1 | /* -*- C++ -*- |
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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) 2003-2008 |
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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 | namespace lemon { |
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20 | /*! |
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21 | |
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22 | |
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23 | \page graph-io-page Graph Input-Output |
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24 | |
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25 | The standard graph IO enables one to store graphs and additional maps |
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26 | (i.e. functions on the nodes or edges) in a flexible and efficient way. |
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27 | Before you read this page you should be familiar with LEMON |
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28 | \ref graphs "graphs" and \ref maps-page "maps". |
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29 | |
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30 | \section format The general file format |
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31 | |
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32 | The file contains sections in the following order: |
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33 | |
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34 | \li nodeset |
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35 | \li edgeset |
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36 | \li nodes |
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37 | \li edges |
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38 | \li attributes |
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39 | |
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40 | Some of these sections can be omitted, but you will basicly need the nodeset |
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41 | section (unless your graph has no nodes at all) and the edgeset section |
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42 | (unless your graph has no edges at all). |
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43 | |
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44 | The nodeset section describes the nodes of your graph: it identifies the nodes |
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45 | and gives the maps defined on them, if any. It starts with the |
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46 | following line: |
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47 | |
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48 | <tt>\@nodeset</tt> |
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49 | |
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50 | The next line contains the names of the nodemaps, separated by whitespaces. Each |
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51 | following line describes a node in the graph: it contains the values of the |
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52 | maps in the right order. The map named "label" should contain unique values |
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53 | because it is regarded as a label map. These labels need not be numbers but they |
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54 | must identify the nodes uniquely for later reference. For example: |
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55 | |
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56 | \code |
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57 | @nodeset |
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58 | label x-coord y-coord color |
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59 | 3 1.0 4.0 blue |
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60 | 5 2.3 5.7 red |
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61 | 12 7.8 2.3 green |
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62 | \endcode |
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63 | |
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64 | The edgeset section is very similar to the nodeset section, it has |
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65 | the same coloumn oriented structure. It starts with the line |
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66 | |
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67 | <tt>\@edgeset</tt> |
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68 | |
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69 | The next line contains the whitespace separated list of names of the edge |
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70 | maps. Each of the next lines describes one edge. The first two elements in |
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71 | the line are the labels of the source and target (or tail and head) nodes of the |
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72 | edge as they occur in the label node map of the nodeset section. You can also |
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73 | have an optional label map on the edges for later reference (which has to be |
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74 | unique in this case). |
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75 | |
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76 | \code |
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77 | @edgeset |
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78 | label weight note |
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79 | 3 5 a 4.3 a-edge |
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80 | 5 12 c 2.6 c-edge |
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81 | 3 12 g 3.4 g-edge |
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82 | \endcode |
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83 | |
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84 | The \e nodes section contains <em>labeled (distinguished) nodes</em> |
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85 | (i.e. nodes having a special |
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86 | label on them). The section starts with |
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87 | |
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88 | <tt> \@nodes </tt> |
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89 | |
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90 | Each of the next lines contains a label for a node in the graph |
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91 | and then the label as described in the \e nodeset section. |
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92 | |
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93 | \code |
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94 | @nodes |
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95 | source 3 |
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96 | target 12 |
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97 | \endcode |
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98 | |
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99 | The last section describes the <em>labeled (distinguished) edges</em> |
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100 | (i.e. edges having a special label on them). It starts with \c \@edges |
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101 | and then each line contains the name of the edge and the label. |
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102 | |
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103 | \code |
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104 | @edges |
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105 | observed c |
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106 | \endcode |
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107 | |
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108 | |
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109 | The file may contain empty lines and comment lines. The comment lines |
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110 | start with an \c # character. |
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111 | |
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112 | The attributes section can handle some information about the graph. It |
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113 | contains key-value pairs in each line (a key and the mapped value to key). The |
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114 | key should be a string without whitespaces, the value can be of various types. |
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115 | |
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116 | \code |
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117 | @attributes |
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118 | title "Four colored planar graph" |
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119 | author "Balazs DEZSO" |
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120 | copyright "Lemon Library" |
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121 | version 12 |
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122 | \endcode |
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123 | |
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124 | Finally, the file should be closed with \c \@end line. |
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125 | |
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126 | |
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127 | \section use Using graph input-output |
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128 | |
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129 | |
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130 | The graph input and output is based on <em> reading and writing |
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131 | commands</em>. The user gives reading and writing commands to the reader or |
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132 | writer class, then he calls the \c run() method that executes all the given |
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133 | commands. |
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134 | |
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135 | \subsection write Writing a graph |
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136 | |
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137 | The \ref lemon::GraphWriter "GraphWriter" template class |
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138 | provides the graph output. To write a graph |
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139 | you should first give writing commands to the writer. You can declare |
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140 | writing command as \c NodeMap or \c EdgeMap writing and labeled Node and |
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141 | Edge writing. |
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142 | |
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143 | \code |
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144 | GraphWriter<ListGraph> writer(std::cout, graph); |
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145 | \endcode |
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146 | |
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147 | The \ref lemon::GraphWriter::writeNodeMap() "writeNodeMap()" |
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148 | function declares a \c NodeMap writing command in the |
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149 | \ref lemon::GraphWriter "GraphWriter". |
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150 | You should give a name to the map and the map |
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151 | object as parameters. The NodeMap writing command with name "label" should write a |
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152 | unique map because it will be regarded as a label map. |
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153 | |
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154 | \see IdMap, DescriptorMap |
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155 | |
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156 | \code |
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157 | IdMap<ListGraph, Node> nodeLabelMap; |
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158 | writer.writeNodeMap("label", nodeLabelMap); |
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159 | |
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160 | writer.writeNodeMap("x-coord", xCoordMap); |
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161 | writer.writeNodeMap("y-coord", yCoordMap); |
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162 | writer.writeNodeMap("color", colorMap); |
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163 | \endcode |
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164 | |
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165 | With the \ref lemon::GraphWriter::writeEdgeMap() "writeEdgeMap()" |
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166 | member function you can give an edge map |
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167 | writing command similar to the NodeMaps. |
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168 | |
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169 | \see IdMap, DescriptorMap |
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170 | |
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171 | \code |
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172 | DescriptorMap<ListGraph, Edge, ListGraph::EdgeMap<int> > edgeDescMap(graph); |
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173 | writer.writeEdgeMap("descriptor", edgeDescMap); |
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174 | |
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175 | writer.writeEdgeMap("weight", weightMap); |
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176 | writer.writeEdgeMap("note", noteMap); |
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177 | \endcode |
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178 | |
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179 | With \ref lemon::GraphWriter::writeNode() "writeNode()" |
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180 | and \ref lemon::GraphWriter::writeEdge() "writeEdge()" |
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181 | functions you can designate Nodes and |
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182 | Edges in the graph. For example, you can write out the source and target node |
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183 | of a maximum flow instance. |
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184 | |
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185 | \code |
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186 | writer.writeNode("source", sourceNode); |
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187 | writer.writeNode("target", targetNode); |
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188 | |
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189 | writer.writeEdge("observed", edge); |
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190 | \endcode |
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191 | |
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192 | With \ref lemon::GraphWriter::writeAttribute() "writeAttribute()" |
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193 | function you can write an attribute to the file. |
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194 | |
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195 | \code |
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196 | writer.writeAttribute("author", "Balazs DEZSO"); |
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197 | writer.writeAttribute("version", 12); |
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198 | \endcode |
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199 | |
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200 | After you give all write commands you must call the |
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201 | \ref lemon::GraphWriter::run() "run()" member |
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202 | function, which executes all the writing commands. |
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203 | |
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204 | \code |
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205 | writer.run(); |
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206 | \endcode |
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207 | |
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208 | \subsection reading Reading a graph |
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209 | |
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210 | The file to be read may contain several maps and labeled nodes or edges. |
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211 | If you read a graph you need not read all the maps and items just those |
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212 | that you need. The interface of the \ref lemon::GraphReader "GraphReader" |
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213 | is very similar to |
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214 | the \ref lemon::GraphWriter "GraphWriter" |
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215 | but the reading method does not depend on the order of the |
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216 | given commands. |
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217 | |
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218 | The reader object assumes that each not read value does not contain |
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219 | whitespaces, therefore it has some extra possibilities to control how |
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220 | it should skip the values when the string representation contains spaces. |
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221 | |
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222 | \code |
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223 | GraphReader<ListGraph> reader(std::cin, graph); |
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224 | \endcode |
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225 | |
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226 | The \ref lemon::GraphReader::readNodeMap() "readNodeMap()" |
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227 | function reads a map from the \c nodeset section. |
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228 | If there is a map that you do not want to read from the file and there are |
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229 | whitespaces in the string represenation of the values then you should |
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230 | call the \ref lemon::GraphReader::skipNodeMap() "skipNodeMap()" |
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231 | template member function with proper parameters. |
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232 | |
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233 | \see QuotedStringReader |
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234 | |
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235 | \code |
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236 | reader.readNodeMap("x-coord", xCoordMap); |
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237 | reader.readNodeMap("y-coord", yCoordMap); |
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238 | |
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239 | reader.readNodeMap<QuotedStringReader>("label", labelMap); |
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240 | reader.skipNodeMap<QuotedStringReader>("description"); |
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241 | |
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242 | reader.readNodeMap("color", colorMap); |
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243 | \endcode |
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244 | |
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245 | With the \ref lemon::GraphReader::readEdgeMap() "readEdgeMap()" |
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246 | member function you can give an edge map |
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247 | reading command similar to the NodeMaps. |
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248 | |
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249 | \code |
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250 | reader.readEdgeMap("weight", weightMap); |
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251 | reader.readEdgeMap("label", labelMap); |
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252 | \endcode |
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253 | |
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254 | With \ref lemon::GraphReader::readNode() "readNode()" |
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255 | and \ref lemon::GraphReader::readEdge() "readEdge()" |
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256 | functions you can read labeled Nodes and |
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257 | Edges. |
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258 | |
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259 | \code |
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260 | reader.readNode("source", sourceNode); |
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261 | reader.readNode("target", targetNode); |
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262 | |
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263 | reader.readEdge("observed", edge); |
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264 | \endcode |
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265 | |
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266 | With \ref lemon::GraphReader::readAttribute() "readAttribute()" |
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267 | function you can read an attribute from the file. |
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268 | |
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269 | \code |
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270 | std::string author; |
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271 | writer.readAttribute("author", author); |
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272 | int version; |
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273 | writer.writeAttribute("version", version); |
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274 | \endcode |
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275 | |
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276 | After you give all read commands you must call the |
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277 | \ref lemon::GraphReader::run() "run()" member |
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278 | function, which executes all the commands. |
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279 | |
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280 | \code |
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281 | reader.run(); |
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282 | \endcode |
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283 | |
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284 | \anchor rwbackground |
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285 | \section types Background of Reading and Writing |
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286 | |
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287 | |
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288 | To read a map (on the nodes or edges) |
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289 | the \ref lemon::GraphReader "GraphReader" |
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290 | should know how to read a Value from the given map. |
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291 | By the default implementation the input operator reads a value from |
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292 | the stream and the type of the read value is the value type of the given map. |
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293 | When the reader should skip a value in the stream, because you do not |
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294 | want to store it in a map, the reader skips a character sequence without |
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295 | whitespaces. |
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296 | |
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297 | If you want to change the functionality of the reader, you can use |
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298 | template parameters to specialize it. When you give a reading |
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299 | command for a map you can give a Reader type as template parameter. |
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300 | With this template parameter you can control how the Reader reads |
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301 | a value from the stream. |
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302 | |
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303 | The reader has the next structure: |
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304 | \code |
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305 | struct TypeReader { |
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306 | typedef TypeName Value; |
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307 | |
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308 | void read(std::istream& is, Value& value); |
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309 | }; |
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310 | \endcode |
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311 | |
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312 | For example, the \c "strings" nodemap contains strings and you do not need |
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313 | the value of the string just the length. Then you can implement an own Reader |
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314 | struct. |
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315 | |
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316 | \code |
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317 | struct LengthReader { |
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318 | typedef int Value; |
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319 | |
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320 | void read(std::istream& is, Value& value) { |
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321 | std::string tmp; |
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322 | is >> tmp; |
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323 | value = tmp.length(); |
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324 | } |
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325 | }; |
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326 | ... |
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327 | reader.readNodeMap<LengthReader>("strings", lengthMap); |
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328 | \endcode |
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329 | |
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330 | The global functionality of the reader class can be changed by giving a |
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331 | special template parameter to the GraphReader class. By default, the |
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332 | template parameter is \c DefaultReaderTraits. A reader traits class |
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333 | should provide a nested template class Reader for each type, and a |
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334 | DefaultReader for skipping a value. |
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335 | |
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336 | The specialization of writing is very similar to that of reading. |
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337 | |
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338 | \section undir Undirected and Bipartite graphs |
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339 | |
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340 | In a file describing an undirected graph (ugraph, for short) you find an |
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341 | \c uedgeset section instead of the \c edgeset section. The first line of |
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342 | the section describes the names of the maps on the undirected egdes and all |
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343 | next lines describe one undirected edge with the the incident nodes and the |
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344 | values of the map. |
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345 | |
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346 | The format could store directed edge maps, if there are two maps with |
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347 | names being the same with a \c '+' and a \c '-' prefix then this could |
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348 | be read as such a map. |
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349 | |
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350 | \code |
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351 | @uedgeset |
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352 | label capacity +flow -flow |
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353 | 32 2 1 4.3 2.0 0.0 |
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354 | 21 21 5 2.6 0.0 2.6 |
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355 | 21 12 8 3.4 0.0 0.0 |
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356 | \endcode |
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357 | |
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358 | The \c edges section is changed to \c uedges section. This section |
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359 | describes labeled edges and undirected edges. The directed edge label |
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360 | should start with a \c '+' or a \c '-' prefix to decide the direction |
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361 | of the edge. |
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362 | |
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363 | \code |
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364 | @uedges |
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365 | uedge 1 |
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366 | +edge 5 |
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367 | -back 5 |
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368 | \endcode |
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369 | |
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370 | There are similar classes to the \ref lemon::GraphReader "GraphReader" and |
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371 | \ref lemon::GraphWriter "GraphWriter" which |
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372 | handle the undirected graphs. These classes are |
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373 | the \ref lemon::UGraphReader "UGraphReader" |
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374 | and \ref lemon::UGraphWriter "UGraphWriter". |
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375 | |
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376 | The \ref lemon::UGraphReader::readUEdgeMap() "readUEdgeMap()" |
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377 | function reads an undirected map and the |
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378 | \ref lemon::UGraphReader::readUEdge() "readUEdge()" |
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379 | reads an undirected edge from the file, |
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380 | |
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381 | \code |
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382 | reader.readUEdgeMap("capacity", capacityMap); |
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383 | reader.readEdgeMap("flow", flowMap); |
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384 | ... |
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385 | reader.readUEdge("u_edge", u_edge); |
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386 | reader.readEdge("edge", edge); |
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387 | \endcode |
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388 | |
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389 | The undirected bipartite graphs could be read with the \c BpUGraph |
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390 | class and it has specialized nodeset section, which should be start |
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391 | with \c "@bpnodeset". This section is separated to two |
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392 | subsections. The header line of these sections start with "&anodeset" |
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393 | or "&bnodeset" and after that the line contains the names of the |
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394 | regular and A-node or B-node maps accordingly. The lines of each |
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395 | section contains the mapped values. The labels of the graph should be |
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396 | unique overall both subsections. |
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397 | |
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398 | \code |
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399 | @bpnodeset |
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400 | &anodeset label coords radius |
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401 | 0 (0, 0) 14.0 |
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402 | 1 (0, 1) 12.0 |
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403 | &bnodeset label coords |
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404 | 2 (1, 0) |
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405 | 3 (1, 1) |
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406 | \endcode |
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407 | |
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408 | The reading can be done with \ref lemon::BpUGraphReader::readANodeMap() |
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409 | "readANodeMap()", \ref lemon::BpUGraphReader::readBNodeMap() |
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410 | "readBNodeMap()" or \ref lemon::BpUGraphReader::readNodeMap() |
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411 | "readNodeMap()" members. |
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412 | |
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413 | \code |
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414 | reader.readNodeMap("coords", coords); |
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415 | reader.readAnodeMap("radius", radius); |
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416 | \endcode |
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417 | |
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418 | \section advanced Advanced features |
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419 | |
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420 | The graph reader and writer classes give an easy way to read and write |
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421 | graphs. But sometimes we want more advanced features. In this case we can |
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422 | use the more general <tt>lemon reader and writer</tt> interface. |
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423 | |
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424 | The LEMON file format is a section oriented file format. It contains one or |
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425 | more sections, each starting with a line identifying its type |
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426 | (the word starting with the \c \@ character). |
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427 | The content of the section this way cannot contain line with \c \@ first |
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428 | character. The file may contains comment lines with \c # first character. |
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429 | |
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430 | The \ref lemon::LemonReader "LemonReader" |
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431 | and \ref lemon::LemonWriter "LemonWriter" |
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432 | gives a framework to read and |
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433 | write sections. There are various section reader and section writer |
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434 | classes which can be attached to a \ref lemon::LemonReader "LemonReader" |
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435 | or a \ref lemon::LemonWriter "LemonWriter". |
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436 | |
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437 | There are default section readers and writers for reading and writing |
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438 | item sets, and labeled items in the graph. These read and write |
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439 | the format described above. Other type of data can be handled with own |
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440 | section reader and writer classes which are inherited from the |
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441 | \c LemonReader::SectionReader or the |
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442 | \ref lemon::LemonWriter::SectionWriter "LemonWriter::SectionWriter" |
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443 | classes. |
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444 | |
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445 | The next example defines a special section reader which reads the |
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446 | \c \@description sections into a string: |
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447 | |
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448 | \code |
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449 | class DescriptionReader : LemonReader::SectionReader { |
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450 | protected: |
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451 | virtual bool header(const std::string& line) { |
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452 | std::istringstream ls(line); |
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453 | std::string head; |
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454 | ls >> head; |
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455 | return head == "@description"; |
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456 | } |
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457 | |
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458 | virtual void read(std::istream& is) { |
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459 | std::string line; |
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460 | while (getline(is, line)) { |
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461 | desc += line; |
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462 | } |
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463 | } |
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464 | public: |
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465 | |
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466 | typedef LemonReader::SectionReader Parent; |
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467 | |
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468 | DescriptionReader(LemonReader& reader) : Parent(reader) {} |
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469 | |
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470 | const std::string& description() const { |
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471 | return description; |
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472 | } |
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473 | |
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474 | private: |
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475 | std::string desc; |
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476 | }; |
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477 | \endcode |
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478 | |
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479 | The other advanced stuff of the generalized file format is that |
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480 | multiple edgesets can be stored to the same nodeset. It can be used |
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481 | for example as a network traffic matrix. |
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482 | |
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483 | In our example there is a network with symmetric links and there are assymetric |
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484 | traffic request on the network. This construction can be stored in an |
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485 | undirected graph and in a directed \c ListEdgeSet class. The example |
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486 | shows the input with the \ref lemon::LemonReader "LemonReader" class: |
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487 | |
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488 | \code |
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489 | ListUGraph network; |
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490 | ListUGraph::UEdgeMap<double> capacity; |
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491 | ListEdgeSet<ListUGraph> traffic(network); |
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492 | ListEdgeSet<ListUGraph>::EdgeMap<double> request(network); |
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493 | |
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494 | LemonReader reader(std::cin); |
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495 | NodeSetReader<ListUGraph> nodesetReader(reader, network); |
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496 | UEdgeSetReader<ListUGraph> |
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497 | uEdgesetReader(reader, network, nodesetReader); |
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498 | uEdgesetReader.readEdgeMap("capacity", capacity); |
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499 | EdgeSetReader<ListEdgeSet<ListUGraph> > |
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500 | edgesetReader(reader, traffic, nodesetReader, "traffic"); |
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501 | edgesetReader.readEdgeMap("request", request); |
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502 | |
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503 | reader.run(); |
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504 | \endcode |
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505 | |
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506 | Because both the \ref lemon::GraphReader "GraphReader" |
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507 | and the \ref lemon::UGraphReader "UGraphReader" can be converted |
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508 | to \ref lemon::LemonReader "LemonReader" |
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509 | and it can resolve the label's of the items, the previous |
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510 | result can be achived with the \ref lemon::UGraphReader "UGraphReader" |
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511 | class, too. |
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512 | |
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513 | |
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514 | \code |
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515 | ListUGraph network; |
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516 | ListUGraph::UEdgeSet<double> capacity; |
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517 | ListEdgeSet<ListUGraph> traffic(network); |
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518 | ListEdgeSet<ListUGraph>::EdgeMap<double> request(network); |
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519 | |
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520 | UGraphReader<ListUGraph> reader(std::cin, network); |
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521 | reader.readEdgeMap("capacity", capacity); |
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522 | EdgeSetReader<ListEdgeSet<ListUGraph> > |
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523 | edgesetReader(reader, traffic, reader, "traffic"); |
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524 | edgesetReader.readEdgeMap("request", request); |
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525 | |
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526 | reader.run(); |
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527 | \endcode |
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528 | |
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529 | \author Balazs Dezso |
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530 | */ |
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531 | } |
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