RhodeCode

#ifndef LEMON_BELLMAN_FORD_H

#define LEMON_BELLMAN_FORD_H

#include <lemon/path.h>

  /// This operation traits class defines all computational operations

  /// and constants that are used in the Bellman-Ford algorithm.

  /// The default implementation is based on the \c numeric_limits class.

  /// If the numeric type does not have infinity value, then the maximum

  /// value is used as extremal infinity value.

    typename V, 

    bool has_inf = std::numeric_limits<V>::has_infinity>

    /// \e

    typedef V Value;

    /// \brief Gives back \c true only if the first value is less than

    /// the second.

  template <typename V>

  struct BellmanFordDefaultOperationTraits<V, false> {

    typedef V Value;

  /// \param GR The type of the digraph.

  /// \param LEN The type of the length map.

  template<typename GR, typename LEN>

    /// The type of the digraph the algorithm runs on. 

    typedef GR Digraph;

    /// It must conform to the \ref concepts::ReadMap "ReadMap" concept.

    typedef LEN LengthMap;

    /// The type of the arc lengths.

    typedef typename LEN::Value Value;

    /// It defines the used operations and the infinity value for the

    /// given \c Value type.

    /// It must conform to the \ref concepts::WriteMap "WriteMap" concept.

    typedef typename GR::template NodeMap<typename GR::Arc> PredMap;

    /// \brief Instantiates a \c PredMap.

    /// \param g is the digraph to which we would like to define the

    /// \ref PredMap.

    static PredMap *createPredMap(const GR& g) {

      return new PredMap(g);

    /// \brief The type of the map that stores the distances of the nodes.

    /// The type of the map that stores the distances of the nodes.

    /// It must conform to the \ref concepts::WriteMap "WriteMap" concept.

    typedef typename GR::template NodeMap<typename LEN::Value> DistMap;

    /// \brief Instantiates a \c DistMap.

    /// \param g is the digraph to which we would like to define the 

    /// \ref DistMap.

    static DistMap *createDistMap(const GR& g) {

      return new DistMap(g);

  /// This class provides an efficient implementation of the Bellman-Ford 

  /// algorithm. The maximum time complexity of the algorithm is

  /// <tt>O(ne)</tt>.

  ///

  /// The Bellman-Ford algorithm solves the single-source shortest path

  /// problem when the arcs can have negative lengths, but the digraph

  /// should not contain directed cycles with negative total length.

  /// If all arc costs are non-negative, consider to use the Dijkstra

  /// algorithm instead, since it is more efficient.

  ///

  /// The arc lengths are passed to the algorithm using a

  /// kind of length. The type of the length values is determined by the

  /// \ref concepts::ReadMap::Value "Value" type of the length map.

  /// There is also a \ref bellmanFord() "function-type interface" for the

  /// Bellman-Ford algorithm, which is convenient in the simplier cases and

  /// it can be used easier.

  /// \tparam GR The type of the digraph the algorithm runs on.

  /// The default type is \ref ListDigraph.

  /// \tparam LEN A \ref concepts::ReadMap "readable" arc map that specifies

  /// the lengths of the arcs. The default map type is

  /// \ref concepts::Digraph::ArcMap "GR::ArcMap<int>".

  template <typename GR, typename LEN, typename TR>

  template <typename GR=ListDigraph,

            typename LEN=typename GR::template ArcMap<int>,

            typename TR=BellmanFordDefaultTraits<GR,LEN> >

    typedef typename TR::Digraph Digraph;

    /// \brief The type of the arc lengths.

    typedef typename TR::LengthMap::Value Value;

    /// \brief The type of the map that stores the arc lengths.

    typedef typename TR::LengthMap LengthMap;

    /// \brief The type of the map that stores the last

    /// arcs of the shortest paths.

    typedef typename TR::PredMap PredMap;

    /// \brief The type of the map that stores the distances of the nodes.

    typedef typename TR::DistMap DistMap;

    /// The type of the paths.

    typedef PredMapPath<Digraph, PredMap> Path;

    ///\brief The \ref BellmanFordDefaultOperationTraits

    /// "operation traits class" of the algorithm.

    typedef typename TR::OperationTraits OperationTraits;

    ///The \ref BellmanFordDefaultTraits "traits class" of the algorithm.

    typedef TR Traits;

  private:

    // Pointer to the underlying digraph.

    const Digraph *_gr;

    // Pointer to the length map

    const LengthMap *_length;

    // Pointer to the map of predecessors arcs.

    // Indicates if _pred is locally allocated (true) or not.

    bool _local_pred;

    // Pointer to the map of distances.

    // Indicates if _dist is locally allocated (true) or not.

    bool _local_dist;

    // Creates the maps if necessary.

	_local_pred = true;

	_pred = Traits::createPredMap(*_gr);

	_local_dist = true;

	_dist = Traits::createDistMap(*_gr);

      _mask = new MaskMap(*_gr, false);

    /// \name Named Template Parameters

    struct SetPredMapTraits : public Traits {

    /// \brief \ref named-templ-param "Named parameter" for setting

    /// \c PredMap type.

    /// \ref named-templ-param "Named parameter" for setting

    /// \c PredMap type.

    /// It must conform to the \ref concepts::WriteMap "WriteMap" concept.

      : public BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > {

      typedef BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > Create;

    struct SetDistMapTraits : public Traits {

    /// \brief \ref named-templ-param "Named parameter" for setting

    /// \c DistMap type.

    /// \ref named-templ-param "Named parameter" for setting

    /// \c DistMap type.

    /// It must conform to the \ref concepts::WriteMap "WriteMap" concept.

      : public BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > {

      typedef BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > Create;

    struct SetOperationTraitsTraits : public Traits {

    /// \c OperationTraits type.

    /// \ref named-templ-param "Named parameter" for setting

    /// \c OperationTraits type.

    /// For more information see \ref BellmanFordDefaultOperationTraits.

      : public BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > {

      typedef BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> >

    /// Constructor.

    /// \param g The digraph the algorithm runs on.

    /// \param length The length map used by the algorithm.

    BellmanFord(const Digraph& g, const LengthMap& length) :

      _gr(&g), _length(&length),

      _pred(0), _local_pred(false),

      _dist(0), _local_dist(false), _mask(0) {}

      if(_local_pred) delete _pred;

      if(_local_dist) delete _dist;

    /// \return <tt>(*this)</tt>

    BellmanFord &lengthMap(const LengthMap &map) {

      _length = ↦

    /// \brief Sets the map that stores the predecessor arcs.

    /// Sets the map that stores the predecessor arcs.

    /// If you don't use this function before calling \ref run()

    /// or \ref init(), an instance will be allocated automatically.

    /// The destructor deallocates this automatically allocated map,

    /// of course.

    /// \return <tt>(*this)</tt>

    BellmanFord &predMap(PredMap &map) {

      if(_local_pred) {

	_local_pred=false;

      _pred = ↦

    /// \brief Sets the map that stores the distances of the nodes.

    /// Sets the map that stores the distances of the nodes calculated

    /// by the algorithm.

    /// If you don't use this function before calling \ref run()

    /// or \ref init(), an instance will be allocated automatically.

    /// The destructor deallocates this automatically allocated map,

    /// of course.

    /// \return <tt>(*this)</tt>

    BellmanFord &distMap(DistMap &map) {

      if(_local_dist) {

	_local_dist=false;

      _dist = ↦

    /// \name Execution Control

    /// The simplest way to execute the Bellman-Ford algorithm is to use

    /// one of the member functions called \ref run().\n

    /// If you need better control on the execution, you have to call

    /// \ref init() first, then you can add several source nodes

    /// with \ref addSource(). Finally the actual path computation can be

    /// performed with \ref start(), \ref checkedStart() or

    /// \ref limitedStart().

    /// Initializes the internal data structures. The optional parameter

    /// is the initial distance of each node.

      for (NodeIt it(*_gr); it != INVALID; ++it) {

	for (NodeIt it(*_gr); it != INVALID; ++it) {

    /// This function adds a new source node. The optional second parameter

    /// is the initial distance of the node.

    /// exactly for the paths of at most \c k arcs, then this function

    /// will calculate the distances exactly for the paths of at most

    /// <tt>k+1</tt> arcs. Performing \c k iterations using this function

    /// calculates the shortest path distances exactly for the paths

    /// consisting of at most \c k arcs.

    /// easily with \ref path() or \ref predArc() functions. If you also

    /// need the shortest paths and not only the distances, you should

    /// store the \ref predMap() "predecessor map" after each iteration

    /// and build the path manually.

    ///

    /// \see ActiveIt

	for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) {

	  Node target = _gr->target(it);

	  Value relaxed = OperationTraits::plus(values[i], (*_length)[it]);

    /// If the algorithm calculated the distances in the previous round

    /// at least for the paths of at most \c k arcs, then this function

    /// will calculate the distances at least for the paths of at most

    /// <tt>k+1</tt> arcs.

    /// This function does not make it possible to calculate the shortest

    /// path distances exactly for paths consisting of at most \c k arcs,

    /// this is why it is called weak round.

    ///

    /// \return \c true when the algorithm have not found more shorter

    /// paths.

    ///

    /// \see ActiveIt

	for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) {

	  Node target = _gr->target(it);

	    OperationTraits::plus((*_dist)[_process[i]], (*_length)[it]);

    /// Executes the algorithm.

    /// This method runs the Bellman-Ford algorithm from the root node(s)

    /// in order to compute the shortest path to each node.

    ///

    /// The algorithm computes

    /// - the shortest path tree (forest),

    /// - the distance of each node from the root(s).

    ///

    /// \pre init() must be called and at least one root node should be

    /// added with addSource() before using this function.

      int num = countNodes(*_gr) - 1;

    /// Executes the algorithm and checks the negative cycles.

    /// This method runs the Bellman-Ford algorithm from the root node(s)

    /// in order to compute the shortest path to each node and also checks

    /// if the digraph contains cycles with negative total length.

    ///

    /// The algorithm computes 

    /// - the shortest path tree (forest),

    /// - the distance of each node from the root(s).

    ///

    /// \pre init() must be called and at least one root node should be

    /// added with addSource() before using this function. 

      int num = countNodes(*_gr);

    /// \brief Executes the algorithm with arc number limit.

    /// Executes the algorithm with arc number limit.

    /// This method runs the Bellman-Ford algorithm from the root node(s)

    /// in order to compute the shortest path distance for each node

    /// using only the paths consisting of at most \c num arcs.

    ///

    /// The algorithm computes

    /// - the limited distance of each node from the root(s),

    /// - the predecessor arc for each node.

    /// easily with \ref path() or \ref predArc() functions. If you also

    /// need the shortest paths and not only the distances, you should

    /// store the \ref predMap() "predecessor map" after each iteration

    /// and build the path manually.

    /// \pre init() must be called and at least one root node should be

    /// added with addSource() before using this function. 

    /// \brief Runs the algorithm from the given root node.

    /// This method runs the Bellman-Ford algorithm from the given root

    /// node \c s in order to compute the shortest path to each node.

    /// The algorithm computes

    /// - the shortest path tree (forest),

    /// - the distance of each node from the root(s).

    ///

    /// \note bf.run(s) is just a shortcut of the following code.

    /// \code

    ///   bf.init();

    ///   bf.addSource(s);

    ///   bf.start();

    /// \endcode

    /// \brief Runs the algorithm from the given root node with arc

    /// number limit.

    /// This method runs the Bellman-Ford algorithm from the given root

    /// node \c s in order to compute the shortest path distance for each

    /// node using only the paths consisting of at most \c num arcs.

    /// The algorithm computes

    /// - the limited distance of each node from the root(s),

    /// - the predecessor arc for each node.

    ///

    /// \warning The paths with limited arc number cannot be retrieved

    /// easily with \ref path() or \ref predArc() functions. If you also

    /// need the shortest paths and not only the distances, you should

    /// store the \ref predMap() "predecessor map" after each iteration

    /// and build the path manually.

    ///

    /// \note bf.run(s, num) is just a shortcut of the following code.

    /// \code

    ///   bf.init();

    ///   bf.addSource(s);

    ///   bf.limitedStart(num);

    /// \endcode

    /// \brief LEMON iterator for getting the active nodes.

    /// This class provides a common style LEMON iterator that traverses

    /// the active nodes of the Bellman-Ford algorithm after the last

    /// phase. These nodes should be checked in the next phase to

    /// find augmenting arcs outgoing from them.

      /// Constructor for getting the active nodes of the given BellmanFord

      /// instance. 

      /// \brief Conversion to \c Node.

      /// Conversion to \c Node.

    /// \name Query Functions

    /// The result of the Bellman-Ford algorithm can be obtained using these

    /// functions.\n

    /// Either \ref run() or \ref init() should be called before using them.

    ///@{

    /// \brief The shortest path to the given node.

    ///    

    /// Gives back the shortest path to the given node from the root(s).

    ///

    /// \warning \c t should be reached from the root(s).

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    Path path(Node t) const

    {

      return Path(*_gr, *_pred, t);

    }

    /// \brief The distance of the given node from the root(s).

    ///

    /// Returns the distance of the given node from the root(s).

    ///

    /// \warning If node \c v is not reached from the root(s), then

    /// the return value of this function is undefined.

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    Value dist(Node v) const { return (*_dist)[v]; }

    /// \brief Returns the 'previous arc' of the shortest path tree for

    /// the given node.

    ///

    /// This function returns the 'previous arc' of the shortest path

    /// tree for node \c v, i.e. it returns the last arc of a

    /// shortest path from a root to \c v. It is \c INVALID if \c v

    /// is not reached from the root(s) or if \c v is a root.

    ///

    /// The shortest path tree used here is equal to the shortest path

    /// tree used in \ref predNode() and \predMap().

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    Arc predArc(Node v) const { return (*_pred)[v]; }

    /// \brief Returns the 'previous node' of the shortest path tree for

    /// the given node.

    ///

    /// This function returns the 'previous node' of the shortest path

    /// tree for node \c v, i.e. it returns the last but one node of

    /// a shortest path from a root to \c v. It is \c INVALID if \c v

    /// is not reached from the root(s) or if \c v is a root.

    ///

    /// The shortest path tree used here is equal to the shortest path

    /// tree used in \ref predArc() and \predMap().

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    Node predNode(Node v) const { 

      return (*_pred)[v] == INVALID ? INVALID : _gr->source((*_pred)[v]); 

    }

    /// \brief Returns a const reference to the node map that stores the

    /// distances of the nodes.

    ///

    /// Returns a const reference to the node map that stores the distances

    /// of the nodes calculated by the algorithm.

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    const DistMap &distMap() const { return *_dist;}

    /// \brief Returns a const reference to the node map that stores the

    /// predecessor arcs.

    ///

    /// Returns a const reference to the node map that stores the predecessor

    /// arcs, which form the shortest path tree (forest).

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    const PredMap &predMap() const { return *_pred; }

    /// \brief Checks if a node is reached from the root(s).

    ///

    /// Returns \c true if \c v is reached from the root(s).

    ///

    /// \pre Either \ref run() or \ref init() must be called before

    /// using this function.

    bool reached(Node v) const {

      return (*_dist)[v] != OperationTraits::infinity();

    // TODO: implement negative cycle

//    /// \brief Gives back a negative cycle.

//    ///    

//    /// This function gives back a negative cycle.

//    /// If the algorithm have not found yet negative cycle it will give back

//    /// an empty path.

//    Path negativeCycle() {

//      typename Digraph::template NodeMap<int> state(*digraph, 0);

//      for (ActiveIt it(*this); it != INVALID; ++it) {

//        if (state[it] == 0) {

//          for (Node t = it; predArc(t) != INVALID; t = predNode(t)) {

//            if (state[t] == 0) {

//              state[t] = 1;

//            } else if (state[t] == 2) {

//              break;

//            } else {

//              p.clear();

//              typename Path::Builder b(p);

//              b.setStartNode(t);

//              b.pushFront(predArc(t));

//              for(Node s = predNode(t); s != t; s = predNode(s)) {

//                b.pushFront(predArc(s));

//              }

//              b.commit();

//              return true;