COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/hugo/dijkstra.h @ 880:9d0bfd35b97c

Last change on this file since 880:9d0bfd35b97c was 880:9d0bfd35b97c, checked in by Alpar Juttner, 16 years ago
  • Name changing: XYZGraphSkeleton -> XYZGraph
  • Fix some bad \ref's in the doc.
File size: 9.8 KB
Line 
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 skeleton::ReadMap "ReadMap",
22  ///so it is easy to change it to any kind of length.
23  ///
24  ///The type of the length is determined by the
25  ///\ref skeleton::ReadMap::ValueType "ValueType" of the length map.
26  ///
27  ///It is also possible to change the underlying priority heap.
28  ///
29  ///\param GR The graph type the algorithm runs on.
30  ///\param LM This read-only
31  ///EdgeMap
32  ///determines the
33  ///lengths of the edges. It is read once for each edge, so the map
34  ///may involve in relatively time consuming process to compute the edge
35  ///length if it is necessary. The default map type is
36  ///\ref skeleton::StaticGraph::EdgeMap "Graph::EdgeMap<int>"
37  ///\param Heap The heap type used by the %Dijkstra
38  ///algorithm. The default
39  ///is using \ref BinHeap "binary heap".
40  ///
41  ///\author Jacint Szabo and Alpar Juttner
42  ///\todo We need a typedef-names should be standardized. (-:
43  ///\todo Type of \c PredMap, \c PredNodeMap and \c DistMap
44  ///should not be fixed. (Problematic to solve).
45
46#ifdef DOXYGEN
47  template <typename GR,
48            typename LM,
49            typename Heap>
50#else
51  template <typename GR,
52            typename LM=typename GR::template EdgeMap<int>,
53            template <class,class,class,class> class Heap = BinHeap >
54#endif
55  class Dijkstra{
56  public:
57    ///The type of the underlying graph.
58    typedef GR Graph;
59    ///.
60    typedef typename Graph::Node Node;
61    ///.
62    typedef typename Graph::NodeIt NodeIt;
63    ///.
64    typedef typename Graph::Edge Edge;
65    ///.
66    typedef typename Graph::OutEdgeIt OutEdgeIt;
67   
68    ///The type of the length of the edges.
69    typedef typename LM::ValueType ValueType;
70    ///The type of the map that stores the edge lengths.
71    typedef LM LengthMap;
72    ///\brief The type of the map that stores the last
73    ///edges of the shortest paths.
74    typedef typename Graph::template NodeMap<Edge> PredMap;
75    ///\brief The type of the map that stores the last but one
76    ///nodes of the shortest paths.
77    typedef typename Graph::template NodeMap<Node> PredNodeMap;
78    ///The type of the map that stores the dists of the nodes.
79    typedef typename Graph::template NodeMap<ValueType> DistMap;
80
81  private:
82    /// Pointer to the underlying graph.
83    const Graph *G;
84    /// Pointer to the length map
85    const LM *length;
86    ///Pointer to the map of predecessors edges.
87    PredMap *predecessor;
88    ///Indicates if \ref predecessor is locally allocated (\c true) or not.
89    bool local_predecessor;
90    ///Pointer to the map of predecessors nodes.
91    PredNodeMap *pred_node;
92    ///Indicates if \ref pred_node is locally allocated (\c true) or not.
93    bool local_pred_node;
94    ///Pointer to the map of distances.
95    DistMap *distance;
96    ///Indicates if \ref distance is locally allocated (\c true) or not.
97    bool local_distance;
98
99    ///The source node of the last execution.
100    Node source;
101
102    ///Initializes the maps.
103   
104    ///\todo Error if \c G or are \c NULL. What about \c length?
105    ///\todo Better memory allocation (instead of new).
106    void init_maps()
107    {
108      if(!predecessor) {
109        local_predecessor = true;
110        predecessor = new PredMap(*G);
111      }
112      if(!pred_node) {
113        local_pred_node = true;
114        pred_node = new PredNodeMap(*G);
115      }
116      if(!distance) {
117        local_distance = true;
118        distance = new DistMap(*G);
119      }
120    }
121   
122  public :
123    ///Constructor.
124   
125    ///\param _G the graph the algorithm will run on.
126    ///\param _length the length map used by the algorithm.
127    Dijkstra(const Graph& _G, const LM& _length) :
128      G(&_G), length(&_length),
129      predecessor(NULL), local_predecessor(false),
130      pred_node(NULL), local_pred_node(false),
131      distance(NULL), local_distance(false)
132    { }
133   
134    ///Destructor.
135    ~Dijkstra()
136    {
137      if(local_predecessor) delete predecessor;
138      if(local_pred_node) delete pred_node;
139      if(local_distance) delete distance;
140    }
141
142    ///Sets the length map.
143
144    ///Sets the length map.
145    ///\return <tt> (*this) </tt>
146    Dijkstra &setLengthMap(const LM &m)
147    {
148      length = &m;
149      return *this;
150    }
151
152    ///Sets the map storing the predecessor edges.
153
154    ///Sets the map storing the predecessor edges.
155    ///If you don't use this function before calling \ref run(),
156    ///it will allocate one. The destuctor deallocates this
157    ///automatically allocated map, of course.
158    ///\return <tt> (*this) </tt>
159    Dijkstra &setPredMap(PredMap &m)
160    {
161      if(local_predecessor) {
162        delete predecessor;
163        local_predecessor=false;
164      }
165      predecessor = &m;
166      return *this;
167    }
168
169    ///Sets the map storing the predecessor nodes.
170
171    ///Sets the map storing the predecessor nodes.
172    ///If you don't use this function before calling \ref run(),
173    ///it will allocate one. The destuctor deallocates this
174    ///automatically allocated map, of course.
175    ///\return <tt> (*this) </tt>
176    Dijkstra &setPredNodeMap(PredNodeMap &m)
177    {
178      if(local_pred_node) {
179        delete pred_node;
180        local_pred_node=false;
181      }
182      pred_node = &m;
183      return *this;
184    }
185
186    ///Sets the map storing the distances calculated by the algorithm.
187
188    ///Sets the map storing the distances calculated by the algorithm.
189    ///If you don't use this function before calling \ref run(),
190    ///it will allocate one. The destuctor deallocates this
191    ///automatically allocated map, of course.
192    ///\return <tt> (*this) </tt>
193    Dijkstra &setDistMap(DistMap &m)
194    {
195      if(local_distance) {
196        delete distance;
197        local_distance=false;
198      }
199      distance = &m;
200      return *this;
201    }
202   
203  ///Runs %Dijkstra algorithm from node \c s.
204
205  ///This method runs the %Dijkstra algorithm from a root node \c s
206  ///in order to
207  ///compute the
208  ///shortest path to each node. The algorithm computes
209  ///- The shortest path tree.
210  ///- The distance of each node from the root.
211   
212    void run(Node s) {
213     
214      init_maps();
215     
216      source = s;
217     
218      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
219        predecessor->set(u,INVALID);
220        pred_node->set(u,INVALID);
221      }
222     
223      typename GR::template NodeMap<int> heap_map(*G,-1);
224     
225      typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
226      std::less<ValueType> >
227      HeapType;
228     
229      HeapType heap(heap_map);
230     
231      heap.push(s,0);
232     
233      while ( !heap.empty() ) {
234       
235        Node v=heap.top();
236        ValueType oldvalue=heap[v];
237        heap.pop();
238        distance->set(v, oldvalue);
239       
240       
241        for(OutEdgeIt e(*G,v); e!=INVALID; ++e) {
242          Node w=G->head(e);
243          switch(heap.state(w)) {
244          case HeapType::PRE_HEAP:
245            heap.push(w,oldvalue+(*length)[e]);
246            predecessor->set(w,e);
247            pred_node->set(w,v);
248            break;
249          case HeapType::IN_HEAP:
250            if ( oldvalue+(*length)[e] < heap[w] ) {
251              heap.decrease(w, oldvalue+(*length)[e]);
252              predecessor->set(w,e);
253              pred_node->set(w,v);
254            }
255            break;
256          case HeapType::POST_HEAP:
257            break;
258          }
259        }
260      }
261    }
262   
263    ///The distance of a node from the root.
264
265    ///Returns the distance of a node from the root.
266    ///\pre \ref run() must be called before using this function.
267    ///\warning If node \c v in unreachable from the root the return value
268    ///of this funcion is undefined.
269    ValueType dist(Node v) const { return (*distance)[v]; }
270
271    ///Returns the 'previous edge' of the shortest path tree.
272
273    ///For a node \c v it returns the 'previous edge' of the shortest path tree,
274    ///i.e. it returns the last edge of a shortest path from the root to \c
275    ///v. It is \ref INVALID
276    ///if \c v is unreachable from the root or if \c v=s. The
277    ///shortest path tree used here is equal to the shortest path tree used in
278    ///\ref predNode(Node v).  \pre \ref run() must be called before using
279    ///this function.
280    ///\todo predEdge could be a better name.
281    Edge pred(Node v) const { return (*predecessor)[v]; }
282
283    ///Returns the 'previous node' of the shortest path tree.
284
285    ///For a node \c v it returns the 'previous node' of the shortest path tree,
286    ///i.e. it returns the last but one node from a shortest path from the
287    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
288    ///\c v=s. The shortest path tree used here is equal to the shortest path
289    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
290    ///using this function.
291    Node predNode(Node v) const { return (*pred_node)[v]; }
292   
293    ///Returns a reference to the NodeMap of distances.
294
295    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
296    ///be called before using this function.
297    const DistMap &distMap() const { return *distance;}
298 
299    ///Returns a reference to the shortest path tree map.
300
301    ///Returns a reference to the NodeMap of the edges of the
302    ///shortest path tree.
303    ///\pre \ref run() must be called before using this function.
304    const PredMap &predMap() const { return *predecessor;}
305 
306    ///Returns a reference to the map of nodes of shortest paths.
307
308    ///Returns a reference to the NodeMap of the last but one nodes of the
309    ///shortest path tree.
310    ///\pre \ref run() must be called before using this function.
311    const PredNodeMap &predNodeMap() const { return *pred_node;}
312
313    ///Checks if a node is reachable from the root.
314
315    ///Returns \c true if \c v is reachable from the root.
316    ///\note The root node is reported to be reached!
317    ///\pre \ref run() must be called before using this function.
318    ///
319    bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
320   
321  };
322 
323/// @}
324 
325} //END OF NAMESPACE HUGO
326
327#endif
328
329
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