kpeter@765: /* -*- C++ -*-
kpeter@765:  *
kpeter@765:  * This file is a part of LEMON, a generic C++ optimization library
kpeter@765:  *
kpeter@765:  * Copyright (C) 2003-2008
kpeter@765:  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
kpeter@765:  * (Egervary Research Group on Combinatorial Optimization, EGRES).
kpeter@765:  *
kpeter@765:  * Permission to use, modify and distribute this software is granted
kpeter@765:  * provided that this copyright notice appears in all copies. For
kpeter@765:  * precise terms see the accompanying LICENSE file.
kpeter@765:  *
kpeter@765:  * This software is provided "AS IS" with no warranty of any kind,
kpeter@765:  * express or implied, and with no claim as to its suitability for any
kpeter@765:  * purpose.
kpeter@765:  *
kpeter@765:  */
kpeter@765: 
kpeter@765: #ifndef LEMON_KARP_H
kpeter@765: #define LEMON_KARP_H
kpeter@765: 
kpeter@768: /// \ingroup min_mean_cycle
kpeter@765: ///
kpeter@765: /// \file
kpeter@765: /// \brief Karp's algorithm for finding a minimum mean cycle.
kpeter@765: 
kpeter@765: #include <vector>
kpeter@765: #include <limits>
kpeter@765: #include <lemon/core.h>
kpeter@765: #include <lemon/path.h>
kpeter@765: #include <lemon/tolerance.h>
kpeter@765: #include <lemon/connectivity.h>
kpeter@765: 
kpeter@765: namespace lemon {
kpeter@765: 
kpeter@765:   /// \brief Default traits class of Karp algorithm.
kpeter@765:   ///
kpeter@765:   /// Default traits class of Karp algorithm.
kpeter@765:   /// \tparam GR The type of the digraph.
kpeter@765:   /// \tparam LEN The type of the length map.
kpeter@765:   /// It must conform to the \ref concepts::ReadMap "ReadMap" concept.
kpeter@765: #ifdef DOXYGEN
kpeter@765:   template <typename GR, typename LEN>
kpeter@765: #else
kpeter@765:   template <typename GR, typename LEN,
kpeter@765:     bool integer = std::numeric_limits<typename LEN::Value>::is_integer>
kpeter@765: #endif
kpeter@765:   struct KarpDefaultTraits
kpeter@765:   {
kpeter@765:     /// The type of the digraph
kpeter@765:     typedef GR Digraph;
kpeter@765:     /// The type of the length map
kpeter@765:     typedef LEN LengthMap;
kpeter@765:     /// The type of the arc lengths
kpeter@765:     typedef typename LengthMap::Value Value;
kpeter@765: 
kpeter@765:     /// \brief The large value type used for internal computations
kpeter@765:     ///
kpeter@765:     /// The large value type used for internal computations.
kpeter@765:     /// It is \c long \c long if the \c Value type is integer,
kpeter@765:     /// otherwise it is \c double.
kpeter@765:     /// \c Value must be convertible to \c LargeValue.
kpeter@765:     typedef double LargeValue;
kpeter@765: 
kpeter@765:     /// The tolerance type used for internal computations
kpeter@765:     typedef lemon::Tolerance<LargeValue> Tolerance;
kpeter@765: 
kpeter@765:     /// \brief The path type of the found cycles
kpeter@765:     ///
kpeter@765:     /// The path type of the found cycles.
kpeter@765:     /// It must conform to the \ref lemon::concepts::Path "Path" concept
kpeter@765:     /// and it must have an \c addBack() function.
kpeter@765:     typedef lemon::Path<Digraph> Path;
kpeter@765:   };
kpeter@765: 
kpeter@765:   // Default traits class for integer value types
kpeter@765:   template <typename GR, typename LEN>
kpeter@765:   struct KarpDefaultTraits<GR, LEN, true>
kpeter@765:   {
kpeter@765:     typedef GR Digraph;
kpeter@765:     typedef LEN LengthMap;
kpeter@765:     typedef typename LengthMap::Value Value;
kpeter@765: #ifdef LEMON_HAVE_LONG_LONG
kpeter@765:     typedef long long LargeValue;
kpeter@765: #else
kpeter@765:     typedef long LargeValue;
kpeter@765: #endif
kpeter@765:     typedef lemon::Tolerance<LargeValue> Tolerance;
kpeter@765:     typedef lemon::Path<Digraph> Path;
kpeter@765:   };
kpeter@765: 
kpeter@765: 
kpeter@768:   /// \addtogroup min_mean_cycle
kpeter@765:   /// @{
kpeter@765: 
kpeter@765:   /// \brief Implementation of Karp's algorithm for finding a minimum
kpeter@765:   /// mean cycle.
kpeter@765:   ///
kpeter@765:   /// This class implements Karp's algorithm for finding a directed
kpeter@765:   /// cycle of minimum mean length (cost) in a digraph.
kpeter@768:   /// It runs in time O(ne) and uses space O(n<sup>2</sup>+e).
kpeter@765:   ///
kpeter@765:   /// \tparam GR The type of the digraph the algorithm runs on.
kpeter@765:   /// \tparam LEN The type of the length map. The default
kpeter@765:   /// map type is \ref concepts::Digraph::ArcMap "GR::ArcMap<int>".
kpeter@765: #ifdef DOXYGEN
kpeter@765:   template <typename GR, typename LEN, typename TR>
kpeter@765: #else
kpeter@765:   template < typename GR,
kpeter@765:              typename LEN = typename GR::template ArcMap<int>,
kpeter@765:              typename TR = KarpDefaultTraits<GR, LEN> >
kpeter@765: #endif
kpeter@765:   class Karp
kpeter@765:   {
kpeter@765:   public:
kpeter@765: 
kpeter@765:     /// The type of the digraph
kpeter@765:     typedef typename TR::Digraph Digraph;
kpeter@765:     /// The type of the length map
kpeter@765:     typedef typename TR::LengthMap LengthMap;
kpeter@765:     /// The type of the arc lengths
kpeter@765:     typedef typename TR::Value Value;
kpeter@765: 
kpeter@765:     /// \brief The large value type
kpeter@765:     ///
kpeter@765:     /// The large value type used for internal computations.
kpeter@765:     /// Using the \ref KarpDefaultTraits "default traits class",
kpeter@765:     /// it is \c long \c long if the \c Value type is integer,
kpeter@765:     /// otherwise it is \c double.
kpeter@765:     typedef typename TR::LargeValue LargeValue;
kpeter@765: 
kpeter@765:     /// The tolerance type
kpeter@765:     typedef typename TR::Tolerance Tolerance;
kpeter@765: 
kpeter@765:     /// \brief The path type of the found cycles
kpeter@765:     ///
kpeter@765:     /// The path type of the found cycles.
kpeter@765:     /// Using the \ref KarpDefaultTraits "default traits class",
kpeter@765:     /// it is \ref lemon::Path "Path<Digraph>".
kpeter@765:     typedef typename TR::Path Path;
kpeter@765: 
kpeter@765:     /// The \ref KarpDefaultTraits "traits class" of the algorithm
kpeter@765:     typedef TR Traits;
kpeter@765: 
kpeter@765:   private:
kpeter@765: 
kpeter@765:     TEMPLATE_DIGRAPH_TYPEDEFS(Digraph);
kpeter@765: 
kpeter@765:     // Data sturcture for path data
kpeter@765:     struct PathData
kpeter@765:     {
kpeter@765:       LargeValue dist;
kpeter@765:       Arc pred;
kpeter@767:       PathData(LargeValue d, Arc p = INVALID) :
kpeter@767:         dist(d), pred(p) {}
kpeter@765:     };
kpeter@765: 
kpeter@765:     typedef typename Digraph::template NodeMap<std::vector<PathData> >
kpeter@765:       PathDataNodeMap;
kpeter@765: 
kpeter@765:   private:
kpeter@765: 
kpeter@765:     // The digraph the algorithm runs on
kpeter@765:     const Digraph &_gr;
kpeter@765:     // The length of the arcs
kpeter@765:     const LengthMap &_length;
kpeter@765: 
kpeter@765:     // Data for storing the strongly connected components
kpeter@765:     int _comp_num;
kpeter@765:     typename Digraph::template NodeMap<int> _comp;
kpeter@765:     std::vector<std::vector<Node> > _comp_nodes;
kpeter@765:     std::vector<Node>* _nodes;
kpeter@765:     typename Digraph::template NodeMap<std::vector<Arc> > _out_arcs;
kpeter@765: 
kpeter@765:     // Data for the found cycle
kpeter@765:     LargeValue _cycle_length;
kpeter@765:     int _cycle_size;
kpeter@765:     Node _cycle_node;
kpeter@765: 
kpeter@765:     Path *_cycle_path;
kpeter@765:     bool _local_path;
kpeter@765: 
kpeter@765:     // Node map for storing path data
kpeter@765:     PathDataNodeMap _data;
kpeter@765:     // The processed nodes in the last round
kpeter@765:     std::vector<Node> _process;
kpeter@765: 
kpeter@765:     Tolerance _tolerance;
kpeter@767:     
kpeter@767:     // Infinite constant
kpeter@767:     const LargeValue INF;
kpeter@765: 
kpeter@765:   public:
kpeter@765: 
kpeter@765:     /// \name Named Template Parameters
kpeter@765:     /// @{
kpeter@765: 
kpeter@765:     template <typename T>
kpeter@765:     struct SetLargeValueTraits : public Traits {
kpeter@765:       typedef T LargeValue;
kpeter@765:       typedef lemon::Tolerance<T> Tolerance;
kpeter@765:     };
kpeter@765: 
kpeter@765:     /// \brief \ref named-templ-param "Named parameter" for setting
kpeter@765:     /// \c LargeValue type.
kpeter@765:     ///
kpeter@765:     /// \ref named-templ-param "Named parameter" for setting \c LargeValue
kpeter@765:     /// type. It is used for internal computations in the algorithm.
kpeter@765:     template <typename T>
kpeter@765:     struct SetLargeValue
kpeter@765:       : public Karp<GR, LEN, SetLargeValueTraits<T> > {
kpeter@765:       typedef Karp<GR, LEN, SetLargeValueTraits<T> > Create;
kpeter@765:     };
kpeter@765: 
kpeter@765:     template <typename T>
kpeter@765:     struct SetPathTraits : public Traits {
kpeter@765:       typedef T Path;
kpeter@765:     };
kpeter@765: 
kpeter@765:     /// \brief \ref named-templ-param "Named parameter" for setting
kpeter@765:     /// \c %Path type.
kpeter@765:     ///
kpeter@765:     /// \ref named-templ-param "Named parameter" for setting the \c %Path
kpeter@765:     /// type of the found cycles.
kpeter@765:     /// It must conform to the \ref lemon::concepts::Path "Path" concept
kpeter@765:     /// and it must have an \c addFront() function.
kpeter@765:     template <typename T>
kpeter@765:     struct SetPath
kpeter@765:       : public Karp<GR, LEN, SetPathTraits<T> > {
kpeter@765:       typedef Karp<GR, LEN, SetPathTraits<T> > Create;
kpeter@765:     };
kpeter@765: 
kpeter@765:     /// @}
kpeter@765: 
kpeter@765:   public:
kpeter@765: 
kpeter@765:     /// \brief Constructor.
kpeter@765:     ///
kpeter@765:     /// The constructor of the class.
kpeter@765:     ///
kpeter@765:     /// \param digraph The digraph the algorithm runs on.
kpeter@765:     /// \param length The lengths (costs) of the arcs.
kpeter@765:     Karp( const Digraph &digraph,
kpeter@765:           const LengthMap &length ) :
kpeter@765:       _gr(digraph), _length(length), _comp(digraph), _out_arcs(digraph),
kpeter@765:       _cycle_length(0), _cycle_size(1), _cycle_node(INVALID),
kpeter@767:       _cycle_path(NULL), _local_path(false), _data(digraph),
kpeter@767:       INF(std::numeric_limits<LargeValue>::has_infinity ?
kpeter@767:           std::numeric_limits<LargeValue>::infinity() :
kpeter@767:           std::numeric_limits<LargeValue>::max())
kpeter@765:     {}
kpeter@765: 
kpeter@765:     /// Destructor.
kpeter@765:     ~Karp() {
kpeter@765:       if (_local_path) delete _cycle_path;
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \brief Set the path structure for storing the found cycle.
kpeter@765:     ///
kpeter@765:     /// This function sets an external path structure for storing the
kpeter@765:     /// found cycle.
kpeter@765:     ///
kpeter@765:     /// If you don't call this function before calling \ref run() or
kpeter@765:     /// \ref findMinMean(), it will allocate a local \ref Path "path"
kpeter@765:     /// structure. The destuctor deallocates this automatically
kpeter@765:     /// allocated object, of course.
kpeter@765:     ///
kpeter@765:     /// \note The algorithm calls only the \ref lemon::Path::addFront()
kpeter@765:     /// "addFront()" function of the given path structure.
kpeter@765:     ///
kpeter@765:     /// \return <tt>(*this)</tt>
kpeter@765:     Karp& cycle(Path &path) {
kpeter@765:       if (_local_path) {
kpeter@765:         delete _cycle_path;
kpeter@765:         _local_path = false;
kpeter@765:       }
kpeter@765:       _cycle_path = &path;
kpeter@765:       return *this;
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \name Execution control
kpeter@765:     /// The simplest way to execute the algorithm is to call the \ref run()
kpeter@765:     /// function.\n
kpeter@765:     /// If you only need the minimum mean length, you may call
kpeter@765:     /// \ref findMinMean().
kpeter@765: 
kpeter@765:     /// @{
kpeter@765: 
kpeter@765:     /// \brief Run the algorithm.
kpeter@765:     ///
kpeter@765:     /// This function runs the algorithm.
kpeter@765:     /// It can be called more than once (e.g. if the underlying digraph
kpeter@765:     /// and/or the arc lengths have been modified).
kpeter@765:     ///
kpeter@765:     /// \return \c true if a directed cycle exists in the digraph.
kpeter@765:     ///
kpeter@765:     /// \note <tt>mmc.run()</tt> is just a shortcut of the following code.
kpeter@765:     /// \code
kpeter@765:     ///   return mmc.findMinMean() && mmc.findCycle();
kpeter@765:     /// \endcode
kpeter@765:     bool run() {
kpeter@765:       return findMinMean() && findCycle();
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \brief Find the minimum cycle mean.
kpeter@765:     ///
kpeter@765:     /// This function finds the minimum mean length of the directed
kpeter@765:     /// cycles in the digraph.
kpeter@765:     ///
kpeter@765:     /// \return \c true if a directed cycle exists in the digraph.
kpeter@765:     bool findMinMean() {
kpeter@765:       // Initialization and find strongly connected components
kpeter@765:       init();
kpeter@765:       findComponents();
kpeter@765:       
kpeter@765:       // Find the minimum cycle mean in the components
kpeter@765:       for (int comp = 0; comp < _comp_num; ++comp) {
kpeter@765:         if (!initComponent(comp)) continue;
kpeter@765:         processRounds();
kpeter@765:         updateMinMean();
kpeter@765:       }
kpeter@765:       return (_cycle_node != INVALID);
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \brief Find a minimum mean directed cycle.
kpeter@765:     ///
kpeter@765:     /// This function finds a directed cycle of minimum mean length
kpeter@765:     /// in the digraph using the data computed by findMinMean().
kpeter@765:     ///
kpeter@765:     /// \return \c true if a directed cycle exists in the digraph.
kpeter@765:     ///
kpeter@765:     /// \pre \ref findMinMean() must be called before using this function.
kpeter@765:     bool findCycle() {
kpeter@765:       if (_cycle_node == INVALID) return false;
kpeter@765:       IntNodeMap reached(_gr, -1);
kpeter@765:       int r = _data[_cycle_node].size();
kpeter@765:       Node u = _cycle_node;
kpeter@765:       while (reached[u] < 0) {
kpeter@765:         reached[u] = --r;
kpeter@765:         u = _gr.source(_data[u][r].pred);
kpeter@765:       }
kpeter@765:       r = reached[u];
kpeter@765:       Arc e = _data[u][r].pred;
kpeter@765:       _cycle_path->addFront(e);
kpeter@765:       _cycle_length = _length[e];
kpeter@765:       _cycle_size = 1;
kpeter@765:       Node v;
kpeter@765:       while ((v = _gr.source(e)) != u) {
kpeter@765:         e = _data[v][--r].pred;
kpeter@765:         _cycle_path->addFront(e);
kpeter@765:         _cycle_length += _length[e];
kpeter@765:         ++_cycle_size;
kpeter@765:       }
kpeter@765:       return true;
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// @}
kpeter@765: 
kpeter@765:     /// \name Query Functions
kpeter@765:     /// The results of the algorithm can be obtained using these
kpeter@765:     /// functions.\n
kpeter@765:     /// The algorithm should be executed before using them.
kpeter@765: 
kpeter@765:     /// @{
kpeter@765: 
kpeter@765:     /// \brief Return the total length of the found cycle.
kpeter@765:     ///
kpeter@765:     /// This function returns the total length of the found cycle.
kpeter@765:     ///
kpeter@765:     /// \pre \ref run() or \ref findMinMean() must be called before
kpeter@765:     /// using this function.
kpeter@765:     LargeValue cycleLength() const {
kpeter@765:       return _cycle_length;
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \brief Return the number of arcs on the found cycle.
kpeter@765:     ///
kpeter@765:     /// This function returns the number of arcs on the found cycle.
kpeter@765:     ///
kpeter@765:     /// \pre \ref run() or \ref findMinMean() must be called before
kpeter@765:     /// using this function.
kpeter@765:     int cycleArcNum() const {
kpeter@765:       return _cycle_size;
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \brief Return the mean length of the found cycle.
kpeter@765:     ///
kpeter@765:     /// This function returns the mean length of the found cycle.
kpeter@765:     ///
kpeter@765:     /// \note <tt>alg.cycleMean()</tt> is just a shortcut of the
kpeter@765:     /// following code.
kpeter@765:     /// \code
kpeter@765:     ///   return static_cast<double>(alg.cycleLength()) / alg.cycleArcNum();
kpeter@765:     /// \endcode
kpeter@765:     ///
kpeter@765:     /// \pre \ref run() or \ref findMinMean() must be called before
kpeter@765:     /// using this function.
kpeter@765:     double cycleMean() const {
kpeter@765:       return static_cast<double>(_cycle_length) / _cycle_size;
kpeter@765:     }
kpeter@765: 
kpeter@765:     /// \brief Return the found cycle.
kpeter@765:     ///
kpeter@765:     /// This function returns a const reference to the path structure
kpeter@765:     /// storing the found cycle.
kpeter@765:     ///
kpeter@765:     /// \pre \ref run() or \ref findCycle() must be called before using
kpeter@765:     /// this function.
kpeter@765:     const Path& cycle() const {
kpeter@765:       return *_cycle_path;
kpeter@765:     }
kpeter@765: 
kpeter@765:     ///@}
kpeter@765: 
kpeter@765:   private:
kpeter@765: 
kpeter@765:     // Initialization
kpeter@765:     void init() {
kpeter@765:       if (!_cycle_path) {
kpeter@765:         _local_path = true;
kpeter@765:         _cycle_path = new Path;
kpeter@765:       }
kpeter@765:       _cycle_path->clear();
kpeter@765:       _cycle_length = 0;
kpeter@765:       _cycle_size = 1;
kpeter@765:       _cycle_node = INVALID;
kpeter@765:       for (NodeIt u(_gr); u != INVALID; ++u)
kpeter@765:         _data[u].clear();
kpeter@765:     }
kpeter@765: 
kpeter@765:     // Find strongly connected components and initialize _comp_nodes
kpeter@765:     // and _out_arcs
kpeter@765:     void findComponents() {
kpeter@765:       _comp_num = stronglyConnectedComponents(_gr, _comp);
kpeter@765:       _comp_nodes.resize(_comp_num);
kpeter@765:       if (_comp_num == 1) {
kpeter@765:         _comp_nodes[0].clear();
kpeter@765:         for (NodeIt n(_gr); n != INVALID; ++n) {
kpeter@765:           _comp_nodes[0].push_back(n);
kpeter@765:           _out_arcs[n].clear();
kpeter@765:           for (OutArcIt a(_gr, n); a != INVALID; ++a) {
kpeter@765:             _out_arcs[n].push_back(a);
kpeter@765:           }
kpeter@765:         }
kpeter@765:       } else {
kpeter@765:         for (int i = 0; i < _comp_num; ++i)
kpeter@765:           _comp_nodes[i].clear();
kpeter@765:         for (NodeIt n(_gr); n != INVALID; ++n) {
kpeter@765:           int k = _comp[n];
kpeter@765:           _comp_nodes[k].push_back(n);
kpeter@765:           _out_arcs[n].clear();
kpeter@765:           for (OutArcIt a(_gr, n); a != INVALID; ++a) {
kpeter@765:             if (_comp[_gr.target(a)] == k) _out_arcs[n].push_back(a);
kpeter@765:           }
kpeter@765:         }
kpeter@765:       }
kpeter@765:     }
kpeter@765: 
kpeter@765:     // Initialize path data for the current component
kpeter@765:     bool initComponent(int comp) {
kpeter@765:       _nodes = &(_comp_nodes[comp]);
kpeter@765:       int n = _nodes->size();
kpeter@765:       if (n < 1 || (n == 1 && _out_arcs[(*_nodes)[0]].size() == 0)) {
kpeter@765:         return false;
kpeter@765:       }      
kpeter@765:       for (int i = 0; i < n; ++i) {
kpeter@767:         _data[(*_nodes)[i]].resize(n + 1, PathData(INF));
kpeter@765:       }
kpeter@765:       return true;
kpeter@765:     }
kpeter@765: 
kpeter@765:     // Process all rounds of computing path data for the current component.
kpeter@765:     // _data[v][k] is the length of a shortest directed walk from the root
kpeter@765:     // node to node v containing exactly k arcs.
kpeter@765:     void processRounds() {
kpeter@765:       Node start = (*_nodes)[0];
kpeter@767:       _data[start][0] = PathData(0);
kpeter@765:       _process.clear();
kpeter@765:       _process.push_back(start);
kpeter@765: 
kpeter@765:       int k, n = _nodes->size();
kpeter@765:       for (k = 1; k <= n && int(_process.size()) < n; ++k) {
kpeter@765:         processNextBuildRound(k);
kpeter@765:       }
kpeter@765:       for ( ; k <= n; ++k) {
kpeter@765:         processNextFullRound(k);
kpeter@765:       }
kpeter@765:     }
kpeter@765: 
kpeter@765:     // Process one round and rebuild _process
kpeter@765:     void processNextBuildRound(int k) {
kpeter@765:       std::vector<Node> next;
kpeter@765:       Node u, v;
kpeter@765:       Arc e;
kpeter@765:       LargeValue d;
kpeter@765:       for (int i = 0; i < int(_process.size()); ++i) {
kpeter@765:         u = _process[i];
kpeter@765:         for (int j = 0; j < int(_out_arcs[u].size()); ++j) {
kpeter@765:           e = _out_arcs[u][j];
kpeter@765:           v = _gr.target(e);
kpeter@765:           d = _data[u][k-1].dist + _length[e];
kpeter@767:           if (_tolerance.less(d, _data[v][k].dist)) {
kpeter@767:             if (_data[v][k].dist == INF) next.push_back(v);
kpeter@767:             _data[v][k] = PathData(d, e);
kpeter@765:           }
kpeter@765:         }
kpeter@765:       }
kpeter@765:       _process.swap(next);
kpeter@765:     }
kpeter@765: 
kpeter@765:     // Process one round using _nodes instead of _process
kpeter@765:     void processNextFullRound(int k) {
kpeter@765:       Node u, v;
kpeter@765:       Arc e;
kpeter@765:       LargeValue d;
kpeter@765:       for (int i = 0; i < int(_nodes->size()); ++i) {
kpeter@765:         u = (*_nodes)[i];
kpeter@765:         for (int j = 0; j < int(_out_arcs[u].size()); ++j) {
kpeter@765:           e = _out_arcs[u][j];
kpeter@765:           v = _gr.target(e);
kpeter@765:           d = _data[u][k-1].dist + _length[e];
kpeter@767:           if (_tolerance.less(d, _data[v][k].dist)) {
kpeter@767:             _data[v][k] = PathData(d, e);
kpeter@765:           }
kpeter@765:         }
kpeter@765:       }
kpeter@765:     }
kpeter@765: 
kpeter@765:     // Update the minimum cycle mean
kpeter@765:     void updateMinMean() {
kpeter@765:       int n = _nodes->size();
kpeter@765:       for (int i = 0; i < n; ++i) {
kpeter@765:         Node u = (*_nodes)[i];
kpeter@767:         if (_data[u][n].dist == INF) continue;
kpeter@765:         LargeValue length, max_length = 0;
kpeter@765:         int size, max_size = 1;
kpeter@765:         bool found_curr = false;
kpeter@765:         for (int k = 0; k < n; ++k) {
kpeter@767:           if (_data[u][k].dist == INF) continue;
kpeter@765:           length = _data[u][n].dist - _data[u][k].dist;
kpeter@765:           size = n - k;
kpeter@765:           if (!found_curr || length * max_size > max_length * size) {
kpeter@765:             found_curr = true;
kpeter@765:             max_length = length;
kpeter@765:             max_size = size;
kpeter@765:           }
kpeter@765:         }
kpeter@765:         if ( found_curr && (_cycle_node == INVALID ||
kpeter@765:              max_length * _cycle_size < _cycle_length * max_size) ) {
kpeter@765:           _cycle_length = max_length;
kpeter@765:           _cycle_size = max_size;
kpeter@765:           _cycle_node = u;
kpeter@765:         }
kpeter@765:       }
kpeter@765:     }
kpeter@765: 
kpeter@765:   }; //class Karp
kpeter@765: 
kpeter@765:   ///@}
kpeter@765: 
kpeter@765: } //namespace lemon
kpeter@765: 
kpeter@765: #endif //LEMON_KARP_H