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