src/hugo/dijkstra.h
author alpar
Mon, 13 Sep 2004 11:24:35 +0000
changeset 835 eb9587f09b42
parent 785 a9b0863c2265
child 880 9d0bfd35b97c
permissions -rw-r--r--
Remove one remaining range checking.
     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 
    12 namespace 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 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     ///.
    59     typedef typename Graph::Node Node;
    60     ///.
    61     typedef typename Graph::NodeIt NodeIt;
    62     ///.
    63     typedef typename Graph::Edge Edge;
    64     ///.
    65     typedef typename Graph::OutEdgeIt OutEdgeIt;
    66     
    67     ///The type of the length of the edges.
    68     typedef typename LM::ValueType ValueType;
    69     ///The type of the map that stores the edge lengths.
    70     typedef LM LengthMap;
    71     ///\brief The type of the map that stores the last
    72     ///edges of the shortest paths.
    73     typedef typename Graph::template NodeMap<Edge> PredMap;
    74     ///\brief The type of the map that stores the last but one
    75     ///nodes of the shortest paths.
    76     typedef typename Graph::template NodeMap<Node> PredNodeMap;
    77     ///The type of the map that stores the dists of the nodes.
    78     typedef typename Graph::template NodeMap<ValueType> DistMap;
    79 
    80   private:
    81     /// Pointer to the underlying graph.
    82     const Graph *G;
    83     /// Pointer to the length map
    84     const LM *length;
    85     ///Pointer to the map of predecessors edges.
    86     PredMap *predecessor;
    87     ///Indicates if \ref predecessor is locally allocated (\c true) or not.
    88     bool local_predecessor;
    89     ///Pointer to the map of predecessors nodes.
    90     PredNodeMap *pred_node;
    91     ///Indicates if \ref pred_node is locally allocated (\c true) or not.
    92     bool local_pred_node;
    93     ///Pointer to the map of distances.
    94     DistMap *distance;
    95     ///Indicates if \ref distance is locally allocated (\c true) or not.
    96     bool local_distance;
    97 
    98     ///The source node of the last execution.
    99     Node source;
   100 
   101     ///Initializes the maps.
   102     
   103     ///\todo Error if \c G or are \c NULL. What about \c length?
   104     ///\todo Better memory allocation (instead of new).
   105     void init_maps() 
   106     {
   107       if(!predecessor) {
   108 	local_predecessor = true;
   109 	predecessor = new PredMap(*G);
   110       }
   111       if(!pred_node) {
   112 	local_pred_node = true;
   113 	pred_node = new PredNodeMap(*G);
   114       }
   115       if(!distance) {
   116 	local_distance = true;
   117 	distance = new DistMap(*G);
   118       }
   119     }
   120     
   121   public :
   122     ///Constructor.
   123     
   124     ///\param _G the graph the algorithm will run on.
   125     ///\param _length the length map used by the algorithm.
   126     Dijkstra(const Graph& _G, const LM& _length) :
   127       G(&_G), length(&_length),
   128       predecessor(NULL), local_predecessor(false),
   129       pred_node(NULL), local_pred_node(false),
   130       distance(NULL), local_distance(false)
   131     { }
   132     
   133     ///Destructor.
   134     ~Dijkstra() 
   135     {
   136       if(local_predecessor) delete predecessor;
   137       if(local_pred_node) delete pred_node;
   138       if(local_distance) delete distance;
   139     }
   140 
   141     ///Sets the length map.
   142 
   143     ///Sets the length map.
   144     ///\return <tt> (*this) </tt>
   145     Dijkstra &setLengthMap(const LM &m) 
   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       source = s;
   216       
   217       for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
   218 	predecessor->set(u,INVALID);
   219 	pred_node->set(u,INVALID);
   220       }
   221       
   222       typename GR::template NodeMap<int> heap_map(*G,-1);
   223       
   224       typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
   225       std::less<ValueType> > 
   226       HeapType;
   227       
   228       HeapType heap(heap_map);
   229       
   230       heap.push(s,0); 
   231       
   232       while ( !heap.empty() ) {
   233 	
   234 	Node v=heap.top(); 
   235 	ValueType oldvalue=heap[v];
   236 	heap.pop();
   237 	distance->set(v, oldvalue);
   238 	
   239 	
   240 	for(OutEdgeIt e(*G,v); e!=INVALID; ++e) {
   241 	  Node w=G->head(e); 
   242 	  switch(heap.state(w)) {
   243 	  case HeapType::PRE_HEAP:
   244 	    heap.push(w,oldvalue+(*length)[e]); 
   245 	    predecessor->set(w,e);
   246 	    pred_node->set(w,v);
   247 	    break;
   248 	  case HeapType::IN_HEAP:
   249 	    if ( oldvalue+(*length)[e] < heap[w] ) {
   250 	      heap.decrease(w, oldvalue+(*length)[e]); 
   251 	      predecessor->set(w,e);
   252 	      pred_node->set(w,v);
   253 	    }
   254 	    break;
   255 	  case HeapType::POST_HEAP:
   256 	    break;
   257 	  }
   258 	}
   259       }
   260     }
   261     
   262     ///The distance of a node from the root.
   263 
   264     ///Returns the distance of a node from the root.
   265     ///\pre \ref run() must be called before using this function.
   266     ///\warning If node \c v in unreachable from the root the return value
   267     ///of this funcion is undefined.
   268     ValueType dist(Node v) const { return (*distance)[v]; }
   269 
   270     ///Returns the 'previous edge' of the shortest path tree.
   271 
   272     ///For a node \c v it returns the 'previous edge' of the shortest path tree,
   273     ///i.e. it returns the last edge of a shortest path from the root to \c
   274     ///v. It is \ref INVALID
   275     ///if \c v is unreachable from the root or if \c v=s. The
   276     ///shortest path tree used here is equal to the shortest path tree used in
   277     ///\ref predNode(Node v).  \pre \ref run() must be called before using
   278     ///this function.
   279     ///\todo predEdge could be a better name.
   280     Edge pred(Node v) const { return (*predecessor)[v]; }
   281 
   282     ///Returns the 'previous node' of the shortest path tree.
   283 
   284     ///For a node \c v it returns the 'previous node' of the shortest path tree,
   285     ///i.e. it returns the last but one node from a shortest path from the
   286     ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
   287     ///\c v=s. The shortest path tree used here is equal to the shortest path
   288     ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
   289     ///using this function.
   290     Node predNode(Node v) const { return (*pred_node)[v]; }
   291     
   292     ///Returns a reference to the NodeMap of distances.
   293 
   294     ///Returns a reference to the NodeMap of distances. \pre \ref run() must
   295     ///be called before using this function.
   296     const DistMap &distMap() const { return *distance;}
   297  
   298     ///Returns a reference to the shortest path tree map.
   299 
   300     ///Returns a reference to the NodeMap of the edges of the
   301     ///shortest path tree.
   302     ///\pre \ref run() must be called before using this function.
   303     const PredMap &predMap() const { return *predecessor;}
   304  
   305     ///Returns a reference to the map of nodes of shortest paths.
   306 
   307     ///Returns a reference to the NodeMap of the last but one nodes of the
   308     ///shortest path tree.
   309     ///\pre \ref run() must be called before using this function.
   310     const PredNodeMap &predNodeMap() const { return *pred_node;}
   311 
   312     ///Checks if a node is reachable from the root.
   313 
   314     ///Returns \c true if \c v is reachable from the root.
   315     ///\note The root node is reported to be reached!
   316     ///\pre \ref run() must be called before using this function.
   317     ///
   318     bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
   319     
   320   };
   321   
   322 /// @}
   323   
   324 } //END OF NAMESPACE HUGO
   325 
   326 #endif
   327 
   328