# Changeset 596:293551ad254f in lemon-1.2 for lemon/hao_orlin.h

Ignore:
Timestamp:
04/15/09 09:37:51 (11 years ago)
Branch:
default
Phase:
public
Message:

Improvements and fixes for the minimum cut algorithms (#264)

File:
1 edited

### Legend:

Unmodified
 r581 /// \brief Implementation of the Hao-Orlin algorithm. /// /// Implementation of the Hao-Orlin algorithm class for testing network /// reliability. /// Implementation of the Hao-Orlin algorithm for finding a minimum cut /// in a digraph. namespace lemon { /// \ingroup min_cut /// /// \brief %Hao-Orlin algorithm to find a minimum cut in directed graphs. /// \brief Hao-Orlin algorithm for finding a minimum cut in a digraph. /// /// Hao-Orlin calculates a minimum cut in a directed graph /// \f$D=(V,A)\f$. It takes a fixed node \f$source \in V \f$ and /// This class implements the Hao-Orlin algorithm for finding a minimum /// value cut in a directed graph \f$D=(V,A)\f$. /// It takes a fixed node \f$source \in V \f$ and /// consists of two phases: in the first phase it determines a /// minimum cut with \f$source \f$ on the source-side (i.e. a set /// \f$X\subsetneq V \f$ with \f$source \in X \f$ and minimal /// out-degree) and in the second phase it determines a minimum cut /// \f$X\subsetneq V \f$ with \f$source \in X \f$ and minimal outgoing /// capacity) and in the second phase it determines a minimum cut /// with \f$source \f$ on the sink-side (i.e. a set /// \f$X\subsetneq V \f$ with \f$source \notin X \f$ and minimal /// out-degree). Obviously, the smaller of these two cuts will be a /// \f$X\subsetneq V \f$ with \f$source \notin X \f$ and minimal outgoing /// capacity). Obviously, the smaller of these two cuts will be a /// minimum cut of \f$D \f$. The algorithm is a modified /// push-relabel preflow algorithm and our implementation calculates /// preflow push-relabel algorithm. Our implementation calculates /// the minimum cut in \f$O(n^2\sqrt{m}) \f$ time (we use the /// highest-label rule), or in \f$O(nm)\f$ for unit capacities. The /// purpose of such algorithm is testing network reliability. For an /// undirected graph you can run just the first phase of the /// algorithm or you can use the algorithm of Nagamochi and Ibaraki /// which solves the undirected problem in /// \f$O(nm + n^2 \log n) \f$ time: it is implemented in the /// NagamochiIbaraki algorithm class. /// purpose of such algorithm is e.g. testing network reliability. /// /// \param GR The digraph class the algorithm runs on. /// \param CAP An arc map of capacities which can be any numreric type. /// The default type is \ref concepts::Digraph::ArcMap "GR::ArcMap". /// \param TOL Tolerance class for handling inexact computations. The /// For an undirected graph you can run just the first phase of the /// algorithm or you can use the algorithm of Nagamochi and Ibaraki, /// which solves the undirected problem in \f$O(nm + n^2 \log n) \f$ /// time. It is implemented in the NagamochiIbaraki algorithm class. /// /// \tparam GR The type of the digraph the algorithm runs on. /// \tparam CAP The type of the arc map containing the capacities, /// which can be any numreric type. The default map type is /// \ref concepts::Digraph::ArcMap "GR::ArcMap". /// \tparam TOL Tolerance class for handling inexact computations. The /// default tolerance type is \ref Tolerance "Tolerance". #ifdef DOXYGEN #endif class HaoOrlin { public: /// The digraph type of the algorithm typedef GR Digraph; /// The capacity map type of the algorithm typedef CAP CapacityMap; /// The tolerance type of the algorithm typedef TOL Tolerance; private: typedef GR Digraph; typedef CAP CapacityMap; typedef TOL Tolerance; typedef typename CapacityMap::Value Value; TEMPLATE_GRAPH_TYPEDEFS(Digraph); TEMPLATE_DIGRAPH_TYPEDEFS(Digraph); const Digraph& _graph; public: /// \name Execution control /// \name Execution Control /// The simplest way to execute the algorithm is to use /// one of the member functions called \ref run(). /// \n /// If you need more control on the execution, /// first you must call \ref init(), then the \ref calculateIn() or /// \ref calculateOut() functions. /// If you need better control on the execution, /// you have to call one of the \ref init() functions first, then /// \ref calculateOut() and/or \ref calculateIn(). /// @{ /// \brief Initializes the internal data structures. /// /// Initializes the internal data structures. It creates /// the maps, residual graph adaptors and some bucket structures /// for the algorithm. /// \brief Initialize the internal data structures. /// /// This function initializes the internal data structures. It creates /// the maps and some bucket structures for the algorithm. /// The first node is used as the source node for the push-relabel /// algorithm. void init() { init(NodeIt(_graph)); } /// \brief Initializes the internal data structures. /// /// Initializes the internal data structures. It creates /// the maps, residual graph adaptor and some bucket structures /// for the algorithm. Node \c source  is used as the push-relabel /// algorithm's source. /// \brief Initialize the internal data structures. /// /// This function initializes the internal data structures. It creates /// the maps and some bucket structures for the algorithm. /// The given node is used as the source node for the push-relabel /// algorithm. void init(const Node& source) { _source = source; /// \brief Calculates a minimum cut with \f$source \f$ on the /// \brief Calculate a minimum cut with \f$source \f$ on the /// source-side. /// /// Calculates a minimum cut with \f$source \f$ on the /// This function calculates a minimum cut with \f$source \f$ on the /// source-side (i.e. a set \f$X\subsetneq V \f$ with /// \f$source \in X \f$ and minimal out-degree). /// \f$source \in X \f$ and minimal outgoing capacity). /// /// \pre \ref init() must be called before using this function. void calculateOut() { findMinCutOut(); } /// \brief Calculates a minimum cut with \f$source \f$ on the /// target-side. /// /// Calculates a minimum cut with \f$source \f$ on the /// target-side (i.e. a set \f$X\subsetneq V \f$ with /// \f$source \in X \f$ and minimal out-degree). /// \brief Calculate a minimum cut with \f$source \f$ on the /// sink-side. /// /// This function calculates a minimum cut with \f$source \f$ on the /// sink-side (i.e. a set \f$X\subsetneq V \f$ with /// \f$source \notin X \f$ and minimal outgoing capacity). /// /// \pre \ref init() must be called before using this function. void calculateIn() { findMinCutIn(); /// \brief Runs the algorithm. /// /// Runs the algorithm. It finds nodes \c source and \c target /// arbitrarily and then calls \ref init(), \ref calculateOut() /// \brief Run the algorithm. /// /// This function runs the algorithm. It finds nodes \c source and /// \c target arbitrarily and then calls \ref init(), \ref calculateOut() /// and \ref calculateIn(). void run() { } /// \brief Runs the algorithm. /// /// Runs the algorithm. It uses the given \c source node, finds a /// proper \c target and then calls the \ref init(), \ref /// calculateOut() and \ref calculateIn(). /// \brief Run the algorithm. /// /// This function runs the algorithm. It uses the given \c source node, /// finds a proper \c target node and then calls the \ref init(), /// \ref calculateOut() and \ref calculateIn(). void run(const Node& s) { init(s); /// \name Query Functions /// The result of the %HaoOrlin algorithm /// can be obtained using these functions. /// \n /// Before using these functions, either \ref run(), \ref /// calculateOut() or \ref calculateIn() must be called. /// can be obtained using these functions.\n /// \ref run(), \ref calculateOut() or \ref calculateIn() /// should be called before using them. /// @{ /// \brief Returns the value of the minimum value cut. /// /// Returns the value of the minimum value cut. /// \brief Return the value of the minimum cut. /// /// This function returns the value of the minimum cut. /// /// \pre \ref run(), \ref calculateOut() or \ref calculateIn() /// must be called before using this function. Value minCutValue() const { return _min_cut; /// \brief Returns a minimum cut. /// /// Sets \c nodeMap to the characteristic vector of a minimum /// value cut: it will give a nonempty set \f$X\subsetneq V \f$ /// with minimal out-degree (i.e. \c nodeMap will be true exactly /// for the nodes of \f$X \f$).  \pre nodeMap should be a /// bool-valued node-map. template Value minCutMap(NodeMap& nodeMap) const { /// \brief Return a minimum cut. /// /// This function sets \c cutMap to the characteristic vector of a /// minimum value cut: it will give a non-empty set \f$X\subsetneq V \f$ /// with minimal outgoing capacity (i.e. \c cutMap will be \c true exactly /// for the nodes of \f$X \f$). /// /// \param cutMap A \ref concepts::WriteMap "writable" node map with /// \c bool (or convertible) value type. /// /// \return The value of the minimum cut. /// /// \pre \ref run(), \ref calculateOut() or \ref calculateIn() /// must be called before using this function. template Value minCutMap(CutMap& cutMap) const { for (NodeIt it(_graph); it != INVALID; ++it) { nodeMap.set(it, (*_min_cut_map)[it]); cutMap.set(it, (*_min_cut_map)[it]); } return _min_cut; }; //class HaoOrlin } //namespace lemon