COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/hugo/dijkstra.h @ 739:3bb5553ec41b

Last change on this file since 739:3bb5553ec41b was 734:329832ac02b7, checked in by Alpar Juttner, 17 years ago

A remark added.

File size: 9.7 KB
Line 
1// -*- C++ -*-
2#ifndef HUGO_DIJKSTRA_H
3#define HUGO_DIJKSTRA_H
4
5///\ingroup galgs
6///\file
7///\brief Dijkstra algorithm.
8
9#include <hugo/bin_heap.h>
10#include <hugo/invalid.h>
11
12namespace hugo {
13
14/// \addtogroup galgs
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    typedef typename Graph::Node Node;
59    typedef typename Graph::NodeIt NodeIt;
60    typedef typename Graph::Edge Edge;
61    typedef typename Graph::OutEdgeIt OutEdgeIt;
62   
63    ///The type of the length of the edges.
64    typedef typename LM::ValueType ValueType;
65    ///The type of the map that stores the edge lengths.
66    typedef LM LengthMap;
67    ///\brief The type of the map that stores the last
68    ///edges of the shortest paths.
69    typedef typename Graph::template NodeMap<Edge> PredMap;
70    ///\brief The type of the map that stores the last but one
71    ///nodes of the shortest paths.
72    typedef typename Graph::template NodeMap<Node> PredNodeMap;
73    ///The type of the map that stores the dists of the nodes.
74    typedef typename Graph::template NodeMap<ValueType> DistMap;
75
76  private:
77    const Graph *G;
78    const LM *length;
79    //    bool local_length;
80    PredMap *predecessor;
81    bool local_predecessor;
82    PredNodeMap *pred_node;
83    bool local_pred_node;
84    DistMap *distance;
85    bool local_distance;
86
87    ///Initialize maps
88   
89    ///\todo Error if \c G or are \c NULL. What about \c length?
90    ///\todo Better memory allocation (instead of new).
91    void init_maps()
92    {
93//       if(!length) {
94//      local_length = true;
95//      length = new LM(G);
96//       }
97      if(!predecessor) {
98        local_predecessor = true;
99        predecessor = new PredMap(*G);
100      }
101      if(!pred_node) {
102        local_pred_node = true;
103        pred_node = new PredNodeMap(*G);
104      }
105      if(!distance) {
106        local_distance = true;
107        distance = new DistMap(*G);
108      }
109    }
110   
111  public :
112   
113    Dijkstra(const Graph& _G, const LM& _length) :
114      G(&_G), length(&_length),
115      predecessor(NULL), local_predecessor(false),
116      pred_node(NULL), local_pred_node(false),
117      distance(NULL), local_distance(false)
118    { }
119   
120    ~Dijkstra()
121    {
122      //      if(local_length) delete length;
123      if(local_predecessor) delete predecessor;
124      if(local_pred_node) delete pred_node;
125      if(local_distance) delete distance;
126    }
127
128    ///Sets the graph the algorithm will run on.
129
130    ///Sets the graph the algorithm will run on.
131    ///\return <tt> (*this) </tt>
132    Dijkstra &setGraph(const Graph &_G)
133    {
134      G = &_G;
135      return *this;
136    }
137    ///Sets the length map.
138
139    ///Sets the length map.
140    ///\return <tt> (*this) </tt>
141    Dijkstra &setLengthMap(const LM &m)
142    {
143//       if(local_length) {
144//      delete length;
145//      local_length=false;
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      for ( NodeIt u(*G) ; G->valid(u) ; G->next(u) ) {
216        predecessor->set(u,INVALID);
217        pred_node->set(u,INVALID);
218      }
219     
220      typename GR::template NodeMap<int> heap_map(*G,-1);
221     
222      typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
223      std::less<ValueType> >
224      HeapType;
225     
226      HeapType heap(heap_map);
227     
228      heap.push(s,0);
229     
230      while ( !heap.empty() ) {
231       
232        Node v=heap.top();
233        ValueType oldvalue=heap[v];
234        heap.pop();
235        distance->set(v, oldvalue);
236       
237       
238        for(OutEdgeIt e(*G,v); G->valid(e); G->next(e)) {
239          Node w=G->bNode(e);
240         
241          switch(heap.state(w)) {
242          case HeapType::PRE_HEAP:
243            heap.push(w,oldvalue+(*length)[e]);
244            predecessor->set(w,e);
245            pred_node->set(w,v);
246            break;
247          case HeapType::IN_HEAP:
248            if ( oldvalue+(*length)[e] < heap[w] ) {
249              heap.decrease(w, oldvalue+(*length)[e]);
250              predecessor->set(w,e);
251              pred_node->set(w,v);
252            }
253            break;
254          case HeapType::POST_HEAP:
255            break;
256          }
257        }
258      }
259    }
260   
261    ///The distance of a node from the root.
262
263    ///Returns the distance of a node from the root.
264    ///\pre \ref run() must be called before using this function.
265    ///\warning If node \c v in unreachable from the root the return value
266    ///of this funcion is undefined.
267    ValueType dist(Node v) const { return (*distance)[v]; }
268
269    ///Returns the 'previous edge' of the shortest path tree.
270
271    ///For a node \c v it returns the 'previous edge' of the shortest path tree,
272    ///i.e. it returns the last edge from a shortest path from the root to \c
273    ///v. It is \ref INVALID
274    ///if \c v is unreachable from the root or if \c v=s. The
275    ///shortest path tree used here is equal to the shortest path tree used in
276    ///\ref predNode(Node v).  \pre \ref run() must be called before using
277    ///this function.
278    Edge pred(Node v) const { return (*predecessor)[v]; }
279
280    ///Returns the 'previous node' of the shortest path tree.
281
282    ///For a node \c v it returns the 'previous node' of the shortest path tree,
283    ///i.e. it returns the last but one node from a shortest path from the
284    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
285    ///\c v=s. The shortest path tree used here is equal to the shortest path
286    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
287    ///using this function.
288    Node predNode(Node v) const { return (*pred_node)[v]; }
289   
290    ///Returns a reference to the NodeMap of distances.
291
292    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
293    ///be called before using this function.
294    const DistMap &distMap() const { return *distance;}
295 
296    ///Returns a reference to the shortest path tree map.
297
298    ///Returns a reference to the NodeMap of the edges of the
299    ///shortest path tree.
300    ///\pre \ref run() must be called before using this function.
301    const PredMap &predMap() const { return *predecessor;}
302 
303    ///Returns a reference to the map of nodes of shortest paths.
304
305    ///Returns a reference to the NodeMap of the last but one nodes of the
306    ///shortest path tree.
307    ///\pre \ref run() must be called before using this function.
308    const PredNodeMap &predNodeMap() const { return *pred_node;}
309
310    ///Checks if a node is reachable from the root.
311
312    ///Returns \c true if \c v is reachable from the root.
313    ///\warning the root node is reported to be unreached!
314    ///\todo Is this what we want?
315    ///\pre \ref run() must be called before using this function.
316    ///
317    bool reached(Node v) { return G->valid((*predecessor)[v]); }
318   
319  };
320 
321
322  // **********************************************************************
323  //  IMPLEMENTATIONS
324  // **********************************************************************
325
326/// @}
327 
328} //END OF NAMESPACE HUGO
329
330#endif
331
332
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