klao@308: // -*- c++ -*-
klao@308: #ifndef HUGO_MINLENGTHPATHS_H
klao@308: #define HUGO_MINLENGTHPATHS_H
klao@308: 
klao@308: ///\file
klao@308: ///\brief An algorithm for finding k paths of minimal total length.
klao@308: 
klao@308: #include <iostream>
klao@308: #include <dijkstra.h>
klao@308: #include <graph_wrapper.h>
klao@308: #include <maps.h>
klao@308: 
klao@308: namespace hugo {
klao@308: 
klao@308: 
klao@308: ///\brief Implementation of an algorithm for finding k paths between 2 nodes 
klao@308:   /// of minimal total length 
klao@308: ///
klao@308: /// The class \ref hugo::MinLengthPaths "MinLengthPaths" implements
klao@308: /// an algorithm which finds k edge-disjoint paths
klao@308: /// from a given source node to a given target node in an
klao@308: /// edge-weighted directed graph having minimal total weigth (length).
klao@308: /// 
klao@308: /// 
klao@308: 
klao@308:   template <typename Graph, typename T, 
klao@308:     typename LengthMap=typename Graph::EdgeMap<T> >
klao@308:   class MinLengthPaths {
klao@308: 
klao@308: 
klao@308: //      class ConstMap {
klao@308: //      public :
klao@308: //        typedef int ValueType;
klao@308: //        typedef typename Graph::Edge KeyType;
klao@308: 
klao@308: //        int operator[](typename Graph::Edge e) const { 
klao@308: //  	return 1;
klao@308: //        } 
klao@308: //      };
klao@308: 
klao@308: 
klao@308:     typedef typename Graph::Node Node;
klao@308:     typedef typename Graph::NodeIt NodeIt;
klao@308:     typedef typename Graph::Edge Edge;
klao@308:     typedef typename Graph::OutEdgeIt OutEdgeIt;
klao@308:     typedef typename Graph::EdgeMap<int> EdgeIntMap;
klao@308: 
klao@308:     typedef ConstMap<Edge,int> ConstMap;
klao@308: 
klao@308:     typedef TrivGraphWrapper<const Graph> TrivGraphType;
klao@308:     typedef ResGraphWrapper<TrivGraphType,int,EdgeIntMap,
klao@308:       ConstMap> ResGraphType;
klao@308: 
klao@308: 
klao@308:     //template <typename Graph, typename T>
klao@308:     class ModLengthMap {   
klao@308:       typedef typename ResGraphType::NodeMap<T> NodeMap;
klao@308:       const ResGraphType& G;
klao@308:       const EdgeIntMap& rev; 
klao@308:       const LengthMap &ol;   
klao@308:       const NodeMap &pot;     
klao@308:     public :
klao@308:       typedef typename LengthMap::KeyType KeyType;
klao@308:       typedef typename LengthMap::ValueType ValueType;
klao@308: 
klao@308:       ValueType operator[](typename ResGraphType::Edge e) const {     
klao@308: 	if ( (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)] ) <0 ){
klao@308: 	  ///\TODO This has to be removed
klao@308: 	  std::cout<<"Negative length!!"<<std::endl;
klao@308: 	}
klao@308: 	return (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)]);   
klao@308:       }     
klao@308: 
klao@308:       ModLengthMap(  const ResGraphType& _G, const EdgeIntMap& _rev, 
klao@308: 		     const LengthMap &o,  const NodeMap &p) : 
klao@308: 	G(_G), rev(_rev), ol(o), pot(p){}; 
klao@308:     };
klao@308:     
klao@308: 
klao@308:     const Graph& G;
klao@308:     const LengthMap& length;
klao@308: 
klao@308:     //auxiliary variable
klao@308:     //The value is 1 iff the edge is reversed
klao@308:     EdgeIntMap reversed; 
klao@308: 
klao@308:     
klao@308:   public :
klao@308:     
klao@308: 
klao@308:     MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G), 
klao@308:       length(_length), reversed(_G)/*, dijkstra_dist(_G)*/{ }
klao@308: 
klao@308:     ///Runs the algorithm
klao@308:     
klao@308:     ///Runs the algorithm
klao@308:     ///Returns k if there are at least k edge-disjoint paths from s to t.
klao@308:     ///Otherwise it returns the number of edge-disjoint paths from s to t.
klao@308:     int run(Node s, Node t, int k) {
klao@308:       ConstMap const1map(1);
klao@308: 
klao@308:       ResGraphType res_graph(G, reversed, const1map);
klao@308: 
klao@308:       //Initialize the copy of the Dijkstra potential to zero
klao@308:       typename ResGraphType::NodeMap<T> dijkstra_dist(G);
klao@308:       ModLengthMap mod_length( res_graph, reversed, length, dijkstra_dist);
klao@308: 
klao@308:       Dijkstra<ResGraphType, ModLengthMap> dijkstra(res_graph, mod_length);
klao@308:       
klao@308:       for (int i=0; i<k; ++i){
klao@308: 	dijkstra.run(s);
klao@308: 	if (!dijkstra.reached(t)){
klao@308: 	  //There is no k path from s to t
klao@308: 	  return ++i;
klao@308: 	};
klao@308: 	
klao@308: 	{
klao@308: 	  //We have to copy the potential
klao@308: 	  typename ResGraphType::NodeIt n;
klao@308: 	  for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) {
klao@308: 	      dijkstra_dist[n] += dijkstra.distMap()[n];
klao@308: 	  }
klao@308: 	}
klao@308: 
klao@308: 
klao@308: 	/*
klao@308: 	{
klao@308: 	  //We have to copy the potential
klao@308: 	  typename ResGraphType::EdgeIt e;
klao@308: 	  for ( res_graph.first(e) ; res_graph.valid(e) ; res_graph.next(e) ) {
klao@308: 	    //dijkstra_dist[e] = dijkstra.distMap()[e];
klao@308: 	    mod_length_c[Edge(e)] = mod_length_c[Edge(e)] - 
klao@308: 	      dijkstra.distMap()[res_graph.head(e)] +  
klao@308: 	      dijkstra.distMap()[res_graph.tail(e)];
klao@308: 	  }
klao@308: 	}
klao@308: 	*/
klao@308: 
klao@308: 	//Reversing the sortest path
klao@308: 	Node n=t;
klao@308: 	Edge e;
klao@308: 	while (n!=s){
klao@308: 	  e = dijkstra.pred(n);
klao@308: 	  n = dijkstra.predNode(n);
klao@308: 	  reversed[e] = 1-reversed[e];
klao@308: 	}
klao@308: 
klao@308: 	  
klao@308:       }
klao@308:       return k;
klao@308:     }
klao@308:            
klao@308:       
klao@308: 
klao@308: 
klao@308: 
klao@308:   };//class MinLengthPaths
klao@308: 
klao@308: 
klao@308: 
klao@308: 
klao@308: } //namespace hugo
klao@308: 
klao@308: #endif //HUGO_MINLENGTHPATHS_H