[1118] | 1 | namespace lemon { |
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[1114] | 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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[1540] | 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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[1114] | 11 | |
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| 12 | \section format The general file format |
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| 13 | |
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[1532] | 14 | The file contains sections in the following order: |
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[1114] | 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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[1532] | 20 | \li attributes |
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[1114] | 21 | |
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[1540] | 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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[1522] | 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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[1540] | 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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[1114] | 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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[1522] | 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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[1540] | 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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[1114] | 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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[1540] | 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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[1118] | 68 | label on them). The section starts with |
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[1522] | 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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[1540] | 73 | and then the ID as described in the \e nodeset section. |
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[1114] | 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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[1540] | 81 | The last section describes the <em>labeled (distinguished) edges</em> |
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[1333] | 82 | (i.e. edges having a special label on them). It starts with \c \@edges |
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[1114] | 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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[1540] | 86 | @edges |
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[1114] | 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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[1532] | 94 | The attributes section can handle some information about the graph. It |
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[1540] | 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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[1532] | 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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[1522] | 106 | <tt> \@end </tt> |
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| 107 | |
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| 108 | line. |
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| 109 | |
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[1114] | 110 | |
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| 111 | \section use Using graph input-output |
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[1540] | 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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[1114] | 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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[1526] | 126 | you should first give writing commands to the writer. You can declare |
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[1540] | 127 | writing command as \c NodeMap or \c EdgeMap writing and labeled Node and |
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[1114] | 128 | Edge writing. |
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| 129 | |
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| 130 | \code |
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[1333] | 131 | GraphWriter<ListGraph> writer(std::cout, graph); |
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[1114] | 132 | \endcode |
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| 133 | |
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[1394] | 134 | The \c writeNodeMap() function declares a \c NodeMap writing command in the |
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[1540] | 135 | \c GraphWriter. You should give a name to the map and the map |
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[1522] | 136 | object as parameters. The NodeMap writing command with name "id" should write a |
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[1540] | 137 | unique map because it will be regarded as an ID map. |
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[1114] | 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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[1394] | 143 | writer.writeNodeMap("id", nodeIdMap); |
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[1114] | 144 | |
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[1394] | 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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[1114] | 148 | \endcode |
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| 149 | |
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[1394] | 150 | With the \c writeEdgeMap() member function you can give an edge map |
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[1333] | 151 | writing command similar to the NodeMaps. |
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[1114] | 152 | |
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| 153 | \see IdMap, DescriptorMap |
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[1522] | 154 | |
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[1114] | 155 | \code |
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| 156 | DescriptorMap<ListGraph, Edge, ListGraph::EdgeMap<int> > edgeDescMap(graph); |
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[1394] | 157 | writer.writeEdgeMap("descriptor", edgeDescMap); |
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[1114] | 158 | |
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[1394] | 159 | writer.writeEdgeMap("weight", weightMap); |
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| 160 | writer.writeEdgeMap("label", labelMap); |
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[1114] | 161 | \endcode |
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| 162 | |
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[1522] | 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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[1114] | 166 | |
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| 167 | \code |
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[1394] | 168 | writer.writeNode("source", sourceNode); |
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| 169 | writer.writeNode("target", targetNode); |
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[1114] | 170 | |
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[1394] | 171 | writer.writeEdge("observed", edge); |
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[1114] | 172 | \endcode |
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| 173 | |
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[1532] | 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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[1114] | 181 | After you give all write commands you must call the \c run() member |
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[1522] | 182 | function, which executes all the writing commands. |
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[1114] | 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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[1540] | 190 | The file to be read may contain several maps and labeled nodes or edges. |
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[1114] | 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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[1522] | 193 | the GraphWriter but the reading method does not depend on the order of the |
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[1114] | 194 | given commands. |
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| 195 | |
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[1522] | 196 | The reader object assumes that each not readed value does not contain |
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[1118] | 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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[1114] | 199 | |
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| 200 | \code |
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[1333] | 201 | GraphReader<ListGraph> reader(std::cin, graph); |
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[1114] | 202 | \endcode |
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| 203 | |
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[1540] | 204 | The \c readNodeMap() function reads a map from the \c nodeset section. |
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[1522] | 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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[1114] | 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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[1522] | 210 | |
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[1114] | 211 | \code |
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[1394] | 212 | reader.readNodeMap("x-coord", xCoordMap); |
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| 213 | reader.readNodeMap("y-coord", yCoordMap); |
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[1114] | 214 | |
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[1394] | 215 | reader.readNodeMap<QuotedStringReader>("label", labelMap); |
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[1114] | 216 | reader.skipNodeMap<QuotedStringReader>("description"); |
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| 217 | |
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[1394] | 218 | reader.readNodeMap("color", colorMap); |
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[1114] | 219 | \endcode |
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| 220 | |
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[1394] | 221 | With the \c readEdgeMap() member function you can give an edge map |
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[1114] | 222 | reading command similar to the NodeMaps. |
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| 223 | |
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| 224 | \code |
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[1394] | 225 | reader.readEdgeMap("weight", weightMap); |
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| 226 | reader.readEdgeMap("label", labelMap); |
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[1114] | 227 | \endcode |
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| 228 | |
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[1394] | 229 | With \c readNode() and \c readEdge() functions you can read labeled Nodes and |
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[1114] | 230 | Edges. |
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| 231 | |
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| 232 | \code |
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[1394] | 233 | reader.readNode("source", sourceNode); |
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| 234 | reader.readNode("target", targetNode); |
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[1114] | 235 | |
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[1394] | 236 | reader.readEdge("observed", edge); |
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[1114] | 237 | \endcode |
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| 238 | |
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[1532] | 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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[1114] | 248 | After you give all read commands you must call the \c run() member |
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[1522] | 249 | function, which executes all the commands. |
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[1114] | 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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[1540] | 255 | \anchor rwbackground |
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[1527] | 256 | \section types Background of Reading and Writing |
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[1540] | 257 | |
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| 258 | |
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[1527] | 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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[1114] | 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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[1527] | 264 | want to store it in a map, the reader skips a character sequence without |
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[1540] | 265 | whitespaces. |
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[1114] | 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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[1333] | 270 | With this template parameter you can control how the Reader reads |
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[1114] | 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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[1527] | 282 | For example, the \c "strings" nodemap contains strings and you do not need |
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[1540] | 283 | the value of the string just the length. Then you can implement an own Reader |
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[1114] | 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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[1394] | 297 | reader.readNodeMap<LengthReader>("strings", lengthMap); |
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[1114] | 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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[1526] | 301 | special template parameter to the GraphReader class. By default, the |
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[1118] | 302 | template parameter is \c DefaultReaderTraits. A reader traits class |
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[1540] | 303 | should provide an inner template class Reader for each type, and a |
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[1114] | 304 | DefaultReader for skipping a value. |
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| 305 | |
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[1540] | 306 | The specialization of writing is very similar to that of reading. |
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[1114] | 307 | |
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[1540] | 308 | \section undir Undirected graphs |
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[1532] | 309 | |
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[1540] | 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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[1532] | 315 | |
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[1540] | 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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[1532] | 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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[1540] | 328 | The \c edges section is changed to \c undiredges section. This section |
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[1532] | 329 | describes labeled edges and undirected edges. The directed edge label |
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[1540] | 330 | should start with a \c '+' or a \c '-' prefix to decide the direction |
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[1532] | 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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[1540] | 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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[1532] | 360 | |
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[1540] | 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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[1532] | 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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[1540] | 372 | item sets, and labeled items in the graph. These read and write |
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[1532] | 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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[1540] | 413 | for example as a network traffic matrix. |
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[1532] | 414 | |
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[1540] | 415 | In our example there is a network with symmetric links and there are assymetric |
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[1532] | 416 | traffic request on the network. This construction can be stored in an |
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[1540] | 417 | undirected graph and in a directed NewEdgeSetAdaptor class. The example |
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[1532] | 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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[1540] | 438 | result can be achived with the UndirGraphReader class, too. |
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[1532] | 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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[1333] | 455 | \author Balazs Dezso |
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[1114] | 456 | */ |
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[1333] | 457 | } |
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