 | _matching->set(odd, (*_pred)[odd]); |
---|
934 | _status->set(odd, MATCHED); |
---|
935 | oddToMatched(odd); |
---|
936 | |
---|
937 | prev = (*_matching)[even]; |
---|
938 | _status->set(even, MATCHED); |
---|
939 | _matching->set(even, _graph.oppositeArc((*_matching)[odd])); |
---|
940 | evenToMatched(even, tree); |
---|
941 | } |
---|
942 | } |
---|
943 | |
---|
944 | void destroyTree(int tree) { |
---|
945 | for (typename TreeSet::ItemIt n(*_tree_set, tree); n != INVALID; ++n) { |
---|
946 | if ((*_status)[n] == EVEN) { |
---|
947 | _status->set(n, MATCHED); |
---|
948 | evenToMatched(n, tree); |
---|
949 | } else if ((*_status)[n] == ODD) { |
---|
950 | _status->set(n, MATCHED); |
---|
951 | oddToMatched(n); |
---|
952 | } |
---|
953 | } |
---|
954 | _tree_set->eraseClass(tree); |
---|
955 | } |
---|
956 | |
---|
957 | |
---|
958 | void unmatchNode(const Node& node) { |
---|
959 | int tree = _tree_set->find(node); |
---|
960 | |
---|
961 | alternatePath(node, tree); |
---|
962 | destroyTree(tree); |
---|
963 | |
---|
964 | _matching->set(node, INVALID); |
---|
965 | } |
---|
966 | |
---|
967 | |
---|
968 | void augmentOnEdge(const Edge& edge) { |
---|
969 | Node left = _graph.u(edge); |
---|
970 | int left_tree = _tree_set->find(left); |
---|
971 | |
---|
972 | alternatePath(left, left_tree); |
---|
973 | destroyTree(left_tree); |
---|
974 | _matching->set(left, _graph.direct(edge, true)); |
---|
975 | |
---|
976 | Node right = _graph.v(edge); |
---|
977 | int right_tree = _tree_set->find(right); |
---|
978 | |
---|
979 | alternatePath(right, right_tree); |
---|
980 | destroyTree(right_tree); |
---|
981 | _matching->set(right, _graph.direct(edge, false)); |
---|
982 | } |
---|
983 | |
---|
984 | void augmentOnArc(const Arc& arc) { |
---|
985 | Node left = _graph.source(arc); |
---|
986 | _status->set(left, MATCHED); |
---|
987 | _matching->set(left, arc); |
---|
988 | _pred->set(left, arc); |
---|
989 | |
---|
990 | Node right = _graph.target(arc); |
---|
991 | int right_tree = _tree_set->find(right); |
---|
992 | |
---|
993 | alternatePath(right, right_tree); |
---|
994 | destroyTree(right_tree); |
---|
995 | _matching->set(right, _graph.oppositeArc(arc)); |
---|
996 | } |
---|
997 | |
---|
998 | void extendOnArc(const Arc& arc) { |
---|
999 | Node base = _graph.target(arc); |
---|
1000 | int tree = _tree_set->find(base); |
---|
1001 | |
---|
1002 | Node odd = _graph.source(arc); |
---|
1003 | _tree_set->insert(odd, tree); |
---|
1004 | _status->set(odd, ODD); |
---|
1005 | matchedToOdd(odd, tree); |
---|
1006 | _pred->set(odd, arc); |
---|
1007 | |
---|
1008 | Node even = _graph.target((*_matching)[odd]); |
---|
1009 | _tree_set->insert(even, tree); |
---|
1010 | _status->set(even, EVEN); |
---|
1011 | matchedToEven(even, tree); |
---|
1012 | } |
---|
1013 | |
---|
1014 | void cycleOnEdge(const Edge& edge, int tree) { |
---|
1015 | Node nca = INVALID; |
---|
1016 | std::vector<Node> left_path, right_path; |
---|
1017 | |
---|
1018 | { |
---|
1019 | std::set<Node> left_set, right_set; |
---|
1020 | Node left = _graph.u(edge); |
---|
1021 | left_path.push_back(left); |
---|
1022 | left_set.insert(left); |
---|
1023 | |
---|
1024 | Node right = _graph.v(edge); |
---|
1025 | right_path.push_back(right); |
---|
1026 | right_set.insert(right); |
---|
1027 | |
---|
1028 | while (true) { |
---|
1029 | |
---|
1030 | if (left_set.find(right) != left_set.end()) { |
---|
1031 | nca = right; |
---|
1032 | break; |
---|
1033 | } |
---|
1034 | |
---|
1035 | if ((*_matching)[left] == INVALID) break; |
---|
1036 | |
---|
1037 | left = _graph.target((*_matching)[left]); |
---|
1038 | left_path.push_back(left); |
---|
1039 | left = _graph.target((*_pred)[left]); |
---|
1040 | left_path.push_back(left); |
---|
1041 | |
---|
1042 | left_set.insert(left); |
---|
1043 | |
---|
1044 | if (right_set.find(left) != right_set.end()) { |
---|
1045 | nca = left; |
---|
1046 | break; |
---|
1047 | } |
---|
1048 | |
---|
1049 | if ((*_matching)[right] == INVALID) break; |
---|
1050 | |
---|
1051 | right = _graph.target((*_matching)[right]); |
---|
1052 | right_path.push_back(right); |
---|
1053 | right = _graph.target((*_pred)[right]); |
---|
1054 | right_path.push_back(right); |
---|
1055 | |
---|
1056 | right_set.insert(right); |
---|
1057 | |
---|
1058 | } |
---|
1059 | |
---|
1060 | if (nca == INVALID) { |
---|
1061 | if ((*_matching)[left] == INVALID) { |
---|
1062 | nca = right; |
---|
1063 | while (left_set.find(nca) == left_set.end()) { |
---|
1064 | nca = _graph.target((*_matching)[nca]); |
---|
1065 | right_path.push_back(nca); |
---|
1066 | nca = _graph.target((*_pred)[nca]); |
---|
1067 | right_path.push_back(nca); |
---|
1068 | } |
---|
1069 | } else { |
---|
1070 | nca = left; |
---|
1071 | while (right_set.find(nca) == right_set.end()) { |
---|
1072 | nca = _graph.target((*_matching)[nca]); |
---|
1073 | left_path.push_back(nca); |
---|
1074 | nca = _graph.target((*_pred)[nca]); |
---|
1075 | left_path.push_back(nca); |
---|
1076 | } |
---|
1077 | } |
---|
1078 | } |
---|
1079 | } |
---|
1080 | |
---|
1081 | alternatePath(nca, tree); |
---|
1082 | Arc prev; |
---|
1083 | |
---|
1084 | prev = _graph.direct(edge, true); |
---|
1085 | for (int i = 0; left_path[i] != nca; i += 2) { |
---|
1086 | _matching->set(left_path[i], prev); |
---|
1087 | _status->set(left_path[i], MATCHED); |
---|
1088 | evenToMatched(left_path[i], tree); |
---|
1089 | |
---|
1090 | prev = _graph.oppositeArc((*_pred)[left_path[i + 1]]); |
---|
1091 | _status->set(left_path[i + 1], MATCHED); |
---|
1092 | oddToMatched(left_path[i + 1]); |
---|
1093 | } |
---|
1094 | _matching->set(nca, prev); |
---|
1095 | |
---|
1096 | for (int i = 0; right_path[i] != nca; i += 2) { |
---|
1097 | _status->set(right_path[i], MATCHED); |
---|
1098 | evenToMatched(right_path[i], tree); |
---|
1099 | |
---|
1100 | _matching->set(right_path[i + 1], (*_pred)[right_path[i + 1]]); |
---|
1101 | _status->set(right_path[i + 1], MATCHED); |
---|
1102 | oddToMatched(right_path[i + 1]); |
---|
1103 | } |
---|
1104 | |
---|
1105 | destroyTree(tree); |
---|
1106 | } |
---|
1107 | |
---|
1108 | void extractCycle(const Arc &arc) { |
---|
1109 | Node left = _graph.source(arc); |
---|
1110 | Node odd = _graph.target((*_matching)[left]); |
---|
1111 | Arc prev; |
---|
1112 | while (odd != left) { |
---|
1113 | Node even = _graph.target((*_matching)[odd]); |
---|
1114 | prev = (*_matching)[odd]; |
---|
1115 | odd = _graph.target((*_matching)[even]); |
---|
1116 | _matching->set(even, _graph.oppositeArc(prev)); |
---|
1117 | } |
---|
1118 | _matching->set(left, arc); |
---|
1119 | |
---|
1120 | Node right = _graph.target(arc); |
---|
1121 | int right_tree = _tree_set->find(right); |
---|
1122 | alternatePath(right, right_tree); |
---|
1123 | destroyTree(right_tree); |
---|
1124 | _matching->set(right, _graph.oppositeArc(arc)); |
---|
1125 | } |
---|
1126 | |
---|
1127 | public: |
---|
1128 | |
---|
1129 | /// \brief Constructor |
---|
1130 | /// |
---|
1131 | /// Constructor. |
---|
1132 | MaxWeightedFractionalMatching(const Graph& graph, const WeightMap& weight, |
---|
1133 | bool allow_loops = true) |
---|
1134 | : _graph(graph), _weight(weight), _matching(0), |
---|
1135 | _node_potential(0), _node_num(0), _allow_loops(allow_loops), |
---|
1136 | _status(0), _pred(0), |
---|
1137 | _tree_set_index(0), _tree_set(0), |
---|
1138 | |
---|
1139 | _delta1_index(0), _delta1(0), |
---|
1140 | _delta2_index(0), _delta2(0), |
---|
1141 | _delta3_index(0), _delta3(0), |
---|
1142 | |
---|
1143 | _delta_sum() {} |
---|
1144 | |
---|
1145 | ~MaxWeightedFractionalMatching() { |
---|
1146 | destroyStructures(); |
---|
1147 | } |
---|
1148 | |
---|
1149 | /// \name Execution Control |
---|
1150 | /// The simplest way to execute the algorithm is to use the |
---|
1151 | /// \ref run() member function. |
---|
1152 | |
---|
1153 | ///@{ |
---|
1154 | |
---|
1155 | /// \brief Initialize the algorithm |
---|
1156 | /// |
---|
1157 | /// This function initializes the algorithm. |
---|
1158 | void init() { |
---|
1159 | createStructures(); |
---|
1160 | |
---|
1161 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1162 | (*_delta1_index)[n] = _delta1->PRE_HEAP; |
---|
1163 | (*_delta2_index)[n] = _delta2->PRE_HEAP; |
---|
1164 | } |
---|
1165 | for (EdgeIt e(_graph); e != INVALID; ++e) { |
---|
1166 | (*_delta3_index)[e] = _delta3->PRE_HEAP; |
---|
1167 | } |
---|
1168 | |
---|
1169 | _delta1->clear(); |
---|
1170 | _delta2->clear(); |
---|
1171 | _delta3->clear(); |
---|
1172 | _tree_set->clear(); |
---|
1173 | |
---|
1174 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1175 | Value max = 0; |
---|
1176 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
1177 | if (_graph.target(e) == n && !_allow_loops) continue; |
---|
1178 | if ((dualScale * _weight[e]) / 2 > max) { |
---|
1179 | max = (dualScale * _weight[e]) / 2; |
---|
1180 | } |
---|
1181 | } |
---|
1182 | _node_potential->set(n, max); |
---|
1183 | _delta1->push(n, max); |
---|
1184 | |
---|
1185 | _tree_set->insert(n); |
---|
1186 | |
---|
1187 | _matching->set(n, INVALID); |
---|
1188 | _status->set(n, EVEN); |
---|
1189 | } |
---|
1190 | |
---|
1191 | for (EdgeIt e(_graph); e != INVALID; ++e) { |
---|
1192 | Node left = _graph.u(e); |
---|
1193 | Node right = _graph.v(e); |
---|
1194 | if (left == right && !_allow_loops) continue; |
---|
1195 | _delta3->push(e, ((*_node_potential)[left] + |
---|
1196 | (*_node_potential)[right] - |
---|
1197 | dualScale * _weight[e]) / 2); |
---|
1198 | } |
---|
1199 | } |
---|
1200 | |
---|
1201 | /// \brief Start the algorithm |
---|
1202 | /// |
---|
1203 | /// This function starts the algorithm. |
---|
1204 | /// |
---|
1205 | /// \pre \ref init() must be called before using this function. |
---|
1206 | void start() { |
---|
1207 | enum OpType { |
---|
1208 | D1, D2, D3 |
---|
1209 | }; |
---|
1210 | |
---|
1211 | int unmatched = _node_num; |
---|
1212 | while (unmatched > 0) { |
---|
1213 | Value d1 = !_delta1->empty() ? |
---|
1214 | _delta1->prio() : std::numeric_limits<Value>::max(); |
---|
1215 | |
---|
1216 | Value d2 = !_delta2->empty() ? |
---|
1217 | _delta2->prio() : std::numeric_limits<Value>::max(); |
---|
1218 | |
---|
1219 | Value d3 = !_delta3->empty() ? |
---|
1220 | _delta3->prio() : std::numeric_limits<Value>::max(); |
---|
1221 | |
---|
1222 | _delta_sum = d3; OpType ot = D3; |
---|
1223 | if (d1 < _delta_sum) { _delta_sum = d1; ot = D1; } |
---|
1224 | if (d2 < _delta_sum) { _delta_sum = d2; ot = D2; } |
---|
1225 | |
---|
1226 | switch (ot) { |
---|
1227 | case D1: |
---|
1228 | { |
---|
1229 | Node n = _delta1->top(); |
---|
1230 | unmatchNode(n); |
---|
1231 | --unmatched; |
---|
1232 | } |
---|
1233 | break; |
---|
1234 | case D2: |
---|
1235 | { |
---|
1236 | Node n = _delta2->top(); |
---|
1237 | Arc a = (*_pred)[n]; |
---|
1238 | if ((*_matching)[n] == INVALID) { |
---|
1239 | augmentOnArc(a); |
---|
1240 | --unmatched; |
---|
1241 | } else { |
---|
1242 | Node v = _graph.target((*_matching)[n]); |
---|
1243 | if ((*_matching)[n] != |
---|
1244 | _graph.oppositeArc((*_matching)[v])) { |
---|
1245 | extractCycle(a); |
---|
1246 | --unmatched; |
---|
1247 | } else { |
---|
1248 | extendOnArc(a); |
---|
1249 | } |
---|
1250 | } |
---|
1251 | } break; |
---|
1252 | case D3: |
---|
1253 | { |
---|
1254 | Edge e = _delta3->top(); |
---|
1255 | |
---|
1256 | Node left = _graph.u(e); |
---|
1257 | Node right = _graph.v(e); |
---|
1258 | |
---|
1259 | int left_tree = _tree_set->find(left); |
---|
1260 | int right_tree = _tree_set->find(right); |
---|
1261 | |
---|
1262 | if (left_tree == right_tree) { |
---|
1263 | cycleOnEdge(e, left_tree); |
---|
1264 | --unmatched; |
---|
1265 | } else { |
---|
1266 | augmentOnEdge(e); |
---|
1267 | unmatched -= 2; |
---|
1268 | } |
---|
1269 | } break; |
---|
1270 | } |
---|
1271 | } |
---|
1272 | } |
---|
1273 | |
---|
1274 | /// \brief Run the algorithm. |
---|
1275 | /// |
---|
1276 | /// This method runs the \c %MaxWeightedFractionalMatching algorithm. |
---|
1277 | /// |
---|
1278 | /// \note mwfm.run() is just a shortcut of the following code. |
---|
1279 | /// \code |
---|
1280 | /// mwfm.init(); |
---|
1281 | /// mwfm.start(); |
---|
1282 | /// \endcode |
---|
1283 | void run() { |
---|
1284 | init(); |
---|
1285 | start(); |
---|
1286 | } |
---|
1287 | |
---|
1288 | /// @} |
---|
1289 | |
---|
1290 | /// \name Primal Solution |
---|
1291 | /// Functions to get the primal solution, i.e. the maximum weighted |
---|
1292 | /// matching.\n |
---|
1293 | /// Either \ref run() or \ref start() function should be called before |
---|
1294 | /// using them. |
---|
1295 | |
---|
1296 | /// @{ |
---|
1297 | |
---|
1298 | /// \brief Return the weight of the matching. |
---|
1299 | /// |
---|
1300 | /// This function returns the weight of the found matching. This |
---|
1301 | /// value is scaled by \ref primalScale "primal scale". |
---|
1302 | /// |
---|
1303 | /// \pre Either run() or start() must be called before using this function. |
---|
1304 | Value matchingWeight() const { |
---|
1305 | Value sum = 0; |
---|
1306 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1307 | if ((*_matching)[n] != INVALID) { |
---|
1308 | sum += _weight[(*_matching)[n]]; |
---|
1309 | } |
---|
1310 | } |
---|
1311 | return sum * primalScale / 2; |
---|
1312 | } |
---|
1313 | |
---|
1314 | /// \brief Return the number of covered nodes in the matching. |
---|
1315 | /// |
---|
1316 | /// This function returns the number of covered nodes in the matching. |
---|
1317 | /// |
---|
1318 | /// \pre Either run() or start() must be called before using this function. |
---|
1319 | int matchingSize() const { |
---|
1320 | int num = 0; |
---|
1321 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1322 | if ((*_matching)[n] != INVALID) { |
---|
1323 | ++num; |
---|
1324 | } |
---|
1325 | } |
---|
1326 | return num; |
---|
1327 | } |
---|
1328 | |
---|
1329 | /// \brief Return \c true if the given edge is in the matching. |
---|
1330 | /// |
---|
1331 | /// This function returns \c true if the given edge is in the |
---|
1332 | /// found matching. The result is scaled by \ref primalScale |
---|
1333 | /// "primal scale". |
---|
1334 | /// |
---|
1335 | /// \pre Either run() or start() must be called before using this function. |
---|
1336 | int matching(const Edge& edge) const { |
---|
1337 | return (edge == (*_matching)[_graph.u(edge)] ? 1 : 0) |
---|
1338 | + (edge == (*_matching)[_graph.v(edge)] ? 1 : 0); |
---|
1339 | } |
---|
1340 | |
---|
1341 | /// \brief Return the fractional matching arc (or edge) incident |
---|
1342 | /// to the given node. |
---|
1343 | /// |
---|
1344 | /// This function returns one of the fractional matching arc (or |
---|
1345 | /// edge) incident to the given node in the found matching or \c |
---|
1346 | /// INVALID if the node is not covered by the matching or if the |
---|
1347 | /// node is on an odd length cycle then it is the successor edge |
---|
1348 | /// on the cycle. |
---|
1349 | /// |
---|
1350 | /// \pre Either run() or start() must be called before using this function. |
---|
1351 | Arc matching(const Node& node) const { |
---|
1352 | return (*_matching)[node]; |
---|
1353 | } |
---|
1354 | |
---|
1355 | /// \brief Return a const reference to the matching map. |
---|
1356 | /// |
---|
1357 | /// This function returns a const reference to a node map that stores |
---|
1358 | /// the matching arc (or edge) incident to each node. |
---|
1359 | const MatchingMap& matchingMap() const { |
---|
1360 | return *_matching; |
---|
1361 | } |
---|
1362 | |
---|
1363 | /// @} |
---|
1364 | |
---|
1365 | /// \name Dual Solution |
---|
1366 | /// Functions to get the dual solution.\n |
---|
1367 | /// Either \ref run() or \ref start() function should be called before |
---|
1368 | /// using them. |
---|
1369 | |
---|
1370 | /// @{ |
---|
1371 | |
---|
1372 | /// \brief Return the value of the dual solution. |
---|
1373 | /// |
---|
1374 | /// This function returns the value of the dual solution. |
---|
1375 | /// It should be equal to the primal value scaled by \ref dualScale |
---|
1376 | /// "dual scale". |
---|
1377 | /// |
---|
1378 | /// \pre Either run() or start() must be called before using this function. |
---|
1379 | Value dualValue() const { |
---|
1380 | Value sum = 0; |
---|
1381 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1382 | sum += nodeValue(n); |
---|
1383 | } |
---|
1384 | return sum; |
---|
1385 | } |
---|
1386 | |
---|
1387 | /// \brief Return the dual value (potential) of the given node. |
---|
1388 | /// |
---|
1389 | /// This function returns the dual value (potential) of the given node. |
---|
1390 | /// |
---|
1391 | /// \pre Either run() or start() must be called before using this function. |
---|
1392 | Value nodeValue(const Node& n) const { |
---|
1393 | return (*_node_potential)[n]; |
---|
1394 | } |
---|
1395 | |
---|
1396 | /// @} |
---|
1397 | |
---|
1398 | }; |
---|
1399 | |
---|
1400 | /// \ingroup matching |
---|
1401 | /// |
---|
1402 | /// \brief Weighted fractional perfect matching in general graphs |
---|
1403 | /// |
---|
1404 | /// This class provides an efficient implementation of fractional |
---|
1405 | /// matching algorithm. The implementation uses priority queues and |
---|
1406 | /// provides \f$O(nm\log n)\f$ time complexity. |
---|
1407 | /// |
---|
1408 | /// The maximum weighted fractional perfect matching is a relaxation |
---|
1409 | /// of the maximum weighted perfect matching problem where the odd |
---|
1410 | /// set constraints are omitted. |
---|
1411 | /// It can be formulated with the following linear program. |
---|
1412 | /// \f[ \sum_{e \in \delta(u)}x_e = 1 \quad \forall u\in V\f] |
---|
1413 | /// \f[x_e \ge 0\quad \forall e\in E\f] |
---|
1414 | /// \f[\max \sum_{e\in E}x_ew_e\f] |
---|
1415 | /// where \f$\delta(X)\f$ is the set of edges incident to a node in |
---|
1416 | /// \f$X\f$. The result must be the union of a matching with one |
---|
1417 | /// value edges and a set of odd length cycles with half value edges. |
---|
1418 | /// |
---|
1419 | /// The algorithm calculates an optimal fractional matching and a |
---|
1420 | /// proof of the optimality. The solution of the dual problem can be |
---|
1421 | /// used to check the result of the algorithm. The dual linear |
---|
1422 | /// problem is the following. |
---|
1423 | /// \f[ y_u + y_v \ge w_{uv} \quad \forall uv\in E\f] |
---|
1424 | /// \f[\min \sum_{u \in V}y_u \f] |
---|
1425 | /// |
---|
1426 | /// The algorithm can be executed with the run() function. |
---|
1427 | /// After it the matching (the primal solution) and the dual solution |
---|
1428 | /// can be obtained using the query functions. |
---|
1429 | /// |
---|
1430 | /// The primal solution is multiplied by |
---|
1431 | /// \ref MaxWeightedPerfectFractionalMatching::primalScale "2". |
---|
1432 | /// If the value type is integer, then the dual |
---|
1433 | /// solution is scaled by |
---|
1434 | /// \ref MaxWeightedPerfectFractionalMatching::dualScale "4". |
---|
1435 | /// |
---|
1436 | /// \tparam GR The undirected graph type the algorithm runs on. |
---|
1437 | /// \tparam WM The type edge weight map. The default type is |
---|
1438 | /// \ref concepts::Graph::EdgeMap "GR::EdgeMap<int>". |
---|
1439 | #ifdef DOXYGEN |
---|
1440 | template <typename GR, typename WM> |
---|
1441 | #else |
---|
1442 | template <typename GR, |
---|
1443 | typename WM = typename GR::template EdgeMap<int> > |
---|
1444 | #endif |
---|
1445 | class MaxWeightedPerfectFractionalMatching { |
---|
1446 | public: |
---|
1447 | |
---|
1448 | /// The graph type of the algorithm |
---|
1449 | typedef GR Graph; |
---|
1450 | /// The type of the edge weight map |
---|
1451 | typedef WM WeightMap; |
---|
1452 | /// The value type of the edge weights |
---|
1453 | typedef typename WeightMap::Value Value; |
---|
1454 | |
---|
1455 | /// The type of the matching map |
---|
1456 | typedef typename Graph::template NodeMap<typename Graph::Arc> |
---|
1457 | MatchingMap; |
---|
1458 | |
---|
1459 | /// \brief Scaling factor for primal solution |
---|
1460 | /// |
---|
1461 | /// Scaling factor for primal solution. |
---|
1462 | static const int primalScale = 2; |
---|
1463 | |
---|
1464 | /// \brief Scaling factor for dual solution |
---|
1465 | /// |
---|
1466 | /// Scaling factor for dual solution. It is equal to 4 or 1 |
---|
1467 | /// according to the value type. |
---|
1468 | static const int dualScale = |
---|
1469 | std::numeric_limits<Value>::is_integer ? 4 : 1; |
---|
1470 | |
---|
1471 | private: |
---|
1472 | |
---|
1473 | TEMPLATE_GRAPH_TYPEDEFS(Graph); |
---|
1474 | |
---|
1475 | typedef typename Graph::template NodeMap<Value> NodePotential; |
---|
1476 | |
---|
1477 | const Graph& _graph; |
---|
1478 | const WeightMap& _weight; |
---|
1479 | |
---|
1480 | MatchingMap* _matching; |
---|
1481 | NodePotential* _node_potential; |
---|
1482 | |
---|
1483 | int _node_num; |
---|
1484 | bool _allow_loops; |
---|
1485 | |
---|
1486 | enum Status { |
---|
1487 | EVEN = -1, MATCHED = 0, ODD = 1 |
---|
1488 | }; |
---|
1489 | |
---|
1490 | typedef typename Graph::template NodeMap<Status> StatusMap; |
---|
1491 | StatusMap* _status; |
---|
1492 | |
---|
1493 | typedef typename Graph::template NodeMap<Arc> PredMap; |
---|
1494 | PredMap* _pred; |
---|
1495 | |
---|
1496 | typedef ExtendFindEnum<IntNodeMap> TreeSet; |
---|
1497 | |
---|
1498 | IntNodeMap *_tree_set_index; |
---|
1499 | TreeSet *_tree_set; |
---|
1500 | |
---|
1501 | IntNodeMap *_delta2_index; |
---|
1502 | BinHeap<Value, IntNodeMap> *_delta2; |
---|
1503 | |
---|
1504 | IntEdgeMap *_delta3_index; |
---|
1505 | BinHeap<Value, IntEdgeMap> *_delta3; |
---|
1506 | |
---|
1507 | Value _delta_sum; |
---|
1508 | |
---|
1509 | void createStructures() { |
---|
1510 | _node_num = countNodes(_graph); |
---|
1511 | |
---|
1512 | if (!_matching) { |
---|
1513 | _matching = new MatchingMap(_graph); |
---|
1514 | } |
---|
1515 | if (!_node_potential) { |
---|
1516 | _node_potential = new NodePotential(_graph); |
---|
1517 | } |
---|
1518 | if (!_status) { |
---|
1519 | _status = new StatusMap(_graph); |
---|
1520 | } |
---|
1521 | if (!_pred) { |
---|
1522 | _pred = new PredMap(_graph); |
---|
1523 | } |
---|
1524 | if (!_tree_set) { |
---|
1525 | _tree_set_index = new IntNodeMap(_graph); |
---|
1526 | _tree_set = new TreeSet(*_tree_set_index); |
---|
1527 | } |
---|
1528 | if (!_delta2) { |
---|
1529 | _delta2_index = new IntNodeMap(_graph); |
---|
1530 | _delta2 = new BinHeap<Value, IntNodeMap>(*_delta2_index); |
---|
1531 | } |
---|
1532 | if (!_delta3) { |
---|
1533 | _delta3_index = new IntEdgeMap(_graph); |
---|
1534 | _delta3 = new BinHeap<Value, IntEdgeMap>(*_delta3_index); |
---|
1535 | } |
---|
1536 | } |
---|
1537 | |
---|
1538 | void destroyStructures() { |
---|
1539 | if (_matching) { |
---|
1540 | delete _matching; |
---|
1541 | } |
---|
1542 | if (_node_potential) { |
---|
1543 | delete _node_potential; |
---|
1544 | } |
---|
1545 | if (_status) { |
---|
1546 | delete _status; |
---|
1547 | } |
---|
1548 | if (_pred) { |
---|
1549 | delete _pred; |
---|
1550 | } |
---|
1551 | if (_tree_set) { |
---|
1552 | delete _tree_set_index; |
---|
1553 | delete _tree_set; |
---|
1554 | } |
---|
1555 | if (_delta2) { |
---|
1556 | delete _delta2_index; |
---|
1557 | delete _delta2; |
---|
1558 | } |
---|
1559 | if (_delta3) { |
---|
1560 | delete _delta3_index; |
---|
1561 | delete _delta3; |
---|
1562 | } |
---|
1563 | } |
---|
1564 | |
---|
1565 | void matchedToEven(Node node, int tree) { |
---|
1566 | _tree_set->insert(node, tree); |
---|
1567 | _node_potential->set(node, (*_node_potential)[node] + _delta_sum); |
---|
1568 | |
---|
1569 | if (_delta2->state(node) == _delta2->IN_HEAP) { |
---|
1570 | _delta2->erase(node); |
---|
1571 | } |
---|
1572 | |
---|
1573 | for (InArcIt a(_graph, node); a != INVALID; ++a) { |
---|
1574 | Node v = _graph.source(a); |
---|
1575 | Value rw = (*_node_potential)[node] + (*_node_potential)[v] - |
---|
1576 | dualScale * _weight[a]; |
---|
1577 | if (node == v) { |
---|
1578 | if (_allow_loops && _graph.direction(a)) { |
---|
1579 | _delta3->push(a, rw / 2); |
---|
1580 | } |
---|
1581 | } else if ((*_status)[v] == EVEN) { |
---|
1582 | _delta3->push(a, rw / 2); |
---|
1583 | } else if ((*_status)[v] == MATCHED) { |
---|
1584 | if (_delta2->state(v) != _delta2->IN_HEAP) { |
---|
1585 | _pred->set(v, a); |
---|
1586 | _delta2->push(v, rw); |
---|
1587 | } else if ((*_delta2)[v] > rw) { |
---|
1588 | _pred->set(v, a); |
---|
1589 | _delta2->decrease(v, rw); |
---|
1590 | } |
---|
1591 | } |
---|
1592 | } |
---|
1593 | } |
---|
1594 | |
---|
1595 | void matchedToOdd(Node node, int tree) { |
---|
1596 | _tree_set->insert(node, tree); |
---|
1597 | _node_potential->set(node, (*_node_potential)[node] - _delta_sum); |
---|
1598 | |
---|
1599 | if (_delta2->state(node) == _delta2->IN_HEAP) { |
---|
1600 | _delta2->erase(node); |
---|
1601 | } |
---|
1602 | } |
---|
1603 | |
---|
1604 | void evenToMatched(Node node, int tree) { |
---|
1605 | _node_potential->set(node, (*_node_potential)[node] - _delta_sum); |
---|
1606 | Arc min = INVALID; |
---|
1607 | Value minrw = std::numeric_limits<Value>::max(); |
---|
1608 | for (InArcIt a(_graph, node); a != INVALID; ++a) { |
---|
1609 | Node v = _graph.source(a); |
---|
1610 | Value rw = (*_node_potential)[node] + (*_node_potential)[v] - |
---|
1611 | dualScale * _weight[a]; |
---|
1612 | |
---|
1613 | if (node == v) { |
---|
1614 | if (_allow_loops && _graph.direction(a)) { |
---|
1615 | _delta3->erase(a); |
---|
1616 | } |
---|
1617 | } else if ((*_status)[v] == EVEN) { |
---|
1618 | _delta3->erase(a); |
---|
1619 | if (minrw > rw) { |
---|
1620 | min = _graph.oppositeArc(a); |
---|
1621 | minrw = rw; |
---|
1622 | } |
---|
1623 | } else if ((*_status)[v] == MATCHED) { |
---|
1624 | if ((*_pred)[v] == a) { |
---|
1625 | Arc mina = INVALID; |
---|
1626 | Value minrwa = std::numeric_limits<Value>::max(); |
---|
1627 | for (OutArcIt aa(_graph, v); aa != INVALID; ++aa) { |
---|
1628 | Node va = _graph.target(aa); |
---|
1629 | if ((*_status)[va] != EVEN || |
---|
1630 | _tree_set->find(va) == tree) continue; |
---|
1631 | Value rwa = (*_node_potential)[v] + (*_node_potential)[va] - |
---|
1632 | dualScale * _weight[aa]; |
---|
1633 | if (minrwa > rwa) { |
---|
1634 | minrwa = rwa; |
---|
1635 | mina = aa; |
---|
1636 | } |
---|
1637 | } |
---|
1638 | if (mina != INVALID) { |
---|
1639 | _pred->set(v, mina); |
---|
1640 | _delta2->increase(v, minrwa); |
---|
1641 | } else { |
---|
1642 | _pred->set(v, INVALID); |
---|
1643 | _delta2->erase(v); |
---|
1644 | } |
---|
1645 | } |
---|
1646 | } |
---|
1647 | } |
---|
1648 | if (min != INVALID) { |
---|
1649 | _pred->set(node, min); |
---|
1650 | _delta2->push(node, minrw); |
---|
1651 | } else { |
---|
1652 | _pred->set(node, INVALID); |
---|
1653 | } |
---|
1654 | } |
---|
1655 | |
---|
1656 | void oddToMatched(Node node) { |
---|
1657 | _node_potential->set(node, (*_node_potential)[node] + _delta_sum); |
---|
1658 | Arc min = INVALID; |
---|
1659 | Value minrw = std::numeric_limits<Value>::max(); |
---|
1660 | for (InArcIt a(_graph, node); a != INVALID; ++a) { |
---|
1661 | Node v = _graph.source(a); |
---|
1662 | if ((*_status)[v] != EVEN) continue; |
---|
1663 | Value rw = (*_node_potential)[node] + (*_node_potential)[v] - |
---|
1664 | dualScale * _weight[a]; |
---|
1665 | |
---|
1666 | if (minrw > rw) { |
---|
1667 | min = _graph.oppositeArc(a); |
---|
1668 | minrw = rw; |
---|
1669 | } |
---|
1670 | } |
---|
1671 | if (min != INVALID) { |
---|
1672 | _pred->set(node, min); |
---|
1673 | _delta2->push(node, minrw); |
---|
1674 | } else { |
---|
1675 | _pred->set(node, INVALID); |
---|
1676 | } |
---|
1677 | } |
---|
1678 | |
---|
1679 | void alternatePath(Node even, int tree) { |
---|
1680 | Node odd; |
---|
1681 | |
---|
1682 | _status->set(even, MATCHED); |
---|
1683 | evenToMatched(even, tree); |
---|
1684 | |
---|
1685 | Arc prev = (*_matching)[even]; |
---|
1686 | while (prev != INVALID) { |
---|
1687 | odd = _graph.target(prev); |
---|
1688 | even = _graph.target((*_pred)[odd]); |
---|
1689 | _matching->set(odd, (*_pred)[odd]); |
---|
1690 | _status->set(odd, MATCHED); |
---|
1691 | oddToMatched(odd); |
---|
1692 | |
---|
1693 | prev = (*_matching)[even]; |
---|
1694 | _status->set(even, MATCHED); |
---|
1695 | _matching->set(even, _graph.oppositeArc((*_matching)[odd])); |
---|
1696 | evenToMatched(even, tree); |
---|
1697 | } |
---|
1698 | } |
---|
1699 | |
---|
1700 | void destroyTree(int tree) { |
---|
1701 | for (typename TreeSet::ItemIt n(*_tree_set, tree); n != INVALID; ++n) { |
---|
1702 | if ((*_status)[n] == EVEN) { |
---|
1703 | _status->set(n, MATCHED); |
---|
1704 | evenToMatched(n, tree); |
---|
1705 | } else if ((*_status)[n] == ODD) { |
---|
1706 | _status->set(n, MATCHED); |
---|
1707 | oddToMatched(n); |
---|
1708 | } |
---|
1709 | } |
---|
1710 | _tree_set->eraseClass(tree); |
---|
1711 | } |
---|
1712 | |
---|
1713 | void augmentOnEdge(const Edge& edge) { |
---|
1714 | Node left = _graph.u(edge); |
---|
1715 | int left_tree = _tree_set->find(left); |
---|
1716 | |
---|
1717 | alternatePath(left, left_tree); |
---|
1718 | destroyTree(left_tree); |
---|
1719 | _matching->set(left, _graph.direct(edge, true)); |
---|
1720 | |
---|
1721 | Node right = _graph.v(edge); |
---|
1722 | int right_tree = _tree_set->find(right); |
---|
1723 | |
---|
1724 | alternatePath(right, right_tree); |
---|
1725 | destroyTree(right_tree); |
---|
1726 | _matching->set(right, _graph.direct(edge, false)); |
---|
1727 | } |
---|
1728 | |
---|
1729 | void augmentOnArc(const Arc& arc) { |
---|
1730 | Node left = _graph.source(arc); |
---|
1731 | _status->set(left, MATCHED); |
---|
1732 | _matching->set(left, arc); |
---|
1733 | _pred->set(left, arc); |
---|
1734 | |
---|
1735 | Node right = _graph.target(arc); |
---|
1736 | int right_tree = _tree_set->find(right); |
---|
1737 | |
---|
1738 | alternatePath(right, right_tree); |
---|
1739 | destroyTree(right_tree); |
---|
1740 | _matching->set(right, _graph.oppositeArc(arc)); |
---|
1741 | } |
---|
1742 | |
---|
1743 | void extendOnArc(const Arc& arc) { |
---|
1744 | Node base = _graph.target(arc); |
---|
1745 | int tree = _tree_set->find(base); |
---|
1746 | |
---|
1747 | Node odd = _graph.source(arc); |
---|
1748 | _tree_set->insert(odd, tree); |
---|
1749 | _status->set(odd, ODD); |
---|
1750 | matchedToOdd(odd, tree); |
---|
1751 | _pred->set(odd, arc); |
---|
1752 | |
---|
1753 | Node even = _graph.target((*_matching)[odd]); |
---|
1754 | _tree_set->insert(even, tree); |
---|
1755 | _status->set(even, EVEN); |
---|
1756 | matchedToEven(even, tree); |
---|
1757 | } |
---|
1758 | |
---|
1759 | void cycleOnEdge(const Edge& edge, int tree) { |
---|
1760 | Node nca = INVALID; |
---|
1761 | std::vector<Node> left_path, right_path; |
---|
1762 | |
---|
1763 | { |
---|
1764 | std::set<Node> left_set, right_set; |
---|
1765 | Node left = _graph.u(edge); |
---|
1766 | left_path.push_back(left); |
---|
1767 | left_set.insert(left); |
---|
1768 | |
---|
1769 | Node right = _graph.v(edge); |
---|
1770 | right_path.push_back(right); |
---|
1771 | right_set.insert(right); |
---|
1772 | |
---|
1773 | while (true) { |
---|
1774 | |
---|
1775 | if (left_set.find(right) != left_set.end()) { |
---|
1776 | nca = right; |
---|
1777 | break; |
---|
1778 | } |
---|
1779 | |
---|
1780 | if ((*_matching)[left] == INVALID) break; |
---|
1781 | |
---|
1782 | left = _graph.target((*_matching)[left]); |
---|
1783 | left_path.push_back(left); |
---|
1784 | left = _graph.target((*_pred)[left]); |
---|
1785 | left_path.push_back(left); |
---|
1786 | |
---|
1787 | left_set.insert(left); |
---|
1788 | |
---|
1789 | if (right_set.find(left) != right_set.end()) { |
---|
1790 | nca = left; |
---|
1791 | break; |
---|
1792 | } |
---|
1793 | |
---|
1794 | if ((*_matching)[right] == INVALID) break; |
---|
1795 | |
---|
1796 | right = _graph.target((*_matching)[right]); |
---|
1797 | right_path.push_back(right); |
---|
1798 | right = _graph.target((*_pred)[right]); |
---|
1799 | right_path.push_back(right); |
---|
1800 | |
---|
1801 | right_set.insert(right); |
---|
1802 | |
---|
1803 | } |
---|
1804 | |
---|
1805 | if (nca == INVALID) { |
---|
1806 | if ((*_matching)[left] == INVALID) { |
---|
1807 | nca = right; |
---|
1808 | while (left_set.find(nca) == left_set.end()) { |
---|
1809 | nca = _graph.target((*_matching)[nca]); |
---|
1810 | right_path.push_back(nca); |
---|
1811 | nca = _graph.target((*_pred)[nca]); |
---|
1812 | right_path.push_back(nca); |
---|
1813 | } |
---|
1814 | } else { |
---|
1815 | nca = left; |
---|
1816 | while (right_set.find(nca) == right_set.end()) { |
---|
1817 | nca = _graph.target((*_matching)[nca]); |
---|
1818 | left_path.push_back(nca); |
---|
1819 | nca = _graph.target((*_pred)[nca]); |
---|
1820 | left_path.push_back(nca); |
---|
1821 | } |
---|
1822 | } |
---|
1823 | } |
---|
1824 | } |
---|
1825 | |
---|
1826 | alternatePath(nca, tree); |
---|
1827 | Arc prev; |
---|
1828 | |
---|
1829 | prev = _graph.direct(edge, true); |
---|
1830 | for (int i = 0; left_path[i] != nca; i += 2) { |
---|
1831 | _matching->set(left_path[i], prev); |
---|
1832 | _status->set(left_path[i], MATCHED); |
---|
1833 | evenToMatched(left_path[i], tree); |
---|
1834 | |
---|
1835 | prev = _graph.oppositeArc((*_pred)[left_path[i + 1]]); |
---|
1836 | _status->set(left_path[i + 1], MATCHED); |
---|
1837 | oddToMatched(left_path[i + 1]); |
---|
1838 | } |
---|
1839 | _matching->set(nca, prev); |
---|
1840 | |
---|
1841 | for (int i = 0; right_path[i] != nca; i += 2) { |
---|
1842 | _status->set(right_path[i], MATCHED); |
---|
1843 | evenToMatched(right_path[i], tree); |
---|
1844 | |
---|
1845 | _matching->set(right_path[i + 1], (*_pred)[right_path[i + 1]]); |
---|
1846 | _status->set(right_path[i + 1], MATCHED); |
---|
1847 | oddToMatched(right_path[i + 1]); |
---|
1848 | } |
---|
1849 | |
---|
1850 | destroyTree(tree); |
---|
1851 | } |
---|
1852 | |
---|
1853 | void extractCycle(const Arc &arc) { |
---|
1854 | Node left = _graph.source(arc); |
---|
1855 | Node odd = _graph.target((*_matching)[left]); |
---|
1856 | Arc prev; |
---|
1857 | while (odd != left) { |
---|
1858 | Node even = _graph.target((*_matching)[odd]); |
---|
1859 | prev = (*_matching)[odd]; |
---|
1860 | odd = _graph.target((*_matching)[even]); |
---|
1861 | _matching->set(even, _graph.oppositeArc(prev)); |
---|
1862 | } |
---|
1863 | _matching->set(left, arc); |
---|
1864 | |
---|
1865 | Node right = _graph.target(arc); |
---|
1866 | int right_tree = _tree_set->find(right); |
---|
1867 | alternatePath(right, right_tree); |
---|
1868 | destroyTree(right_tree); |
---|
1869 | _matching->set(right, _graph.oppositeArc(arc)); |
---|
1870 | } |
---|
1871 | |
---|
1872 | public: |
---|
1873 | |
---|
1874 | /// \brief Constructor |
---|
1875 | /// |
---|
1876 | /// Constructor. |
---|
1877 | MaxWeightedPerfectFractionalMatching(const Graph& graph, |
---|
1878 | const WeightMap& weight, |
---|
1879 | bool allow_loops = true) |
---|
1880 | : _graph(graph), _weight(weight), _matching(0), |
---|
1881 | _node_potential(0), _node_num(0), _allow_loops(allow_loops), |
---|
1882 | _status(0), _pred(0), |
---|
1883 | _tree_set_index(0), _tree_set(0), |
---|
1884 | |
---|
1885 | _delta2_index(0), _delta2(0), |
---|
1886 | _delta3_index(0), _delta3(0), |
---|
1887 | |
---|
1888 | _delta_sum() {} |
---|
1889 | |
---|
1890 | ~MaxWeightedPerfectFractionalMatching() { |
---|
1891 | destroyStructures(); |
---|
1892 | } |
---|
1893 | |
---|
1894 | /// \name Execution Control |
---|
1895 | /// The simplest way to execute the algorithm is to use the |
---|
1896 | /// \ref run() member function. |
---|
1897 | |
---|
1898 | ///@{ |
---|
1899 | |
---|
1900 | /// \brief Initialize the algorithm |
---|
1901 | /// |
---|
1902 | /// This function initializes the algorithm. |
---|
1903 | void init() { |
---|
1904 | createStructures(); |
---|
1905 | |
---|
1906 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1907 | (*_delta2_index)[n] = _delta2->PRE_HEAP; |
---|
1908 | } |
---|
1909 | for (EdgeIt e(_graph); e != INVALID; ++e) { |
---|
1910 | (*_delta3_index)[e] = _delta3->PRE_HEAP; |
---|
1911 | } |
---|
1912 | |
---|
1913 | _delta2->clear(); |
---|
1914 | _delta3->clear(); |
---|
1915 | _tree_set->clear(); |
---|
1916 | |
---|
1917 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1918 | Value max = - std::numeric_limits<Value>::max(); |
---|
1919 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
1920 | if (_graph.target(e) == n && !_allow_loops) continue; |
---|
1921 | if ((dualScale * _weight[e]) / 2 > max) { |
---|
1922 | max = (dualScale * _weight[e]) / 2; |
---|
1923 | } |
---|
1924 | } |
---|
1925 | _node_potential->set(n, max); |
---|
1926 | |
---|
1927 | _tree_set->insert(n); |
---|
1928 | |
---|
1929 | _matching->set(n, INVALID); |
---|
1930 | _status->set(n, EVEN); |
---|
1931 | } |
---|
1932 | |
---|
1933 | for (EdgeIt e(_graph); e != INVALID; ++e) { |
---|
1934 | Node left = _graph.u(e); |
---|
1935 | Node right = _graph.v(e); |
---|
1936 | if (left == right && !_allow_loops) continue; |
---|
1937 | _delta3->push(e, ((*_node_potential)[left] + |
---|
1938 | (*_node_potential)[right] - |
---|
1939 | dualScale * _weight[e]) / 2); |
---|
1940 | } |
---|
1941 | } |
---|
1942 | |
---|
1943 | /// \brief Start the algorithm |
---|
1944 | /// |
---|
1945 | /// This function starts the algorithm. |
---|
1946 | /// |
---|
1947 | /// \pre \ref init() must be called before using this function. |
---|
1948 | bool start() { |
---|
1949 | enum OpType { |
---|
1950 | D2, D3 |
---|
1951 | }; |
---|
1952 | |
---|
1953 | int unmatched = _node_num; |
---|
1954 | while (unmatched > 0) { |
---|
1955 | Value d2 = !_delta2->empty() ? |
---|
1956 | _delta2->prio() : std::numeric_limits<Value>::max(); |
---|
1957 | |
---|
1958 | Value d3 = !_delta3->empty() ? |
---|
1959 | _delta3->prio() : std::numeric_limits<Value>::max(); |
---|
1960 | |
---|
1961 | _delta_sum = d3; OpType ot = D3; |
---|
1962 | if (d2 < _delta_sum) { _delta_sum = d2; ot = D2; } |
---|
1963 | |
---|
1964 | if (_delta_sum == std::numeric_limits<Value>::max()) { |
---|
1965 | return false; |
---|
1966 | } |
---|
1967 | |
---|
1968 | switch (ot) { |
---|
1969 | case D2: |
---|
1970 | { |
---|
1971 | Node n = _delta2->top(); |
---|
1972 | Arc a = (*_pred)[n]; |
---|
1973 | if ((*_matching)[n] == INVALID) { |
---|
1974 | augmentOnArc(a); |
---|
1975 | --unmatched; |
---|
1976 | } else { |
---|
1977 | Node v = _graph.target((*_matching)[n]); |
---|
1978 | if ((*_matching)[n] != |
---|
1979 | _graph.oppositeArc((*_matching)[v])) { |
---|
1980 | extractCycle(a); |
---|
1981 | --unmatched; |
---|
1982 | } else { |
---|
1983 | extendOnArc(a); |
---|
1984 | } |
---|
1985 | } |
---|
1986 | } break; |
---|
1987 | case D3: |
---|
1988 | { |
---|
1989 | Edge e = _delta3->top(); |
---|
1990 | |
---|
1991 | Node left = _graph.u(e); |
---|
1992 | Node right = _graph.v(e); |
---|
1993 | |
---|
1994 | int left_tree = _tree_set->find(left); |
---|
1995 | int right_tree = _tree_set->find(right); |
---|
1996 | |
---|
1997 | if (left_tree == right_tree) { |
---|
1998 | cycleOnEdge(e, left_tree); |
---|
1999 | --unmatched; |
---|
2000 | } else { |
---|
2001 | augmentOnEdge(e); |
---|
2002 | unmatched -= 2; |
---|
2003 | } |
---|
2004 | } break; |
---|
2005 | } |
---|
2006 | } |
---|
2007 | return true; |
---|
2008 | } |
---|
2009 | |
---|
2010 | /// \brief Run the algorithm. |
---|
2011 | /// |
---|
2012 | /// This method runs the \c %MaxWeightedPerfectFractionalMatching |
---|
2013 | /// algorithm. |
---|
2014 | /// |
---|
2015 | /// \note mwfm.run() is just a shortcut of the following code. |
---|
2016 | /// \code |
---|
2017 | /// mwpfm.init(); |
---|
2018 | /// mwpfm.start(); |
---|
2019 | /// \endcode |
---|
2020 | bool run() { |
---|
2021 | init(); |
---|
2022 | return start(); |
---|
2023 | } |
---|
2024 | |
---|
2025 | /// @} |
---|
2026 | |
---|
2027 | /// \name Primal Solution |
---|
2028 | /// Functions to get the primal solution, i.e. the maximum weighted |
---|
2029 | /// matching.\n |
---|
2030 | /// Either \ref run() or \ref start() function should be called before |
---|
2031 | /// using them. |
---|
2032 | |
---|
2033 | /// @{ |
---|
2034 | |
---|
2035 | /// \brief Return the weight of the matching. |
---|
2036 | /// |
---|
2037 | /// This function returns the weight of the found matching. This |
---|
2038 | /// value is scaled by \ref primalScale "primal scale". |
---|
2039 | /// |
---|
2040 | /// \pre Either run() or start() must be called before using this function. |
---|
2041 | Value matchingWeight() const { |
---|
2042 | Value sum = 0; |
---|
2043 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
2044 | if ((*_matching)[n] != INVALID) { |
---|
2045 | sum += _weight[(*_matching)[n]]; |
---|
2046 | } |
---|
2047 | } |
---|
2048 | return sum * primalScale / 2; |
---|
2049 | } |
---|
2050 | |
---|
2051 | /// \brief Return the number of covered nodes in the matching. |
---|
2052 | /// |
---|
2053 | /// This function returns the number of covered nodes in the matching. |
---|
2054 | /// |
---|
2055 | /// \pre Either run() or start() must be called before using this function. |
---|
2056 | int matchingSize() const { |
---|
2057 | int num = 0; |
---|
2058 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
2059 | if ((*_matching)[n] != INVALID) { |
---|
2060 | ++num; |
---|
2061 | } |
---|
2062 | } |
---|
2063 | return num; |
---|
2064 | } |
---|
2065 | |
---|
2066 | /// \brief Return \c true if the given edge is in the matching. |
---|
2067 | /// |
---|
2068 | /// This function returns \c true if the given edge is in the |
---|
2069 | /// found matching. The result is scaled by \ref primalScale |
---|
2070 | /// "primal scale". |
---|
2071 | /// |
---|
2072 | /// \pre Either run() or start() must be called before using this function. |
---|
2073 | int matching(const Edge& edge) const { |
---|
2074 | return (edge == (*_matching)[_graph.u(edge)] ? 1 : 0) |
---|
2075 | + (edge == (*_matching)[_graph.v(edge)] ? 1 : 0); |
---|
2076 | } |
---|
2077 | |
---|
2078 | /// \brief Return the fractional matching arc (or edge) incident |
---|
2079 | /// to the given node. |
---|
2080 | /// |
---|
2081 | /// This function returns one of the fractional matching arc (or |
---|
2082 | /// edge) incident to the given node in the found matching or \c |
---|
2083 | /// INVALID if the node is not covered by the matching or if the |
---|
2084 | /// node is on an odd length cycle then it is the successor edge |
---|
2085 | /// on the cycle. |
---|
2086 | /// |
---|
2087 | /// \pre Either run() or start() must be called before using this function. |
---|
2088 | Arc matching(const Node& node) const { |
---|
2089 | return (*_matching)[node]; |
---|
2090 | } |
---|
2091 | |
---|
2092 | /// \brief Return a const reference to the matching map. |
---|
2093 | /// |
---|
2094 | /// This function returns a const reference to a node map that stores |
---|
2095 | /// the matching arc (or edge) incident to each node. |
---|
2096 | const MatchingMap& matchingMap() const { |
---|
2097 | return *_matching; |
---|
2098 | } |
---|
2099 | |
---|
2100 | /// @} |
---|
2101 | |
---|
2102 | /// \name Dual Solution |
---|
2103 | /// Functions to get the dual solution.\n |
---|
2104 | /// Either \ref run() or \ref start() function should be called before |
---|
2105 | /// using them. |
---|
2106 | |
---|
2107 | /// @{ |
---|
2108 | |
---|
2109 | /// \brief Return the value of the dual solution. |
---|
2110 | /// |
---|
2111 | /// This function returns the value of the dual solution. |
---|
2112 | /// It should be equal to the primal value scaled by \ref dualScale |
---|
2113 | /// "dual scale". |
---|
2114 | /// |
---|
2115 | /// \pre Either run() or start() must be called before using this function. |
---|
2116 | Value dualValue() const { |
---|
2117 | Value sum = 0; |
---|
2118 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
2119 | sum += nodeValue(n); |
---|
2120 | } |
---|
2121 | return sum; |
---|
2122 | } |
---|
2123 | |
---|
2124 | /// \brief Return the dual value (potential) of the given node. |
---|
2125 | /// |
---|
2126 | /// This function returns the dual value (potential) of the given node. |
---|
2127 | /// |
---|
2128 | /// \pre Either run() or start() must be called before using this function. |
---|
2129 | Value nodeValue(const Node& n) const { |
---|
2130 | return (*_node_potential)[n]; |
---|
2131 | } |
---|
2132 | |
---|
2133 | /// @} |
---|
2134 | |
---|
2135 | }; |
---|
2136 | |
---|
2137 | } //END OF NAMESPACE LEMON |
---|
2138 | |
---|
2139 | #endif //LEMON_FRACTIONAL_MATCHING_H |
---|