1 | #ifndef HUGO_PREFLOW_PUSH_HH |
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2 | #define HUGO_PREFLOW_PUSH_HH |
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3 | |
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4 | //#include <algorithm> |
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5 | #include <list> |
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6 | #include <vector> |
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7 | #include <queue> |
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8 | //#include "pf_hiba.hh" |
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9 | //#include <marci_list_graph.hh> |
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10 | //#include <marci_graph_traits.hh> |
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11 | #include <invalid.h> |
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12 | //#include <reverse_bfs.hh> |
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13 | |
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14 | using namespace std; |
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15 | |
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16 | namespace hugo { |
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17 | |
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18 | template <typename Graph, typename T> |
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19 | class preflow_push { |
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20 | |
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21 | //Useful typedefs |
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22 | typedef typename Graph::Node Node; |
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23 | typedef typename Graph::NodeIt NodeIt; |
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24 | typedef typename Graph::Edge Edge; |
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25 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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26 | typedef typename Graph::InEdgeIt InEdgeIt; |
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27 | |
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28 | |
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29 | //--------------------------------------------- |
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30 | //Parameters of the algorithm |
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31 | //--------------------------------------------- |
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32 | //Fully examine an active node until excess becomes 0 |
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33 | enum node_examination_t {examine_full, examine_to_relabel}; |
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34 | //No more implemented yet:, examine_only_one_edge}; |
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35 | node_examination_t node_examination; |
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36 | //Which implementation to be used |
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37 | enum implementation_t {impl_fifo, impl_highest_label}; |
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38 | //No more implemented yet:}; |
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39 | implementation_t implementation; |
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40 | //--------------------------------------------- |
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41 | //Parameters of the algorithm |
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42 | //--------------------------------------------- |
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43 | |
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44 | private: |
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45 | //input |
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46 | Graph& G; |
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47 | Node s; |
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48 | Node t; |
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49 | typename Graph::EdgeMap<T> &capacity; |
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50 | |
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51 | //output |
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52 | typename Graph::EdgeMap<T> preflow; |
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53 | T maxflow_value; |
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54 | |
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55 | //auxiliary variables for computation |
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56 | //The number of the nodes |
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57 | int number_of_nodes; |
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58 | //A nodemap for the level |
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59 | typename Graph::NodeMap<int> level; |
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60 | //A nodemap for the excess |
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61 | typename Graph::NodeMap<T> excess; |
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62 | |
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63 | //Number of nodes on each level |
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64 | vector<int> num_of_nodes_on_level; |
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65 | |
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66 | //For the FIFO implementation |
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67 | list<Node> fifo_nodes; |
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68 | //For 'highest label' implementation |
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69 | int highest_active; |
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70 | //int second_highest_active; |
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71 | vector< list<Node> > active_nodes; |
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72 | |
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73 | public: |
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74 | |
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75 | //Constructing the object using the graph, source, sink and capacity vector |
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76 | preflow_push( |
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77 | Graph& _G, |
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78 | Node _s, |
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79 | Node _t, |
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80 | typename Graph::EdgeMap<T> & _capacity) |
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81 | : G(_G), s(_s), t(_t), |
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82 | capacity(_capacity), |
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83 | preflow(_G), |
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84 | //Counting the number of nodes |
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85 | //number_of_nodes(count(G.first<EachNodeIt>())), |
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86 | number_of_nodes(G.nodeNum()), |
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87 | |
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88 | level(_G), |
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89 | excess(_G)//, |
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90 | // Default constructor: active_nodes() |
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91 | { |
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92 | //Simplest parameter settings |
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93 | node_examination = examine_full;//examine_to_relabel;// |
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94 | //Which implementation to be usedexamine_full |
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95 | implementation = impl_highest_label;//impl_fifo; |
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96 | |
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97 | // |
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98 | num_of_nodes_on_level.resize(2*number_of_nodes-1); |
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99 | num_of_nodes_on_level.clear(); |
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100 | |
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101 | switch(implementation){ |
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102 | case impl_highest_label :{ |
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103 | active_nodes.clear(); |
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104 | active_nodes.resize(2*number_of_nodes-1); |
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105 | |
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106 | break; |
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107 | } |
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108 | default: |
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109 | break; |
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110 | } |
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111 | |
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112 | } |
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113 | |
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114 | //Returns the value of a maximal flow |
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115 | T run(); |
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116 | |
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117 | typename Graph::EdgeMap<T> getmaxflow(){ |
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118 | return preflow; |
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119 | } |
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120 | |
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121 | |
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122 | private: |
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123 | //For testing purposes only |
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124 | //Lists the node_properties |
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125 | void write_property_vector(typename Graph::NodeMap<T> a, |
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126 | //node_property_vector<Graph, T> a, |
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127 | char* prop_name="property"){ |
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128 | for(NodeIt i=G.template first<NodeIt>(); G.valid(i); G.next(i)) { |
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129 | cout<<"Node id.: "<<G.id(i)<<", "<<prop_name<<" value: "<<a[i]<<endl; |
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130 | } |
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131 | cout<<endl; |
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132 | } |
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133 | |
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134 | //Modifies the excess of the node and makes sufficient changes |
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135 | void modify_excess(const Node& a ,T v){ |
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136 | //T old_value=excess[a]; |
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137 | excess[a] += v; |
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138 | } |
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139 | |
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140 | //This private procedure is supposed to modify the preflow on edge j |
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141 | //by value v (which can be positive or negative as well) |
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142 | //and maintain the excess on the head and tail |
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143 | //Here we do not check whether this is possible or not |
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144 | void modify_preflow(Edge j, const T& v){ |
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145 | |
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146 | //Modifiyng the edge |
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147 | preflow[j] += v; |
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148 | |
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149 | |
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150 | //Modifiyng the head |
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151 | modify_excess(G.head(j),v); |
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152 | |
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153 | //Modifiyng the tail |
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154 | modify_excess(G.tail(j),-v); |
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155 | |
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156 | } |
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157 | |
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158 | //Gives the active node to work with |
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159 | //(depending on the implementation to be used) |
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160 | Node get_active_node(){ |
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161 | |
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162 | |
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163 | switch(implementation) { |
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164 | case impl_highest_label : { |
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165 | |
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166 | //First need to find the highest label for which there's an active node |
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167 | while( highest_active>=0 && active_nodes[highest_active].empty() ){ |
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168 | --highest_active; |
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169 | } |
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170 | |
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171 | if( highest_active>=0) { |
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172 | |
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173 | |
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174 | Node a=active_nodes[highest_active].front(); |
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175 | active_nodes[highest_active].pop_front(); |
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176 | |
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177 | return a; |
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178 | } |
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179 | else { |
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180 | return INVALID; |
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181 | } |
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182 | |
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183 | break; |
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184 | |
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185 | } |
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186 | case impl_fifo : { |
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187 | |
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188 | if( ! fifo_nodes.empty() ) { |
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189 | Node a=fifo_nodes.front(); |
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190 | fifo_nodes.pop_front(); |
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191 | return a; |
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192 | } |
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193 | else { |
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194 | return INVALID; |
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195 | } |
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196 | break; |
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197 | } |
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198 | } |
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199 | // |
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200 | return INVALID; |
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201 | } |
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202 | |
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203 | //Puts node 'a' among the active nodes |
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204 | void make_active(const Node& a){ |
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205 | //s and t never become active |
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206 | if (a!=s && a!= t){ |
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207 | switch(implementation){ |
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208 | case impl_highest_label : |
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209 | active_nodes[level[a]].push_back(a); |
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210 | break; |
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211 | case impl_fifo : |
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212 | fifo_nodes.push_back(a); |
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213 | break; |
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214 | } |
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215 | |
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216 | } |
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217 | |
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218 | //Update highest_active label |
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219 | if (highest_active<level[a]){ |
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220 | highest_active=level[a]; |
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221 | } |
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222 | |
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223 | } |
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224 | |
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225 | //Changes the level of node a and make sufficent changes |
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226 | void change_level_to(Node a, int new_value){ |
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227 | int seged = level[a]; |
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228 | level.set(a,new_value); |
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229 | --num_of_nodes_on_level[seged]; |
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230 | ++num_of_nodes_on_level[new_value]; |
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231 | } |
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232 | |
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233 | //Collection of things useful (or necessary) to do before running |
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234 | |
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235 | void preprocess(){ |
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236 | |
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237 | //--------------------------------------- |
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238 | //Initialize parameters |
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239 | //--------------------------------------- |
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240 | |
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241 | //Setting starting preflow, level and excess values to zero |
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242 | //This can be important, if the algorithm is run more then once |
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243 | for(NodeIt i=G.template first<NodeIt>(); G.valid(i); G.next(i)) { |
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244 | level.set(i,0); |
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245 | excess.set(i,0); |
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246 | for(OutEdgeIt j=G.template first<OutEdgeIt>(i); G.valid(j); G.next(j)) |
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247 | preflow.set(j, 0); |
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248 | } |
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249 | num_of_nodes_on_level[0]=number_of_nodes; |
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250 | highest_active=0; |
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251 | //--------------------------------------- |
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252 | //Initialize parameters |
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253 | //--------------------------------------- |
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254 | |
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255 | |
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256 | //------------------------------------ |
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257 | //This is the only part that uses BFS |
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258 | //------------------------------------ |
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259 | |
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260 | /*Reverse_bfs from t, to find the starting level.*/ |
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261 | //Copyright: Jacint |
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262 | change_level_to(t,0); |
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263 | |
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264 | std::queue<Node> bfs_queue; |
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265 | bfs_queue.push(t); |
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266 | |
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267 | while (!bfs_queue.empty()) { |
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268 | |
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269 | Node v=bfs_queue.front(); |
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270 | bfs_queue.pop(); |
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271 | int l=level[v]+1; |
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272 | |
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273 | InEdgeIt e; |
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274 | for(G.first(e,v); G.valid(e); G.next(e)) { |
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275 | Node w=G.tail(e); |
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276 | if ( level[w] == number_of_nodes && w != s ) { |
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277 | bfs_queue.push(w); |
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278 | //Node first=level_list[l]; |
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279 | //if ( G.valid(first) ) left.set(first,w); |
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280 | //right.set(w,first); |
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281 | //level_list[l]=w; |
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282 | change_level_to(w, l); |
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283 | //level.set(w, l); |
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284 | } |
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285 | } |
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286 | } |
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287 | change_level_to(s,number_of_nodes); |
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288 | //level.set(s,number_of_nodes); |
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289 | |
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290 | /* |
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291 | //Setting starting level values using reverse bfs |
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292 | reverse_bfs<Graph> rev_bfs(G,t); |
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293 | rev_bfs.run(); |
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294 | //write_property_vector(rev_bfs.dist,"rev_bfs"); |
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295 | for(NodeIt i=G.template first<NodeIt>(); G.valid(i); G.next(i)) { |
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296 | change_level_to(i,rev_bfs.dist(i)); |
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297 | //level.put(i,rev_bfs.dist.get(i)); |
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298 | } |
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299 | */ |
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300 | //------------------------------------ |
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301 | //This is the only part that uses BFS |
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302 | //------------------------------------ |
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303 | |
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304 | |
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305 | //Starting level of s |
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306 | change_level_to(s,number_of_nodes); |
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307 | //level.put(s,number_of_nodes); |
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308 | |
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309 | |
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310 | //we push as much preflow from s as possible to start with |
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311 | for(OutEdgeIt j=G.template first<OutEdgeIt>(s); G.valid(j); G.next(j)){ |
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312 | modify_preflow(j,capacity[j] ); |
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313 | make_active(G.head(j)); |
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314 | int lev=level[G.head(j)]; |
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315 | if(highest_active<lev){ |
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316 | highest_active=lev; |
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317 | } |
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318 | } |
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319 | //cout<<highest_active<<endl; |
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320 | } |
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321 | |
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322 | |
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323 | //If the preflow is less than the capacity on the given edge |
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324 | //then it is an edge in the residual graph |
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325 | bool is_admissible_forward_edge(Edge j, int& new_level){ |
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326 | |
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327 | if (capacity[j]>preflow[j]){ |
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328 | if(level[G.tail(j)]==level[G.head(j)]+1){ |
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329 | return true; |
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330 | } |
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331 | else{ |
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332 | if (level[G.head(j)] < new_level) |
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333 | new_level=level[G.head(j)]; |
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334 | } |
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335 | } |
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336 | return false; |
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337 | } |
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338 | |
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339 | //If the preflow is greater than 0 on the given edge |
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340 | //then the edge reversd is an edge in the residual graph |
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341 | bool is_admissible_backward_edge(Edge j, int& new_level){ |
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342 | |
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343 | if (0<preflow[j]){ |
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344 | if(level[G.tail(j)]==level[G.head(j)]-1){ |
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345 | |
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346 | return true; |
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347 | } |
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348 | else{ |
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349 | if (level[G.tail(j)] < new_level) |
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350 | new_level=level[G.tail(j)]; |
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351 | } |
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352 | |
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353 | } |
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354 | return false; |
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355 | } |
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356 | |
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357 | |
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358 | }; //class preflow_push |
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359 | |
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360 | template<typename Graph, typename T> |
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361 | T preflow_push<Graph, T>::run() { |
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362 | |
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363 | preprocess(); |
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364 | //write_property_vector(level,"level"); |
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365 | T e,v; |
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366 | Node a; |
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367 | while (a=get_active_node(), G.valid(a)){ |
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368 | |
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369 | //cout<<G.id(a)<<endl; |
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370 | //write_property_vector(excess,"excess"); |
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371 | //write_property_vector(level,"level"); |
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372 | |
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373 | |
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374 | bool go_to_next_node=false; |
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375 | e = excess[a]; |
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376 | while (!go_to_next_node){ |
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377 | //Initial value for the new level for the active node we are dealing with |
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378 | int new_level=2*number_of_nodes; |
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379 | //write_property_vector(excess,"excess"); |
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380 | //write_property_vector(level,"level"); |
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381 | //cout<<G.id(a)<<endl; |
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382 | //Out edges from node a |
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383 | { |
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384 | OutEdgeIt j=G.template first<OutEdgeIt>(a); |
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385 | while (G.valid(j) && e){ |
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386 | |
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387 | if (is_admissible_forward_edge(j,new_level)){ |
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388 | v=min(e,capacity[j] - preflow[j]); |
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389 | e -= v; |
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390 | //New node might become active |
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391 | if (excess[G.head(j)]==0){ |
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392 | make_active(G.head(j)); |
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393 | } |
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394 | modify_preflow(j,v); |
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395 | } |
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396 | G.next(j); |
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397 | } |
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398 | } |
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399 | //In edges to node a |
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400 | { |
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401 | InEdgeIt j=G.template first<InEdgeIt>(a); |
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402 | while (G.valid(j) && e){ |
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403 | if (is_admissible_backward_edge(j,new_level)){ |
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404 | v=min(e,preflow[j]); |
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405 | e -= v; |
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406 | //New node might become active |
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407 | if (excess[G.tail(j)]==0){ |
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408 | make_active(G.tail(j)); |
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409 | } |
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410 | modify_preflow(j,-v); |
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411 | } |
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412 | G.next(j); |
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413 | } |
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414 | } |
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415 | |
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416 | //if (G.id(a)==999) |
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417 | //cout<<new_level<<" e: "<<e<<endl; |
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418 | //cout<<G.id(a)<<" "<<new_level<<endl; |
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419 | |
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420 | if (0==e){ |
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421 | //Saturating push |
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422 | go_to_next_node=true; |
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423 | } |
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424 | else{//If there is still excess in node a |
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425 | |
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426 | //change_level_to(a,new_level+1); |
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427 | |
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428 | //Level remains empty |
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429 | if (num_of_nodes_on_level[level[a]]==1){ |
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430 | change_level_to(a,number_of_nodes); |
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431 | //go_to_next_node=True; |
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432 | } |
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433 | else{ |
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434 | change_level_to(a,new_level+1); |
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435 | //increase_level(a); |
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436 | } |
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437 | |
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438 | |
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439 | |
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440 | |
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441 | switch(node_examination){ |
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442 | case examine_to_relabel: |
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443 | make_active(a); |
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444 | |
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445 | go_to_next_node = true; |
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446 | break; |
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447 | default: |
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448 | break; |
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449 | } |
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450 | |
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451 | |
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452 | |
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453 | }//if (0==e) |
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454 | } |
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455 | } |
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456 | maxflow_value = excess[t]; |
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457 | return maxflow_value; |
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458 | }//run |
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459 | |
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460 | |
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461 | }//namespace hugo |
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462 | |
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463 | #endif //PREFLOW_PUSH_HH |
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