COIN-OR::LEMON - Graph Library

Changeset 1183:8f623d1833a7 in lemon-0.x for doc/quicktour.dox

03/03/05 18:20:08 (19 years ago)

Some more documentation (sorry, I forgot to check the doxygen.log and now I am under windows)

1 edited


  • doc/quicktour.dox

    r1181 r1183  
    1111in telecommunication, computer networks, and other areas that I cannot
    1212think of now. A very natural way of modelling these networks is by means
    13 of a <b> graph</b> (we will always mean a directed graph by that).
     13of a <b> graph</b> (we will always mean a directed graph by that and say
     14<b> undirected graph </b> otherwise).
    1415So if you want to write a program that works with
    15 graphs then you might find it useful to use our library LEMON.
     16graphs then you might find it useful to use our library LEMON. LEMON
     17defines various graph concepts depending on what you want to do with the
     18graph: a very good description can be found in the page
     19about \ref graphs "graphs".
     21You will also want to assign data to the edges or nodes of the graph, for example a length or capacity function defined on the edges. You can do this in LEMON using so called \ref maps "maps". You can define a map on the nodes or on the edges of the graph and the value of the map (the range of the function) can be practically almost any type. Read more about maps \ref maps-page "here".
    1923Some examples are the following (you will find links next to the code fragments that help to download full demo programs):
    4650-# The following code shows how to read a graph from a stream (e.g. a file). LEMON supports the DIMACS file format: it can read a graph instance from a file
    47 in that format (find the documentation of the format on the web).
     51in that format (find the documentation of the DIMECS file format on the web).
    4953Graph g;
    5155readDimacs(f, g);
    53 One can also store network (graph+capacity on the edges) instances and other things in DIMACS format: to see the details read the documentation of the \ref dimacs.h "Dimacs file format reader".
     57One can also store network (graph+capacity on the edges) instances and other things in DIMACS format and use these in LEMON: to see the details read the documentation of the \ref dimacs.h "Dimacs file format reader".
    5862usually solved using Dijkstra's algorithm. A utility
    5963that solves this is  the \ref lemon::Dijkstra "LEMON Dijkstra class".
    60 A simple program using the \ref lemon::Dijkstra "LEMON Dijkstra class" is
    61 as follows (we do not include the part that instantiates the graph and the length function):
     64The following code is a simple program using the \ref lemon::Dijkstra "LEMON
     65Dijkstra class" and it also shows how to define a map on the edges (the length
    64   typedef Graph::EdgeMap<int> LengthMap;
    65   Graph G;
    66   Node s, t;
    67   LengthMap cap(G);
    68         ...
    69   Dijkstra<Graph, LengthMap>
    70         dijkstra_test(G, cap);
     70    typedef ListGraph Graph;
     71    typedef Graph::Node Node;
     72    typedef Graph::Edge Edge;
     73    typedef Graph::EdgeMap<int> LengthMap;
     75    Graph g;
     77    //An example from Ahuja's book
     79    Node s=g.addNode();
     80    Node v2=g.addNode();
     81    Node v3=g.addNode();
     82    Node v4=g.addNode();
     83    Node v5=g.addNode();
     84    Node t=g.addNode();
     86    Edge s_v2=g.addEdge(s, v2);
     87    Edge s_v3=g.addEdge(s, v3);
     88    Edge v2_v4=g.addEdge(v2, v4);
     89    Edge v2_v5=g.addEdge(v2, v5);
     90    Edge v3_v5=g.addEdge(v3, v5);
     91    Edge v4_t=g.addEdge(v4, t);
     92    Edge v5_t=g.addEdge(v5, t);
     94    LengthMap len(g);
     96    len.set(s_v2, 10);
     97    len.set(s_v3, 10);
     98    len.set(v2_v4, 5);
     99    len.set(v2_v5, 8);
     100    len.set(v3_v5, 5);
     101    len.set(v4_t, 8);
     102    len.set(v5_t, 8);
     104    std::cout << "The id of s is " <<<< ", the id of t is " <<<<"."<<std::endl;
     106    std::cout << "Dijkstra algorithm test..." << std::endl;
     108    Dijkstra<Graph, LengthMap> dijkstra_test(g,len);
     113    std::cout << "The distance of node t from node s: " << dijkstra_test.dist(t)<<std::endl;
     115    std::cout << "The shortest path from s to t goes through the following nodes (the first one is t, the last one is s): "<<std::endl;
     117    for (Node v=t;v != s; v=dijkstra_test.predNode(v)){
     118        std::cout << << "<-";
     119    }
     120    std::cout << << std::endl; 
     123See the whole program in \file
     125The first part of the code is self-explanatory: we build the graph and set the
     126length values of the edges. Then we instantiate a member of the Dijkstra class
     127and run the Dijkstra algorithm from node \c s. After this we read some of the
     129You can do much more with the Dijkstra class, for example you can run it step
     130by step and gain full control of the execution. For a detailed description, see the documentation of the \ref lemon::Dijkstra "LEMON Dijkstra class".
    74133- If you want to design a network and want to minimize the total length
    86 Some more detailed introduction can be obtained by following the links
    87 below:
    89 \ref graphs "Graph structures"
    90 play a central role in LEMON, so if you are new to the library,
    91 you probably should start \ref graphs "here".
    92 (You can also find that page along with others under
    93 <a class="el" href="pages.html"> Related Pages </a>.)
    95 If you are
    96 interested in data structures and algorithms in more details, then
    97 you should browse the reference manual part of the documentation.
    98 Section <a class="el" href="modules.html"> Modules </a>
    99  is a good starting point for this.
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