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