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) 2003-2009 |
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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_NETWORK_SIMPLEX_H |
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20 | #define LEMON_NETWORK_SIMPLEX_H |
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21 | |
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22 | /// \ingroup min_cost_flow |
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23 | /// |
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24 | /// \file |
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25 | /// \brief Network Simplex algorithm for finding a minimum cost flow. |
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26 | |
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27 | #include <vector> |
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28 | #include <limits> |
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29 | #include <algorithm> |
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30 | |
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31 | #include <lemon/core.h> |
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32 | #include <lemon/math.h> |
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33 | |
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34 | namespace lemon { |
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35 | |
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36 | /// \addtogroup min_cost_flow |
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37 | /// @{ |
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38 | |
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39 | /// \brief Implementation of the primal Network Simplex algorithm |
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40 | /// for finding a \ref min_cost_flow "minimum cost flow". |
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41 | /// |
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42 | /// \ref NetworkSimplex implements the primal Network Simplex algorithm |
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43 | /// for finding a \ref min_cost_flow "minimum cost flow". |
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44 | /// This algorithm is a specialized version of the linear programming |
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45 | /// simplex method directly for the minimum cost flow problem. |
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46 | /// It is one of the most efficient solution methods. |
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47 | /// |
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48 | /// In general this class is the fastest implementation available |
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49 | /// in LEMON for the minimum cost flow problem. |
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50 | /// Moreover it supports both directions of the supply/demand inequality |
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51 | /// constraints. For more information see \ref SupplyType. |
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52 | /// |
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53 | /// Most of the parameters of the problem (except for the digraph) |
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54 | /// can be given using separate functions, and the algorithm can be |
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55 | /// executed using the \ref run() function. If some parameters are not |
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56 | /// specified, then default values will be used. |
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57 | /// |
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58 | /// \tparam GR The digraph type the algorithm runs on. |
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59 | /// \tparam V The value type used for flow amounts, capacity bounds |
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60 | /// and supply values in the algorithm. By default it is \c int. |
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61 | /// \tparam C The value type used for costs and potentials in the |
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62 | /// algorithm. By default it is the same as \c V. |
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63 | /// |
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64 | /// \warning Both value types must be signed and all input data must |
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65 | /// be integer. |
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66 | /// |
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67 | /// \note %NetworkSimplex provides five different pivot rule |
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68 | /// implementations, from which the most efficient one is used |
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69 | /// by default. For more information see \ref PivotRule. |
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70 | template <typename GR, typename V = int, typename C = V> |
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71 | class NetworkSimplex |
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72 | { |
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73 | public: |
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74 | |
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75 | /// The type of the flow amounts, capacity bounds and supply values |
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76 | typedef V Value; |
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77 | /// The type of the arc costs |
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78 | typedef C Cost; |
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79 | |
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80 | public: |
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81 | |
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82 | /// \brief Problem type constants for the \c run() function. |
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83 | /// |
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84 | /// Enum type containing the problem type constants that can be |
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85 | /// returned by the \ref run() function of the algorithm. |
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86 | enum ProblemType { |
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87 | /// The problem has no feasible solution (flow). |
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88 | INFEASIBLE, |
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89 | /// The problem has optimal solution (i.e. it is feasible and |
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90 | /// bounded), and the algorithm has found optimal flow and node |
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91 | /// potentials (primal and dual solutions). |
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92 | OPTIMAL, |
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93 | /// The objective function of the problem is unbounded, i.e. |
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94 | /// there is a directed cycle having negative total cost and |
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95 | /// infinite upper bound. |
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96 | UNBOUNDED |
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97 | }; |
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98 | |
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99 | /// \brief Constants for selecting the type of the supply constraints. |
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100 | /// |
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101 | /// Enum type containing constants for selecting the supply type, |
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102 | /// i.e. the direction of the inequalities in the supply/demand |
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103 | /// constraints of the \ref min_cost_flow "minimum cost flow problem". |
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104 | /// |
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105 | /// The default supply type is \c GEQ, since this form is supported |
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106 | /// by other minimum cost flow algorithms and the \ref Circulation |
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107 | /// algorithm, as well. |
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108 | /// The \c LEQ problem type can be selected using the \ref supplyType() |
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109 | /// function. |
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110 | /// |
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111 | /// Note that the equality form is a special case of both supply types. |
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112 | enum SupplyType { |
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113 | |
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114 | /// This option means that there are <em>"greater or equal"</em> |
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115 | /// supply/demand constraints in the definition, i.e. the exact |
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116 | /// formulation of the problem is the following. |
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117 | /** |
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118 | \f[ \min\sum_{uv\in A} f(uv) \cdot cost(uv) \f] |
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119 | \f[ \sum_{uv\in A} f(uv) - \sum_{vu\in A} f(vu) \geq |
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120 | sup(u) \quad \forall u\in V \f] |
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121 | \f[ lower(uv) \leq f(uv) \leq upper(uv) \quad \forall uv\in A \f] |
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122 | */ |
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123 | /// It means that the total demand must be greater or equal to the |
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124 | /// total supply (i.e. \f$\sum_{u\in V} sup(u)\f$ must be zero or |
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125 | /// negative) and all the supplies have to be carried out from |
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126 | /// the supply nodes, but there could be demands that are not |
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127 | /// satisfied. |
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128 | GEQ, |
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129 | /// It is just an alias for the \c GEQ option. |
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130 | CARRY_SUPPLIES = GEQ, |
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131 | |
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132 | /// This option means that there are <em>"less or equal"</em> |
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133 | /// supply/demand constraints in the definition, i.e. the exact |
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134 | /// formulation of the problem is the following. |
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135 | /** |
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136 | \f[ \min\sum_{uv\in A} f(uv) \cdot cost(uv) \f] |
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137 | \f[ \sum_{uv\in A} f(uv) - \sum_{vu\in A} f(vu) \leq |
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138 | sup(u) \quad \forall u\in V \f] |
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139 | \f[ lower(uv) \leq f(uv) \leq upper(uv) \quad \forall uv\in A \f] |
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140 | */ |
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141 | /// It means that the total demand must be less or equal to the |
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142 | /// total supply (i.e. \f$\sum_{u\in V} sup(u)\f$ must be zero or |
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143 | /// positive) and all the demands have to be satisfied, but there |
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144 | /// could be supplies that are not carried out from the supply |
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145 | /// nodes. |
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146 | LEQ, |
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147 | /// It is just an alias for the \c LEQ option. |
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148 | SATISFY_DEMANDS = LEQ |
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149 | }; |
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150 | |
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151 | /// \brief Constants for selecting the pivot rule. |
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152 | /// |
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153 | /// Enum type containing constants for selecting the pivot rule for |
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154 | /// the \ref run() function. |
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155 | /// |
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156 | /// \ref NetworkSimplex provides five different pivot rule |
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157 | /// implementations that significantly affect the running time |
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158 | /// of the algorithm. |
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159 | /// By default \ref BLOCK_SEARCH "Block Search" is used, which |
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160 | /// proved to be the most efficient and the most robust on various |
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161 | /// test inputs according to our benchmark tests. |
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162 | /// However another pivot rule can be selected using the \ref run() |
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163 | /// function with the proper parameter. |
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164 | enum PivotRule { |
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165 | |
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166 | /// The First Eligible pivot rule. |
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167 | /// The next eligible arc is selected in a wraparound fashion |
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168 | /// in every iteration. |
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169 | FIRST_ELIGIBLE, |
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170 | |
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171 | /// The Best Eligible pivot rule. |
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172 | /// The best eligible arc is selected in every iteration. |
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173 | BEST_ELIGIBLE, |
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174 | |
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175 | /// The Block Search pivot rule. |
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176 | /// A specified number of arcs are examined in every iteration |
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177 | /// in a wraparound fashion and the best eligible arc is selected |
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178 | /// from this block. |
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179 | BLOCK_SEARCH, |
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180 | |
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181 | /// The Candidate List pivot rule. |
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182 | /// In a major iteration a candidate list is built from eligible arcs |
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183 | /// in a wraparound fashion and in the following minor iterations |
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184 | /// the best eligible arc is selected from this list. |
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185 | CANDIDATE_LIST, |
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186 | |
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187 | /// The Altering Candidate List pivot rule. |
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188 | /// It is a modified version of the Candidate List method. |
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189 | /// It keeps only the several best eligible arcs from the former |
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190 | /// candidate list and extends this list in every iteration. |
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191 | ALTERING_LIST |
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192 | }; |
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193 | |
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194 | private: |
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195 | |
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196 | TEMPLATE_DIGRAPH_TYPEDEFS(GR); |
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197 | |
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198 | typedef std::vector<Arc> ArcVector; |
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199 | typedef std::vector<Node> NodeVector; |
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200 | typedef std::vector<int> IntVector; |
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201 | typedef std::vector<bool> BoolVector; |
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202 | typedef std::vector<Value> ValueVector; |
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203 | typedef std::vector<Cost> CostVector; |
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204 | |
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205 | // State constants for arcs |
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206 | enum ArcStateEnum { |
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207 | STATE_UPPER = -1, |
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208 | STATE_TREE = 0, |
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209 | STATE_LOWER = 1 |
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210 | }; |
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211 | |
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212 | private: |
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213 | |
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214 | // Data related to the underlying digraph |
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215 | const GR &_graph; |
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216 | int _node_num; |
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217 | int _arc_num; |
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218 | |
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219 | // Parameters of the problem |
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220 | bool _have_lower; |
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221 | SupplyType _stype; |
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222 | Value _sum_supply; |
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223 | |
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224 | // Data structures for storing the digraph |
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225 | IntNodeMap _node_id; |
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226 | IntArcMap _arc_id; |
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227 | IntVector _source; |
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228 | IntVector _target; |
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229 | |
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230 | // Node and arc data |
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231 | ValueVector _lower; |
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232 | ValueVector _upper; |
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233 | ValueVector _cap; |
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234 | CostVector _cost; |
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235 | ValueVector _supply; |
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236 | ValueVector _flow; |
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237 | CostVector _pi; |
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238 | |
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239 | // Data for storing the spanning tree structure |
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240 | IntVector _parent; |
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241 | IntVector _pred; |
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242 | IntVector _thread; |
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243 | IntVector _rev_thread; |
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244 | IntVector _succ_num; |
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245 | IntVector _last_succ; |
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246 | IntVector _dirty_revs; |
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247 | BoolVector _forward; |
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248 | IntVector _state; |
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249 | int _root; |
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250 | |
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251 | // Temporary data used in the current pivot iteration |
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252 | int in_arc, join, u_in, v_in, u_out, v_out; |
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253 | int first, second, right, last; |
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254 | int stem, par_stem, new_stem; |
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255 | Value delta; |
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256 | |
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257 | public: |
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258 | |
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259 | /// \brief Constant for infinite upper bounds (capacities). |
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260 | /// |
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261 | /// Constant for infinite upper bounds (capacities). |
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262 | /// It is \c std::numeric_limits<Value>::infinity() if available, |
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263 | /// \c std::numeric_limits<Value>::max() otherwise. |
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264 | const Value INF; |
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265 | |
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266 | private: |
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267 | |
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268 | // Implementation of the First Eligible pivot rule |
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269 | class FirstEligiblePivotRule |
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270 | { |
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271 | private: |
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272 | |
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273 | // References to the NetworkSimplex class |
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274 | const IntVector &_source; |
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275 | const IntVector &_target; |
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276 | const CostVector &_cost; |
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277 | const IntVector &_state; |
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278 | const CostVector &_pi; |
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279 | int &_in_arc; |
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280 | int _arc_num; |
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281 | |
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282 | // Pivot rule data |
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283 | int _next_arc; |
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284 | |
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285 | public: |
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286 | |
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287 | // Constructor |
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288 | FirstEligiblePivotRule(NetworkSimplex &ns) : |
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289 | _source(ns._source), _target(ns._target), |
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290 | _cost(ns._cost), _state(ns._state), _pi(ns._pi), |
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291 | _in_arc(ns.in_arc), _arc_num(ns._arc_num), _next_arc(0) |
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292 | {} |
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293 | |
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294 | // Find next entering arc |
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295 | bool findEnteringArc() { |
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296 | Cost c; |
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297 | for (int e = _next_arc; e < _arc_num; ++e) { |
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298 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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299 | if (c < 0) { |
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300 | _in_arc = e; |
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301 | _next_arc = e + 1; |
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302 | return true; |
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303 | } |
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304 | } |
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305 | for (int e = 0; e < _next_arc; ++e) { |
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306 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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307 | if (c < 0) { |
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308 | _in_arc = e; |
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309 | _next_arc = e + 1; |
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310 | return true; |
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311 | } |
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312 | } |
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313 | return false; |
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314 | } |
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315 | |
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316 | }; //class FirstEligiblePivotRule |
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317 | |
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318 | |
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319 | // Implementation of the Best Eligible pivot rule |
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320 | class BestEligiblePivotRule |
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321 | { |
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322 | private: |
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323 | |
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324 | // References to the NetworkSimplex class |
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325 | const IntVector &_source; |
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326 | const IntVector &_target; |
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327 | const CostVector &_cost; |
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328 | const IntVector &_state; |
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329 | const CostVector &_pi; |
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330 | int &_in_arc; |
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331 | int _arc_num; |
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332 | |
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333 | public: |
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334 | |
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335 | // Constructor |
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336 | BestEligiblePivotRule(NetworkSimplex &ns) : |
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337 | _source(ns._source), _target(ns._target), |
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338 | _cost(ns._cost), _state(ns._state), _pi(ns._pi), |
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339 | _in_arc(ns.in_arc), _arc_num(ns._arc_num) |
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340 | {} |
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341 | |
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342 | // Find next entering arc |
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343 | bool findEnteringArc() { |
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344 | Cost c, min = 0; |
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345 | for (int e = 0; e < _arc_num; ++e) { |
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346 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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347 | if (c < min) { |
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348 | min = c; |
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349 | _in_arc = e; |
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350 | } |
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351 | } |
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352 | return min < 0; |
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353 | } |
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354 | |
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355 | }; //class BestEligiblePivotRule |
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356 | |
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357 | |
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358 | // Implementation of the Block Search pivot rule |
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359 | class BlockSearchPivotRule |
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360 | { |
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361 | private: |
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362 | |
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363 | // References to the NetworkSimplex class |
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364 | const IntVector &_source; |
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365 | const IntVector &_target; |
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366 | const CostVector &_cost; |
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367 | const IntVector &_state; |
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368 | const CostVector &_pi; |
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369 | int &_in_arc; |
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370 | int _arc_num; |
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371 | |
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372 | // Pivot rule data |
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373 | int _block_size; |
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374 | int _next_arc; |
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375 | |
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376 | public: |
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377 | |
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378 | // Constructor |
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379 | BlockSearchPivotRule(NetworkSimplex &ns) : |
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380 | _source(ns._source), _target(ns._target), |
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381 | _cost(ns._cost), _state(ns._state), _pi(ns._pi), |
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382 | _in_arc(ns.in_arc), _arc_num(ns._arc_num), _next_arc(0) |
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383 | { |
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384 | // The main parameters of the pivot rule |
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385 | const double BLOCK_SIZE_FACTOR = 2.0; |
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386 | const int MIN_BLOCK_SIZE = 10; |
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387 | |
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388 | _block_size = std::max( int(BLOCK_SIZE_FACTOR * |
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389 | std::sqrt(double(_arc_num))), |
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390 | MIN_BLOCK_SIZE ); |
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391 | } |
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392 | |
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393 | // Find next entering arc |
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394 | bool findEnteringArc() { |
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395 | Cost c, min = 0; |
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396 | int cnt = _block_size; |
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397 | int e, min_arc = _next_arc; |
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398 | for (e = _next_arc; e < _arc_num; ++e) { |
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399 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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400 | if (c < min) { |
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401 | min = c; |
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402 | min_arc = e; |
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403 | } |
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404 | if (--cnt == 0) { |
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405 | if (min < 0) break; |
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406 | cnt = _block_size; |
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407 | } |
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408 | } |
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409 | if (min == 0 || cnt > 0) { |
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410 | for (e = 0; e < _next_arc; ++e) { |
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411 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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412 | if (c < min) { |
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413 | min = c; |
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414 | min_arc = e; |
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415 | } |
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416 | if (--cnt == 0) { |
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417 | if (min < 0) break; |
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418 | cnt = _block_size; |
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419 | } |
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420 | } |
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421 | } |
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422 | if (min >= 0) return false; |
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423 | _in_arc = min_arc; |
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424 | _next_arc = e; |
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425 | return true; |
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426 | } |
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427 | |
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428 | }; //class BlockSearchPivotRule |
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429 | |
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430 | |
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431 | // Implementation of the Candidate List pivot rule |
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432 | class CandidateListPivotRule |
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433 | { |
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434 | private: |
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435 | |
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436 | // References to the NetworkSimplex class |
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437 | const IntVector &_source; |
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438 | const IntVector &_target; |
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439 | const CostVector &_cost; |
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440 | const IntVector &_state; |
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441 | const CostVector &_pi; |
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442 | int &_in_arc; |
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443 | int _arc_num; |
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444 | |
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445 | // Pivot rule data |
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446 | IntVector _candidates; |
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447 | int _list_length, _minor_limit; |
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448 | int _curr_length, _minor_count; |
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449 | int _next_arc; |
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450 | |
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451 | public: |
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452 | |
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453 | /// Constructor |
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454 | CandidateListPivotRule(NetworkSimplex &ns) : |
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455 | _source(ns._source), _target(ns._target), |
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456 | _cost(ns._cost), _state(ns._state), _pi(ns._pi), |
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457 | _in_arc(ns.in_arc), _arc_num(ns._arc_num), _next_arc(0) |
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458 | { |
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459 | // The main parameters of the pivot rule |
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460 | const double LIST_LENGTH_FACTOR = 1.0; |
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461 | const int MIN_LIST_LENGTH = 10; |
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462 | const double MINOR_LIMIT_FACTOR = 0.1; |
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463 | const int MIN_MINOR_LIMIT = 3; |
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464 | |
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465 | _list_length = std::max( int(LIST_LENGTH_FACTOR * |
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466 | std::sqrt(double(_arc_num))), |
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467 | MIN_LIST_LENGTH ); |
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468 | _minor_limit = std::max( int(MINOR_LIMIT_FACTOR * _list_length), |
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469 | MIN_MINOR_LIMIT ); |
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470 | _curr_length = _minor_count = 0; |
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471 | _candidates.resize(_list_length); |
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472 | } |
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473 | |
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474 | /// Find next entering arc |
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475 | bool findEnteringArc() { |
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476 | Cost min, c; |
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477 | int e, min_arc = _next_arc; |
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478 | if (_curr_length > 0 && _minor_count < _minor_limit) { |
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479 | // Minor iteration: select the best eligible arc from the |
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480 | // current candidate list |
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481 | ++_minor_count; |
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482 | min = 0; |
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483 | for (int i = 0; i < _curr_length; ++i) { |
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484 | e = _candidates[i]; |
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485 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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486 | if (c < min) { |
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487 | min = c; |
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488 | min_arc = e; |
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489 | } |
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490 | if (c >= 0) { |
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491 | _candidates[i--] = _candidates[--_curr_length]; |
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492 | } |
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493 | } |
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494 | if (min < 0) { |
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495 | _in_arc = min_arc; |
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496 | return true; |
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497 | } |
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498 | } |
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499 | |
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500 | // Major iteration: build a new candidate list |
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501 | min = 0; |
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502 | _curr_length = 0; |
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503 | for (e = _next_arc; e < _arc_num; ++e) { |
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504 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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505 | if (c < 0) { |
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506 | _candidates[_curr_length++] = e; |
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507 | if (c < min) { |
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508 | min = c; |
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509 | min_arc = e; |
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510 | } |
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511 | if (_curr_length == _list_length) break; |
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512 | } |
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513 | } |
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514 | if (_curr_length < _list_length) { |
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515 | for (e = 0; e < _next_arc; ++e) { |
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516 | c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
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517 | if (c < 0) { |
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518 | _candidates[_curr_length++] = e; |
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519 | if (c < min) { |
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520 | min = c; |
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521 | min_arc = e; |
---|
522 | } |
---|
523 | if (_curr_length == _list_length) break; |
---|
524 | } |
---|
525 | } |
---|
526 | } |
---|
527 | if (_curr_length == 0) return false; |
---|
528 | _minor_count = 1; |
---|
529 | _in_arc = min_arc; |
---|
530 | _next_arc = e; |
---|
531 | return true; |
---|
532 | } |
---|
533 | |
---|
534 | }; //class CandidateListPivotRule |
---|
535 | |
---|
536 | |
---|
537 | // Implementation of the Altering Candidate List pivot rule |
---|
538 | class AlteringListPivotRule |
---|
539 | { |
---|
540 | private: |
---|
541 | |
---|
542 | // References to the NetworkSimplex class |
---|
543 | const IntVector &_source; |
---|
544 | const IntVector &_target; |
---|
545 | const CostVector &_cost; |
---|
546 | const IntVector &_state; |
---|
547 | const CostVector &_pi; |
---|
548 | int &_in_arc; |
---|
549 | int _arc_num; |
---|
550 | |
---|
551 | // Pivot rule data |
---|
552 | int _block_size, _head_length, _curr_length; |
---|
553 | int _next_arc; |
---|
554 | IntVector _candidates; |
---|
555 | CostVector _cand_cost; |
---|
556 | |
---|
557 | // Functor class to compare arcs during sort of the candidate list |
---|
558 | class SortFunc |
---|
559 | { |
---|
560 | private: |
---|
561 | const CostVector &_map; |
---|
562 | public: |
---|
563 | SortFunc(const CostVector &map) : _map(map) {} |
---|
564 | bool operator()(int left, int right) { |
---|
565 | return _map[left] > _map[right]; |
---|
566 | } |
---|
567 | }; |
---|
568 | |
---|
569 | SortFunc _sort_func; |
---|
570 | |
---|
571 | public: |
---|
572 | |
---|
573 | // Constructor |
---|
574 | AlteringListPivotRule(NetworkSimplex &ns) : |
---|
575 | _source(ns._source), _target(ns._target), |
---|
576 | _cost(ns._cost), _state(ns._state), _pi(ns._pi), |
---|
577 | _in_arc(ns.in_arc), _arc_num(ns._arc_num), |
---|
578 | _next_arc(0), _cand_cost(ns._arc_num), _sort_func(_cand_cost) |
---|
579 | { |
---|
580 | // The main parameters of the pivot rule |
---|
581 | const double BLOCK_SIZE_FACTOR = 1.5; |
---|
582 | const int MIN_BLOCK_SIZE = 10; |
---|
583 | const double HEAD_LENGTH_FACTOR = 0.1; |
---|
584 | const int MIN_HEAD_LENGTH = 3; |
---|
585 | |
---|
586 | _block_size = std::max( int(BLOCK_SIZE_FACTOR * |
---|
587 | std::sqrt(double(_arc_num))), |
---|
588 | MIN_BLOCK_SIZE ); |
---|
589 | _head_length = std::max( int(HEAD_LENGTH_FACTOR * _block_size), |
---|
590 | MIN_HEAD_LENGTH ); |
---|
591 | _candidates.resize(_head_length + _block_size); |
---|
592 | _curr_length = 0; |
---|
593 | } |
---|
594 | |
---|
595 | // Find next entering arc |
---|
596 | bool findEnteringArc() { |
---|
597 | // Check the current candidate list |
---|
598 | int e; |
---|
599 | for (int i = 0; i < _curr_length; ++i) { |
---|
600 | e = _candidates[i]; |
---|
601 | _cand_cost[e] = _state[e] * |
---|
602 | (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
---|
603 | if (_cand_cost[e] >= 0) { |
---|
604 | _candidates[i--] = _candidates[--_curr_length]; |
---|
605 | } |
---|
606 | } |
---|
607 | |
---|
608 | // Extend the list |
---|
609 | int cnt = _block_size; |
---|
610 | int last_arc = 0; |
---|
611 | int limit = _head_length; |
---|
612 | |
---|
613 | for (int e = _next_arc; e < _arc_num; ++e) { |
---|
614 | _cand_cost[e] = _state[e] * |
---|
615 | (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
---|
616 | if (_cand_cost[e] < 0) { |
---|
617 | _candidates[_curr_length++] = e; |
---|
618 | last_arc = e; |
---|
619 | } |
---|
620 | if (--cnt == 0) { |
---|
621 | if (_curr_length > limit) break; |
---|
622 | limit = 0; |
---|
623 | cnt = _block_size; |
---|
624 | } |
---|
625 | } |
---|
626 | if (_curr_length <= limit) { |
---|
627 | for (int e = 0; e < _next_arc; ++e) { |
---|
628 | _cand_cost[e] = _state[e] * |
---|
629 | (_cost[e] + _pi[_source[e]] - _pi[_target[e]]); |
---|
630 | if (_cand_cost[e] < 0) { |
---|
631 | _candidates[_curr_length++] = e; |
---|
632 | last_arc = e; |
---|
633 | } |
---|
634 | if (--cnt == 0) { |
---|
635 | if (_curr_length > limit) break; |
---|
636 | limit = 0; |
---|
637 | cnt = _block_size; |
---|
638 | } |
---|
639 | } |
---|
640 | } |
---|
641 | if (_curr_length == 0) return false; |
---|
642 | _next_arc = last_arc + 1; |
---|
643 | |
---|
644 | // Make heap of the candidate list (approximating a partial sort) |
---|
645 | make_heap( _candidates.begin(), _candidates.begin() + _curr_length, |
---|
646 | _sort_func ); |
---|
647 | |
---|
648 | // Pop the first element of the heap |
---|
649 | _in_arc = _candidates[0]; |
---|
650 | pop_heap( _candidates.begin(), _candidates.begin() + _curr_length, |
---|
651 | _sort_func ); |
---|
652 | _curr_length = std::min(_head_length, _curr_length - 1); |
---|
653 | return true; |
---|
654 | } |
---|
655 | |
---|
656 | }; //class AlteringListPivotRule |
---|
657 | |
---|
658 | public: |
---|
659 | |
---|
660 | /// \brief Constructor. |
---|
661 | /// |
---|
662 | /// The constructor of the class. |
---|
663 | /// |
---|
664 | /// \param graph The digraph the algorithm runs on. |
---|
665 | NetworkSimplex(const GR& graph) : |
---|
666 | _graph(graph), _node_id(graph), _arc_id(graph), |
---|
667 | INF(std::numeric_limits<Value>::has_infinity ? |
---|
668 | std::numeric_limits<Value>::infinity() : |
---|
669 | std::numeric_limits<Value>::max()) |
---|
670 | { |
---|
671 | // Check the value types |
---|
672 | LEMON_ASSERT(std::numeric_limits<Value>::is_signed, |
---|
673 | "The flow type of NetworkSimplex must be signed"); |
---|
674 | LEMON_ASSERT(std::numeric_limits<Cost>::is_signed, |
---|
675 | "The cost type of NetworkSimplex must be signed"); |
---|
676 | |
---|
677 | // Resize vectors |
---|
678 | _node_num = countNodes(_graph); |
---|
679 | _arc_num = countArcs(_graph); |
---|
680 | int all_node_num = _node_num + 1; |
---|
681 | int all_arc_num = _arc_num + _node_num; |
---|
682 | |
---|
683 | _source.resize(all_arc_num); |
---|
684 | _target.resize(all_arc_num); |
---|
685 | |
---|
686 | _lower.resize(all_arc_num); |
---|
687 | _upper.resize(all_arc_num); |
---|
688 | _cap.resize(all_arc_num); |
---|
689 | _cost.resize(all_arc_num); |
---|
690 | _supply.resize(all_node_num); |
---|
691 | _flow.resize(all_arc_num); |
---|
692 | _pi.resize(all_node_num); |
---|
693 | |
---|
694 | _parent.resize(all_node_num); |
---|
695 | _pred.resize(all_node_num); |
---|
696 | _forward.resize(all_node_num); |
---|
697 | _thread.resize(all_node_num); |
---|
698 | _rev_thread.resize(all_node_num); |
---|
699 | _succ_num.resize(all_node_num); |
---|
700 | _last_succ.resize(all_node_num); |
---|
701 | _state.resize(all_arc_num); |
---|
702 | |
---|
703 | // Copy the graph (store the arcs in a mixed order) |
---|
704 | int i = 0; |
---|
705 | for (NodeIt n(_graph); n != INVALID; ++n, ++i) { |
---|
706 | _node_id[n] = i; |
---|
707 | } |
---|
708 | int k = std::max(int(std::sqrt(double(_arc_num))), 10); |
---|
709 | i = 0; |
---|
710 | for (ArcIt a(_graph); a != INVALID; ++a) { |
---|
711 | _arc_id[a] = i; |
---|
712 | _source[i] = _node_id[_graph.source(a)]; |
---|
713 | _target[i] = _node_id[_graph.target(a)]; |
---|
714 | if ((i += k) >= _arc_num) i = (i % k) + 1; |
---|
715 | } |
---|
716 | |
---|
717 | // Initialize maps |
---|
718 | for (int i = 0; i != _node_num; ++i) { |
---|
719 | _supply[i] = 0; |
---|
720 | } |
---|
721 | for (int i = 0; i != _arc_num; ++i) { |
---|
722 | _lower[i] = 0; |
---|
723 | _upper[i] = INF; |
---|
724 | _cost[i] = 1; |
---|
725 | } |
---|
726 | _have_lower = false; |
---|
727 | _stype = GEQ; |
---|
728 | } |
---|
729 | |
---|
730 | /// \name Parameters |
---|
731 | /// The parameters of the algorithm can be specified using these |
---|
732 | /// functions. |
---|
733 | |
---|
734 | /// @{ |
---|
735 | |
---|
736 | /// \brief Set the lower bounds on the arcs. |
---|
737 | /// |
---|
738 | /// This function sets the lower bounds on the arcs. |
---|
739 | /// If it is not used before calling \ref run(), the lower bounds |
---|
740 | /// will be set to zero on all arcs. |
---|
741 | /// |
---|
742 | /// \param map An arc map storing the lower bounds. |
---|
743 | /// Its \c Value type must be convertible to the \c Value type |
---|
744 | /// of the algorithm. |
---|
745 | /// |
---|
746 | /// \return <tt>(*this)</tt> |
---|
747 | template <typename LowerMap> |
---|
748 | NetworkSimplex& lowerMap(const LowerMap& map) { |
---|
749 | _have_lower = true; |
---|
750 | for (ArcIt a(_graph); a != INVALID; ++a) { |
---|
751 | _lower[_arc_id[a]] = map[a]; |
---|
752 | } |
---|
753 | return *this; |
---|
754 | } |
---|
755 | |
---|
756 | /// \brief Set the upper bounds (capacities) on the arcs. |
---|
757 | /// |
---|
758 | /// This function sets the upper bounds (capacities) on the arcs. |
---|
759 | /// If it is not used before calling \ref run(), the upper bounds |
---|
760 | /// will be set to \ref INF on all arcs (i.e. the flow value will be |
---|
761 | /// unbounded from above on each arc). |
---|
762 | /// |
---|
763 | /// \param map An arc map storing the upper bounds. |
---|
764 | /// Its \c Value type must be convertible to the \c Value type |
---|
765 | /// of the algorithm. |
---|
766 | /// |
---|
767 | /// \return <tt>(*this)</tt> |
---|
768 | template<typename UpperMap> |
---|
769 | NetworkSimplex& upperMap(const UpperMap& map) { |
---|
770 | for (ArcIt a(_graph); a != INVALID; ++a) { |
---|
771 | _upper[_arc_id[a]] = map[a]; |
---|
772 | } |
---|
773 | return *this; |
---|
774 | } |
---|
775 | |
---|
776 | /// \brief Set the costs of the arcs. |
---|
777 | /// |
---|
778 | /// This function sets the costs of the arcs. |
---|
779 | /// If it is not used before calling \ref run(), the costs |
---|
780 | /// will be set to \c 1 on all arcs. |
---|
781 | /// |
---|
782 | /// \param map An arc map storing the costs. |
---|
783 | /// Its \c Value type must be convertible to the \c Cost type |
---|
784 | /// of the algorithm. |
---|
785 | /// |
---|
786 | /// \return <tt>(*this)</tt> |
---|
787 | template<typename CostMap> |
---|
788 | NetworkSimplex& costMap(const CostMap& map) { |
---|
789 | for (ArcIt a(_graph); a != INVALID; ++a) { |
---|
790 | _cost[_arc_id[a]] = map[a]; |
---|
791 | } |
---|
792 | return *this; |
---|
793 | } |
---|
794 | |
---|
795 | /// \brief Set the supply values of the nodes. |
---|
796 | /// |
---|
797 | /// This function sets the supply values of the nodes. |
---|
798 | /// If neither this function nor \ref stSupply() is used before |
---|
799 | /// calling \ref run(), the supply of each node will be set to zero. |
---|
800 | /// (It makes sense only if non-zero lower bounds are given.) |
---|
801 | /// |
---|
802 | /// \param map A node map storing the supply values. |
---|
803 | /// Its \c Value type must be convertible to the \c Value type |
---|
804 | /// of the algorithm. |
---|
805 | /// |
---|
806 | /// \return <tt>(*this)</tt> |
---|
807 | template<typename SupplyMap> |
---|
808 | NetworkSimplex& supplyMap(const SupplyMap& map) { |
---|
809 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
810 | _supply[_node_id[n]] = map[n]; |
---|
811 | } |
---|
812 | return *this; |
---|
813 | } |
---|
814 | |
---|
815 | /// \brief Set single source and target nodes and a supply value. |
---|
816 | /// |
---|
817 | /// This function sets a single source node and a single target node |
---|
818 | /// and the required flow value. |
---|
819 | /// If neither this function nor \ref supplyMap() is used before |
---|
820 | /// calling \ref run(), the supply of each node will be set to zero. |
---|
821 | /// (It makes sense only if non-zero lower bounds are given.) |
---|
822 | /// |
---|
823 | /// Using this function has the same effect as using \ref supplyMap() |
---|
824 | /// with such a map in which \c k is assigned to \c s, \c -k is |
---|
825 | /// assigned to \c t and all other nodes have zero supply value. |
---|
826 | /// |
---|
827 | /// \param s The source node. |
---|
828 | /// \param t The target node. |
---|
829 | /// \param k The required amount of flow from node \c s to node \c t |
---|
830 | /// (i.e. the supply of \c s and the demand of \c t). |
---|
831 | /// |
---|
832 | /// \return <tt>(*this)</tt> |
---|
833 | NetworkSimplex& stSupply(const Node& s, const Node& t, Value k) { |
---|
834 | for (int i = 0; i != _node_num; ++i) { |
---|
835 | _supply[i] = 0; |
---|
836 | } |
---|
837 | _supply[_node_id[s]] = k; |
---|
838 | _supply[_node_id[t]] = -k; |
---|
839 | return *this; |
---|
840 | } |
---|
841 | |
---|
842 | /// \brief Set the type of the supply constraints. |
---|
843 | /// |
---|
844 | /// This function sets the type of the supply/demand constraints. |
---|
845 | /// If it is not used before calling \ref run(), the \ref GEQ supply |
---|
846 | /// type will be used. |
---|
847 | /// |
---|
848 | /// For more information see \ref SupplyType. |
---|
849 | /// |
---|
850 | /// \return <tt>(*this)</tt> |
---|
851 | NetworkSimplex& supplyType(SupplyType supply_type) { |
---|
852 | _stype = supply_type; |
---|
853 | return *this; |
---|
854 | } |
---|
855 | |
---|
856 | /// @} |
---|
857 | |
---|
858 | /// \name Execution Control |
---|
859 | /// The algorithm can be executed using \ref run(). |
---|
860 | |
---|
861 | /// @{ |
---|
862 | |
---|
863 | /// \brief Run the algorithm. |
---|
864 | /// |
---|
865 | /// This function runs the algorithm. |
---|
866 | /// The paramters can be specified using functions \ref lowerMap(), |
---|
867 | /// \ref upperMap(), \ref costMap(), \ref supplyMap(), \ref stSupply(), |
---|
868 | /// \ref supplyType(). |
---|
869 | /// For example, |
---|
870 | /// \code |
---|
871 | /// NetworkSimplex<ListDigraph> ns(graph); |
---|
872 | /// ns.lowerMap(lower).upperMap(upper).costMap(cost) |
---|
873 | /// .supplyMap(sup).run(); |
---|
874 | /// \endcode |
---|
875 | /// |
---|
876 | /// This function can be called more than once. All the parameters |
---|
877 | /// that have been given are kept for the next call, unless |
---|
878 | /// \ref reset() is called, thus only the modified parameters |
---|
879 | /// have to be set again. See \ref reset() for examples. |
---|
880 | /// However the underlying digraph must not be modified after this |
---|
881 | /// class have been constructed, since it copies and extends the graph. |
---|
882 | /// |
---|
883 | /// \param pivot_rule The pivot rule that will be used during the |
---|
884 | /// algorithm. For more information see \ref PivotRule. |
---|
885 | /// |
---|
886 | /// \return \c INFEASIBLE if no feasible flow exists, |
---|
887 | /// \n \c OPTIMAL if the problem has optimal solution |
---|
888 | /// (i.e. it is feasible and bounded), and the algorithm has found |
---|
889 | /// optimal flow and node potentials (primal and dual solutions), |
---|
890 | /// \n \c UNBOUNDED if the objective function of the problem is |
---|
891 | /// unbounded, i.e. there is a directed cycle having negative total |
---|
892 | /// cost and infinite upper bound. |
---|
893 | /// |
---|
894 | /// \see ProblemType, PivotRule |
---|
895 | ProblemType run(PivotRule pivot_rule = BLOCK_SEARCH) { |
---|
896 | if (!init()) return INFEASIBLE; |
---|
897 | return start(pivot_rule); |
---|
898 | } |
---|
899 | |
---|
900 | /// \brief Reset all the parameters that have been given before. |
---|
901 | /// |
---|
902 | /// This function resets all the paramaters that have been given |
---|
903 | /// before using functions \ref lowerMap(), \ref upperMap(), |
---|
904 | /// \ref costMap(), \ref supplyMap(), \ref stSupply(), \ref supplyType(). |
---|
905 | /// |
---|
906 | /// It is useful for multiple run() calls. If this function is not |
---|
907 | /// used, all the parameters given before are kept for the next |
---|
908 | /// \ref run() call. |
---|
909 | /// However the underlying digraph must not be modified after this |
---|
910 | /// class have been constructed, since it copies and extends the graph. |
---|
911 | /// |
---|
912 | /// For example, |
---|
913 | /// \code |
---|
914 | /// NetworkSimplex<ListDigraph> ns(graph); |
---|
915 | /// |
---|
916 | /// // First run |
---|
917 | /// ns.lowerMap(lower).upperMap(upper).costMap(cost) |
---|
918 | /// .supplyMap(sup).run(); |
---|
919 | /// |
---|
920 | /// // Run again with modified cost map (reset() is not called, |
---|
921 | /// // so only the cost map have to be set again) |
---|
922 | /// cost[e] += 100; |
---|
923 | /// ns.costMap(cost).run(); |
---|
924 | /// |
---|
925 | /// // Run again from scratch using reset() |
---|
926 | /// // (the lower bounds will be set to zero on all arcs) |
---|
927 | /// ns.reset(); |
---|
928 | /// ns.upperMap(capacity).costMap(cost) |
---|
929 | /// .supplyMap(sup).run(); |
---|
930 | /// \endcode |
---|
931 | /// |
---|
932 | /// \return <tt>(*this)</tt> |
---|
933 | NetworkSimplex& reset() { |
---|
934 | for (int i = 0; i != _node_num; ++i) { |
---|
935 | _supply[i] = 0; |
---|
936 | } |
---|
937 | for (int i = 0; i != _arc_num; ++i) { |
---|
938 | _lower[i] = 0; |
---|
939 | _upper[i] = INF; |
---|
940 | _cost[i] = 1; |
---|
941 | } |
---|
942 | _have_lower = false; |
---|
943 | _stype = GEQ; |
---|
944 | return *this; |
---|
945 | } |
---|
946 | |
---|
947 | /// @} |
---|
948 | |
---|
949 | /// \name Query Functions |
---|
950 | /// The results of the algorithm can be obtained using these |
---|
951 | /// functions.\n |
---|
952 | /// The \ref run() function must be called before using them. |
---|
953 | |
---|
954 | /// @{ |
---|
955 | |
---|
956 | /// \brief Return the total cost of the found flow. |
---|
957 | /// |
---|
958 | /// This function returns the total cost of the found flow. |
---|
959 | /// Its complexity is O(e). |
---|
960 | /// |
---|
961 | /// \note The return type of the function can be specified as a |
---|
962 | /// template parameter. For example, |
---|
963 | /// \code |
---|
964 | /// ns.totalCost<double>(); |
---|
965 | /// \endcode |
---|
966 | /// It is useful if the total cost cannot be stored in the \c Cost |
---|
967 | /// type of the algorithm, which is the default return type of the |
---|
968 | /// function. |
---|
969 | /// |
---|
970 | /// \pre \ref run() must be called before using this function. |
---|
971 | template <typename Number> |
---|
972 | Number totalCost() const { |
---|
973 | Number c = 0; |
---|
974 | for (ArcIt a(_graph); a != INVALID; ++a) { |
---|
975 | int i = _arc_id[a]; |
---|
976 | c += Number(_flow[i]) * Number(_cost[i]); |
---|
977 | } |
---|
978 | return c; |
---|
979 | } |
---|
980 | |
---|
981 | #ifndef DOXYGEN |
---|
982 | Cost totalCost() const { |
---|
983 | return totalCost<Cost>(); |
---|
984 | } |
---|
985 | #endif |
---|
986 | |
---|
987 | /// \brief Return the flow on the given arc. |
---|
988 | /// |
---|
989 | /// This function returns the flow on the given arc. |
---|
990 | /// |
---|
991 | /// \pre \ref run() must be called before using this function. |
---|
992 | Value flow(const Arc& a) const { |
---|
993 | return _flow[_arc_id[a]]; |
---|
994 | } |
---|
995 | |
---|
996 | /// \brief Return the flow map (the primal solution). |
---|
997 | /// |
---|
998 | /// This function copies the flow value on each arc into the given |
---|
999 | /// map. The \c Value type of the algorithm must be convertible to |
---|
1000 | /// the \c Value type of the map. |
---|
1001 | /// |
---|
1002 | /// \pre \ref run() must be called before using this function. |
---|
1003 | template <typename FlowMap> |
---|
1004 | void flowMap(FlowMap &map) const { |
---|
1005 | for (ArcIt a(_graph); a != INVALID; ++a) { |
---|
1006 | map.set(a, _flow[_arc_id[a]]); |
---|
1007 | } |
---|
1008 | } |
---|
1009 | |
---|
1010 | /// \brief Return the potential (dual value) of the given node. |
---|
1011 | /// |
---|
1012 | /// This function returns the potential (dual value) of the |
---|
1013 | /// given node. |
---|
1014 | /// |
---|
1015 | /// \pre \ref run() must be called before using this function. |
---|
1016 | Cost potential(const Node& n) const { |
---|
1017 | return _pi[_node_id[n]]; |
---|
1018 | } |
---|
1019 | |
---|
1020 | /// \brief Return the potential map (the dual solution). |
---|
1021 | /// |
---|
1022 | /// This function copies the potential (dual value) of each node |
---|
1023 | /// into the given map. |
---|
1024 | /// The \c Cost type of the algorithm must be convertible to the |
---|
1025 | /// \c Value type of the map. |
---|
1026 | /// |
---|
1027 | /// \pre \ref run() must be called before using this function. |
---|
1028 | template <typename PotentialMap> |
---|
1029 | void potentialMap(PotentialMap &map) const { |
---|
1030 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
1031 | map.set(n, _pi[_node_id[n]]); |
---|
1032 | } |
---|
1033 | } |
---|
1034 | |
---|
1035 | /// @} |
---|
1036 | |
---|
1037 | private: |
---|
1038 | |
---|
1039 | // Initialize internal data structures |
---|
1040 | bool init() { |
---|
1041 | if (_node_num == 0) return false; |
---|
1042 | |
---|
1043 | // Check the sum of supply values |
---|
1044 | _sum_supply = 0; |
---|
1045 | for (int i = 0; i != _node_num; ++i) { |
---|
1046 | _sum_supply += _supply[i]; |
---|
1047 | } |
---|
1048 | if ( !(_stype == GEQ && _sum_supply <= 0 || |
---|
1049 | _stype == LEQ && _sum_supply >= 0) ) return false; |
---|
1050 | |
---|
1051 | // Remove non-zero lower bounds |
---|
1052 | if (_have_lower) { |
---|
1053 | for (int i = 0; i != _arc_num; ++i) { |
---|
1054 | Value c = _lower[i]; |
---|
1055 | if (c >= 0) { |
---|
1056 | _cap[i] = _upper[i] < INF ? _upper[i] - c : INF; |
---|
1057 | } else { |
---|
1058 | _cap[i] = _upper[i] < INF + c ? _upper[i] - c : INF; |
---|
1059 | } |
---|
1060 | _supply[_source[i]] -= c; |
---|
1061 | _supply[_target[i]] += c; |
---|
1062 | } |
---|
1063 | } else { |
---|
1064 | for (int i = 0; i != _arc_num; ++i) { |
---|
1065 | _cap[i] = _upper[i]; |
---|
1066 | } |
---|
1067 | } |
---|
1068 | |
---|
1069 | // Initialize artifical cost |
---|
1070 | Cost ART_COST; |
---|
1071 | if (std::numeric_limits<Cost>::is_exact) { |
---|
1072 | ART_COST = std::numeric_limits<Cost>::max() / 4 + 1; |
---|
1073 | } else { |
---|
1074 | ART_COST = std::numeric_limits<Cost>::min(); |
---|
1075 | for (int i = 0; i != _arc_num; ++i) { |
---|
1076 | if (_cost[i] > ART_COST) ART_COST = _cost[i]; |
---|
1077 | } |
---|
1078 | ART_COST = (ART_COST + 1) * _node_num; |
---|
1079 | } |
---|
1080 | |
---|
1081 | // Initialize arc maps |
---|
1082 | for (int i = 0; i != _arc_num; ++i) { |
---|
1083 | _flow[i] = 0; |
---|
1084 | _state[i] = STATE_LOWER; |
---|
1085 | } |
---|
1086 | |
---|
1087 | // Set data for the artificial root node |
---|
1088 | _root = _node_num; |
---|
1089 | _parent[_root] = -1; |
---|
1090 | _pred[_root] = -1; |
---|
1091 | _thread[_root] = 0; |
---|
1092 | _rev_thread[0] = _root; |
---|
1093 | _succ_num[_root] = _node_num + 1; |
---|
1094 | _last_succ[_root] = _root - 1; |
---|
1095 | _supply[_root] = -_sum_supply; |
---|
1096 | _pi[_root] = _sum_supply < 0 ? -ART_COST : ART_COST; |
---|
1097 | |
---|
1098 | // Add artificial arcs and initialize the spanning tree data structure |
---|
1099 | for (int u = 0, e = _arc_num; u != _node_num; ++u, ++e) { |
---|
1100 | _parent[u] = _root; |
---|
1101 | _pred[u] = e; |
---|
1102 | _thread[u] = u + 1; |
---|
1103 | _rev_thread[u + 1] = u; |
---|
1104 | _succ_num[u] = 1; |
---|
1105 | _last_succ[u] = u; |
---|
1106 | _cost[e] = ART_COST; |
---|
1107 | _cap[e] = INF; |
---|
1108 | _state[e] = STATE_TREE; |
---|
1109 | if (_supply[u] > 0 || (_supply[u] == 0 && _sum_supply <= 0)) { |
---|
1110 | _flow[e] = _supply[u]; |
---|
1111 | _forward[u] = true; |
---|
1112 | _pi[u] = -ART_COST + _pi[_root]; |
---|
1113 | } else { |
---|
1114 | _flow[e] = -_supply[u]; |
---|
1115 | _forward[u] = false; |
---|
1116 | _pi[u] = ART_COST + _pi[_root]; |
---|
1117 | } |
---|
1118 | } |
---|
1119 | |
---|
1120 | return true; |
---|
1121 | } |
---|
1122 | |
---|
1123 | // Find the join node |
---|
1124 | void findJoinNode() { |
---|
1125 | int u = _source[in_arc]; |
---|
1126 | int v = _target[in_arc]; |
---|
1127 | while (u != v) { |
---|
1128 | if (_succ_num[u] < _succ_num[v]) { |
---|
1129 | u = _parent[u]; |
---|
1130 | } else { |
---|
1131 | v = _parent[v]; |
---|
1132 | } |
---|
1133 | } |
---|
1134 | join = u; |
---|
1135 | } |
---|
1136 | |
---|
1137 | // Find the leaving arc of the cycle and returns true if the |
---|
1138 | // leaving arc is not the same as the entering arc |
---|
1139 | bool findLeavingArc() { |
---|
1140 | // Initialize first and second nodes according to the direction |
---|
1141 | // of the cycle |
---|
1142 | if (_state[in_arc] == STATE_LOWER) { |
---|
1143 | first = _source[in_arc]; |
---|
1144 | second = _target[in_arc]; |
---|
1145 | } else { |
---|
1146 | first = _target[in_arc]; |
---|
1147 | second = _source[in_arc]; |
---|
1148 | } |
---|
1149 | delta = _cap[in_arc]; |
---|
1150 | int result = 0; |
---|
1151 | Value d; |
---|
1152 | int e; |
---|
1153 | |
---|
1154 | // Search the cycle along the path form the first node to the root |
---|
1155 | for (int u = first; u != join; u = _parent[u]) { |
---|
1156 | e = _pred[u]; |
---|
1157 | d = _forward[u] ? |
---|
1158 | _flow[e] : (_cap[e] == INF ? INF : _cap[e] - _flow[e]); |
---|
1159 | if (d < delta) { |
---|
1160 | delta = d; |
---|
1161 | u_out = u; |
---|
1162 | result = 1; |
---|
1163 | } |
---|
1164 | } |
---|
1165 | // Search the cycle along the path form the second node to the root |
---|
1166 | for (int u = second; u != join; u = _parent[u]) { |
---|
1167 | e = _pred[u]; |
---|
1168 | d = _forward[u] ? |
---|
1169 | (_cap[e] == INF ? INF : _cap[e] - _flow[e]) : _flow[e]; |
---|
1170 | if (d <= delta) { |
---|
1171 | delta = d; |
---|
1172 | u_out = u; |
---|
1173 | result = 2; |
---|
1174 | } |
---|
1175 | } |
---|
1176 | |
---|
1177 | if (result == 1) { |
---|
1178 | u_in = first; |
---|
1179 | v_in = second; |
---|
1180 | } else { |
---|
1181 | u_in = second; |
---|
1182 | v_in = first; |
---|
1183 | } |
---|
1184 | return result != 0; |
---|
1185 | } |
---|
1186 | |
---|
1187 | // Change _flow and _state vectors |
---|
1188 | void changeFlow(bool change) { |
---|
1189 | // Augment along the cycle |
---|
1190 | if (delta > 0) { |
---|
1191 | Value val = _state[in_arc] * delta; |
---|
1192 | _flow[in_arc] += val; |
---|
1193 | for (int u = _source[in_arc]; u != join; u = _parent[u]) { |
---|
1194 | _flow[_pred[u]] += _forward[u] ? -val : val; |
---|
1195 | } |
---|
1196 | for (int u = _target[in_arc]; u != join; u = _parent[u]) { |
---|
1197 | _flow[_pred[u]] += _forward[u] ? val : -val; |
---|
1198 | } |
---|
1199 | } |
---|
1200 | // Update the state of the entering and leaving arcs |
---|
1201 | if (change) { |
---|
1202 | _state[in_arc] = STATE_TREE; |
---|
1203 | _state[_pred[u_out]] = |
---|
1204 | (_flow[_pred[u_out]] == 0) ? STATE_LOWER : STATE_UPPER; |
---|
1205 | } else { |
---|
1206 | _state[in_arc] = -_state[in_arc]; |
---|
1207 | } |
---|
1208 | } |
---|
1209 | |
---|
1210 | // Update the tree structure |
---|
1211 | void updateTreeStructure() { |
---|
1212 | int u, w; |
---|
1213 | int old_rev_thread = _rev_thread[u_out]; |
---|
1214 | int old_succ_num = _succ_num[u_out]; |
---|
1215 | int old_last_succ = _last_succ[u_out]; |
---|
1216 | v_out = _parent[u_out]; |
---|
1217 | |
---|
1218 | u = _last_succ[u_in]; // the last successor of u_in |
---|
1219 | right = _thread[u]; // the node after it |
---|
1220 | |
---|
1221 | // Handle the case when old_rev_thread equals to v_in |
---|
1222 | // (it also means that join and v_out coincide) |
---|
1223 | if (old_rev_thread == v_in) { |
---|
1224 | last = _thread[_last_succ[u_out]]; |
---|
1225 | } else { |
---|
1226 | last = _thread[v_in]; |
---|
1227 | } |
---|
1228 | |
---|
1229 | // Update _thread and _parent along the stem nodes (i.e. the nodes |
---|
1230 | // between u_in and u_out, whose parent have to be changed) |
---|
1231 | _thread[v_in] = stem = u_in; |
---|
1232 | _dirty_revs.clear(); |
---|
1233 | _dirty_revs.push_back(v_in); |
---|
1234 | par_stem = v_in; |
---|
1235 | while (stem != u_out) { |
---|
1236 | // Insert the next stem node into the thread list |
---|
1237 | new_stem = _parent[stem]; |
---|
1238 | _thread[u] = new_stem; |
---|
1239 | _dirty_revs.push_back(u); |
---|
1240 | |
---|
1241 | // Remove the subtree of stem from the thread list |
---|
1242 | w = _rev_thread[stem]; |
---|
1243 | _thread[w] = right; |
---|
1244 | _rev_thread[right] = w; |
---|
1245 | |
---|
1246 | // Change the parent node and shift stem nodes |
---|
1247 | _parent[stem] = par_stem; |
---|
1248 | par_stem = stem; |
---|
1249 | stem = new_stem; |
---|
1250 | |
---|
1251 | // Update u and right |
---|
1252 | u = _last_succ[stem] == _last_succ[par_stem] ? |
---|
1253 | _rev_thread[par_stem] : _last_succ[stem]; |
---|
1254 | right = _thread[u]; |
---|
1255 | } |
---|
1256 | _parent[u_out] = par_stem; |
---|
1257 | _thread[u] = last; |
---|
1258 | _rev_thread[last] = u; |
---|
1259 | _last_succ[u_out] = u; |
---|
1260 | |
---|
1261 | // Remove the subtree of u_out from the thread list except for |
---|
1262 | // the case when old_rev_thread equals to v_in |
---|
1263 | // (it also means that join and v_out coincide) |
---|
1264 | if (old_rev_thread != v_in) { |
---|
1265 | _thread[old_rev_thread] = right; |
---|
1266 | _rev_thread[right] = old_rev_thread; |
---|
1267 | } |
---|
1268 | |
---|
1269 | // Update _rev_thread using the new _thread values |
---|
1270 | for (int i = 0; i < int(_dirty_revs.size()); ++i) { |
---|
1271 | u = _dirty_revs[i]; |
---|
1272 | _rev_thread[_thread[u]] = u; |
---|
1273 | } |
---|
1274 | |
---|
1275 | // Update _pred, _forward, _last_succ and _succ_num for the |
---|
1276 | // stem nodes from u_out to u_in |
---|
1277 | int tmp_sc = 0, tmp_ls = _last_succ[u_out]; |
---|
1278 | u = u_out; |
---|
1279 | while (u != u_in) { |
---|
1280 | w = _parent[u]; |
---|
1281 | _pred[u] = _pred[w]; |
---|
1282 | _forward[u] = !_forward[w]; |
---|
1283 | tmp_sc += _succ_num[u] - _succ_num[w]; |
---|
1284 | _succ_num[u] = tmp_sc; |
---|
1285 | _last_succ[w] = tmp_ls; |
---|
1286 | u = w; |
---|
1287 | } |
---|
1288 | _pred[u_in] = in_arc; |
---|
1289 | _forward[u_in] = (u_in == _source[in_arc]); |
---|
1290 | _succ_num[u_in] = old_succ_num; |
---|
1291 | |
---|
1292 | // Set limits for updating _last_succ form v_in and v_out |
---|
1293 | // towards the root |
---|
1294 | int up_limit_in = -1; |
---|
1295 | int up_limit_out = -1; |
---|
1296 | if (_last_succ[join] == v_in) { |
---|
1297 | up_limit_out = join; |
---|
1298 | } else { |
---|
1299 | up_limit_in = join; |
---|
1300 | } |
---|
1301 | |
---|
1302 | // Update _last_succ from v_in towards the root |
---|
1303 | for (u = v_in; u != up_limit_in && _last_succ[u] == v_in; |
---|
1304 | u = _parent[u]) { |
---|
1305 | _last_succ[u] = _last_succ[u_out]; |
---|
1306 | } |
---|
1307 | // Update _last_succ from v_out towards the root |
---|
1308 | if (join != old_rev_thread && v_in != old_rev_thread) { |
---|
1309 | for (u = v_out; u != up_limit_out && _last_succ[u] == old_last_succ; |
---|
1310 | u = _parent[u]) { |
---|
1311 | _last_succ[u] = old_rev_thread; |
---|
1312 | } |
---|
1313 | } else { |
---|
1314 | for (u = v_out; u != up_limit_out && _last_succ[u] == old_last_succ; |
---|
1315 | u = _parent[u]) { |
---|
1316 | _last_succ[u] = _last_succ[u_out]; |
---|
1317 | } |
---|
1318 | } |
---|
1319 | |
---|
1320 | // Update _succ_num from v_in to join |
---|
1321 | for (u = v_in; u != join; u = _parent[u]) { |
---|
1322 | _succ_num[u] += old_succ_num; |
---|
1323 | } |
---|
1324 | // Update _succ_num from v_out to join |
---|
1325 | for (u = v_out; u != join; u = _parent[u]) { |
---|
1326 | _succ_num[u] -= old_succ_num; |
---|
1327 | } |
---|
1328 | } |
---|
1329 | |
---|
1330 | // Update potentials |
---|
1331 | void updatePotential() { |
---|
1332 | Cost sigma = _forward[u_in] ? |
---|
1333 | _pi[v_in] - _pi[u_in] - _cost[_pred[u_in]] : |
---|
1334 | _pi[v_in] - _pi[u_in] + _cost[_pred[u_in]]; |
---|
1335 | // Update potentials in the subtree, which has been moved |
---|
1336 | int end = _thread[_last_succ[u_in]]; |
---|
1337 | for (int u = u_in; u != end; u = _thread[u]) { |
---|
1338 | _pi[u] += sigma; |
---|
1339 | } |
---|
1340 | } |
---|
1341 | |
---|
1342 | // Execute the algorithm |
---|
1343 | ProblemType start(PivotRule pivot_rule) { |
---|
1344 | // Select the pivot rule implementation |
---|
1345 | switch (pivot_rule) { |
---|
1346 | case FIRST_ELIGIBLE: |
---|
1347 | return start<FirstEligiblePivotRule>(); |
---|
1348 | case BEST_ELIGIBLE: |
---|
1349 | return start<BestEligiblePivotRule>(); |
---|
1350 | case BLOCK_SEARCH: |
---|
1351 | return start<BlockSearchPivotRule>(); |
---|
1352 | case CANDIDATE_LIST: |
---|
1353 | return start<CandidateListPivotRule>(); |
---|
1354 | case ALTERING_LIST: |
---|
1355 | return start<AlteringListPivotRule>(); |
---|
1356 | } |
---|
1357 | return INFEASIBLE; // avoid warning |
---|
1358 | } |
---|
1359 | |
---|
1360 | template <typename PivotRuleImpl> |
---|
1361 | ProblemType start() { |
---|
1362 | PivotRuleImpl pivot(*this); |
---|
1363 | |
---|
1364 | // Execute the Network Simplex algorithm |
---|
1365 | while (pivot.findEnteringArc()) { |
---|
1366 | findJoinNode(); |
---|
1367 | bool change = findLeavingArc(); |
---|
1368 | if (delta >= INF) return UNBOUNDED; |
---|
1369 | changeFlow(change); |
---|
1370 | if (change) { |
---|
1371 | updateTreeStructure(); |
---|
1372 | updatePotential(); |
---|
1373 | } |
---|
1374 | } |
---|
1375 | |
---|
1376 | // Check feasibility |
---|
1377 | if (_sum_supply < 0) { |
---|
1378 | for (int u = 0, e = _arc_num; u != _node_num; ++u, ++e) { |
---|
1379 | if (_supply[u] >= 0 && _flow[e] != 0) return INFEASIBLE; |
---|
1380 | } |
---|
1381 | } |
---|
1382 | else if (_sum_supply > 0) { |
---|
1383 | for (int u = 0, e = _arc_num; u != _node_num; ++u, ++e) { |
---|
1384 | if (_supply[u] <= 0 && _flow[e] != 0) return INFEASIBLE; |
---|
1385 | } |
---|
1386 | } |
---|
1387 | else { |
---|
1388 | for (int u = 0, e = _arc_num; u != _node_num; ++u, ++e) { |
---|
1389 | if (_flow[e] != 0) return INFEASIBLE; |
---|
1390 | } |
---|
1391 | } |
---|
1392 | |
---|
1393 | // Transform the solution and the supply map to the original form |
---|
1394 | if (_have_lower) { |
---|
1395 | for (int i = 0; i != _arc_num; ++i) { |
---|
1396 | Value c = _lower[i]; |
---|
1397 | if (c != 0) { |
---|
1398 | _flow[i] += c; |
---|
1399 | _supply[_source[i]] += c; |
---|
1400 | _supply[_target[i]] -= c; |
---|
1401 | } |
---|
1402 | } |
---|
1403 | } |
---|
1404 | |
---|
1405 | return OPTIMAL; |
---|
1406 | } |
---|
1407 | |
---|
1408 | }; //class NetworkSimplex |
---|
1409 | |
---|
1410 | ///@} |
---|
1411 | |
---|
1412 | } //namespace lemon |
---|
1413 | |
---|
1414 | #endif //LEMON_NETWORK_SIMPLEX_H |
---|