COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bellman_ford.h @ 2020:332245399dc6

Last change on this file since 2020:332245399dc6 was 2010:08464643a658, checked in by Mihaly Barasz, 14 years ago

unused parameters fix

File size: 31.8 KB
Line 
1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2006
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_BELMANN_FORD_H
20#define LEMON_BELMANN_FORD_H
21
22/// \ingroup flowalgs
23/// \file
24/// \brief BellmanFord algorithm.
25///
26
27#include <lemon/list_graph.h>
28#include <lemon/bits/invalid.h>
29#include <lemon/error.h>
30#include <lemon/maps.h>
31
32#include <limits>
33
34namespace lemon {
35
36  /// \brief Default OperationTraits for the BellmanFord algorithm class.
37  /// 
38  /// It defines all computational operations and constants which are
39  /// used in the bellman ford algorithm. The default implementation
40  /// is based on the numeric_limits class. If the numeric type does not
41  /// have infinity value then the maximum value is used as extremal
42  /// infinity value.
43  template <
44    typename Value,
45    bool has_infinity = std::numeric_limits<Value>::has_infinity>
46  struct BellmanFordDefaultOperationTraits {
47    /// \brief Gives back the zero value of the type.
48    static Value zero() {
49      return static_cast<Value>(0);
50    }
51    /// \brief Gives back the positive infinity value of the type.
52    static Value infinity() {
53      return std::numeric_limits<Value>::infinity();
54    }
55    /// \brief Gives back the sum of the given two elements.
56    static Value plus(const Value& left, const Value& right) {
57      return left + right;
58    }
59    /// \brief Gives back true only if the first value less than the second.
60    static bool less(const Value& left, const Value& right) {
61      return left < right;
62    }
63  };
64
65  template <typename Value>
66  struct BellmanFordDefaultOperationTraits<Value, false> {
67    static Value zero() {
68      return static_cast<Value>(0);
69    }
70    static Value infinity() {
71      return std::numeric_limits<Value>::max();
72    }
73    static Value plus(const Value& left, const Value& right) {
74      if (left == infinity() || right == infinity()) return infinity();
75      return left + right;
76    }
77    static bool less(const Value& left, const Value& right) {
78      return left < right;
79    }
80  };
81 
82  /// \brief Default traits class of BellmanFord class.
83  ///
84  /// Default traits class of BellmanFord class.
85  /// \param _Graph Graph type.
86  /// \param _LegthMap Type of length map.
87  template<class _Graph, class _LengthMap>
88  struct BellmanFordDefaultTraits {
89    /// The graph type the algorithm runs on.
90    typedef _Graph Graph;
91
92    /// \brief The type of the map that stores the edge lengths.
93    ///
94    /// The type of the map that stores the edge lengths.
95    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
96    typedef _LengthMap LengthMap;
97
98    // The type of the length of the edges.
99    typedef typename _LengthMap::Value Value;
100
101    /// \brief Operation traits for bellman-ford algorithm.
102    ///
103    /// It defines the infinity type on the given Value type
104    /// and the used operation.
105    /// \see BellmanFordDefaultOperationTraits
106    typedef BellmanFordDefaultOperationTraits<Value> OperationTraits;
107 
108    /// \brief The type of the map that stores the last edges of the
109    /// shortest paths.
110    ///
111    /// The type of the map that stores the last
112    /// edges of the shortest paths.
113    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
114    ///
115    typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap;
116
117    /// \brief Instantiates a PredMap.
118    ///
119    /// This function instantiates a \ref PredMap.
120    /// \param graph is the graph, to which we would like to define the PredMap.
121    static PredMap *createPredMap(const _Graph& graph) {
122      return new PredMap(graph);
123    }
124
125    /// \brief The type of the map that stores the dists of the nodes.
126    ///
127    /// The type of the map that stores the dists of the nodes.
128    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
129    ///
130    typedef typename Graph::template NodeMap<typename _LengthMap::Value>
131    DistMap;
132
133    /// \brief Instantiates a DistMap.
134    ///
135    /// This function instantiates a \ref DistMap.
136    /// \param graph is the graph, to which we would like to define the
137    /// \ref DistMap
138    static DistMap *createDistMap(const _Graph& graph) {
139      return new DistMap(graph);
140    }
141
142  };
143 
144  /// \brief %BellmanFord algorithm class.
145  ///
146  /// \ingroup flowalgs
147  /// This class provides an efficient implementation of \c Bellman-Ford
148  /// algorithm. The edge lengths are passed to the algorithm using a
149  /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any
150  /// kind of length.
151  ///
152  /// The Bellman-Ford algorithm solves the shortest path from one node
153  /// problem when the edges can have negative length but the graph should
154  /// not contain cycles with negative sum of length. If we can assume
155  /// that all edge is non-negative in the graph then the dijkstra algorithm
156  /// should be used rather.
157  ///
158  /// The complexity of the algorithm is O(n * e).
159  ///
160  /// The type of the length is determined by the
161  /// \ref concept::ReadMap::Value "Value" of the length map.
162  ///
163  /// \param _Graph The graph type the algorithm runs on. The default value
164  /// is \ref ListGraph. The value of _Graph is not used directly by
165  /// BellmanFord, it is only passed to \ref BellmanFordDefaultTraits.
166  /// \param _LengthMap This read-only EdgeMap determines the lengths of the
167  /// edges. The default map type is \ref concept::StaticGraph::EdgeMap
168  /// "Graph::EdgeMap<int>".  The value of _LengthMap is not used directly
169  /// by BellmanFord, it is only passed to \ref BellmanFordDefaultTraits. 
170  /// \param _Traits Traits class to set various data types used by the
171  /// algorithm.  The default traits class is \ref BellmanFordDefaultTraits
172  /// "BellmanFordDefaultTraits<_Graph,_LengthMap>".  See \ref
173  /// BellmanFordDefaultTraits for the documentation of a BellmanFord traits
174  /// class.
175  ///
176  /// \author Balazs Dezso
177
178#ifdef DOXYGEN
179  template <typename _Graph, typename _LengthMap, typename _Traits>
180#else
181  template <typename _Graph=ListGraph,
182            typename _LengthMap=typename _Graph::template EdgeMap<int>,
183            typename _Traits=BellmanFordDefaultTraits<_Graph,_LengthMap> >
184#endif
185  class BellmanFord {
186  public:
187   
188    /// \brief \ref Exception for uninitialized parameters.
189    ///
190    /// This error represents problems in the initialization
191    /// of the parameters of the algorithms.
192
193    class UninitializedParameter : public lemon::UninitializedParameter {
194    public:
195      virtual const char* exceptionName() const {
196        return "lemon::BellmanFord::UninitializedParameter";
197      }
198    };
199
200    typedef _Traits Traits;
201    ///The type of the underlying graph.
202    typedef typename _Traits::Graph Graph;
203
204    typedef typename Graph::Node Node;
205    typedef typename Graph::NodeIt NodeIt;
206    typedef typename Graph::Edge Edge;
207    typedef typename Graph::OutEdgeIt OutEdgeIt;
208   
209    /// \brief The type of the length of the edges.
210    typedef typename _Traits::LengthMap::Value Value;
211    /// \brief The type of the map that stores the edge lengths.
212    typedef typename _Traits::LengthMap LengthMap;
213    /// \brief The type of the map that stores the last
214    /// edges of the shortest paths.
215    typedef typename _Traits::PredMap PredMap;
216    /// \brief The type of the map that stores the dists of the nodes.
217    typedef typename _Traits::DistMap DistMap;
218    /// \brief The operation traits.
219    typedef typename _Traits::OperationTraits OperationTraits;
220  private:
221    /// Pointer to the underlying graph.
222    const Graph *graph;
223    /// Pointer to the length map
224    const LengthMap *length;
225    ///Pointer to the map of predecessors edges.
226    PredMap *_pred;
227    ///Indicates if \ref _pred is locally allocated (\c true) or not.
228    bool local_pred;
229    ///Pointer to the map of distances.
230    DistMap *_dist;
231    ///Indicates if \ref _dist is locally allocated (\c true) or not.
232    bool local_dist;
233
234    typedef typename Graph::template NodeMap<bool> MaskMap;
235    MaskMap *_mask;
236
237    std::vector<Node> _process;
238
239    /// Creates the maps if necessary.
240    void create_maps() {
241      if(!_pred) {
242        local_pred = true;
243        _pred = Traits::createPredMap(*graph);
244      }
245      if(!_dist) {
246        local_dist = true;
247        _dist = Traits::createDistMap(*graph);
248      }
249      _mask = new MaskMap(*graph, false);
250    }
251   
252  public :
253 
254    typedef BellmanFord Create;
255
256    /// \name Named template parameters
257
258    ///@{
259
260    template <class T>
261    struct DefPredMapTraits : public Traits {
262      typedef T PredMap;
263      static PredMap *createPredMap(const Graph&) {
264        throw UninitializedParameter();
265      }
266    };
267
268    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
269    /// type
270    /// \ref named-templ-param "Named parameter" for setting PredMap type
271    ///
272    template <class T>
273    struct DefPredMap
274      : public BellmanFord< Graph, LengthMap, DefPredMapTraits<T> > {
275      typedef BellmanFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
276    };
277   
278    template <class T>
279    struct DefDistMapTraits : public Traits {
280      typedef T DistMap;
281      static DistMap *createDistMap(const Graph&) {
282        throw UninitializedParameter();
283      }
284    };
285
286    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
287    /// type
288    ///
289    /// \ref named-templ-param "Named parameter" for setting DistMap type
290    ///
291    template <class T>
292    struct DefDistMap
293      : public BellmanFord< Graph, LengthMap, DefDistMapTraits<T> > {
294      typedef BellmanFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
295    };
296   
297    template <class T>
298    struct DefOperationTraitsTraits : public Traits {
299      typedef T OperationTraits;
300    };
301   
302    /// \brief \ref named-templ-param "Named parameter" for setting
303    /// OperationTraits type
304    ///
305    /// \ref named-templ-param "Named parameter" for setting OperationTraits
306    /// type
307    template <class T>
308    struct DefOperationTraits
309      : public BellmanFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
310      typedef BellmanFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
311      Create;
312    };
313   
314    ///@}
315
316  protected:
317   
318    BellmanFord() {}
319
320  public:     
321   
322    /// \brief Constructor.
323    ///
324    /// \param _graph the graph the algorithm will run on.
325    /// \param _length the length map used by the algorithm.
326    BellmanFord(const Graph& _graph, const LengthMap& _length) :
327      graph(&_graph), length(&_length),
328      _pred(0), local_pred(false),
329      _dist(0), local_dist(false) {}
330   
331    ///Destructor.
332    ~BellmanFord() {
333      if(local_pred) delete _pred;
334      if(local_dist) delete _dist;
335      delete _mask;
336    }
337
338    /// \brief Sets the length map.
339    ///
340    /// Sets the length map.
341    /// \return \c (*this)
342    BellmanFord &lengthMap(const LengthMap &m) {
343      length = &m;
344      return *this;
345    }
346
347    /// \brief Sets the map storing the predecessor edges.
348    ///
349    /// Sets the map storing the predecessor edges.
350    /// If you don't use this function before calling \ref run(),
351    /// it will allocate one. The destuctor deallocates this
352    /// automatically allocated map, of course.
353    /// \return \c (*this)
354    BellmanFord &predMap(PredMap &m) {
355      if(local_pred) {
356        delete _pred;
357        local_pred=false;
358      }
359      _pred = &m;
360      return *this;
361    }
362
363    /// \brief Sets the map storing the distances calculated by the algorithm.
364    ///
365    /// Sets the map storing the distances calculated by the algorithm.
366    /// If you don't use this function before calling \ref run(),
367    /// it will allocate one. The destuctor deallocates this
368    /// automatically allocated map, of course.
369    /// \return \c (*this)
370    BellmanFord &distMap(DistMap &m) {
371      if(local_dist) {
372        delete _dist;
373        local_dist=false;
374      }
375      _dist = &m;
376      return *this;
377    }
378
379    /// \name Execution control
380    /// The simplest way to execute the algorithm is to use
381    /// one of the member functions called \c run(...).
382    /// \n
383    /// If you need more control on the execution,
384    /// first you must call \ref init(), then you can add several source nodes
385    /// with \ref addSource().
386    /// Finally \ref start() will perform the actual path
387    /// computation.
388
389    ///@{
390
391    /// \brief Initializes the internal data structures.
392    ///
393    /// Initializes the internal data structures.
394    void init(const Value value = OperationTraits::infinity()) {
395      create_maps();
396      for (NodeIt it(*graph); it != INVALID; ++it) {
397        _pred->set(it, INVALID);
398        _dist->set(it, value);
399      }
400      _process.clear();
401      if (OperationTraits::less(value, OperationTraits::infinity())) {
402        for (NodeIt it(*graph); it != INVALID; ++it) {
403          _process.push_back(it);
404          _mask->set(it, true);
405        }
406      }
407    }
408   
409    /// \brief Adds a new source node.
410    ///
411    /// The optional second parameter is the initial distance of the node.
412    /// It just sets the distance of the node to the given value.
413    void addSource(Node source, Value dst = OperationTraits::zero()) {
414      _dist->set(source, dst);
415      if (!(*_mask)[source]) {
416        _process.push_back(source);
417        _mask->set(source, true);
418      }
419    }
420
421    /// \brief Executes one round from the bellman ford algorithm.
422    ///
423    /// If the algoritm calculated the distances in the previous round
424    /// strictly for all at most k length paths then it will calculate the
425    /// distances strictly for all at most k + 1 length paths. With k
426    /// iteration this function calculates the at most k length paths.
427    /// \return %True when the algorithm have not found more shorter paths.
428    bool processNextRound() {
429      for (int i = 0; i < (int)_process.size(); ++i) {
430        _mask->set(_process[i], false);
431      }
432      std::vector<Node> nextProcess;
433      std::vector<Value> values(_process.size());
434      for (int i = 0; i < (int)_process.size(); ++i) {
435        values[i] = (*_dist)[_process[i]];
436      }
437      for (int i = 0; i < (int)_process.size(); ++i) {
438        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
439          Node target = graph->target(it);
440          Value relaxed = OperationTraits::plus(values[i], (*length)[it]);
441          if (OperationTraits::less(relaxed, (*_dist)[target])) {
442            _pred->set(target, it);
443            _dist->set(target, relaxed);
444            if (!(*_mask)[target]) {
445              _mask->set(target, true);
446              nextProcess.push_back(target);
447            }
448          }       
449        }
450      }
451      _process.swap(nextProcess);
452      return _process.empty();
453    }
454
455    /// \brief Executes one weak round from the bellman ford algorithm.
456    ///
457    /// If the algorithm calculated the distances in the
458    /// previous round at least for all at most k length paths then it will
459    /// calculate the distances at least for all at most k + 1 length paths.
460    /// This function does not make it possible to calculate strictly the
461    /// at most k length minimal paths, this is why it is
462    /// called just weak round.
463    /// \return %True when the algorithm have not found more shorter paths.
464    bool processNextWeakRound() {
465      for (int i = 0; i < (int)_process.size(); ++i) {
466        _mask->set(_process[i], false);
467      }
468      std::vector<Node> nextProcess;
469      for (int i = 0; i < (int)_process.size(); ++i) {
470        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
471          Node target = graph->target(it);
472          Value relaxed =
473            OperationTraits::plus((*_dist)[_process[i]], (*length)[it]);
474          if (OperationTraits::less(relaxed, (*_dist)[target])) {
475            _pred->set(target, it);
476            _dist->set(target, relaxed);
477            if (!(*_mask)[target]) {
478              _mask->set(target, true);
479              nextProcess.push_back(target);
480            }
481          }       
482        }
483      }
484      _process.swap(nextProcess);
485      return _process.empty();
486    }
487
488    /// \brief Executes the algorithm.
489    ///
490    /// \pre init() must be called and at least one node should be added
491    /// with addSource() before using this function.
492    ///
493    /// This method runs the %BellmanFord algorithm from the root node(s)
494    /// in order to compute the shortest path to each node. The algorithm
495    /// computes
496    /// - The shortest path tree.
497    /// - The distance of each node from the root(s).
498    void start() {
499      int num = countNodes(*graph) - 1;
500      for (int i = 0; i < num; ++i) {
501        if (processNextWeakRound()) break;
502      }
503    }
504
505    /// \brief Executes the algorithm and checks the negative cycles.
506    ///
507    /// \pre init() must be called and at least one node should be added
508    /// with addSource() before using this function. If there is
509    /// a negative cycles in the graph it gives back false.
510    ///
511    /// This method runs the %BellmanFord algorithm from the root node(s)
512    /// in order to compute the shortest path to each node. The algorithm
513    /// computes
514    /// - The shortest path tree.
515    /// - The distance of each node from the root(s).
516    bool checkedStart() {
517      int num = countNodes(*graph);
518      for (int i = 0; i < num; ++i) {
519        if (processNextWeakRound()) return true;
520      }
521      return false;
522    }
523
524    /// \brief Executes the algorithm with path length limit.
525    ///
526    /// \pre init() must be called and at least one node should be added
527    /// with addSource() before using this function.
528    ///
529    /// This method runs the %BellmanFord algorithm from the root node(s)
530    /// in order to compute the shortest path with at most \c length edge
531    /// long paths to each node. The algorithm computes
532    /// - The shortest path tree.
533    /// - The limited distance of each node from the root(s).
534    void limitedStart(int length) {
535      for (int i = 0; i < length; ++i) {
536        if (processNextRound()) break;
537      }
538    }
539   
540    /// \brief Runs %BellmanFord algorithm from node \c s.
541    ///   
542    /// This method runs the %BellmanFord algorithm from a root node \c s
543    /// in order to compute the shortest path to each node. The algorithm
544    /// computes
545    /// - The shortest path tree.
546    /// - The distance of each node from the root.
547    ///
548    /// \note d.run(s) is just a shortcut of the following code.
549    ///\code
550    ///  d.init();
551    ///  d.addSource(s);
552    ///  d.start();
553    ///\endcode
554    void run(Node s) {
555      init();
556      addSource(s);
557      start();
558    }
559   
560    /// \brief Runs %BellmanFord algorithm with limited path length
561    /// from node \c s.
562    ///   
563    /// This method runs the %BellmanFord algorithm from a root node \c s
564    /// in order to compute the shortest path with at most \c len edges
565    /// to each node. The algorithm computes
566    /// - The shortest path tree.
567    /// - The distance of each node from the root.
568    ///
569    /// \note d.run(s, len) is just a shortcut of the following code.
570    ///\code
571    ///  d.init();
572    ///  d.addSource(s);
573    ///  d.limitedStart(len);
574    ///\endcode
575    void run(Node s, int len) {
576      init();
577      addSource(s);
578      limitedStart(len);
579    }
580   
581    ///@}
582
583    /// \name Query Functions
584    /// The result of the %BellmanFord algorithm can be obtained using these
585    /// functions.\n
586    /// Before the use of these functions,
587    /// either run() or start() must be called.
588   
589    ///@{
590
591    /// \brief Copies the shortest path to \c t into \c p
592    ///   
593    /// This function copies the shortest path to \c t into \c p.
594    /// If it \c t is a source itself or unreachable, then it does not
595    /// alter \c p.
596    ///
597    /// \return Returns \c true if a path to \c t was actually copied to \c p,
598    /// \c false otherwise.
599    /// \sa DirPath
600    template <typename Path>
601    bool getPath(Path &p, Node t) {
602      if(reached(t)) {
603        p.clear();
604        typename Path::Builder b(p);
605        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
606          b.pushFront(predEdge(t));
607        b.commit();
608        return true;
609      }
610      return false;
611    }
612         
613    /// \brief The distance of a node from the root.
614    ///
615    /// Returns the distance of a node from the root.
616    /// \pre \ref run() must be called before using this function.
617    /// \warning If node \c v in unreachable from the root the return value
618    /// of this funcion is undefined.
619    Value dist(Node v) const { return (*_dist)[v]; }
620
621    /// \brief Returns the 'previous edge' of the shortest path tree.
622    ///
623    /// For a node \c v it returns the 'previous edge' of the shortest path
624    /// tree, i.e. it returns the last edge of a shortest path from the root
625    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
626    /// if \c v=s. The shortest path tree used here is equal to the shortest
627    /// path tree used in \ref predNode().
628    /// \pre \ref run() must be called before using
629    /// this function.
630    Edge predEdge(Node v) const { return (*_pred)[v]; }
631
632    /// \brief Returns the 'previous node' of the shortest path tree.
633    ///
634    /// For a node \c v it returns the 'previous node' of the shortest path
635    /// tree, i.e. it returns the last but one node from a shortest path from
636    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
637    /// or if \c v=s. The shortest path tree used here is equal to the
638    /// shortest path tree used in \ref predEdge().  \pre \ref run() must be
639    /// called before using this function.
640    Node predNode(Node v) const {
641      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
642    }
643   
644    /// \brief Returns a reference to the NodeMap of distances.
645    ///
646    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
647    /// be called before using this function.
648    const DistMap &distMap() const { return *_dist;}
649 
650    /// \brief Returns a reference to the shortest path tree map.
651    ///
652    /// Returns a reference to the NodeMap of the edges of the
653    /// shortest path tree.
654    /// \pre \ref run() must be called before using this function.
655    const PredMap &predMap() const { return *_pred; }
656 
657    /// \brief Checks if a node is reachable from the root.
658    ///
659    /// Returns \c true if \c v is reachable from the root.
660    /// \pre \ref run() must be called before using this function.
661    ///
662    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
663   
664    ///@}
665  };
666 
667  /// \brief Default traits class of BellmanFord function.
668  ///
669  /// Default traits class of BellmanFord function.
670  /// \param _Graph Graph type.
671  /// \param _LengthMap Type of length map.
672  template <typename _Graph, typename _LengthMap>
673  struct BellmanFordWizardDefaultTraits {
674    /// \brief The graph type the algorithm runs on.
675    typedef _Graph Graph;
676
677    /// \brief The type of the map that stores the edge lengths.
678    ///
679    /// The type of the map that stores the edge lengths.
680    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
681    typedef _LengthMap LengthMap;
682
683    /// \brief The value type of the length map.
684    typedef typename _LengthMap::Value Value;
685
686    /// \brief Operation traits for bellman-ford algorithm.
687    ///
688    /// It defines the infinity type on the given Value type
689    /// and the used operation.
690    /// \see BellmanFordDefaultOperationTraits
691    typedef BellmanFordDefaultOperationTraits<Value> OperationTraits;
692
693    /// \brief The type of the map that stores the last
694    /// edges of the shortest paths.
695    ///
696    /// The type of the map that stores the last
697    /// edges of the shortest paths.
698    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
699    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
700
701    /// \brief Instantiates a PredMap.
702    ///
703    /// This function instantiates a \ref PredMap.
704    static PredMap *createPredMap(const _Graph &) {
705      return new PredMap();
706    }
707    /// \brief The type of the map that stores the dists of the nodes.
708    ///
709    /// The type of the map that stores the dists of the nodes.
710    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
711    typedef NullMap<typename Graph::Node, Value> DistMap;
712    /// \brief Instantiates a DistMap.
713    ///
714    /// This function instantiates a \ref DistMap.
715    static DistMap *createDistMap(const _Graph &) {
716      return new DistMap();
717    }
718  };
719 
720  /// \brief Default traits used by \ref BellmanFordWizard
721  ///
722  /// To make it easier to use BellmanFord algorithm
723  /// we have created a wizard class.
724  /// This \ref BellmanFordWizard class needs default traits,
725  /// as well as the \ref BellmanFord class.
726  /// The \ref BellmanFordWizardBase is a class to be the default traits of the
727  /// \ref BellmanFordWizard class.
728  /// \todo More named parameters are required...
729  template<class _Graph,class _LengthMap>
730  class BellmanFordWizardBase
731    : public BellmanFordWizardDefaultTraits<_Graph,_LengthMap> {
732
733    typedef BellmanFordWizardDefaultTraits<_Graph,_LengthMap> Base;
734  protected:
735    /// Type of the nodes in the graph.
736    typedef typename Base::Graph::Node Node;
737
738    /// Pointer to the underlying graph.
739    void *_graph;
740    /// Pointer to the length map
741    void *_length;
742    ///Pointer to the map of predecessors edges.
743    void *_pred;
744    ///Pointer to the map of distances.
745    void *_dist;
746    ///Pointer to the source node.
747    Node _source;
748
749    public:
750    /// Constructor.
751   
752    /// This constructor does not require parameters, therefore it initiates
753    /// all of the attributes to default values (0, INVALID).
754    BellmanFordWizardBase() : _graph(0), _length(0), _pred(0),
755                           _dist(0), _source(INVALID) {}
756
757    /// Constructor.
758   
759    /// This constructor requires some parameters,
760    /// listed in the parameters list.
761    /// Others are initiated to 0.
762    /// \param graph is the initial value of  \ref _graph
763    /// \param length is the initial value of  \ref _length
764    /// \param source is the initial value of  \ref _source
765    BellmanFordWizardBase(const _Graph& graph,
766                          const _LengthMap& length,
767                          Node source = INVALID) :
768      _graph((void *)&graph), _length((void *)&length), _pred(0),
769      _dist(0), _source(source) {}
770
771  };
772 
773  /// A class to make the usage of BellmanFord algorithm easier
774
775  /// This class is created to make it easier to use BellmanFord algorithm.
776  /// It uses the functions and features of the plain \ref BellmanFord,
777  /// but it is much simpler to use it.
778  ///
779  /// Simplicity means that the way to change the types defined
780  /// in the traits class is based on functions that returns the new class
781  /// and not on templatable built-in classes.
782  /// When using the plain \ref BellmanFord
783  /// the new class with the modified type comes from
784  /// the original class by using the ::
785  /// operator. In the case of \ref BellmanFordWizard only
786  /// a function have to be called and it will
787  /// return the needed class.
788  ///
789  /// It does not have own \ref run method. When its \ref run method is called
790  /// it initiates a plain \ref BellmanFord class, and calls the \ref
791  /// BellmanFord::run method of it.
792  template<class _Traits>
793  class BellmanFordWizard : public _Traits {
794    typedef _Traits Base;
795
796    ///The type of the underlying graph.
797    typedef typename _Traits::Graph Graph;
798
799    typedef typename Graph::Node Node;
800    typedef typename Graph::NodeIt NodeIt;
801    typedef typename Graph::Edge Edge;
802    typedef typename Graph::OutEdgeIt EdgeIt;
803   
804    ///The type of the map that stores the edge lengths.
805    typedef typename _Traits::LengthMap LengthMap;
806
807    ///The type of the length of the edges.
808    typedef typename LengthMap::Value Value;
809
810    ///\brief The type of the map that stores the last
811    ///edges of the shortest paths.
812    typedef typename _Traits::PredMap PredMap;
813
814    ///The type of the map that stores the dists of the nodes.
815    typedef typename _Traits::DistMap DistMap;
816
817  public:
818    /// Constructor.
819    BellmanFordWizard() : _Traits() {}
820
821    /// \brief Constructor that requires parameters.
822    ///
823    /// Constructor that requires parameters.
824    /// These parameters will be the default values for the traits class.
825    BellmanFordWizard(const Graph& graph, const LengthMap& length,
826                      Node source = INVALID)
827      : _Traits(graph, length, source) {}
828
829    /// \brief Copy constructor
830    BellmanFordWizard(const _Traits &b) : _Traits(b) {}
831
832    ~BellmanFordWizard() {}
833
834    /// \brief Runs BellmanFord algorithm from a given node.
835    ///   
836    /// Runs BellmanFord algorithm from a given node.
837    /// The node can be given by the \ref source function.
838    void run() {
839      if(Base::_source == INVALID) throw UninitializedParameter();
840      BellmanFord<Graph,LengthMap,_Traits>
841        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
842      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
843      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
844      bf.run(Base::_source);
845    }
846
847    /// \brief Runs BellmanFord algorithm from the given node.
848    ///
849    /// Runs BellmanFord algorithm from the given node.
850    /// \param source is the given source.
851    void run(Node source) {
852      Base::_source = source;
853      run();
854    }
855
856    template<class T>
857    struct DefPredMapBase : public Base {
858      typedef T PredMap;
859      static PredMap *createPredMap(const Graph &) { return 0; };
860      DefPredMapBase(const _Traits &b) : _Traits(b) {}
861    };
862   
863    ///\brief \ref named-templ-param "Named parameter"
864    ///function for setting PredMap type
865    ///
866    /// \ref named-templ-param "Named parameter"
867    ///function for setting PredMap type
868    ///
869    template<class T>
870    BellmanFordWizard<DefPredMapBase<T> > predMap(const T &t)
871    {
872      Base::_pred=(void *)&t;
873      return BellmanFordWizard<DefPredMapBase<T> >(*this);
874    }
875   
876    template<class T>
877    struct DefDistMapBase : public Base {
878      typedef T DistMap;
879      static DistMap *createDistMap(const Graph &) { return 0; };
880      DefDistMapBase(const _Traits &b) : _Traits(b) {}
881    };
882   
883    ///\brief \ref named-templ-param "Named parameter"
884    ///function for setting DistMap type
885    ///
886    /// \ref named-templ-param "Named parameter"
887    ///function for setting DistMap type
888    ///
889    template<class T>
890    BellmanFordWizard<DefDistMapBase<T> > distMap(const T &t) {
891      Base::_dist=(void *)&t;
892      return BellmanFordWizard<DefDistMapBase<T> >(*this);
893    }
894
895    template<class T>
896    struct DefOperationTraitsBase : public Base {
897      typedef T OperationTraits;
898      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
899    };
900   
901    ///\brief \ref named-templ-param "Named parameter"
902    ///function for setting OperationTraits type
903    ///
904    /// \ref named-templ-param "Named parameter"
905    ///function for setting OperationTraits type
906    ///
907    template<class T>
908    BellmanFordWizard<DefOperationTraitsBase<T> > distMap() {
909      return BellmanFordWizard<DefDistMapBase<T> >(*this);
910    }
911   
912    /// \brief Sets the source node, from which the BellmanFord algorithm runs.
913    ///
914    /// Sets the source node, from which the BellmanFord algorithm runs.
915    /// \param source is the source node.
916    BellmanFordWizard<_Traits>& source(Node source) {
917      Base::_source = source;
918      return *this;
919    }
920   
921  };
922 
923  /// \brief Function type interface for BellmanFord algorithm.
924  ///
925  /// \ingroup flowalgs
926  /// Function type interface for BellmanFord algorithm.
927  ///
928  /// This function also has several \ref named-templ-func-param
929  /// "named parameters", they are declared as the members of class
930  /// \ref BellmanFordWizard.
931  /// The following
932  /// example shows how to use these parameters.
933  ///\code
934  /// bellmanford(g,length,source).predMap(preds).run();
935  ///\endcode
936  /// \warning Don't forget to put the \ref BellmanFordWizard::run() "run()"
937  /// to the end of the parameter list.
938  /// \sa BellmanFordWizard
939  /// \sa BellmanFord
940  template<class _Graph, class _LengthMap>
941  BellmanFordWizard<BellmanFordWizardBase<_Graph,_LengthMap> >
942  bellmanFord(const _Graph& graph,
943              const _LengthMap& length,
944              typename _Graph::Node source = INVALID) {
945    return BellmanFordWizard<BellmanFordWizardBase<_Graph,_LengthMap> >
946      (graph, length, source);
947  }
948
949} //END OF NAMESPACE LEMON
950
951#endif
952
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