src/work/deba/dijkstra.h
author alpar
Thu, 22 Jul 2004 14:29:20 +0000
changeset 730 af375858f17c
parent 694 2d87cefb35b2
child 880 9d0bfd35b97c
permissions -rw-r--r--
Custom made INSTALL file (will be sometime).
     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 
    12 namespace 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), pred_node(NULL), distance(NULL),
   114       local_predecessor(false), local_pred_node(false), local_distance(false)
   115     { }
   116     
   117     ~Dijkstra() 
   118     {
   119       //      if(local_length) delete length;
   120       if(local_predecessor) delete predecessor;
   121       if(local_pred_node) delete pred_node;
   122       if(local_distance) delete distance;
   123     }
   124 
   125     ///Sets the graph the algorithm will run on.
   126 
   127     ///Sets the graph the algorithm will run on.
   128     ///\return <tt> (*this) </tt>
   129     Dijkstra &setGraph(const Graph &_G) 
   130     {
   131       G = &_G;
   132       return *this;
   133     }
   134     ///Sets the length map.
   135 
   136     ///Sets the length map.
   137     ///\return <tt> (*this) </tt>
   138     Dijkstra &setLengthMap(const LM &m) 
   139     {
   140 //       if(local_length) {
   141 // 	delete length;
   142 // 	local_length=false;
   143 //       }
   144       length = &m;
   145       return *this;
   146     }
   147 
   148     ///Sets the map storing the predecessor edges.
   149 
   150     ///Sets the map storing the predecessor edges.
   151     ///If you don't use this function before calling \ref run(),
   152     ///it will allocate one. The destuctor deallocates this
   153     ///automatically allocated map, of course.
   154     ///\return <tt> (*this) </tt>
   155     Dijkstra &setPredMap(PredMap &m) 
   156     {
   157       if(local_predecessor) {
   158 	delete predecessor;
   159 	local_predecessor=false;
   160       }
   161       predecessor = &m;
   162       return *this;
   163     }
   164 
   165     ///Sets the map storing the predecessor nodes.
   166 
   167     ///Sets the map storing the predecessor nodes.
   168     ///If you don't use this function before calling \ref run(),
   169     ///it will allocate one. The destuctor deallocates this
   170     ///automatically allocated map, of course.
   171     ///\return <tt> (*this) </tt>
   172     Dijkstra &setPredNodeMap(PredNodeMap &m) 
   173     {
   174       if(local_pred_node) {
   175 	delete pred_node;
   176 	local_pred_node=false;
   177       }
   178       pred_node = &m;
   179       return *this;
   180     }
   181 
   182     ///Sets the map storing the distances calculated by the algorithm.
   183 
   184     ///Sets the map storing the distances calculated by the algorithm.
   185     ///If you don't use this function before calling \ref run(),
   186     ///it will allocate one. The destuctor deallocates this
   187     ///automatically allocated map, of course.
   188     ///\return <tt> (*this) </tt>
   189     Dijkstra &setDistMap(DistMap &m) 
   190     {
   191       if(local_distance) {
   192 	delete distance;
   193 	local_distance=false;
   194       }
   195       distance = &m;
   196       return *this;
   197     }
   198     
   199   ///Runs %Dijkstra algorithm from node \c s.
   200 
   201   ///This method runs the %Dijkstra algorithm from a root node \c s
   202   ///in order to
   203   ///compute the
   204   ///shortest path to each node. The algorithm computes
   205   ///- The shortest path tree.
   206   ///- The distance of each node from the root.
   207     
   208     void run(Node s) {
   209       
   210       init_maps();
   211       
   212       for ( NodeIt u(*G) ; G->valid(u) ; G->next(u) ) {
   213 	predecessor->set(u,INVALID);
   214 	pred_node->set(u,INVALID);
   215       }
   216       
   217       typename GR::template NodeMap<int> heap_map(*G,-1);
   218       
   219       typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
   220       std::less<ValueType> > 
   221       HeapType;
   222       
   223       HeapType heap(heap_map);
   224       
   225       heap.push(s,0); 
   226       
   227       while ( !heap.empty() ) {
   228 	
   229 	Node v=heap.top(); 
   230 	ValueType oldvalue=heap[v];
   231 	heap.pop();
   232 	distance->set(v, oldvalue);
   233 	
   234 	
   235 	for(OutEdgeIt e(*G,v); G->valid(e); G->next(e)) {
   236 	  Node w=G->bNode(e); 
   237 	  
   238 	  switch(heap.state(w)) {
   239 	  case HeapType::PRE_HEAP:
   240 	    heap.push(w,oldvalue+(*length)[e]); 
   241 	    predecessor->set(w,e);
   242 	    pred_node->set(w,v);
   243 	    break;
   244 	  case HeapType::IN_HEAP:
   245 	    if ( oldvalue+(*length)[e] < heap[w] ) {
   246 	      heap.decrease(w, oldvalue+(*length)[e]); 
   247 	      predecessor->set(w,e);
   248 	      pred_node->set(w,v);
   249 	    }
   250 	    break;
   251 	  case HeapType::POST_HEAP:
   252 	    break;
   253 	  }
   254 	}
   255       }
   256     }
   257     
   258     ///The distance of a node from the root.
   259 
   260     ///Returns the distance of a node from the root.
   261     ///\pre \ref run() must be called before using this function.
   262     ///\warning If node \c v in unreachable from the root the return value
   263     ///of this funcion is undefined.
   264     ValueType dist(Node v) const { return (*distance)[v]; }
   265 
   266     ///Returns the 'previous edge' of the shortest path tree.
   267 
   268     ///For a node \c v it returns the 'previous edge' of the shortest path tree,
   269     ///i.e. it returns the last edge from a shortest path from the root to \c
   270     ///v. It is \ref INVALID
   271     ///if \c v is unreachable from the root or if \c v=s. The
   272     ///shortest path tree used here is equal to the shortest path tree used in
   273     ///\ref predNode(Node v).  \pre \ref run() must be called before using
   274     ///this function.
   275     Edge pred(Node v) const { return (*predecessor)[v]; }
   276 
   277     ///Returns the 'previous node' of the shortest path tree.
   278 
   279     ///For a node \c v it returns the 'previous node' of the shortest path tree,
   280     ///i.e. it returns the last but one node from a shortest path from the
   281     ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
   282     ///\c v=s. The shortest path tree used here is equal to the shortest path
   283     ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
   284     ///using this function.
   285     Node predNode(Node v) const { return (*pred_node)[v]; }
   286     
   287     ///Returns a reference to the NodeMap of distances.
   288 
   289     ///Returns a reference to the NodeMap of distances. \pre \ref run() must
   290     ///be called before using this function.
   291     const DistMap &distMap() const { return *distance;}
   292  
   293     ///Returns a reference to the shortest path tree map.
   294 
   295     ///Returns a reference to the NodeMap of the edges of the
   296     ///shortest path tree.
   297     ///\pre \ref run() must be called before using this function.
   298     const PredMap &predMap() const { return *predecessor;}
   299  
   300     ///Returns a reference to the map of nodes of shortest paths.
   301 
   302     ///Returns a reference to the NodeMap of the last but one nodes of the
   303     ///shortest path tree.
   304     ///\pre \ref run() must be called before using this function.
   305     const PredNodeMap &predNodeMap() const { return *pred_node;}
   306 
   307     ///Checks if a node is reachable from the root.
   308 
   309     ///Returns \c true if \c v is reachable from the root.
   310     ///\warning the root node is reported to be unreached!
   311     ///\todo Is this what we want?
   312     ///\pre \ref run() must be called before using this function.
   313     ///
   314     bool reached(Node v) { return G->valid((*predecessor)[v]); }
   315     
   316   };
   317   
   318 
   319   // **********************************************************************
   320   //  IMPLEMENTATIONS
   321   // **********************************************************************
   322 
   323 /// @}
   324   
   325 } //END OF NAMESPACE HUGO
   326 
   327 #endif
   328 
   329