1.1 --- a/src/work/athos/minlengthpaths.h Tue May 11 15:42:11 2004 +0000
1.2 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
1.3 @@ -1,164 +0,0 @@
1.4 -// -*- c++ -*-
1.5 -#ifndef HUGO_MINLENGTHPATHS_H
1.6 -#define HUGO_MINLENGTHPATHS_H
1.7 -
1.8 -///\ingroup galgs
1.9 -///\file
1.10 -///\brief An algorithm for finding k paths of minimal total length.
1.11 -
1.12 -#include <iostream>
1.13 -//#include <hugo/dijkstra.h>
1.14 -//#include <hugo/graph_wrapper.h>
1.15 -#include <hugo/maps.h>
1.16 -#include <vector>
1.17 -#include <mincostflows.h>
1.18 -#include <for_each_macros.h>
1.19 -
1.20 -namespace hugo {
1.21 -
1.22 -/// \addtogroup galgs
1.23 -/// @{
1.24 -
1.25 - ///\brief Implementation of an algorithm for finding k paths between 2 nodes
1.26 - /// of minimal total length
1.27 - ///
1.28 - /// The class \ref hugo::MinLengthPaths "MinLengthPaths" implements
1.29 - /// an algorithm for finding k edge-disjoint paths
1.30 - /// from a given source node to a given target node in an
1.31 - /// edge-weighted directed graph having minimal total weigth (length).
1.32 - ///
1.33 - ///\warning It is assumed that the lengths are positive, since the
1.34 - /// general flow-decomposition is not implemented yet.
1.35 - ///
1.36 - ///\author Attila Bernath
1.37 - template <typename Graph, typename LengthMap>
1.38 - class MinLengthPaths{
1.39 -
1.40 -
1.41 - typedef typename LengthMap::ValueType Length;
1.42 -
1.43 - typedef typename Graph::Node Node;
1.44 - typedef typename Graph::NodeIt NodeIt;
1.45 - typedef typename Graph::Edge Edge;
1.46 - typedef typename Graph::OutEdgeIt OutEdgeIt;
1.47 - typedef typename Graph::template EdgeMap<int> EdgeIntMap;
1.48 -
1.49 - typedef ConstMap<Edge,int> ConstMap;
1.50 -
1.51 - //Input
1.52 - const Graph& G;
1.53 -
1.54 - //Auxiliary variables
1.55 - //This is the capacity map for the mincostflow problem
1.56 - ConstMap const1map;
1.57 - //This MinCostFlows instance will actually solve the problem
1.58 - MinCostFlows<Graph, LengthMap, ConstMap> mincost_flow;
1.59 -
1.60 - //Container to store found paths
1.61 - std::vector< std::vector<Edge> > paths;
1.62 -
1.63 - public :
1.64 -
1.65 -
1.66 - MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G),
1.67 - const1map(1), mincost_flow(_G, _length, const1map){}
1.68 -
1.69 - ///Runs the algorithm.
1.70 -
1.71 - ///Runs the algorithm.
1.72 - ///Returns k if there are at least k edge-disjoint paths from s to t.
1.73 - ///Otherwise it returns the number of found edge-disjoint paths from s to t.
1.74 - int run(Node s, Node t, int k) {
1.75 -
1.76 - int i = mincost_flow.run(s,t,k);
1.77 -
1.78 -
1.79 -
1.80 - //Let's find the paths
1.81 - //We put the paths into stl vectors (as an inner representation).
1.82 - //In the meantime we lose the information stored in 'reversed'.
1.83 - //We suppose the lengths to be positive now.
1.84 -
1.85 - //We don't want to change the flow of mincost_flow, so we make a copy
1.86 - //The name here suggests that the flow has only 0/1 values.
1.87 - EdgeIntMap reversed(G);
1.88 -
1.89 - FOR_EACH_LOC(typename Graph::EdgeIt, e, G){
1.90 - reversed[e] = mincost_flow.getFlow()[e];
1.91 - }
1.92 -
1.93 - paths.clear();
1.94 - //total_length=0;
1.95 - paths.resize(k);
1.96 - for (int j=0; j<i; ++j){
1.97 - Node n=s;
1.98 - OutEdgeIt e;
1.99 -
1.100 - while (n!=t){
1.101 -
1.102 -
1.103 - G.first(e,n);
1.104 -
1.105 - while (!reversed[e]){
1.106 - G.next(e);
1.107 - }
1.108 - n = G.head(e);
1.109 - paths[j].push_back(e);
1.110 - //total_length += length[e];
1.111 - reversed[e] = 1-reversed[e];
1.112 - }
1.113 -
1.114 - }
1.115 - return i;
1.116 - }
1.117 -
1.118 -
1.119 - ///This function gives back the total length of the found paths.
1.120 - ///Assumes that \c run() has been run and nothing changed since then.
1.121 - Length totalLength(){
1.122 - return mincost_flow.totalLength();
1.123 - }
1.124 -
1.125 - ///Returns a const reference to the EdgeMap \c flow. \pre \ref run() must
1.126 - ///be called before using this function.
1.127 - const EdgeIntMap &getFlow() const { return mincost_flow.flow;}
1.128 -
1.129 - ///Returns a const reference to the NodeMap \c potential (the dual solution).
1.130 - /// \pre \ref run() must be called before using this function.
1.131 - const EdgeIntMap &getPotential() const { return mincost_flow.potential;}
1.132 -
1.133 - ///This function checks, whether the given solution is optimal
1.134 - ///Running after a \c run() should return with true
1.135 - ///In this "state of the art" this only checks optimality, doesn't bother with feasibility
1.136 - ///
1.137 - ///\todo Is this OK here?
1.138 - bool checkComplementarySlackness(){
1.139 - return mincost_flow.checkComplementarySlackness();
1.140 - }
1.141 -
1.142 - ///This function gives back the \c j-th path in argument p.
1.143 - ///Assumes that \c run() has been run and nothing changed since then.
1.144 - /// \warning It is assumed that \c p is constructed to be a path of graph \c G. If \c j is not less than the result of previous \c run, then the result here will be an empty path (\c j can be 0 as well).
1.145 - template<typename DirPath>
1.146 - void getPath(DirPath& p, size_t j){
1.147 -
1.148 - p.clear();
1.149 - if (j>paths.size()-1){
1.150 - return;
1.151 - }
1.152 - typename DirPath::Builder B(p);
1.153 - for(typename std::vector<Edge>::iterator i=paths[j].begin();
1.154 - i!=paths[j].end(); ++i ){
1.155 - B.pushBack(*i);
1.156 - }
1.157 -
1.158 - B.commit();
1.159 - }
1.160 -
1.161 - }; //class MinLengthPaths
1.162 -
1.163 - ///@}
1.164 -
1.165 -} //namespace hugo
1.166 -
1.167 -#endif //HUGO_MINLENGTHPATHS_H