COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/hugo/dijkstra.h @ 707:ec034cfade65

Last change on this file since 707:ec034cfade65 was 707:ec034cfade65, checked in by Alpar Juttner, 17 years ago

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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
43#ifdef DOXYGEN
44  template <typename GR,
45            typename LM,
46            typename Heap>
47#else
48  template <typename GR,
49            typename LM=typename GR::template EdgeMap<int>,
50            template <class,class,class,class> class Heap = BinHeap >
51#endif
52  class Dijkstra{
53  public:
54    ///The type of the underlying graph.
55    typedef GR Graph;
56    typedef typename Graph::Node Node;
57    typedef typename Graph::NodeIt NodeIt;
58    typedef typename Graph::Edge Edge;
59    typedef typename Graph::OutEdgeIt OutEdgeIt;
60   
61    ///The type of the length of the edges.
62    typedef typename LM::ValueType ValueType;
63    ///The type of the map that stores the edge lengths.
64    typedef LM LengthMap;
65    ///\brief The type of the map that stores the last
66    ///edges of the shortest paths.
67    typedef typename Graph::template NodeMap<Edge> PredMap;
68    ///\brief The type of the map that stores the last but one
69    ///nodes of the shortest paths.
70    typedef typename Graph::template NodeMap<Node> PredNodeMap;
71    ///The type of the map that stores the dists of the nodes.
72    typedef typename Graph::template NodeMap<ValueType> DistMap;
73
74  private:
75    const Graph *G;
76    const LM *length;
77    //    bool local_length;
78    PredMap *predecessor;
79    bool local_predecessor;
80    PredNodeMap *pred_node;
81    bool local_pred_node;
82    DistMap *distance;
83    bool local_distance;
84
85    ///Initialize maps
86   
87    ///\todo Error if \c G or are \c NULL. What about \c length?
88    ///\todo Better memory allocation (instead of new).
89    void init_maps()
90    {
91//       if(!length) {
92//      local_length = true;
93//      length = new LM(G);
94//       }
95      if(!predecessor) {
96        local_predecessor = true;
97        predecessor = new PredMap(*G);
98      }
99      if(!pred_node) {
100        local_pred_node = true;
101        pred_node = new PredNodeMap(*G);
102      }
103      if(!distance) {
104        local_distance = true;
105        distance = new DistMap(*G);
106      }
107    }
108   
109  public :
110   
111    Dijkstra(const Graph& _G, const LM& _length) :
112      G(&_G), length(&_length),
113      predecessor(NULL), local_predecessor(false),
114      pred_node(NULL), local_pred_node(false),
115      distance(NULL), local_distance(false)
116    { }
117   
118    ~Dijkstra()
119    {
120      //      if(local_length) delete length;
121      if(local_predecessor) delete predecessor;
122      if(local_pred_node) delete pred_node;
123      if(local_distance) delete distance;
124    }
125
126    ///Sets the graph the algorithm will run on.
127
128    ///Sets the graph the algorithm will run on.
129    ///\return <tt> (*this) </tt>
130    Dijkstra &setGraph(const Graph &_G)
131    {
132      G = &_G;
133      return *this;
134    }
135    ///Sets the length map.
136
137    ///Sets the length map.
138    ///\return <tt> (*this) </tt>
139    Dijkstra &setLengthMap(const LM &m)
140    {
141//       if(local_length) {
142//      delete length;
143//      local_length=false;
144//       }
145      length = &m;
146      return *this;
147    }
148
149    ///Sets the map storing the predecessor edges.
150
151    ///Sets the map storing the predecessor edges.
152    ///If you don't use this function before calling \ref run(),
153    ///it will allocate one. The destuctor deallocates this
154    ///automatically allocated map, of course.
155    ///\return <tt> (*this) </tt>
156    Dijkstra &setPredMap(PredMap &m)
157    {
158      if(local_predecessor) {
159        delete predecessor;
160        local_predecessor=false;
161      }
162      predecessor = &m;
163      return *this;
164    }
165
166    ///Sets the map storing the predecessor nodes.
167
168    ///Sets the map storing the predecessor nodes.
169    ///If you don't use this function before calling \ref run(),
170    ///it will allocate one. The destuctor deallocates this
171    ///automatically allocated map, of course.
172    ///\return <tt> (*this) </tt>
173    Dijkstra &setPredNodeMap(PredNodeMap &m)
174    {
175      if(local_pred_node) {
176        delete pred_node;
177        local_pred_node=false;
178      }
179      pred_node = &m;
180      return *this;
181    }
182
183    ///Sets the map storing the distances calculated by the algorithm.
184
185    ///Sets the map storing the distances calculated by the algorithm.
186    ///If you don't use this function before calling \ref run(),
187    ///it will allocate one. The destuctor deallocates this
188    ///automatically allocated map, of course.
189    ///\return <tt> (*this) </tt>
190    Dijkstra &setDistMap(DistMap &m)
191    {
192      if(local_distance) {
193        delete distance;
194        local_distance=false;
195      }
196      distance = &m;
197      return *this;
198    }
199   
200  ///Runs %Dijkstra algorithm from node \c s.
201
202  ///This method runs the %Dijkstra algorithm from a root node \c s
203  ///in order to
204  ///compute the
205  ///shortest path to each node. The algorithm computes
206  ///- The shortest path tree.
207  ///- The distance of each node from the root.
208   
209    void run(Node s) {
210     
211      init_maps();
212     
213      for ( NodeIt u(*G) ; G->valid(u) ; G->next(u) ) {
214        predecessor->set(u,INVALID);
215        pred_node->set(u,INVALID);
216      }
217     
218      typename GR::template NodeMap<int> heap_map(*G,-1);
219     
220      typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
221      std::less<ValueType> >
222      HeapType;
223     
224      HeapType heap(heap_map);
225     
226      heap.push(s,0);
227     
228      while ( !heap.empty() ) {
229       
230        Node v=heap.top();
231        ValueType oldvalue=heap[v];
232        heap.pop();
233        distance->set(v, oldvalue);
234       
235       
236        for(OutEdgeIt e(*G,v); G->valid(e); G->next(e)) {
237          Node w=G->bNode(e);
238         
239          switch(heap.state(w)) {
240          case HeapType::PRE_HEAP:
241            heap.push(w,oldvalue+(*length)[e]);
242            predecessor->set(w,e);
243            pred_node->set(w,v);
244            break;
245          case HeapType::IN_HEAP:
246            if ( oldvalue+(*length)[e] < heap[w] ) {
247              heap.decrease(w, oldvalue+(*length)[e]);
248              predecessor->set(w,e);
249              pred_node->set(w,v);
250            }
251            break;
252          case HeapType::POST_HEAP:
253            break;
254          }
255        }
256      }
257    }
258   
259    ///The distance of a node from the root.
260
261    ///Returns the distance of a node from the root.
262    ///\pre \ref run() must be called before using this function.
263    ///\warning If node \c v in unreachable from the root the return value
264    ///of this funcion is undefined.
265    ValueType dist(Node v) const { return (*distance)[v]; }
266
267    ///Returns the 'previous edge' of the shortest path tree.
268
269    ///For a node \c v it returns the 'previous edge' of the shortest path tree,
270    ///i.e. it returns the last edge from a shortest path from the root to \c
271    ///v. It is \ref INVALID
272    ///if \c v is unreachable from the root or if \c v=s. The
273    ///shortest path tree used here is equal to the shortest path tree used in
274    ///\ref predNode(Node v).  \pre \ref run() must be called before using
275    ///this function.
276    Edge pred(Node v) const { return (*predecessor)[v]; }
277
278    ///Returns the 'previous node' of the shortest path tree.
279
280    ///For a node \c v it returns the 'previous node' of the shortest path tree,
281    ///i.e. it returns the last but one node from a shortest path from the
282    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
283    ///\c v=s. The shortest path tree used here is equal to the shortest path
284    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
285    ///using this function.
286    Node predNode(Node v) const { return (*pred_node)[v]; }
287   
288    ///Returns a reference to the NodeMap of distances.
289
290    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
291    ///be called before using this function.
292    const DistMap &distMap() const { return *distance;}
293 
294    ///Returns a reference to the shortest path tree map.
295
296    ///Returns a reference to the NodeMap of the edges of the
297    ///shortest path tree.
298    ///\pre \ref run() must be called before using this function.
299    const PredMap &predMap() const { return *predecessor;}
300 
301    ///Returns a reference to the map of nodes of shortest paths.
302
303    ///Returns a reference to the NodeMap of the last but one nodes of the
304    ///shortest path tree.
305    ///\pre \ref run() must be called before using this function.
306    const PredNodeMap &predNodeMap() const { return *pred_node;}
307
308    ///Checks if a node is reachable from the root.
309
310    ///Returns \c true if \c v is reachable from the root.
311    ///\warning the root node is reported to be unreached!
312    ///\todo Is this what we want?
313    ///\pre \ref run() must be called before using this function.
314    ///
315    bool reached(Node v) { return G->valid((*predecessor)[v]); }
316   
317  };
318 
319
320  // **********************************************************************
321  //  IMPLEMENTATIONS
322  // **********************************************************************
323
324/// @}
325 
326} //END OF NAMESPACE HUGO
327
328#endif
329
330
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