# HG changeset patch
# User athos
# Date 1083672013 0
# Node ID 4da6fb1046642d8c550efe398df7dfe5bab8ce15
# Parent  a0ed1fa1b800c7ec5b80da4b7a3aea1b8cf7f516
Started.

diff -r a0ed1fa1b800 -r 4da6fb104664 src/work/athos/mincostflows.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/work/athos/mincostflows.h	Tue May 04 12:00:13 2004 +0000
@@ -0,0 +1,209 @@
+// -*- c++ -*-
+#ifndef HUGO_MINCOSTFLOWS_H
+#define HUGO_MINCOSTFLOWS_H
+
+///\ingroup galgs
+///\file
+///\brief An algorithm for finding a flow of value \c k (for small values of \c k) having minimal total cost 
+
+#include <iostream>
+#include <dijkstra.h>
+#include <graph_wrapper.h>
+#include <maps.h>
+#include <vector.h>
+
+
+namespace hugo {
+
+/// \addtogroup galgs
+/// @{
+
+  ///\brief Implementation of an algorithm for finding a flow of value \c k 
+  ///(for small values of \c k) having minimal total cost between 2 nodes 
+  /// 
+  ///
+  /// The class \ref hugo::MinCostFlows "MinCostFlows" implements
+  /// an algorithm for finding a flow of value \c k 
+  ///(for small values of \c k) having minimal total cost  
+  /// from a given source node to a given target node in an
+  /// edge-weighted directed graph having nonnegative integer capacities.
+  /// The range of the length (weight) function is nonnegative reals but 
+  /// the range of capacity function is the set of nonnegative integers. 
+  /// It is not a polinomial time algorithm for counting the minimum cost
+  /// maximal flow, since it counts the minimum cost flow for every value 0..M
+  /// where \c M is the value of the maximal flow.
+  ///
+  ///\author Attila Bernath
+  template <typename Graph, typename LengthMap>
+  class MinCostFlows {
+
+    typedef typename LengthMap::ValueType Length;
+    
+    typedef typename Graph::Node Node;
+    typedef typename Graph::NodeIt NodeIt;
+    typedef typename Graph::Edge Edge;
+    typedef typename Graph::OutEdgeIt OutEdgeIt;
+    typedef typename Graph::template EdgeMap<int> EdgeIntMap;
+
+    typedef ConstMap<Edge,int> ConstMap;
+
+    typedef ResGraphWrapper<const Graph,int,ConstMap,EdgeIntMap> ResGraphType;
+
+    class ModLengthMap {   
+      typedef typename ResGraphType::template NodeMap<Length> NodeMap;
+      const ResGraphType& G;
+      const EdgeIntMap& rev;
+      const LengthMap &ol;
+      const NodeMap &pot;
+    public :
+      typedef typename LengthMap::KeyType KeyType;
+      typedef typename LengthMap::ValueType ValueType;
+	
+      ValueType operator[](typename ResGraphType::Edge e) const {     
+	//if ( (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)] ) <0 ){
+	//  std::cout<<"Negative length!!"<<std::endl;
+	//}
+	return (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)]);   
+      }     
+	
+      ModLengthMap(const ResGraphType& _G, const EdgeIntMap& _rev, 
+		   const LengthMap &o,  const NodeMap &p) : 
+	G(_G), rev(_rev), ol(o), pot(p){}; 
+    };//ModLengthMap
+
+
+    
+
+    const Graph& G;
+    const LengthMap& length;
+
+    //auxiliary variables
+
+    //The value is 1 iff the edge is reversed. 
+    //If the algorithm has finished, the edges of the seeked paths are 
+    //exactly those that are reversed 
+    EdgeIntMap reversed; 
+    
+    //Container to store found paths
+    std::vector< std::vector<Edge> > paths;
+    //typedef DirPath<Graph> DPath;
+    //DPath paths;
+
+
+    Length total_length;
+
+  public :
+
+
+    MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G), 
+      length(_length), reversed(_G)/*, dijkstra_dist(_G)*/{ }
+
+    
+    ///Runs the algorithm.
+
+    ///Runs the algorithm.
+    ///Returns k if there are at least k edge-disjoint paths from s to t.
+    ///Otherwise it returns the number of found edge-disjoint paths from s to t.
+    int run(Node s, Node t, int k) {
+      ConstMap const1map(1);
+
+
+      //We need a residual graph, in which some of the edges are reversed
+      ResGraphType res_graph(G, const1map, reversed);
+
+      //Initialize the copy of the Dijkstra potential to zero
+      typename ResGraphType::template NodeMap<Length> dijkstra_dist(res_graph);
+      ModLengthMap mod_length(res_graph, reversed, length, dijkstra_dist);
+
+      Dijkstra<ResGraphType, ModLengthMap> dijkstra(res_graph, mod_length);
+
+      int i;
+      for (i=0; i<k; ++i){
+	dijkstra.run(s);
+	if (!dijkstra.reached(t)){
+	  //There are no k paths from s to t
+	  break;
+	};
+	
+	{
+	  //We have to copy the potential
+	  typename ResGraphType::NodeIt n;
+	  for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) {
+	      dijkstra_dist[n] += dijkstra.distMap()[n];
+	  }
+	}
+
+
+	//Reversing the sortest path
+	Node n=t;
+	Edge e;
+	while (n!=s){
+	  e = dijkstra.pred(n);
+	  n = dijkstra.predNode(n);
+	  reversed[e] = 1-reversed[e];
+	}
+
+	  
+      }
+      
+      //Let's find the paths
+      //We put the paths into stl vectors (as an inner representation). 
+      //In the meantime we lose the information stored in 'reversed'.
+      //We suppose the lengths to be positive now.
+
+      //Meanwhile we put the total length of the found paths 
+      //in the member variable total_length
+      paths.clear();
+      total_length=0;
+      paths.resize(k);
+      for (int j=0; j<i; ++j){
+	Node n=s;
+	OutEdgeIt e;
+
+	while (n!=t){
+
+
+	  G.first(e,n);
+	  
+	  while (!reversed[e]){
+	    G.next(e);
+	  }
+	  n = G.head(e);
+	  paths[j].push_back(e);
+	  total_length += length[e];
+	  reversed[e] = 1-reversed[e];
+	}
+	
+      }
+
+      return i;
+    }
+
+    ///This function gives back the total length of the found paths.
+    ///Assumes that \c run() has been run and nothing changed since then.
+    Length totalLength(){
+      return total_length;
+    }
+
+    ///This function gives back the \c j-th path in argument p.
+    ///Assumes that \c run() has been run and nothing changed since then.
+    /// \warning It is assumed that \c p is constructed to be a path of graph \c G. If \c j is greater than the result of previous \c run, then the result here will be an empty path.
+    template<typename DirPath>
+    void getPath(DirPath& p, int j){
+      p.clear();
+      typename DirPath::Builder B(p);
+      for(typename std::vector<Edge>::iterator i=paths[j].begin(); 
+	  i!=paths[j].end(); ++i ){
+	B.pushBack(*i);
+      }
+
+      B.commit();
+    }
+
+  }; //class MinLengthPaths
+
+  ///@}
+
+} //namespace hugo
+
+#endif //HUGO_MINLENGTHPATHS_H