Last change on this file since 611:83530dad618a was 584:1d4855f5312e, checked in by Alpar Juttner, 20 years ago

Some new typedefs.

File size: 6.8 KB
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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
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
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.
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
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 the type of the map that stores the edge lengths.
64    typedef LM LengthMap;
65    ///\brief The 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 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 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    PredMap predecessor;
78    PredNodeMap pred_node;
79    DistMap distance;
80
81  public :
82
83    Dijkstra(const Graph& _G, const LM& _length) :
84      G(_G), length(_length), predecessor(_G), pred_node(_G), distance(_G) { }
85
86    void run(Node s);
87
88    ///The distance of a node from the root.
89
90    ///Returns the distance of a node from the root.
91    ///\pre \ref run() must be called before using this function.
92    ///\warning If node \c v in unreachable from the root the return value
93    ///of this funcion is undefined.
94    ValueType dist(Node v) const { return distance[v]; }
95
96    ///Returns the 'previous edge' of the shortest path tree.
97
98    ///For a node \c v it returns the 'previous edge' of the shortest path tree,
99    ///i.e. it returns the last edge from a shortest path from the root to \c
100    ///v. It is INVALID if \c v is unreachable from the root or if \c v=s. The
101    ///shortest path tree used here is equal to the shortest path tree used in
102    ///\ref predNode(Node v).  \pre \ref run() must be called before using
103    ///this function.
104    Edge pred(Node v) const { return predecessor[v]; }
105
106    ///Returns the 'previous node' of the shortest path tree.
107
108    ///For a node \c v it returns the 'previous node' of the shortest path tree,
109    ///i.e. it returns the last but one node from a shortest path from the
110    ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
111    ///\c v=s. The shortest path tree used here is equal to the shortest path
112    ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
113    ///using this function.
114    Node predNode(Node v) const { return pred_node[v]; }
115
116    ///Returns a reference to the NodeMap of distances.
117
118    ///Returns a reference to the NodeMap of distances. \pre \ref run() must
119    ///be called before using this function.
120    const DistMap &distMap() const { return distance;}
121
122    ///Returns a reference to the shortest path tree map.
123
124    ///Returns a reference to the NodeMap of the edges of the
125    ///shortest path tree.
126    ///\pre \ref run() must be called before using this function.
127    const PredMap &predMap() const { return predecessor;}
128
129    ///Returns a reference to the map of nodes of shortest paths.
130
131    ///Returns a reference to the NodeMap of the last but one nodes of the
132    ///shortest path tree.
133    ///\pre \ref run() must be called before using this function.
134    const PredNodeMap &predNodeMap() const { return pred_node;}
135
136    ///Checks if a node is reachable from the root.
137
138    ///Returns \c true if \c v is reachable from the root.
139    ///\warning the root node is reported to be unreached!
140    ///\todo Is this what we want?
141    ///\pre \ref run() must be called before using this function.
142    ///
143    bool reached(Node v) { return G.valid(predecessor[v]); }
144
145  };
146
147
148  // **********************************************************************
149  //  IMPLEMENTATIONS
150  // **********************************************************************
151
152  ///Runs %Dijkstra algorithm from node the root.
153
154  ///This method runs the %Dijkstra algorithm from a root node \c s
155  ///in order to
156  ///compute the
157  ///shortest path to each node. The algorithm computes
158  ///- The shortest path tree.
159  ///- The distance of each node from the root.
160  template <typename GR, typename LM,
161            template<class,class,class,class> class Heap >
162  void Dijkstra<GR,LM,Heap>::run(Node s) {
163
164    NodeIt u;
165    for ( G.first(u) ; G.valid(u) ; G.next(u) ) {
166      predecessor.set(u,INVALID);
167      pred_node.set(u,INVALID);
168    }
169
170    typename GR::template NodeMap<int> heap_map(G,-1);
171
172    typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
173      std::less<ValueType> >
174      HeapType;
175
176    HeapType heap(heap_map);
177
178    heap.push(s,0);
179
180      while ( !heap.empty() ) {
181
182        Node v=heap.top();
183        ValueType oldvalue=heap[v];
184        heap.pop();
185        distance.set(v, oldvalue);
186
187        { //FIXME this bracket is for e to be local
188          OutEdgeIt e;
189        for(G.first(e, v);
190            G.valid(e); G.next(e)) {
191          Node w=G.bNode(e);
192
193          switch(heap.state(w)) {
194          case HeapType::PRE_HEAP:
195            heap.push(w,oldvalue+length[e]);
196            predecessor.set(w,e);
197            pred_node.set(w,v);
198            break;
199          case HeapType::IN_HEAP:
200            if ( oldvalue+length[e] < heap[w] ) {
201              heap.decrease(w, oldvalue+length[e]);
202              predecessor.set(w,e);
203              pred_node.set(w,v);
204            }
205            break;
206          case HeapType::POST_HEAP:
207            break;
208          }
209        }
210      } //FIXME tis bracket
211      }
212  }
213
214/// @}
215
216} //END OF NAMESPACE HUGO
217
218#endif
219
220
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