COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/hugo/dijkstra.h @ 802:bc0c74eeb151

Last change on this file since 802:bc0c74eeb151 was 802:bc0c74eeb151, checked in by Alpar Juttner, 16 years ago
  • Changes in doc
  • setGraph(...) finally removed from Dijkstra, Bfs and Dfs.
File size: 9.8 KB
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1// -*- C++ -*-
2#ifndef HUGO_DIJKSTRA_H
3#define HUGO_DIJKSTRA_H
4
5///\ingroup flowalgs
6///\file
7///\brief Dijkstra algorithm.
8
9#include <hugo/bin_heap.h>
10#include <hugo/invalid.h>
11
12namespace hugo {
13
14/// \addtogroup flowalgs
15/// @{
16
17  ///%Dijkstra algorithm class.
18
19  ///This class provides an efficient implementation of %Dijkstra algorithm.
20  ///The edge lengths are passed to the algorithm using a
21  ///\ref ReadMapSkeleton "readable map",
22  ///so it is easy to change it to any kind of length.
23  ///
24  ///The type of the length is determined by the \c ValueType of the length map.
25  ///
26  ///It is also possible to change the underlying priority heap.
27  ///
28  ///\param GR The graph type the algorithm runs on.
29  ///\param LM This read-only
30  ///EdgeMap
31  ///determines the
32  ///lengths of the edges. It is read once for each edge, so the map
33  ///may involve in relatively time consuming process to compute the edge
34  ///length if it is necessary. The default map type is
35  ///\ref GraphSkeleton::EdgeMap "Graph::EdgeMap<int>"
36  ///\param Heap The heap type used by the %Dijkstra
37  ///algorithm. The default
38  ///is using \ref BinHeap "binary heap".
39  ///
40  ///\author Jacint Szabo and Alpar Juttner
41  ///\todo We need a typedef-names should be standardized. (-:
42  ///\todo Type of \c PredMap, \c PredNodeMap and \c DistMap
43  ///should not be fixed. (Problematic to solve).
44
45#ifdef DOXYGEN
46  template <typename GR,
47            typename LM,
48            typename Heap>
49#else
50  template <typename GR,
51            typename LM=typename GR::template EdgeMap<int>,
52            template <class,class,class,class> class Heap = BinHeap >
53#endif
54  class Dijkstra{
55  public:
56    ///The type of the underlying graph.
57    typedef GR Graph;
58    ///.
59    typedef typename Graph::Node Node;
60    ///.
61    typedef typename Graph::NodeIt NodeIt;
62    ///.
63    typedef typename Graph::Edge Edge;
64    ///.
65    typedef typename Graph::OutEdgeIt OutEdgeIt;
66   
67    ///The type of the length of the edges.
68    typedef typename LM::ValueType ValueType;
69    ///The type of the map that stores the edge lengths.
70    typedef LM LengthMap;
71    ///\brief The type of the map that stores the last
72    ///edges of the shortest paths.
73    typedef typename Graph::template NodeMap<Edge> PredMap;
74    ///\brief The type of the map that stores the last but one
75    ///nodes of the shortest paths.
76    typedef typename Graph::template NodeMap<Node> PredNodeMap;
77    ///The type of the map that stores the dists of the nodes.
78    typedef typename Graph::template NodeMap<ValueType> DistMap;
79
80  private:
81    /// Pointer to the underlying graph.
82    const Graph *G;
83    /// Pointer to the length map
84    const LM *length;
85    ///Pointer to the map of predecessors edges.
86    PredMap *predecessor;
87    ///Indicates if \ref predecessor is locally allocated (\c true) or not.
88    bool local_predecessor;
89    ///Pointer to the map of predecessors nodes.
90    PredNodeMap *pred_node;
91    ///Indicates if \ref pred_node is locally allocated (\c true) or not.
92    bool local_pred_node;
93    ///Pointer to the map of distances.
94    DistMap *distance;
95    ///Indicates if \ref distance is locally allocated (\c true) or not.
96    bool local_distance;
97
98    ///The source node of the last execution.
99    Node source;
100
101    ///Initializes the maps.
102   
103    ///\todo Error if \c G or are \c NULL. What about \c length?
104    ///\todo Better memory allocation (instead of new).
105    void init_maps()
106    {
107      if(!predecessor) {
108        local_predecessor = true;
109        predecessor = new PredMap(*G);
110      }
111      if(!pred_node) {
112        local_pred_node = true;
113        pred_node = new PredNodeMap(*G);
114      }
115      if(!distance) {
116        local_distance = true;
117        distance = new DistMap(*G);
118      }
119    }
120   
121  public :
122    ///Constructor.
123   
124    ///\param _G the graph the algorithm will run on.
125    ///\param _length the length map used by the algorithm.
126    Dijkstra(const Graph& _G, const LM& _length) :
127      G(&_G), length(&_length),
128      predecessor(NULL), local_predecessor(false),
129      pred_node(NULL), local_pred_node(false),
130      distance(NULL), local_distance(false)
131    { }
132   
133    ///Destructor.
134    ~Dijkstra()
135    {
136      if(local_predecessor) delete predecessor;
137      if(local_pred_node) delete pred_node;
138      if(local_distance) delete distance;
139    }
140
141    ///Sets the length map.
142
143    ///Sets the length map.
144    ///\return <tt> (*this) </tt>
145    Dijkstra &setLengthMap(const LM &m)
146    {
147      length = &m;
148      return *this;
149    }
150
151    ///Sets the map storing the predecessor edges.
152
153    ///Sets the map storing the predecessor edges.
154    ///If you don't use this function before calling \ref run(),
155    ///it will allocate one. The destuctor deallocates this
156    ///automatically allocated map, of course.
157    ///\return <tt> (*this) </tt>
158    Dijkstra &setPredMap(PredMap &m)
159    {
160      if(local_predecessor) {
161        delete predecessor;
162        local_predecessor=false;
163      }
164      predecessor = &m;
165      return *this;
166    }
167
168    ///Sets the map storing the predecessor nodes.
169
170    ///Sets the map storing the predecessor nodes.
171    ///If you don't use this function before calling \ref run(),
172    ///it will allocate one. The destuctor deallocates this
173    ///automatically allocated map, of course.
174    ///\return <tt> (*this) </tt>
175    Dijkstra &setPredNodeMap(PredNodeMap &m)
176    {
177      if(local_pred_node) {
178        delete pred_node;
179        local_pred_node=false;
180      }
181      pred_node = &m;
182      return *this;
183    }
184
185    ///Sets the map storing the distances calculated by the algorithm.
186
187    ///Sets the map storing the distances calculated by the algorithm.
188    ///If you don't use this function before calling \ref run(),
189    ///it will allocate one. The destuctor deallocates this
190    ///automatically allocated map, of course.
191    ///\return <tt> (*this) </tt>
192    Dijkstra &setDistMap(DistMap &m)
193    {
194      if(local_distance) {
195        delete distance;
196        local_distance=false;
197      }
198      distance = &m;
199      return *this;
200    }
201   
202  ///Runs %Dijkstra algorithm from node \c s.
203
204  ///This method runs the %Dijkstra algorithm from a root node \c s
205  ///in order to
206  ///compute the
207  ///shortest path to each node. The algorithm computes
208  ///- The shortest path tree.
209  ///- The distance of each node from the root.
210   
211    void run(Node s) {
212     
213      init_maps();
214     
215      source = s;
216     
217      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
218        predecessor->set(u,INVALID);
219        pred_node->set(u,INVALID);
220      }
221     
222      typename GR::template NodeMap<int> heap_map(*G,-1);
223     
224      typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
225      std::less<ValueType> >
226      HeapType;
227     
228      HeapType heap(heap_map);
229     
230      heap.push(s,0);
231     
232      while ( !heap.empty() ) {
233       
234        Node v=heap.top();
235        ValueType oldvalue=heap[v];
236        heap.pop();
237        distance->set(v, oldvalue);
238       
239       
240        for(OutEdgeIt e(*G,v); e!=INVALID; ++e) {
241          Node w=G->head(e);
242          switch(heap.state(w)) {
243          case HeapType::PRE_HEAP:
244            heap.push(w,oldvalue+(*length)[e]);
245            predecessor->set(w,e);
246            pred_node->set(w,v);
247            break;
248          case HeapType::IN_HEAP:
249            if ( oldvalue+(*length)[e] < heap[w] ) {
250              heap.decrease(w, oldvalue+(*length)[e]);
251              predecessor->set(w,e);
252              pred_node->set(w,v);
253            }
254            break;
255          case HeapType::POST_HEAP:
256            break;
257          }
258        }
259      }
260    }
261   
262    ///The distance of a node from the root.
263
264    ///Returns the distance of a node from the root.
265    ///\pre \ref run() must be called before using this function.
266    ///\warning If node \c v in unreachable from the root the return value
267    ///of this funcion is undefined.
268    ValueType dist(Node v) const { return (*distance)[v]; }
269
270    ///Returns the 'previous edge' of the shortest path tree.
271
272    ///For a node \c v it returns the 'previous edge' of the shortest path tree,
273    ///i.e. it returns the last edge of a shortest path from the root to \c
274    ///v. It is \ref INVALID
275    ///if \c v is unreachable from the root or if \c v=s. The
276    ///shortest path tree used here is equal to the shortest path tree used in
277    ///\ref predNode(Node v).  \pre \ref run() must be called before using
278    ///this function.
279    ///\todo predEdge could be a better name.
280    Edge pred(Node v) const { return (*predecessor)[v]; }
281
282    ///Returns the 'previous node' of the shortest path tree.
283
284    ///For a node \c v it returns the 'previous node' of the shortest path tree,
285    ///i.e. it returns the last but one node from a shortest path from the
286    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
287    ///\c v=s. The shortest path tree used here is equal to the shortest path
288    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
289    ///using this function.
290    Node predNode(Node v) const { return (*pred_node)[v]; }
291   
292    ///Returns a reference to the NodeMap of distances.
293
294    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
295    ///be called before using this function.
296    const DistMap &distMap() const { return *distance;}
297 
298    ///Returns a reference to the shortest path tree map.
299
300    ///Returns a reference to the NodeMap of the edges of the
301    ///shortest path tree.
302    ///\pre \ref run() must be called before using this function.
303    const PredMap &predMap() const { return *predecessor;}
304 
305    ///Returns a reference to the map of nodes of shortest paths.
306
307    ///Returns a reference to the NodeMap of the last but one nodes of the
308    ///shortest path tree.
309    ///\pre \ref run() must be called before using this function.
310    const PredNodeMap &predNodeMap() const { return *pred_node;}
311
312    ///Checks if a node is reachable from the root.
313
314    ///Returns \c true if \c v is reachable from the root.
315    ///\note The root node is reported to be reached!
316    ///\pre \ref run() must be called before using this function.
317    ///
318    bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
319   
320  };
321 
322/// @}
323 
324} //END OF NAMESPACE HUGO
325
326#endif
327
328
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