[308] | 1 | // -*- c++ -*- |
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| 2 | #ifndef HUGO_MINLENGTHPATHS_H |
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| 3 | #define HUGO_MINLENGTHPATHS_H |
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| 4 | |
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| 5 | ///\file |
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| 6 | ///\brief An algorithm for finding k paths of minimal total length. |
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| 7 | |
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| 8 | #include <iostream> |
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| 9 | #include <dijkstra.h> |
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| 10 | #include <graph_wrapper.h> |
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| 11 | #include <maps.h> |
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| 12 | |
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| 13 | namespace hugo { |
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| 14 | |
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| 15 | |
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[310] | 16 | ///\brief Implementation of an algorithm for finding k paths between 2 nodes |
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[308] | 17 | /// of minimal total length |
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[310] | 18 | /// |
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| 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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| 21 | /// from a given source node to a given target node in an |
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| 22 | /// edge-weighted directed graph having minimal total weigth (length). |
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[308] | 23 | |
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[310] | 24 | template <typename Graph, typename LengthMap> |
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[308] | 25 | class MinLengthPaths { |
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| 26 | |
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[310] | 27 | typedef typename LengthMap::ValueType Length; |
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[308] | 28 | |
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| 29 | typedef typename Graph::Node Node; |
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| 30 | typedef typename Graph::NodeIt NodeIt; |
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| 31 | typedef typename Graph::Edge Edge; |
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| 32 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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| 33 | typedef typename Graph::EdgeMap<int> EdgeIntMap; |
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| 34 | |
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| 35 | typedef ConstMap<Edge,int> ConstMap; |
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| 36 | |
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[310] | 37 | typedef ResGraphWrapper<const Graph,int,EdgeIntMap,ConstMap> ResGraphType; |
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[308] | 38 | |
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| 39 | |
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| 40 | class ModLengthMap { |
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[310] | 41 | typedef typename ResGraphType::NodeMap<Length> NodeMap; |
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[308] | 42 | const ResGraphType& G; |
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[310] | 43 | const EdgeIntMap& rev; |
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| 44 | const LengthMap &ol; |
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| 45 | const NodeMap &pot; |
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[308] | 46 | public : |
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| 47 | typedef typename LengthMap::KeyType KeyType; |
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| 48 | typedef typename LengthMap::ValueType ValueType; |
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| 49 | |
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| 50 | ValueType operator[](typename ResGraphType::Edge e) const { |
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| 51 | if ( (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)] ) <0 ){ |
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| 52 | ///\TODO This has to be removed |
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| 53 | std::cout<<"Negative length!!"<<std::endl; |
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| 54 | } |
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| 55 | return (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)]); |
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| 56 | } |
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| 57 | |
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[310] | 58 | ModLengthMap(const ResGraphType& _G, const EdgeIntMap& _rev, |
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| 59 | const LengthMap &o, const NodeMap &p) : |
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[308] | 60 | G(_G), rev(_rev), ol(o), pot(p){}; |
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| 61 | }; |
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| 62 | |
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| 63 | |
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| 64 | const Graph& G; |
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| 65 | const LengthMap& length; |
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| 66 | |
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| 67 | //auxiliary variable |
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| 68 | //The value is 1 iff the edge is reversed |
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| 69 | EdgeIntMap reversed; |
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| 70 | |
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| 71 | |
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| 72 | public : |
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[310] | 73 | |
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[308] | 74 | |
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| 75 | MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G), |
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| 76 | length(_length), reversed(_G)/*, dijkstra_dist(_G)*/{ } |
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| 77 | |
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| 78 | ///Runs the algorithm |
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| 79 | |
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| 80 | ///Runs the algorithm |
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| 81 | ///Returns k if there are at least k edge-disjoint paths from s to t. |
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| 82 | ///Otherwise it returns the number of edge-disjoint paths from s to t. |
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| 83 | int run(Node s, Node t, int k) { |
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| 84 | ConstMap const1map(1); |
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| 85 | |
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| 86 | ResGraphType res_graph(G, reversed, const1map); |
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| 87 | |
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| 88 | //Initialize the copy of the Dijkstra potential to zero |
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[310] | 89 | typename ResGraphType::NodeMap<Length> dijkstra_dist(res_graph); |
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| 90 | ModLengthMap mod_length(res_graph, reversed, length, dijkstra_dist); |
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[308] | 91 | |
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| 92 | Dijkstra<ResGraphType, ModLengthMap> dijkstra(res_graph, mod_length); |
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| 93 | |
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| 94 | for (int i=0; i<k; ++i){ |
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| 95 | dijkstra.run(s); |
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| 96 | if (!dijkstra.reached(t)){ |
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| 97 | //There is no k path from s to t |
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[310] | 98 | /// \TODO mit keresett itt ez a ++? |
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| 99 | return i; |
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[308] | 100 | }; |
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| 101 | |
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| 102 | { |
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| 103 | //We have to copy the potential |
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| 104 | typename ResGraphType::NodeIt n; |
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| 105 | for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) { |
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| 106 | dijkstra_dist[n] += dijkstra.distMap()[n]; |
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| 107 | } |
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| 108 | } |
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| 109 | |
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| 110 | |
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| 111 | //Reversing the sortest path |
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| 112 | Node n=t; |
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| 113 | Edge e; |
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| 114 | while (n!=s){ |
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| 115 | e = dijkstra.pred(n); |
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| 116 | n = dijkstra.predNode(n); |
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| 117 | reversed[e] = 1-reversed[e]; |
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| 118 | } |
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| 119 | |
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| 120 | |
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| 121 | } |
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| 122 | return k; |
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| 123 | } |
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| 124 | |
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| 125 | |
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| 126 | |
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| 127 | |
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| 128 | |
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[310] | 129 | }; //class MinLengthPaths |
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[308] | 130 | |
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| 131 | |
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| 132 | } //namespace hugo |
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| 133 | |
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| 134 | #endif //HUGO_MINLENGTHPATHS_H |
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