1 | namespace lemon { |
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2 | /*! |
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3 | |
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4 | |
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5 | \page graph-io-page Graph Input-Output |
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6 | |
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7 | The standard graph IO enables one to store graphs and additional maps |
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8 | (i.e. functions on the nodes or edges) in a flexible and efficient way. |
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9 | Before you read this page you should be familiar with LEMON |
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10 | \ref graphs "graphs" and \ref maps-page "maps". |
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11 | |
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12 | \section format The general file format |
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13 | |
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14 | The file contains sections in the following order: |
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15 | |
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16 | \li nodeset |
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17 | \li edgeset |
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18 | \li nodes |
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19 | \li edges |
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20 | \li attributes |
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21 | |
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22 | Some of these sections can be omitted, but you will basicly need the nodeset |
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23 | section (unless your graph has no nodes at all) and the edgeset section |
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24 | (unless your graph has no edges at all). |
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25 | |
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26 | The nodeset section describes the nodes of your graph: it identifies the nodes |
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27 | and gives the maps defined on them, if any. It starts with the |
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28 | following line: |
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29 | |
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30 | <tt>\@nodeset</tt> |
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31 | |
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32 | The next line contains the names of the nodemaps, separated by whitespaces. Each |
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33 | following line describes a node in the graph: it contains the values of the |
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34 | maps in the right order. The map named "id" should contain unique values |
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35 | because it is regarded as an ID-map. These ids need not be numbers but they |
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36 | must identify the nodes uniquely for later reference. For example: |
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37 | |
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38 | \code |
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39 | @nodeset |
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40 | id x-coord y-coord color |
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41 | 3 1.0 4.0 blue |
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42 | 5 2.3 5.7 red |
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43 | 12 7.8 2.3 green |
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44 | \endcode |
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45 | |
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46 | The edgeset section is very similar to the nodeset section, it has |
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47 | the same coloumn oriented structure. It starts with the line |
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48 | |
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49 | <tt>\@edgeset</tt> |
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50 | |
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51 | The next line contains the whitespace separated list of names of the edge |
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52 | maps. Each of the next lines describes one edge. The first two elements in |
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53 | the line are the IDs of the source and target (or tail and head) nodes of the |
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54 | edge as they occur in the ID node map of the nodeset section. You can also |
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55 | have an optional ID map on the edges for later reference (which has to be |
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56 | unique in this case). |
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57 | |
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58 | \code |
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59 | @edgeset |
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60 | id weight label |
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61 | 3 5 a 4.3 a-edge |
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62 | 5 12 c 2.6 c-edge |
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63 | 3 12 g 3.4 g-edge |
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64 | \endcode |
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65 | |
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66 | The \e nodes section contains <em>labeled (distinguished) nodes</em> |
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67 | (i.e. nodes having a special |
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68 | label on them). The section starts with |
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69 | |
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70 | <tt> \@nodes </tt> |
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71 | |
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72 | Each of the next lines contains a label for a node in the graph |
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73 | and then the ID as described in the \e nodeset section. |
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74 | |
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75 | \code |
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76 | @nodes |
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77 | source 3 |
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78 | target 12 |
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79 | \endcode |
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80 | |
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81 | The last section describes the <em>labeled (distinguished) edges</em> |
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82 | (i.e. edges having a special label on them). It starts with \c \@edges |
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83 | and then each line contains the name of the edge and the ID. |
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84 | |
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85 | \code |
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86 | @edges |
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87 | observed c |
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88 | \endcode |
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89 | |
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90 | |
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91 | The file may contain empty lines and comment lines. The comment lines |
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92 | start with an \c # character. |
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93 | |
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94 | The attributes section can handle some information about the graph. It |
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95 | contains key-value pairs in each line (a key and the mapped value to key). The |
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96 | key should be a string without whitespaces, the value can be of various types. |
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97 | |
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98 | \code |
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99 | @attributes |
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100 | title "Four colored plan graph" |
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101 | author "Balazs DEZSO" |
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102 | copyright "Lemon Library" |
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103 | version 12 |
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104 | \endcode |
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105 | |
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106 | <tt> \@end </tt> |
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107 | |
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108 | line. |
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109 | |
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110 | |
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111 | \section use Using graph input-output |
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112 | |
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113 | The easiest way of using graph input and output is using the versions of the |
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114 | public \ref readGraph() and \ref writeGraph() functions; if you don't need |
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115 | very sophisticated behaviour then you might be satisfied with |
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116 | those. Otherwise go on reading this page. |
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117 | |
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118 | The graph input and output is based on <em> reading and writing |
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119 | commands</em>. The user gives reading and writing commands to the reader or |
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120 | writer class, then he calls the \c run() method that executes all the given |
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121 | commands. |
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122 | |
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123 | \subsection write Writing a graph |
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124 | |
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125 | The \c GraphWriter class provides the graph output. To write a graph |
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126 | you should first give writing commands to the writer. You can declare |
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127 | writing command as \c NodeMap or \c EdgeMap writing and labeled Node and |
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128 | Edge writing. |
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129 | |
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130 | \code |
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131 | GraphWriter<ListGraph> writer(std::cout, graph); |
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132 | \endcode |
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133 | |
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134 | The \c writeNodeMap() function declares a \c NodeMap writing command in the |
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135 | \c GraphWriter. You should give a name to the map and the map |
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136 | object as parameters. The NodeMap writing command with name "id" should write a |
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137 | unique map because it will be regarded as an ID map. |
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138 | |
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139 | \see IdMap, DescriptorMap |
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140 | |
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141 | \code |
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142 | IdMap<ListGraph, Node> nodeIdMap; |
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143 | writer.writeNodeMap("id", nodeIdMap); |
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144 | |
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145 | writer.writeNodeMap("x-coord", xCoordMap); |
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146 | writer.writeNodeMap("y-coord", yCoordMap); |
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147 | writer.writeNodeMap("color", colorMap); |
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148 | \endcode |
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149 | |
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150 | With the \c writeEdgeMap() member function you can give an edge map |
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151 | writing command similar to the NodeMaps. |
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152 | |
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153 | \see IdMap, DescriptorMap |
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154 | |
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155 | \code |
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156 | DescriptorMap<ListGraph, Edge, ListGraph::EdgeMap<int> > edgeDescMap(graph); |
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157 | writer.writeEdgeMap("descriptor", edgeDescMap); |
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158 | |
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159 | writer.writeEdgeMap("weight", weightMap); |
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160 | writer.writeEdgeMap("label", labelMap); |
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161 | \endcode |
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162 | |
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163 | With \c writeNode() and \c writeEdge() functions you can designate Nodes and |
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164 | Edges in the graph. For example, you can write out the source and target node |
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165 | of a maximum flow instance. |
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166 | |
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167 | \code |
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168 | writer.writeNode("source", sourceNode); |
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169 | writer.writeNode("target", targetNode); |
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170 | |
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171 | writer.writeEdge("observed", edge); |
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172 | \endcode |
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173 | |
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174 | With \c writeAttribute() function you can write an attribute to the file. |
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175 | |
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176 | \code |
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177 | writer.writeAttribute("author", "Balazs DEZSO"); |
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178 | writer.writeAttribute("version", 12); |
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179 | \endcode |
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180 | |
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181 | After you give all write commands you must call the \c run() member |
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182 | function, which executes all the writing commands. |
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183 | |
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184 | \code |
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185 | writer.run(); |
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186 | \endcode |
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187 | |
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188 | \subsection reading Reading a graph |
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189 | |
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190 | The file to be read may contain several maps and labeled nodes or edges. |
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191 | If you read a graph you need not read all the maps and items just those |
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192 | that you need. The interface of the \c GraphReader is very similar to |
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193 | the GraphWriter but the reading method does not depend on the order of the |
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194 | given commands. |
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195 | |
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196 | The reader object assumes that each not readed value does not contain |
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197 | whitespaces, therefore it has some extra possibilities to control how |
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198 | it should skip the values when the string representation contains spaces. |
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199 | |
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200 | \code |
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201 | GraphReader<ListGraph> reader(std::cin, graph); |
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202 | \endcode |
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203 | |
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204 | The \c readNodeMap() function reads a map from the \c nodeset section. |
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205 | If there is a map that you do not want to read from the file and there are |
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206 | whitespaces in the string represenation of the values then you should |
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207 | call the \c skipNodeMap() template member function with proper parameters. |
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208 | |
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209 | \see QuotedStringReader |
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210 | |
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211 | \code |
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212 | reader.readNodeMap("x-coord", xCoordMap); |
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213 | reader.readNodeMap("y-coord", yCoordMap); |
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214 | |
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215 | reader.readNodeMap<QuotedStringReader>("label", labelMap); |
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216 | reader.skipNodeMap<QuotedStringReader>("description"); |
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217 | |
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218 | reader.readNodeMap("color", colorMap); |
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219 | \endcode |
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220 | |
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221 | With the \c readEdgeMap() member function you can give an edge map |
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222 | reading command similar to the NodeMaps. |
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223 | |
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224 | \code |
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225 | reader.readEdgeMap("weight", weightMap); |
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226 | reader.readEdgeMap("label", labelMap); |
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227 | \endcode |
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228 | |
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229 | With \c readNode() and \c readEdge() functions you can read labeled Nodes and |
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230 | Edges. |
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231 | |
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232 | \code |
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233 | reader.readNode("source", sourceNode); |
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234 | reader.readNode("target", targetNode); |
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235 | |
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236 | reader.readEdge("observed", edge); |
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237 | \endcode |
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238 | |
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239 | With \c readAttribute() function you can read an attribute from the file. |
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240 | |
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241 | \code |
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242 | std::string author; |
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243 | writer.readAttribute("author", author); |
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244 | int version; |
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245 | writer.writeAttribute("version", version); |
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246 | \endcode |
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247 | |
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248 | After you give all read commands you must call the \c run() member |
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249 | function, which executes all the commands. |
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250 | |
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251 | \code |
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252 | reader.run(); |
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253 | \endcode |
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254 | |
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255 | \anchor rwbackground |
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256 | \section types Background of Reading and Writing |
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257 | |
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258 | |
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259 | To read a map (on the nodes or edges) |
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260 | the \c GraphReader should know how to read a Value from the given map. |
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261 | By the default implementation the input operator reads a value from |
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262 | the stream and the type of the readed value is the value type of the given map. |
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263 | When the reader should skip a value in the stream, because you do not |
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264 | want to store it in a map, the reader skips a character sequence without |
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265 | whitespaces. |
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266 | |
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267 | If you want to change the functionality of the reader, you can use |
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268 | template parameters to specialize it. When you give a reading |
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269 | command for a map you can give a Reader type as template parameter. |
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270 | With this template parameter you can control how the Reader reads |
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271 | a value from the stream. |
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272 | |
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273 | The reader has the next structure: |
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274 | \code |
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275 | struct TypeReader { |
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276 | typedef TypeName Value; |
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277 | |
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278 | void read(std::istream& is, Value& value); |
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279 | }; |
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280 | \endcode |
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281 | |
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282 | For example, the \c "strings" nodemap contains strings and you do not need |
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283 | the value of the string just the length. Then you can implement an own Reader |
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284 | struct. |
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285 | |
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286 | \code |
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287 | struct LengthReader { |
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288 | typedef int Value; |
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289 | |
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290 | void read(std::istream& is, Value& value) { |
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291 | std::string tmp; |
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292 | is >> tmp; |
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293 | value = tmp.length(); |
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294 | } |
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295 | }; |
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296 | ... |
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297 | reader.readNodeMap<LengthReader>("strings", lengthMap); |
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298 | \endcode |
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299 | |
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300 | The global functionality of the reader class can be changed by giving a |
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301 | special template parameter to the GraphReader class. By default, the |
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302 | template parameter is \c DefaultReaderTraits. A reader traits class |
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303 | should provide an inner template class Reader for each type, and a |
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304 | DefaultReader for skipping a value. |
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305 | |
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306 | The specialization of writing is very similar to that of reading. |
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307 | |
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308 | \section undir Undirected graphs |
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309 | |
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310 | In a file describing an undirected graph (undir graph, for short) you find an |
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311 | \c undiredgeset section instead of the \c edgeset section. The first line of |
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312 | the section describes the names of the maps on the undirected egdes and all |
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313 | next lines describe one undirected edge with the the incident nodes and the |
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314 | values of the map. |
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315 | |
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316 | The format handles directed edge maps as a syntactical sugar???, if there |
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317 | are two maps with names being the same with a \c '+' and a \c '-' prefix |
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318 | then this will be read as a directed map. |
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319 | |
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320 | \code |
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321 | @undiredgeset |
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322 | id capacity +flow -flow |
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323 | 32 2 1 4.3 2.0 0.0 |
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324 | 21 21 5 2.6 0.0 2.6 |
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325 | 21 12 8 3.4 0.0 0.0 |
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326 | \endcode |
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327 | |
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328 | The \c edges section is changed to \c undiredges section. This section |
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329 | describes labeled edges and undirected edges. The directed edge label |
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330 | should start with a \c '+' or a \c '-' prefix to decide the direction |
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331 | of the edge. |
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332 | |
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333 | \code |
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334 | @undiredges |
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335 | undiredge 1 |
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336 | +edge 5 |
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337 | -back 5 |
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338 | \endcode |
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339 | |
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340 | There are similar classes to the \c GraphReader ans \c GraphWriter |
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341 | which handle the undirected graphs. These classes are the |
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342 | \c UndirGraphReader and \UndirGraphWriter. |
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343 | |
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344 | The \c readUndirMap() function reads an undirected map and the |
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345 | \c readUndirEdge() reads an undirected edge from the file, |
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346 | |
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347 | \code |
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348 | reader.readUndirEdgeMap("capacity", capacityMap); |
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349 | reader.readEdgeMap("flow", flowMap); |
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350 | ... |
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351 | reader.readUndirEdge("undir_edge", undir_edge); |
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352 | reader.readEdge("edge", edge); |
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353 | \endcode |
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354 | |
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355 | \section advanced Advanced features |
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356 | |
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357 | The graph reader and writer classes give an easy way to read and write |
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358 | graphs. But sometimes we want more advanced features. In this case we can |
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359 | use the more general <tt>lemon reader and writer</tt> interface. |
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360 | |
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361 | The LEMON file format is a section oriented file format. It contains one or |
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362 | more sections, each starting with a line identifying its type |
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363 | (the word starting with the \c \@ character). |
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364 | The content of the section this way cannot contain line with \c \@ first |
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365 | character. The file may contains comment lines with \c # first character. |
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366 | |
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367 | The \c LemonReader and \c LemonWriter gives a framework to read and |
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368 | write sections. There are various section reader and section writer |
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369 | classes which can be attached to a \c LemonReader or a \c LemonWriter. |
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370 | |
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371 | There are default section readers and writers for reading and writing |
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372 | item sets, and labeled items in the graph. These read and write |
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373 | the format described above. Other type of data can be handled with own |
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374 | section reader and writer classes which are inherited from the |
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375 | \c LemonReader::SectionReader or the \c LemonWriter::SectionWriter classes. |
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376 | |
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377 | The next example defines a special section reader which reads the |
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378 | \c \@description sections into a string: |
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379 | |
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380 | \code |
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381 | class DescriptionReader : LemonReader::SectionReader { |
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382 | protected: |
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383 | virtual bool header(const std::string& line) { |
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384 | std::istringstream ls(line); |
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385 | std::string head; |
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386 | ls >> head; |
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387 | return head == "@description"; |
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388 | } |
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389 | |
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390 | virtual void read(std::istream& is) { |
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391 | std::string line; |
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392 | while (getline(is, line)) { |
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393 | desc += line; |
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394 | } |
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395 | } |
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396 | public: |
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397 | |
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398 | typedef LemonReader::SectionReader Parent; |
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399 | |
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400 | DescriptionReader(LemonReader& reader) : Parent(reader) {} |
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401 | |
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402 | const std::string& description() const { |
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403 | return description; |
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404 | } |
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405 | |
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406 | private: |
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407 | std::string desc; |
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408 | }; |
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409 | \endcode |
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410 | |
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411 | The other advanced stuff of the generalized file format is that |
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412 | multiple edgesets can be stored to the same nodeset. It can be used |
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413 | for example as a network traffic matrix. |
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414 | |
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415 | In our example there is a network with symmetric links and there are assymetric |
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416 | traffic request on the network. This construction can be stored in an |
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417 | undirected graph and in a directed NewEdgeSetAdaptor class. The example |
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418 | shows the input with the LemonReader class: |
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419 | |
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420 | \code |
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421 | UndirListGraph network; |
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422 | UndirListGraph::UndirEdgeSet<double> capacity; |
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423 | NewEdgeSetAdaptor<UndirListGraph> traffic(network); |
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424 | NewEdgeSetAdaptor<UndirListGraph>::EdgeSet<double> request(network); |
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425 | |
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426 | LemonReader reader(std::cin); |
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427 | NodeSetReader nodesetReader(reader, network); |
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428 | UndirEdgeSetReader undirEdgesetReader(reader, network, nodesetReader); |
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429 | undirEdgesetReader.readEdgeMap("capacity", capacity); |
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430 | EdgeSetReader edgesetReader(reader, traffic, nodesetReader); |
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431 | edgesetReader.readEdgeMap("request", request); |
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432 | |
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433 | reader.run(); |
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434 | \endcode |
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435 | |
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436 | Because the GraphReader and the UndirGraphReader can be converted |
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437 | to LemonReader and it can resolve the ID's of the items, the previous |
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438 | result can be achived with the UndirGraphReader class, too. |
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439 | |
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440 | |
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441 | \code |
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442 | UndirListGraph network; |
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443 | UndirListGraph::UndirEdgeSet<double> capacity; |
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444 | NewEdgeSetAdaptor<UndirListGraph> traffic(network); |
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445 | NewEdgeSetAdaptor<UndirListGraph>::EdgeSet<double> request(network); |
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446 | |
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447 | UndirGraphReader reader(std::cin, network); |
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448 | reader.readEdgeMap("capacity", capacity); |
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449 | EdgeSetReader edgesetReader(reader, traffic, reader); |
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450 | edgesetReader.readEdgeMap("request", request); |
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451 | |
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452 | reader.run(); |
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453 | \endcode |
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454 | |
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455 | \author Balazs Dezso |
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456 | */ |
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457 | } |
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