# Changeset 2216:1e45cdeea3cc in lemon-0.x

Ignore:
Timestamp:
09/14/06 21:11:24 (14 years ago)
Branch:
default
Phase:
public
Convert:
svn:c9d7d8f5-90d6-0310-b91f-818b3a526b0e/lemon/trunk@2946
Message:

The recent progresses on the tutorial due to Mark.

Files:
4 edited

Unmodified
Removed
• ## demo/Makefile.am

 r2195 demo/grid_ugraph_demo \ demo/topology_demo \ demo/topological_ordering \ demo/simann_maxcut_demo \ demo/disjoint_paths_demo \ demo_topology_demo_SOURCES = demo/topology_demo.cc demo_topological_ordering_SOURCES = demo/topological_ordering.cc demo_simann_maxcut_demo_SOURCES = demo/simann_maxcut_demo.cc
• ## doc/Makefile.am

 r2196 doc/graphs.dox \ doc/groups.dox \ doc/lemon_file_format.dox \ doc/license.dox \ doc/mainpage.dox \ doc/namespaces.dox \ doc/quicktour.dox \ doc/read_write_bg.dox \ doc/ugraphs.dox
• ## doc/algorithms.dox

 r2196 namespace lemon { /** \page algorithms Algorithms Place-holder page for algorithms. \section algo_bfs_dfs Bfs/Dfs Both \ref lemon::Bfs "Bfs" and \ref lemon::Dfs "Dfs" are highly adaptable and efficient implementations of the well known algorithms. The algorithms are placed most cases in separated files named after the algorithm itself but lower case as all other header file names. For example the next Bfs class is in the \c lemon/bfs.h. \subsection Bfs The algorithm is implemented in the \ref lemon::Bfs "Bfs" template class - rather than as function. The class has two template parameters: \b GR and \TR.
GR is the graph the algorithm runs on. It has \ref lemon::ListGraph "ListGraph" as default type. TR is a Traits class commonly used to easy the parametrization of templates. In most cases you wont need to modify the default type \ref lemon::BfsDefaultTraits "BfsDefaultTraits". To use the class, declare it! \code Bfs  bfs(gr); \endcode Note the lack of second template argument because of the default parameter. It provides a simple but powerful interface to control the execution. \code int dist = bfs.run(s,t); \endcode It finds the shortest path from node \c s to node \c t and returns it, or zero if there is no path from \c s to \c t.
If you want the shortest path from a specified node to all other node, just write: \code bfs.run(s); \endcode Now the distances and path information are stored in maps which you can access with member functions like \ref lemon::Bfs::distMap "distMap()" or \ref lemon::Bfs::predMap "predMap()".
Or more directly whit other member functions like \c predNode(). Once the algorithm is finished (or to be precise reached that node) \ref lemon::Bfs::dist "dist()" or \ref lemon::Bfs::predNode "predNode()" can be called. For an example let's say we want to print the shortest path of those nodes which are in a certain distance. \code bfs.run(s); for( ListUGraph::NodeIt  n(gr); n != INVALID; ++n ) { if( bfs.reached(n) && bfs.dist(n) <= max_dist ) { std::cout << gr.id(n); Node  prev = bfs.prevNode(n); while( prev != INVALID ) { std::cout << "<-" << gr.id(prev); prev = bfs.prevNode(n); } std::cout << std::endl; } } \endcode \subsubsection bfs_adv_control Advanced control In the previous code we only used \c run(). Now we introduce the way you can directly control the execution of the algorithm. First you have to initialize the variables with \ref lemon::Bfs::init "init()". \code bfs.init(); \endcode Then you add one or more source nodes to the queue. They will be processed, as they would be reached by the algorithm before. And yes - you can add more sources during the execution. \code bfs.addSource(node_1); bfs.addSource(node_2); ... \endcode And finally you can start the process with \ref lemon::Bfs::start "start()", or you can write your own loop to process the nodes one-by-one. \todo demo for bfs advanced control \subsection Dfs Since Dfs is very similar to Bfs with a few tiny differences we only see a bit more complex example to demonstrate Dfs's capabilities. We will see a program, which solves the problem of topological ordering. We need to know in which order we should put on our clothes. The program will do the following:
1. We run the dfs algorithm to all nodes.
2. Put every node into a list when processed completely.
3. Write out the list in reverse order.
\dontinclude topological_ordering.cc First of all we will need an own \ref lemon::Dfs::ProcessedMap "ProcessedMap". The ordering will be done through it. \skip SerializingWriteMap \until }; The class meets the \ref lemon::WriteMap "WriteMap" concept. In it's \c set() method the only thing we need to do is insert the key - that is the node who's processing just finished - into the beginning of the list. First we declare the needed data structures: the graph and a map to store the nodes' label. \skip ListGraph \until label Now we build a graph. But keep in mind that it must be DAG because cyclic graphs has no topological ordering. \skip belt \until trousers We label them... \skip label \until trousers Then add directed edges which represent the precedences between those items. \skip trousers, belt \until ); See how easy is to access the internal information of this algorithm trough maps. We only need to set our own map as the class's \ref lemon::Dfs::ProcessedMap "ProcessedMap". \skip Dfs \until run And now comes the third part. Write out the list in reverse order. But the list was composed in reverse way (with \c push_front() instead of \c push_back() so we just iterate it. \skip std \until endl The program is to be found in the \ref demo directory: \ref topological_ordering.cc */ }
• ## doc/tutorial.dox

 r2195 namespace lemon { /** \page Tutorial LEMON Tutorial
• \ref maps1
• Lemon Graph File Format
• \ref lemon_file_format