[276] | 1 | // -*- c++ -*- |
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[306] | 2 | #ifndef HUGO_MINLENGTHPATHS_H |
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| 3 | #define HUGO_MINLENGTHPATHS_H |
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[276] | 4 | |
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[294] | 5 | ///\file |
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[306] | 6 | ///\brief An algorithm for finding k paths of minimal total length. |
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[294] | 7 | |
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[276] | 8 | #include <iostream> |
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| 9 | #include <dijkstra.h> |
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| 10 | #include <graph_wrapper.h> |
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[306] | 11 | #include <maps.h> |
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| 12 | |
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[276] | 13 | namespace hugo { |
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| 14 | |
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| 15 | |
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[306] | 16 | ///\brief Implementation of an algorithm for finding k paths between 2 nodes |
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| 17 | /// of minimal total length |
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[276] | 18 | /// |
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[306] | 19 | /// The class \ref hugo::MinLengthPaths "MinLengthPaths" implements |
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| 20 | /// an algorithm which finds k edge-disjoint paths |
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[276] | 21 | /// from a given source node to a given target node in an |
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[306] | 22 | /// edge-weighted directed graph having minimal total weigth (length). |
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[276] | 23 | /// |
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| 24 | /// |
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| 25 | |
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| 26 | template <typename Graph, typename T, |
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| 27 | typename LengthMap=typename Graph::EdgeMap<T> > |
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[306] | 28 | class MinLengthPaths { |
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[276] | 29 | |
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| 30 | |
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[306] | 31 | // class ConstMap { |
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| 32 | // public : |
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| 33 | // typedef int ValueType; |
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| 34 | // typedef typename Graph::Edge KeyType; |
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[291] | 35 | |
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[306] | 36 | // int operator[](typename Graph::Edge e) const { |
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| 37 | // return 1; |
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| 38 | // } |
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| 39 | // }; |
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[276] | 40 | |
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| 41 | |
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| 42 | typedef typename Graph::Node Node; |
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| 43 | typedef typename Graph::NodeIt NodeIt; |
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| 44 | typedef typename Graph::Edge Edge; |
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| 45 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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[306] | 46 | typedef typename Graph::EdgeMap<int> EdgeIntMap; |
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| 47 | |
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| 48 | typedef ConstMap<Edge,int> ConstMap; |
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| 49 | |
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[291] | 50 | typedef TrivGraphWrapper<const Graph> TrivGraphType; |
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[306] | 51 | typedef ResGraphWrapper<TrivGraphType,int,EdgeIntMap, |
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[291] | 52 | ConstMap> ResGraphType; |
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[276] | 53 | |
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[306] | 54 | |
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| 55 | //template <typename Graph, typename T> |
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| 56 | class ModLengthMap { |
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| 57 | typedef typename ResGraphType::NodeMap<T> NodeMap; |
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| 58 | const ResGraphType& G; |
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| 59 | const EdgeIntMap& rev; |
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| 60 | const LengthMap &ol; |
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| 61 | const NodeMap &pot; |
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| 62 | public : |
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| 63 | typedef typename LengthMap::KeyType KeyType; |
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| 64 | typedef typename LengthMap::ValueType ValueType; |
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| 65 | |
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| 66 | ValueType operator[](typename ResGraphType::Edge e) const { |
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| 67 | if ( (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)] ) <0 ){ |
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| 68 | ///\TODO This has to be removed |
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| 69 | std::cout<<"Negative length!!"<<std::endl; |
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| 70 | } |
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| 71 | return (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)]); |
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| 72 | } |
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| 73 | |
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| 74 | ModLengthMap( const ResGraphType& _G, const EdgeIntMap& _rev, |
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| 75 | const LengthMap &o, const NodeMap &p) : |
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| 76 | G(_G), rev(_rev), ol(o), pot(p){}; |
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| 77 | }; |
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| 78 | |
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| 79 | |
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[276] | 80 | const Graph& G; |
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| 81 | const LengthMap& length; |
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| 82 | |
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[306] | 83 | //auxiliary variable |
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| 84 | //The value is 1 iff the edge is reversed |
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| 85 | EdgeIntMap reversed; |
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[276] | 86 | |
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| 87 | |
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| 88 | public : |
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| 89 | |
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| 90 | |
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[306] | 91 | MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G), |
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| 92 | length(_length), reversed(_G)/*, dijkstra_dist(_G)*/{ } |
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[276] | 93 | |
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[306] | 94 | ///Runs the algorithm |
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[294] | 95 | |
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[306] | 96 | ///Runs the algorithm |
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| 97 | ///Returns k if there are at least k edge-disjoint paths from s to t. |
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| 98 | ///Otherwise it returns the number of edge-disjoint paths from s to t. |
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| 99 | int run(Node s, Node t, int k) { |
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| 100 | ConstMap const1map(1); |
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[276] | 101 | |
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[306] | 102 | ResGraphType res_graph(G, reversed, const1map); |
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| 103 | |
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| 104 | //Initialize the copy of the Dijkstra potential to zero |
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| 105 | typename ResGraphType::NodeMap<T> dijkstra_dist(G); |
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| 106 | ModLengthMap mod_length( res_graph, reversed, length, dijkstra_dist); |
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| 107 | |
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| 108 | Dijkstra<ResGraphType, ModLengthMap> dijkstra(res_graph, mod_length); |
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[276] | 109 | |
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| 110 | for (int i=0; i<k; ++i){ |
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| 111 | dijkstra.run(s); |
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| 112 | if (!dijkstra.reached(t)){ |
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| 113 | //There is no k path from s to t |
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[306] | 114 | return ++i; |
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[276] | 115 | }; |
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[306] | 116 | |
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| 117 | { |
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| 118 | //We have to copy the potential |
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| 119 | typename ResGraphType::NodeIt n; |
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| 120 | for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) { |
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| 121 | dijkstra_dist[n] += dijkstra.distMap()[n]; |
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| 122 | } |
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| 123 | } |
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| 124 | |
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| 125 | |
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| 126 | /* |
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[276] | 127 | { |
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| 128 | //We have to copy the potential |
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| 129 | typename ResGraphType::EdgeIt e; |
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| 130 | for ( res_graph.first(e) ; res_graph.valid(e) ; res_graph.next(e) ) { |
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| 131 | //dijkstra_dist[e] = dijkstra.distMap()[e]; |
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| 132 | mod_length_c[Edge(e)] = mod_length_c[Edge(e)] - |
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| 133 | dijkstra.distMap()[res_graph.head(e)] + |
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| 134 | dijkstra.distMap()[res_graph.tail(e)]; |
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| 135 | } |
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| 136 | } |
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[306] | 137 | */ |
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| 138 | |
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[276] | 139 | //Reversing the sortest path |
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| 140 | Node n=t; |
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| 141 | Edge e; |
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| 142 | while (n!=s){ |
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[291] | 143 | e = dijkstra.pred(n); |
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| 144 | n = dijkstra.predNode(n); |
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[276] | 145 | reversed[e] = 1-reversed[e]; |
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| 146 | } |
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| 147 | |
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| 148 | |
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| 149 | } |
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[306] | 150 | return k; |
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[276] | 151 | } |
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| 152 | |
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| 153 | |
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| 154 | |
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| 155 | |
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| 156 | |
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[306] | 157 | };//class MinLengthPaths |
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[276] | 158 | |
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| 159 | |
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| 160 | |
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| 161 | |
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| 162 | } //namespace hugo |
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| 163 | |
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[306] | 164 | #endif //HUGO_MINLENGTHPATHS_H |
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