COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/belmann_ford.h @ 1782:cb405cda0205

Last change on this file since 1782:cb405cda0205 was 1782:cb405cda0205, checked in by Balazs Dezso, 14 years ago

Bug fix.

File size: 31.0 KB
Line 
1/* -*- C++ -*-
2 * lemon/belmann_ford.h - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17#ifndef LEMON_BELMANN_FORD_H
18#define LEMON_BELMANN_FORD_H
19
20///\ingroup flowalgs
21/// \file
22/// \brief BelmannFord algorithm.
23///
24
25#include <lemon/list_graph.h>
26#include <lemon/invalid.h>
27#include <lemon/error.h>
28#include <lemon/maps.h>
29
30#include <limits>
31
32namespace lemon {
33
34  /// \brief Default OperationTraits for the BelmannFord algorithm class.
35  /// 
36  /// It defines all computational operations and constants which are
37  /// used in the belmann ford algorithm. The default implementation
38  /// is based on the numeric_limits class. If the numeric type does not
39  /// have infinity value then the maximum value is used as extremal
40  /// infinity value.
41  template <
42    typename Value,
43    bool has_infinity = std::numeric_limits<Value>::has_infinity>
44  struct BelmannFordDefaultOperationTraits {
45    /// \brief Gives back the zero value of the type.
46    static Value zero() {
47      return static_cast<Value>(0);
48    }
49    /// \brief Gives back the positive infinity value of the type.
50    static Value infinity() {
51      return std::numeric_limits<Value>::infinity();
52    }
53    /// \brief Gives back the sum of the given two elements.
54    static Value plus(const Value& left, const Value& right) {
55      return left + right;
56    }
57    /// \brief Gives back true only if the first value less than the second.
58    static bool less(const Value& left, const Value& right) {
59      return left < right;
60    }
61  };
62
63  template <typename Value>
64  struct BelmannFordDefaultOperationTraits<Value, false> {
65    static Value zero() {
66      return static_cast<Value>(0);
67    }
68    static Value infinity() {
69      return std::numeric_limits<Value>::max();
70    }
71    static Value plus(const Value& left, const Value& right) {
72      if (left == infinity() || right == infinity()) return infinity();
73      return left + right;
74    }
75    static bool less(const Value& left, const Value& right) {
76      return left < right;
77    }
78  };
79 
80  /// \brief Default traits class of BelmannFord class.
81  ///
82  /// Default traits class of BelmannFord class.
83  /// \param _Graph Graph type.
84  /// \param _LegthMap Type of length map.
85  template<class _Graph, class _LengthMap>
86  struct BelmannFordDefaultTraits {
87    /// The graph type the algorithm runs on.
88    typedef _Graph Graph;
89
90    /// \brief The type of the map that stores the edge lengths.
91    ///
92    /// The type of the map that stores the edge lengths.
93    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
94    typedef _LengthMap LengthMap;
95
96    // The type of the length of the edges.
97    typedef typename _LengthMap::Value Value;
98
99    /// \brief Operation traits for belmann-ford algorithm.
100    ///
101    /// It defines the infinity type on the given Value type
102    /// and the used operation.
103    /// \see BelmannFordDefaultOperationTraits
104    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
105 
106    /// \brief The type of the map that stores the last edges of the
107    /// shortest paths.
108    ///
109    /// The type of the map that stores the last
110    /// edges of the shortest paths.
111    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
112    ///
113    typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap;
114
115    /// \brief Instantiates a PredMap.
116    ///
117    /// This function instantiates a \ref PredMap.
118    /// \param G is the graph, to which we would like to define the PredMap.
119    /// \todo The graph alone may be insufficient for the initialization
120    static PredMap *createPredMap(const _Graph& graph) {
121      return new PredMap(graph);
122    }
123
124    /// \brief The type of the map that stores the dists of the nodes.
125    ///
126    /// The type of the map that stores the dists of the nodes.
127    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
128    ///
129    typedef typename Graph::template NodeMap<typename _LengthMap::Value>
130    DistMap;
131
132    /// \brief Instantiates a DistMap.
133    ///
134    /// This function instantiates a \ref DistMap.
135    /// \param G is the graph, to which we would like to define the
136    /// \ref DistMap
137    static DistMap *createDistMap(const _Graph& graph) {
138      return new DistMap(graph);
139    }
140
141  };
142 
143  /// \brief %BelmannFord algorithm class.
144  ///
145  /// \ingroup flowalgs
146  /// This class provides an efficient implementation of \c Belmann-Ford
147  /// algorithm. The edge lengths are passed to the algorithm using a
148  /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any
149  /// kind of length.
150  ///
151  /// The Belmann-Ford algorithm solves the shortest path from one node
152  /// problem when the edges can have negative length but the graph should
153  /// not contain cycles with negative sum of length. If we can assume
154  /// that all edge is non-negative in the graph then the dijkstra algorithm
155  /// should be used rather.
156  ///
157  /// The complexity of the algorithm is O(n * e).
158  ///
159  /// The type of the length is determined by the
160  /// \ref concept::ReadMap::Value "Value" of the length map.
161  ///
162  /// \param _Graph The graph type the algorithm runs on. The default value
163  /// is \ref ListGraph. The value of _Graph is not used directly by
164  /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
165  /// \param _LengthMap This read-only EdgeMap determines the lengths of the
166  /// edges. The default map type is \ref concept::StaticGraph::EdgeMap
167  /// "Graph::EdgeMap<int>".  The value of _LengthMap is not used directly
168  /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits. 
169  /// \param _Traits Traits class to set various data types used by the
170  /// algorithm.  The default traits class is \ref BelmannFordDefaultTraits
171  /// "BelmannFordDefaultTraits<_Graph,_LengthMap>".  See \ref
172  /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits
173  /// class.
174  ///
175  /// \author Balazs Dezso
176
177#ifdef DOXYGEN
178  template <typename _Graph, typename _LengthMap, typename _Traits>
179#else
180  template <typename _Graph=ListGraph,
181            typename _LengthMap=typename _Graph::template EdgeMap<int>,
182            typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
183#endif
184  class BelmannFord {
185  public:
186   
187    /// \brief \ref Exception for uninitialized parameters.
188    ///
189    /// This error represents problems in the initialization
190    /// of the parameters of the algorithms.
191
192    class UninitializedParameter : public lemon::UninitializedParameter {
193    public:
194      virtual const char* exceptionName() const {
195        return "lemon::BelmannFord::UninitializedParameter";
196      }
197    };
198
199    typedef _Traits Traits;
200    ///The type of the underlying graph.
201    typedef typename _Traits::Graph Graph;
202
203    typedef typename Graph::Node Node;
204    typedef typename Graph::NodeIt NodeIt;
205    typedef typename Graph::Edge Edge;
206    typedef typename Graph::OutEdgeIt OutEdgeIt;
207   
208    /// \brief The type of the length of the edges.
209    typedef typename _Traits::LengthMap::Value Value;
210    /// \brief The type of the map that stores the edge lengths.
211    typedef typename _Traits::LengthMap LengthMap;
212    /// \brief The type of the map that stores the last
213    /// edges of the shortest paths.
214    typedef typename _Traits::PredMap PredMap;
215    /// \brief The type of the map that stores the dists of the nodes.
216    typedef typename _Traits::DistMap DistMap;
217    /// \brief The operation traits.
218    typedef typename _Traits::OperationTraits OperationTraits;
219  private:
220    /// Pointer to the underlying graph.
221    const Graph *graph;
222    /// Pointer to the length map
223    const LengthMap *length;
224    ///Pointer to the map of predecessors edges.
225    PredMap *_pred;
226    ///Indicates if \ref _pred is locally allocated (\c true) or not.
227    bool local_pred;
228    ///Pointer to the map of distances.
229    DistMap *_dist;
230    ///Indicates if \ref _dist is locally allocated (\c true) or not.
231    bool local_dist;
232
233    typedef typename Graph::template NodeMap<bool> MaskMap;
234    MaskMap *_mask;
235
236    std::vector<Node> _process;
237
238    /// Creates the maps if necessary.
239    void create_maps() {
240      if(!_pred) {
241        local_pred = true;
242        _pred = Traits::createPredMap(*graph);
243      }
244      if(!_dist) {
245        local_dist = true;
246        _dist = Traits::createDistMap(*graph);
247      }
248      _mask = new MaskMap(*graph, false);
249    }
250   
251  public :
252 
253    typedef BelmannFord Create;
254
255    /// \name Named template parameters
256
257    ///@{
258
259    template <class T>
260    struct DefPredMapTraits : public Traits {
261      typedef T PredMap;
262      static PredMap *createPredMap(const Graph&) {
263        throw UninitializedParameter();
264      }
265    };
266
267    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
268    /// type
269    /// \ref named-templ-param "Named parameter" for setting PredMap type
270    ///
271    template <class T>
272    struct DefPredMap {
273      typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
274    };
275   
276    template <class T>
277    struct DefDistMapTraits : public Traits {
278      typedef T DistMap;
279      static DistMap *createDistMap(const Graph& graph) {
280        throw UninitializedParameter();
281      }
282    };
283
284    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
285    /// type
286    ///
287    /// \ref named-templ-param "Named parameter" for setting DistMap type
288    ///
289    template <class T>
290    struct DefDistMap
291      : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
292      typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
293    };
294   
295    template <class T>
296    struct DefOperationTraitsTraits : public Traits {
297      typedef T OperationTraits;
298    };
299   
300    /// \brief \ref named-templ-param "Named parameter" for setting
301    /// OperationTraits type
302    ///
303    /// \ref named-templ-param "Named parameter" for setting OperationTraits
304    /// type
305    template <class T>
306    struct DefOperationTraits
307      : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
308      typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
309      Create;
310    };
311   
312    ///@}
313
314  protected:
315   
316    BelmannFord() {}
317
318  public:     
319   
320    /// \brief Constructor.
321    ///
322    /// \param _graph the graph the algorithm will run on.
323    /// \param _length the length map used by the algorithm.
324    BelmannFord(const Graph& _graph, const LengthMap& _length) :
325      graph(&_graph), length(&_length),
326      _pred(0), local_pred(false),
327      _dist(0), local_dist(false) {}
328   
329    ///Destructor.
330    ~BelmannFord() {
331      if(local_pred) delete _pred;
332      if(local_dist) delete _dist;
333      delete _mask;
334    }
335
336    /// \brief Sets the length map.
337    ///
338    /// Sets the length map.
339    /// \return \c (*this)
340    BelmannFord &lengthMap(const LengthMap &m) {
341      length = &m;
342      return *this;
343    }
344
345    /// \brief Sets the map storing the predecessor edges.
346    ///
347    /// Sets the map storing the predecessor edges.
348    /// If you don't use this function before calling \ref run(),
349    /// it will allocate one. The destuctor deallocates this
350    /// automatically allocated map, of course.
351    /// \return \c (*this)
352    BelmannFord &predMap(PredMap &m) {
353      if(local_pred) {
354        delete _pred;
355        local_pred=false;
356      }
357      _pred = &m;
358      return *this;
359    }
360
361    /// \brief Sets the map storing the distances calculated by the algorithm.
362    ///
363    /// Sets the map storing the distances calculated by the algorithm.
364    /// If you don't use this function before calling \ref run(),
365    /// it will allocate one. The destuctor deallocates this
366    /// automatically allocated map, of course.
367    /// \return \c (*this)
368    BelmannFord &distMap(DistMap &m) {
369      if(local_dist) {
370        delete _dist;
371        local_dist=false;
372      }
373      _dist = &m;
374      return *this;
375    }
376
377    /// \name Execution control
378    /// The simplest way to execute the algorithm is to use
379    /// one of the member functions called \c run(...).
380    /// \n
381    /// If you need more control on the execution,
382    /// first you must call \ref init(), then you can add several source nodes
383    /// with \ref addSource().
384    /// Finally \ref start() will perform the actual path
385    /// computation.
386
387    ///@{
388
389    /// \brief Initializes the internal data structures.
390    ///
391    /// Initializes the internal data structures.
392    void init(const Value value = OperationTraits::infinity()) {
393      create_maps();
394      for (NodeIt it(*graph); it != INVALID; ++it) {
395        _pred->set(it, INVALID);
396        _dist->set(it, value);
397      }
398      _process.clear();
399      if (OperationTraits::less(value, OperationTraits::infinity())) {
400        for (NodeIt it(*graph); it != INVALID; ++it) {
401          _process.push_back(it);
402          _mask.set(it, true);
403        }
404      }
405    }
406   
407    /// \brief Adds a new source node.
408    ///
409    /// The optional second parameter is the initial distance of the node.
410    /// It just sets the distance of the node to the given value.
411    void addSource(Node source, Value dst = OperationTraits::zero()) {
412      _dist->set(source, dst);
413      if (!(*_mask)[source]) {
414        _process.push_back(source);
415        _mask->set(source, true);
416      }
417    }
418
419    /// \brief Executes one round from the belmann ford algorithm.
420    ///
421    /// If the algoritm calculated the distances in the previous round
422    /// strictly for all at most k length pathes then it will calculate the
423    /// distances strictly for all at most k + 1 length pathes. With k
424    /// iteration this function calculates the at most k length pathes.
425    bool processNextRound() {
426      for (int i = 0; i < (int)_process.size(); ++i) {
427        _mask->set(_process[i], false);
428      }
429      std::vector<Node> nextProcess;
430      std::vector<Value> values(_process.size());
431      for (int i = 0; i < (int)_process.size(); ++i) {
432        values[i] = _dist[_process[i]];
433      }
434      for (int i = 0; i < (int)_process.size(); ++i) {
435        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
436          Node target = graph->target(it);
437          Value relaxed = OperationTraits::plus(values[i], (*length)[it]);
438          if (OperationTraits::less(relaxed, (*_dist)[target])) {
439            _pred->set(target, it);
440            _dist->set(target, relaxed);
441            if (!(*_mask)[target]) {
442              _mask->set(target, true);
443              nextProcess.push_back(target);
444            }
445          }       
446        }
447      }
448      _process.swap(nextProcess);
449      return _process.empty();
450    }
451
452    /// \brief Executes one weak round from the belmann ford algorithm.
453    ///
454    /// If the algorithm calculated the distances in the
455    /// previous round at least for all at most k length pathes then it will
456    /// calculate the distances at least for all at most k + 1 length pathes.
457    /// This function does not make possible to calculate strictly the
458    /// at most k length minimal pathes, this way it called just weak round.
459    bool processNextWeakRound() {
460      for (int i = 0; i < (int)_process.size(); ++i) {
461        _mask->set(_process[i], false);
462      }
463      std::vector<Node> nextProcess;
464      for (int i = 0; i < (int)_process.size(); ++i) {
465        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
466          Node target = graph->target(it);
467          Value relaxed =
468            OperationTraits::plus((*_dist)[_process[i]], (*length)[it]);
469          if (OperationTraits::less(relaxed, (*_dist)[target])) {
470            _pred->set(target, it);
471            _dist->set(target, relaxed);
472            if (!(*_mask)[target]) {
473              _mask->set(target, true);
474              nextProcess.push_back(target);
475            }
476          }       
477        }
478      }
479      _process.swap(nextProcess);
480      return _process.empty();
481    }
482
483    /// \brief Executes the algorithm.
484    ///
485    /// \pre init() must be called and at least one node should be added
486    /// with addSource() before using this function.
487    ///
488    /// This method runs the %BelmannFord algorithm from the root node(s)
489    /// in order to compute the shortest path to each node. The algorithm
490    /// computes
491    /// - The shortest path tree.
492    /// - The distance of each node from the root(s).
493    void start() {
494      int num = countNodes(*graph) - 1;
495      for (int i = 0; i < num; ++i) {
496        if (processNextWeakRound()) break;
497      }
498    }
499
500    /// \brief Executes the algorithm and checks the negative cycles.
501    ///
502    /// \pre init() must be called and at least one node should be added
503    /// with addSource() before using this function. If there is
504    /// a negative cycles in the graph it gives back false.
505    ///
506    /// This method runs the %BelmannFord algorithm from the root node(s)
507    /// in order to compute the shortest path to each node. The algorithm
508    /// computes
509    /// - The shortest path tree.
510    /// - The distance of each node from the root(s).
511    bool checkedStart() {
512      int num = countNodes(*graph);
513      for (int i = 0; i < num; ++i) {
514        if (processNextWeakRound()) return true;
515      }
516      return false;
517    }
518
519    /// \brief Executes the algorithm with path length limit.
520    ///
521    /// \pre init() must be called and at least one node should be added
522    /// with addSource() before using this function.
523    ///
524    /// This method runs the %BelmannFord algorithm from the root node(s)
525    /// in order to compute the shortest path with at most \c length edge
526    /// long pathes to each node. The algorithm computes
527    /// - The shortest path tree.
528    /// - The limited distance of each node from the root(s).
529    void limitedStart(int length) {
530      for (int i = 0; i < length; ++i) {
531        if (processNextRound()) break;
532      }
533    }
534   
535    /// \brief Runs %BelmannFord algorithm from node \c s.
536    ///   
537    /// This method runs the %BelmannFord algorithm from a root node \c s
538    /// in order to compute the shortest path to each node. The algorithm
539    /// computes
540    /// - The shortest path tree.
541    /// - The distance of each node from the root.
542    ///
543    /// \note d.run(s) is just a shortcut of the following code.
544    /// \code
545    ///  d.init();
546    ///  d.addSource(s);
547    ///  d.start();
548    /// \endcode
549    void run(Node s) {
550      init();
551      addSource(s);
552      start();
553    }
554   
555    ///@}
556
557    /// \name Query Functions
558    /// The result of the %BelmannFord algorithm can be obtained using these
559    /// functions.\n
560    /// Before the use of these functions,
561    /// either run() or start() must be called.
562   
563    ///@{
564
565    /// \brief Copies the shortest path to \c t into \c p
566    ///   
567    /// This function copies the shortest path to \c t into \c p.
568    /// If it \c t is a source itself or unreachable, then it does not
569    /// alter \c p.
570    ///
571    /// \return Returns \c true if a path to \c t was actually copied to \c p,
572    /// \c false otherwise.
573    /// \sa DirPath
574    template <typename Path>
575    bool getPath(Path &p, Node t) {
576      if(reached(t)) {
577        p.clear();
578        typename Path::Builder b(p);
579        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
580          b.pushFront(predEdge(t));
581        b.commit();
582        return true;
583      }
584      return false;
585    }
586         
587    /// \brief The distance of a node from the root.
588    ///
589    /// Returns the distance of a node from the root.
590    /// \pre \ref run() must be called before using this function.
591    /// \warning If node \c v in unreachable from the root the return value
592    /// of this funcion is undefined.
593    Value dist(Node v) const { return (*_dist)[v]; }
594
595    /// \brief Returns the 'previous edge' of the shortest path tree.
596    ///
597    /// For a node \c v it returns the 'previous edge' of the shortest path
598    /// tree, i.e. it returns the last edge of a shortest path from the root
599    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
600    /// if \c v=s. The shortest path tree used here is equal to the shortest
601    /// path tree used in \ref predNode().
602    /// \pre \ref run() must be called before using
603    /// this function.
604    Edge predEdge(Node v) const { return (*_pred)[v]; }
605
606    /// \brief Returns the 'previous node' of the shortest path tree.
607    ///
608    /// For a node \c v it returns the 'previous node' of the shortest path
609    /// tree, i.e. it returns the last but one node from a shortest path from
610    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
611    /// or if \c v=s. The shortest path tree used here is equal to the
612    /// shortest path tree used in \ref predEdge().  \pre \ref run() must be
613    /// called before using this function.
614    Node predNode(Node v) const {
615      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
616    }
617   
618    /// \brief Returns a reference to the NodeMap of distances.
619    ///
620    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
621    /// be called before using this function.
622    const DistMap &distMap() const { return *_dist;}
623 
624    /// \brief Returns a reference to the shortest path tree map.
625    ///
626    /// Returns a reference to the NodeMap of the edges of the
627    /// shortest path tree.
628    /// \pre \ref run() must be called before using this function.
629    const PredMap &predMap() const { return *_pred; }
630 
631    /// \brief Checks if a node is reachable from the root.
632    ///
633    /// Returns \c true if \c v is reachable from the root.
634    /// \pre \ref run() must be called before using this function.
635    ///
636    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
637   
638    ///@}
639  };
640 
641  /// \brief Default traits class of BelmannFord function.
642  ///
643  /// Default traits class of BelmannFord function.
644  /// \param _Graph Graph type.
645  /// \param _LengthMap Type of length map.
646  template <typename _Graph, typename _LengthMap>
647  struct BelmannFordWizardDefaultTraits {
648    /// \brief The graph type the algorithm runs on.
649    typedef _Graph Graph;
650
651    /// \brief The type of the map that stores the edge lengths.
652    ///
653    /// The type of the map that stores the edge lengths.
654    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
655    typedef _LengthMap LengthMap;
656
657    /// \brief The value type of the length map.
658    typedef typename _LengthMap::Value Value;
659
660    /// \brief Operation traits for belmann-ford algorithm.
661    ///
662    /// It defines the infinity type on the given Value type
663    /// and the used operation.
664    /// \see BelmannFordDefaultOperationTraits
665    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
666
667    /// \brief The type of the map that stores the last
668    /// edges of the shortest paths.
669    ///
670    /// The type of the map that stores the last
671    /// edges of the shortest paths.
672    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
673    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
674
675    /// \brief Instantiates a PredMap.
676    ///
677    /// This function instantiates a \ref PredMap.
678    static PredMap *createPredMap(const _Graph &) {
679      return new PredMap();
680    }
681    /// \brief The type of the map that stores the dists of the nodes.
682    ///
683    /// The type of the map that stores the dists of the nodes.
684    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
685    typedef NullMap<typename Graph::Node, Value> DistMap;
686    /// \brief Instantiates a DistMap.
687    ///
688    /// This function instantiates a \ref DistMap.
689    static DistMap *createDistMap(const _Graph &) {
690      return new DistMap();
691    }
692  };
693 
694  /// \brief Default traits used by \ref BelmannFordWizard
695  ///
696  /// To make it easier to use BelmannFord algorithm
697  /// we have created a wizard class.
698  /// This \ref BelmannFordWizard class needs default traits,
699  /// as well as the \ref BelmannFord class.
700  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
701  /// \ref BelmannFordWizard class.
702  /// \todo More named parameters are required...
703  template<class _Graph,class _LengthMap>
704  class BelmannFordWizardBase
705    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
706
707    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
708  protected:
709    /// Type of the nodes in the graph.
710    typedef typename Base::Graph::Node Node;
711
712    /// Pointer to the underlying graph.
713    void *_graph;
714    /// Pointer to the length map
715    void *_length;
716    ///Pointer to the map of predecessors edges.
717    void *_pred;
718    ///Pointer to the map of distances.
719    void *_dist;
720    ///Pointer to the source node.
721    Node _source;
722
723    public:
724    /// Constructor.
725   
726    /// This constructor does not require parameters, therefore it initiates
727    /// all of the attributes to default values (0, INVALID).
728    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
729                           _dist(0), _source(INVALID) {}
730
731    /// Constructor.
732   
733    /// This constructor requires some parameters,
734    /// listed in the parameters list.
735    /// Others are initiated to 0.
736    /// \param graph is the initial value of  \ref _graph
737    /// \param length is the initial value of  \ref _length
738    /// \param source is the initial value of  \ref _source
739    BelmannFordWizardBase(const _Graph& graph,
740                          const _LengthMap& length,
741                          Node source = INVALID) :
742      _graph((void *)&graph), _length((void *)&length), _pred(0),
743      _dist(0), _source(source) {}
744
745  };
746 
747  /// A class to make the usage of BelmannFord algorithm easier
748
749  /// This class is created to make it easier to use BelmannFord algorithm.
750  /// It uses the functions and features of the plain \ref BelmannFord,
751  /// but it is much simpler to use it.
752  ///
753  /// Simplicity means that the way to change the types defined
754  /// in the traits class is based on functions that returns the new class
755  /// and not on templatable built-in classes.
756  /// When using the plain \ref BelmannFord
757  /// the new class with the modified type comes from
758  /// the original class by using the ::
759  /// operator. In the case of \ref BelmannFordWizard only
760  /// a function have to be called and it will
761  /// return the needed class.
762  ///
763  /// It does not have own \ref run method. When its \ref run method is called
764  /// it initiates a plain \ref BelmannFord class, and calls the \ref
765  /// BelmannFord::run method of it.
766  template<class _Traits>
767  class BelmannFordWizard : public _Traits {
768    typedef _Traits Base;
769
770    ///The type of the underlying graph.
771    typedef typename _Traits::Graph Graph;
772
773    typedef typename Graph::Node Node;
774    typedef typename Graph::NodeIt NodeIt;
775    typedef typename Graph::Edge Edge;
776    typedef typename Graph::OutEdgeIt EdgeIt;
777   
778    ///The type of the map that stores the edge lengths.
779    typedef typename _Traits::LengthMap LengthMap;
780
781    ///The type of the length of the edges.
782    typedef typename LengthMap::Value Value;
783
784    ///\brief The type of the map that stores the last
785    ///edges of the shortest paths.
786    typedef typename _Traits::PredMap PredMap;
787
788    ///The type of the map that stores the dists of the nodes.
789    typedef typename _Traits::DistMap DistMap;
790
791  public:
792    /// Constructor.
793    BelmannFordWizard() : _Traits() {}
794
795    /// \brief Constructor that requires parameters.
796    ///
797    /// Constructor that requires parameters.
798    /// These parameters will be the default values for the traits class.
799    BelmannFordWizard(const Graph& graph, const LengthMap& length,
800                      Node source = INVALID)
801      : _Traits(graph, length, source) {}
802
803    /// \brief Copy constructor
804    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
805
806    ~BelmannFordWizard() {}
807
808    /// \brief Runs BelmannFord algorithm from a given node.
809    ///   
810    /// Runs BelmannFord algorithm from a given node.
811    /// The node can be given by the \ref source function.
812    void run() {
813      if(Base::_source == INVALID) throw UninitializedParameter();
814      BelmannFord<Graph,LengthMap,_Traits>
815        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
816      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
817      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
818      bf.run(Base::_source);
819    }
820
821    /// \brief Runs BelmannFord algorithm from the given node.
822    ///
823    /// Runs BelmannFord algorithm from the given node.
824    /// \param s is the given source.
825    void run(Node source) {
826      Base::_source = source;
827      run();
828    }
829
830    template<class T>
831    struct DefPredMapBase : public Base {
832      typedef T PredMap;
833      static PredMap *createPredMap(const Graph &) { return 0; };
834      DefPredMapBase(const _Traits &b) : _Traits(b) {}
835    };
836   
837    ///\brief \ref named-templ-param "Named parameter"
838    ///function for setting PredMap type
839    ///
840    /// \ref named-templ-param "Named parameter"
841    ///function for setting PredMap type
842    ///
843    template<class T>
844    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
845    {
846      Base::_pred=(void *)&t;
847      return BelmannFordWizard<DefPredMapBase<T> >(*this);
848    }
849   
850    template<class T>
851    struct DefDistMapBase : public Base {
852      typedef T DistMap;
853      static DistMap *createDistMap(const Graph &) { return 0; };
854      DefDistMapBase(const _Traits &b) : _Traits(b) {}
855    };
856   
857    ///\brief \ref named-templ-param "Named parameter"
858    ///function for setting DistMap type
859    ///
860    /// \ref named-templ-param "Named parameter"
861    ///function for setting DistMap type
862    ///
863    template<class T>
864    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
865      Base::_dist=(void *)&t;
866      return BelmannFordWizard<DefDistMapBase<T> >(*this);
867    }
868
869    template<class T>
870    struct DefOperationTraitsBase : public Base {
871      typedef T OperationTraits;
872      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
873    };
874   
875    ///\brief \ref named-templ-param "Named parameter"
876    ///function for setting OperationTraits type
877    ///
878    /// \ref named-templ-param "Named parameter"
879    ///function for setting OperationTraits type
880    ///
881    template<class T>
882    BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
883      return BelmannFordWizard<DefDistMapBase<T> >(*this);
884    }
885   
886    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
887    ///
888    /// Sets the source node, from which the BelmannFord algorithm runs.
889    /// \param s is the source node.
890    BelmannFordWizard<_Traits>& source(Node source) {
891      Base::_source = source;
892      return *this;
893    }
894   
895  };
896 
897  /// \brief Function type interface for BelmannFord algorithm.
898  ///
899  /// \ingroup flowalgs
900  /// Function type interface for BelmannFord algorithm.
901  ///
902  /// This function also has several \ref named-templ-func-param
903  /// "named parameters", they are declared as the members of class
904  /// \ref BelmannFordWizard.
905  /// The following
906  /// example shows how to use these parameters.
907  /// \code
908  /// belmannford(g,length,source).predMap(preds).run();
909  /// \endcode
910  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
911  /// to the end of the parameter list.
912  /// \sa BelmannFordWizard
913  /// \sa BelmannFord
914  template<class _Graph, class _LengthMap>
915  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
916  belmannFord(const _Graph& graph,
917              const _LengthMap& length,
918              typename _Graph::Node source = INVALID) {
919    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
920      (graph, length, source);
921  }
922
923} //END OF NAMESPACE LEMON
924
925#endif
926
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