[404] | 1 | /* -*- mode: C++; indent-tabs-mode: nil; -*- |
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| 2 | * |
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| 3 | * This file is a part of LEMON, a generic C++ optimization library. |
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| 4 | * |
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| 5 | * Copyright (C) 2003-2008 |
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| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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| 8 | * |
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| 9 | * Permission to use, modify and distribute this software is granted |
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| 10 | * provided that this copyright notice appears in all copies. For |
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| 11 | * precise terms see the accompanying LICENSE file. |
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| 12 | * |
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| 13 | * This software is provided "AS IS" with no warranty of any kind, |
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| 14 | * express or implied, and with no claim as to its suitability for any |
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| 15 | * purpose. |
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| 16 | * |
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| 17 | */ |
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| 18 | |
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| 19 | #ifndef LEMON_PREFLOW_H |
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| 20 | #define LEMON_PREFLOW_H |
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| 21 | |
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| 22 | #include <lemon/error.h> |
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| 23 | #include <lemon/tolerance.h> |
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| 24 | #include <lemon/elevator.h> |
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| 25 | |
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| 26 | /// \file |
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| 27 | /// \ingroup max_flow |
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| 28 | /// \brief Implementation of the preflow algorithm. |
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| 29 | |
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| 30 | namespace lemon { |
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| 31 | |
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| 32 | /// \brief Default traits class of Preflow class. |
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| 33 | /// |
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| 34 | /// Default traits class of Preflow class. |
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| 35 | /// \param _Graph Digraph type. |
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| 36 | /// \param _CapacityMap Type of capacity map. |
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| 37 | template <typename _Graph, typename _CapacityMap> |
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| 38 | struct PreflowDefaultTraits { |
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| 39 | |
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| 40 | /// \brief The digraph type the algorithm runs on. |
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| 41 | typedef _Graph Digraph; |
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| 42 | |
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| 43 | /// \brief The type of the map that stores the arc capacities. |
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| 44 | /// |
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| 45 | /// The type of the map that stores the arc capacities. |
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| 46 | /// It must meet the \ref concepts::ReadMap "ReadMap" concept. |
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| 47 | typedef _CapacityMap CapacityMap; |
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| 48 | |
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| 49 | /// \brief The type of the length of the arcs. |
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| 50 | typedef typename CapacityMap::Value Value; |
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| 51 | |
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| 52 | /// \brief The map type that stores the flow values. |
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| 53 | /// |
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| 54 | /// The map type that stores the flow values. |
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| 55 | /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
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| 56 | typedef typename Digraph::template ArcMap<Value> FlowMap; |
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| 57 | |
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| 58 | /// \brief Instantiates a FlowMap. |
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| 59 | /// |
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| 60 | /// This function instantiates a \ref FlowMap. |
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| 61 | /// \param digraph The digraph, to which we would like to define |
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| 62 | /// the flow map. |
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| 63 | static FlowMap* createFlowMap(const Digraph& digraph) { |
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| 64 | return new FlowMap(digraph); |
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| 65 | } |
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| 66 | |
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| 67 | /// \brief The eleavator type used by Preflow algorithm. |
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| 68 | /// |
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| 69 | /// The elevator type used by Preflow algorithm. |
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| 70 | /// |
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| 71 | /// \sa Elevator |
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| 72 | /// \sa LinkedElevator |
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| 73 | typedef LinkedElevator<Digraph, typename Digraph::Node> Elevator; |
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| 74 | |
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| 75 | /// \brief Instantiates an Elevator. |
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| 76 | /// |
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| 77 | /// This function instantiates a \ref Elevator. |
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| 78 | /// \param digraph The digraph, to which we would like to define |
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| 79 | /// the elevator. |
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| 80 | /// \param max_level The maximum level of the elevator. |
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| 81 | static Elevator* createElevator(const Digraph& digraph, int max_level) { |
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| 82 | return new Elevator(digraph, max_level); |
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| 83 | } |
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| 84 | |
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| 85 | /// \brief The tolerance used by the algorithm |
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| 86 | /// |
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| 87 | /// The tolerance used by the algorithm to handle inexact computation. |
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| 88 | typedef lemon::Tolerance<Value> Tolerance; |
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| 89 | |
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| 90 | }; |
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| 91 | |
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| 92 | |
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| 93 | /// \ingroup max_flow |
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| 94 | /// |
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| 95 | /// \brief %Preflow algorithms class. |
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| 96 | /// |
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| 97 | /// This class provides an implementation of the Goldberg's \e |
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| 98 | /// preflow \e algorithm producing a flow of maximum value in a |
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| 99 | /// digraph. The preflow algorithms are the fastest known max |
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| 100 | /// flow algorithms. The current implementation use a mixture of the |
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| 101 | /// \e "highest label" and the \e "bound decrease" heuristics. |
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| 102 | /// The worst case time complexity of the algorithm is \f$O(n^2\sqrt{e})\f$. |
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| 103 | /// |
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| 104 | /// The algorithm consists from two phases. After the first phase |
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| 105 | /// the maximal flow value and the minimum cut can be obtained. The |
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| 106 | /// second phase constructs the feasible maximum flow on each arc. |
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| 107 | /// |
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| 108 | /// \param _Graph The digraph type the algorithm runs on. |
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| 109 | /// \param _CapacityMap The flow map type. |
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| 110 | /// \param _Traits Traits class to set various data types used by |
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| 111 | /// the algorithm. The default traits class is \ref |
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| 112 | /// PreflowDefaultTraits. See \ref PreflowDefaultTraits for the |
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| 113 | /// documentation of a %Preflow traits class. |
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| 114 | /// |
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| 115 | ///\author Jacint Szabo and Balazs Dezso |
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| 116 | #ifdef DOXYGEN |
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| 117 | template <typename _Graph, typename _CapacityMap, typename _Traits> |
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| 118 | #else |
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| 119 | template <typename _Graph, |
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| 120 | typename _CapacityMap = typename _Graph::template ArcMap<int>, |
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| 121 | typename _Traits = PreflowDefaultTraits<_Graph, _CapacityMap> > |
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| 122 | #endif |
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| 123 | class Preflow { |
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| 124 | public: |
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| 125 | |
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| 126 | typedef _Traits Traits; |
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| 127 | typedef typename Traits::Digraph Digraph; |
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| 128 | typedef typename Traits::CapacityMap CapacityMap; |
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| 129 | typedef typename Traits::Value Value; |
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| 130 | |
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| 131 | typedef typename Traits::FlowMap FlowMap; |
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| 132 | typedef typename Traits::Elevator Elevator; |
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| 133 | typedef typename Traits::Tolerance Tolerance; |
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| 134 | |
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| 135 | /// \brief \ref Exception for uninitialized parameters. |
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| 136 | /// |
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| 137 | /// This error represents problems in the initialization |
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| 138 | /// of the parameters of the algorithms. |
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| 139 | class UninitializedParameter : public lemon::Exception { |
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| 140 | public: |
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| 141 | virtual const char* what() const throw() { |
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| 142 | return "lemon::Preflow::UninitializedParameter"; |
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| 143 | } |
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| 144 | }; |
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| 145 | |
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| 146 | private: |
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| 147 | |
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| 148 | TEMPLATE_DIGRAPH_TYPEDEFS(Digraph); |
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| 149 | |
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| 150 | const Digraph& _graph; |
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| 151 | const CapacityMap* _capacity; |
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| 152 | |
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| 153 | int _node_num; |
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| 154 | |
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| 155 | Node _source, _target; |
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| 156 | |
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| 157 | FlowMap* _flow; |
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| 158 | bool _local_flow; |
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| 159 | |
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| 160 | Elevator* _level; |
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| 161 | bool _local_level; |
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| 162 | |
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| 163 | typedef typename Digraph::template NodeMap<Value> ExcessMap; |
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| 164 | ExcessMap* _excess; |
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| 165 | |
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| 166 | Tolerance _tolerance; |
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| 167 | |
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| 168 | bool _phase; |
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| 169 | |
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| 170 | |
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| 171 | void createStructures() { |
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| 172 | _node_num = countNodes(_graph); |
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| 173 | |
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| 174 | if (!_flow) { |
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| 175 | _flow = Traits::createFlowMap(_graph); |
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| 176 | _local_flow = true; |
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| 177 | } |
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| 178 | if (!_level) { |
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| 179 | _level = Traits::createElevator(_graph, _node_num); |
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| 180 | _local_level = true; |
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| 181 | } |
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| 182 | if (!_excess) { |
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| 183 | _excess = new ExcessMap(_graph); |
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| 184 | } |
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| 185 | } |
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| 186 | |
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| 187 | void destroyStructures() { |
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| 188 | if (_local_flow) { |
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| 189 | delete _flow; |
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| 190 | } |
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| 191 | if (_local_level) { |
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| 192 | delete _level; |
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| 193 | } |
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| 194 | if (_excess) { |
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| 195 | delete _excess; |
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| 196 | } |
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| 197 | } |
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| 198 | |
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| 199 | public: |
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| 200 | |
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| 201 | typedef Preflow Create; |
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| 202 | |
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| 203 | ///\name Named template parameters |
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| 204 | |
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| 205 | ///@{ |
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| 206 | |
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| 207 | template <typename _FlowMap> |
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| 208 | struct DefFlowMapTraits : public Traits { |
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| 209 | typedef _FlowMap FlowMap; |
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| 210 | static FlowMap *createFlowMap(const Digraph&) { |
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| 211 | throw UninitializedParameter(); |
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| 212 | } |
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| 213 | }; |
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| 214 | |
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| 215 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 216 | /// FlowMap type |
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| 217 | /// |
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| 218 | /// \ref named-templ-param "Named parameter" for setting FlowMap |
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| 219 | /// type |
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| 220 | template <typename _FlowMap> |
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| 221 | struct DefFlowMap |
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| 222 | : public Preflow<Digraph, CapacityMap, DefFlowMapTraits<_FlowMap> > { |
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| 223 | typedef Preflow<Digraph, CapacityMap, |
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| 224 | DefFlowMapTraits<_FlowMap> > Create; |
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| 225 | }; |
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| 226 | |
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| 227 | template <typename _Elevator> |
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| 228 | struct DefElevatorTraits : public Traits { |
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| 229 | typedef _Elevator Elevator; |
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| 230 | static Elevator *createElevator(const Digraph&, int) { |
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| 231 | throw UninitializedParameter(); |
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| 232 | } |
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| 233 | }; |
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| 234 | |
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| 235 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 236 | /// Elevator type |
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| 237 | /// |
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| 238 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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| 239 | /// type |
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| 240 | template <typename _Elevator> |
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| 241 | struct DefElevator |
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| 242 | : public Preflow<Digraph, CapacityMap, DefElevatorTraits<_Elevator> > { |
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| 243 | typedef Preflow<Digraph, CapacityMap, |
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| 244 | DefElevatorTraits<_Elevator> > Create; |
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| 245 | }; |
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| 246 | |
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| 247 | template <typename _Elevator> |
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| 248 | struct DefStandardElevatorTraits : public Traits { |
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| 249 | typedef _Elevator Elevator; |
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| 250 | static Elevator *createElevator(const Digraph& digraph, int max_level) { |
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| 251 | return new Elevator(digraph, max_level); |
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| 252 | } |
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| 253 | }; |
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| 254 | |
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| 255 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 256 | /// Elevator type |
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| 257 | /// |
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| 258 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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| 259 | /// type. The Elevator should be standard constructor interface, ie. |
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| 260 | /// the digraph and the maximum level should be passed to it. |
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| 261 | template <typename _Elevator> |
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| 262 | struct DefStandardElevator |
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| 263 | : public Preflow<Digraph, CapacityMap, |
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| 264 | DefStandardElevatorTraits<_Elevator> > { |
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| 265 | typedef Preflow<Digraph, CapacityMap, |
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| 266 | DefStandardElevatorTraits<_Elevator> > Create; |
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| 267 | }; |
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| 268 | |
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| 269 | /// @} |
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| 270 | |
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| 271 | protected: |
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| 272 | |
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| 273 | Preflow() {} |
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| 274 | |
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| 275 | public: |
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| 276 | |
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| 277 | |
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| 278 | /// \brief The constructor of the class. |
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| 279 | /// |
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| 280 | /// The constructor of the class. |
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| 281 | /// \param digraph The digraph the algorithm runs on. |
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| 282 | /// \param capacity The capacity of the arcs. |
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| 283 | /// \param source The source node. |
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| 284 | /// \param target The target node. |
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| 285 | Preflow(const Digraph& digraph, const CapacityMap& capacity, |
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| 286 | Node source, Node target) |
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| 287 | : _graph(digraph), _capacity(&capacity), |
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| 288 | _node_num(0), _source(source), _target(target), |
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| 289 | _flow(0), _local_flow(false), |
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| 290 | _level(0), _local_level(false), |
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| 291 | _excess(0), _tolerance(), _phase() {} |
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| 292 | |
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| 293 | /// \brief Destrcutor. |
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| 294 | /// |
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| 295 | /// Destructor. |
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| 296 | ~Preflow() { |
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| 297 | destroyStructures(); |
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| 298 | } |
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| 299 | |
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| 300 | /// \brief Sets the capacity map. |
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| 301 | /// |
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| 302 | /// Sets the capacity map. |
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| 303 | /// \return \c (*this) |
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| 304 | Preflow& capacityMap(const CapacityMap& map) { |
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| 305 | _capacity = ↦ |
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| 306 | return *this; |
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| 307 | } |
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| 308 | |
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| 309 | /// \brief Sets the flow map. |
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| 310 | /// |
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| 311 | /// Sets the flow map. |
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| 312 | /// \return \c (*this) |
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| 313 | Preflow& flowMap(FlowMap& map) { |
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| 314 | if (_local_flow) { |
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| 315 | delete _flow; |
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| 316 | _local_flow = false; |
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| 317 | } |
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| 318 | _flow = ↦ |
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| 319 | return *this; |
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| 320 | } |
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| 321 | |
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| 322 | /// \brief Returns the flow map. |
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| 323 | /// |
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| 324 | /// \return The flow map. |
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| 325 | const FlowMap& flowMap() { |
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| 326 | return *_flow; |
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| 327 | } |
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| 328 | |
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| 329 | /// \brief Sets the elevator. |
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| 330 | /// |
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| 331 | /// Sets the elevator. |
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| 332 | /// \return \c (*this) |
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| 333 | Preflow& elevator(Elevator& elevator) { |
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| 334 | if (_local_level) { |
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| 335 | delete _level; |
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| 336 | _local_level = false; |
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| 337 | } |
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| 338 | _level = &elevator; |
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| 339 | return *this; |
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| 340 | } |
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| 341 | |
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| 342 | /// \brief Returns the elevator. |
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| 343 | /// |
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| 344 | /// \return The elevator. |
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| 345 | const Elevator& elevator() { |
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| 346 | return *_level; |
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| 347 | } |
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| 348 | |
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| 349 | /// \brief Sets the source node. |
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| 350 | /// |
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| 351 | /// Sets the source node. |
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| 352 | /// \return \c (*this) |
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| 353 | Preflow& source(const Node& node) { |
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| 354 | _source = node; |
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| 355 | return *this; |
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| 356 | } |
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| 357 | |
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| 358 | /// \brief Sets the target node. |
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| 359 | /// |
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| 360 | /// Sets the target node. |
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| 361 | /// \return \c (*this) |
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| 362 | Preflow& target(const Node& node) { |
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| 363 | _target = node; |
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| 364 | return *this; |
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| 365 | } |
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| 366 | |
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| 367 | /// \brief Sets the tolerance used by algorithm. |
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| 368 | /// |
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| 369 | /// Sets the tolerance used by algorithm. |
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| 370 | Preflow& tolerance(const Tolerance& tolerance) const { |
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| 371 | _tolerance = tolerance; |
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| 372 | return *this; |
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| 373 | } |
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| 374 | |
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| 375 | /// \brief Returns the tolerance used by algorithm. |
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| 376 | /// |
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| 377 | /// Returns the tolerance used by algorithm. |
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| 378 | const Tolerance& tolerance() const { |
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| 379 | return tolerance; |
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| 380 | } |
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| 381 | |
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| 382 | /// \name Execution control The simplest way to execute the |
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| 383 | /// algorithm is to use one of the member functions called \c |
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| 384 | /// run(). |
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| 385 | /// \n |
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| 386 | /// If you need more control on initial solution or |
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| 387 | /// execution then you have to call one \ref init() function and then |
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| 388 | /// the startFirstPhase() and if you need the startSecondPhase(). |
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| 389 | |
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| 390 | ///@{ |
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| 391 | |
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| 392 | /// \brief Initializes the internal data structures. |
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| 393 | /// |
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| 394 | /// Initializes the internal data structures. |
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| 395 | /// |
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| 396 | void init() { |
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| 397 | createStructures(); |
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| 398 | |
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| 399 | _phase = true; |
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| 400 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 401 | _excess->set(n, 0); |
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| 402 | } |
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| 403 | |
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| 404 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 405 | _flow->set(e, 0); |
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| 406 | } |
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| 407 | |
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| 408 | typename Digraph::template NodeMap<bool> reached(_graph, false); |
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| 409 | |
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| 410 | _level->initStart(); |
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| 411 | _level->initAddItem(_target); |
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| 412 | |
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| 413 | std::vector<Node> queue; |
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| 414 | reached.set(_source, true); |
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| 415 | |
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| 416 | queue.push_back(_target); |
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| 417 | reached.set(_target, true); |
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| 418 | while (!queue.empty()) { |
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| 419 | _level->initNewLevel(); |
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| 420 | std::vector<Node> nqueue; |
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| 421 | for (int i = 0; i < int(queue.size()); ++i) { |
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| 422 | Node n = queue[i]; |
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| 423 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
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| 424 | Node u = _graph.source(e); |
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| 425 | if (!reached[u] && _tolerance.positive((*_capacity)[e])) { |
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| 426 | reached.set(u, true); |
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| 427 | _level->initAddItem(u); |
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| 428 | nqueue.push_back(u); |
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| 429 | } |
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| 430 | } |
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| 431 | } |
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| 432 | queue.swap(nqueue); |
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| 433 | } |
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| 434 | _level->initFinish(); |
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| 435 | |
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| 436 | for (OutArcIt e(_graph, _source); e != INVALID; ++e) { |
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| 437 | if (_tolerance.positive((*_capacity)[e])) { |
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| 438 | Node u = _graph.target(e); |
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| 439 | if ((*_level)[u] == _level->maxLevel()) continue; |
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| 440 | _flow->set(e, (*_capacity)[e]); |
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| 441 | _excess->set(u, (*_excess)[u] + (*_capacity)[e]); |
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| 442 | if (u != _target && !_level->active(u)) { |
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| 443 | _level->activate(u); |
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| 444 | } |
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| 445 | } |
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| 446 | } |
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| 447 | } |
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| 448 | |
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| 449 | /// \brief Initializes the internal data structures. |
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| 450 | /// |
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| 451 | /// Initializes the internal data structures and sets the initial |
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| 452 | /// flow to the given \c flowMap. The \c flowMap should contain a |
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| 453 | /// flow or at least a preflow, ie. in each node excluding the |
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| 454 | /// target the incoming flow should greater or equal to the |
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| 455 | /// outgoing flow. |
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| 456 | /// \return %False when the given \c flowMap is not a preflow. |
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| 457 | template <typename FlowMap> |
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| 458 | bool flowInit(const FlowMap& flowMap) { |
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| 459 | createStructures(); |
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| 460 | |
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| 461 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 462 | _flow->set(e, flowMap[e]); |
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| 463 | } |
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| 464 | |
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| 465 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 466 | Value excess = 0; |
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| 467 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
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| 468 | excess += (*_flow)[e]; |
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| 469 | } |
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| 470 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
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| 471 | excess -= (*_flow)[e]; |
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| 472 | } |
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| 473 | if (excess < 0 && n != _source) return false; |
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| 474 | _excess->set(n, excess); |
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| 475 | } |
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| 476 | |
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| 477 | typename Digraph::template NodeMap<bool> reached(_graph, false); |
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| 478 | |
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| 479 | _level->initStart(); |
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| 480 | _level->initAddItem(_target); |
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| 481 | |
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| 482 | std::vector<Node> queue; |
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| 483 | reached.set(_source, true); |
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| 484 | |
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| 485 | queue.push_back(_target); |
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| 486 | reached.set(_target, true); |
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| 487 | while (!queue.empty()) { |
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| 488 | _level->initNewLevel(); |
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| 489 | std::vector<Node> nqueue; |
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| 490 | for (int i = 0; i < int(queue.size()); ++i) { |
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| 491 | Node n = queue[i]; |
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| 492 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
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| 493 | Node u = _graph.source(e); |
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| 494 | if (!reached[u] && |
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| 495 | _tolerance.positive((*_capacity)[e] - (*_flow)[e])) { |
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| 496 | reached.set(u, true); |
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| 497 | _level->initAddItem(u); |
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| 498 | nqueue.push_back(u); |
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| 499 | } |
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| 500 | } |
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| 501 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
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| 502 | Node v = _graph.target(e); |
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| 503 | if (!reached[v] && _tolerance.positive((*_flow)[e])) { |
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| 504 | reached.set(v, true); |
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| 505 | _level->initAddItem(v); |
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| 506 | nqueue.push_back(v); |
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| 507 | } |
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| 508 | } |
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| 509 | } |
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| 510 | queue.swap(nqueue); |
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| 511 | } |
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| 512 | _level->initFinish(); |
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| 513 | |
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| 514 | for (OutArcIt e(_graph, _source); e != INVALID; ++e) { |
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| 515 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
| 516 | if (_tolerance.positive(rem)) { |
---|
| 517 | Node u = _graph.target(e); |
---|
| 518 | if ((*_level)[u] == _level->maxLevel()) continue; |
---|
| 519 | _flow->set(e, (*_capacity)[e]); |
---|
| 520 | _excess->set(u, (*_excess)[u] + rem); |
---|
| 521 | if (u != _target && !_level->active(u)) { |
---|
| 522 | _level->activate(u); |
---|
| 523 | } |
---|
| 524 | } |
---|
| 525 | } |
---|
| 526 | for (InArcIt e(_graph, _source); e != INVALID; ++e) { |
---|
| 527 | Value rem = (*_flow)[e]; |
---|
| 528 | if (_tolerance.positive(rem)) { |
---|
| 529 | Node v = _graph.source(e); |
---|
| 530 | if ((*_level)[v] == _level->maxLevel()) continue; |
---|
| 531 | _flow->set(e, 0); |
---|
| 532 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 533 | if (v != _target && !_level->active(v)) { |
---|
| 534 | _level->activate(v); |
---|
| 535 | } |
---|
| 536 | } |
---|
| 537 | } |
---|
| 538 | return true; |
---|
| 539 | } |
---|
| 540 | |
---|
| 541 | /// \brief Starts the first phase of the preflow algorithm. |
---|
| 542 | /// |
---|
| 543 | /// The preflow algorithm consists of two phases, this method runs |
---|
| 544 | /// the first phase. After the first phase the maximum flow value |
---|
| 545 | /// and a minimum value cut can already be computed, although a |
---|
| 546 | /// maximum flow is not yet obtained. So after calling this method |
---|
| 547 | /// \ref flowValue() returns the value of a maximum flow and \ref |
---|
| 548 | /// minCut() returns a minimum cut. |
---|
| 549 | /// \pre One of the \ref init() functions should be called. |
---|
| 550 | void startFirstPhase() { |
---|
| 551 | _phase = true; |
---|
| 552 | |
---|
| 553 | Node n = _level->highestActive(); |
---|
| 554 | int level = _level->highestActiveLevel(); |
---|
| 555 | while (n != INVALID) { |
---|
| 556 | int num = _node_num; |
---|
| 557 | |
---|
| 558 | while (num > 0 && n != INVALID) { |
---|
| 559 | Value excess = (*_excess)[n]; |
---|
| 560 | int new_level = _level->maxLevel(); |
---|
| 561 | |
---|
| 562 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 563 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
| 564 | if (!_tolerance.positive(rem)) continue; |
---|
| 565 | Node v = _graph.target(e); |
---|
| 566 | if ((*_level)[v] < level) { |
---|
| 567 | if (!_level->active(v) && v != _target) { |
---|
| 568 | _level->activate(v); |
---|
| 569 | } |
---|
| 570 | if (!_tolerance.less(rem, excess)) { |
---|
| 571 | _flow->set(e, (*_flow)[e] + excess); |
---|
| 572 | _excess->set(v, (*_excess)[v] + excess); |
---|
| 573 | excess = 0; |
---|
| 574 | goto no_more_push_1; |
---|
| 575 | } else { |
---|
| 576 | excess -= rem; |
---|
| 577 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 578 | _flow->set(e, (*_capacity)[e]); |
---|
| 579 | } |
---|
| 580 | } else if (new_level > (*_level)[v]) { |
---|
| 581 | new_level = (*_level)[v]; |
---|
| 582 | } |
---|
| 583 | } |
---|
| 584 | |
---|
| 585 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 586 | Value rem = (*_flow)[e]; |
---|
| 587 | if (!_tolerance.positive(rem)) continue; |
---|
| 588 | Node v = _graph.source(e); |
---|
| 589 | if ((*_level)[v] < level) { |
---|
| 590 | if (!_level->active(v) && v != _target) { |
---|
| 591 | _level->activate(v); |
---|
| 592 | } |
---|
| 593 | if (!_tolerance.less(rem, excess)) { |
---|
| 594 | _flow->set(e, (*_flow)[e] - excess); |
---|
| 595 | _excess->set(v, (*_excess)[v] + excess); |
---|
| 596 | excess = 0; |
---|
| 597 | goto no_more_push_1; |
---|
| 598 | } else { |
---|
| 599 | excess -= rem; |
---|
| 600 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 601 | _flow->set(e, 0); |
---|
| 602 | } |
---|
| 603 | } else if (new_level > (*_level)[v]) { |
---|
| 604 | new_level = (*_level)[v]; |
---|
| 605 | } |
---|
| 606 | } |
---|
| 607 | |
---|
| 608 | no_more_push_1: |
---|
| 609 | |
---|
| 610 | _excess->set(n, excess); |
---|
| 611 | |
---|
| 612 | if (excess != 0) { |
---|
| 613 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 614 | _level->liftHighestActive(new_level + 1); |
---|
| 615 | } else { |
---|
| 616 | _level->liftHighestActiveToTop(); |
---|
| 617 | } |
---|
| 618 | if (_level->emptyLevel(level)) { |
---|
| 619 | _level->liftToTop(level); |
---|
| 620 | } |
---|
| 621 | } else { |
---|
| 622 | _level->deactivate(n); |
---|
| 623 | } |
---|
| 624 | |
---|
| 625 | n = _level->highestActive(); |
---|
| 626 | level = _level->highestActiveLevel(); |
---|
| 627 | --num; |
---|
| 628 | } |
---|
| 629 | |
---|
| 630 | num = _node_num * 20; |
---|
| 631 | while (num > 0 && n != INVALID) { |
---|
| 632 | Value excess = (*_excess)[n]; |
---|
| 633 | int new_level = _level->maxLevel(); |
---|
| 634 | |
---|
| 635 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 636 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
| 637 | if (!_tolerance.positive(rem)) continue; |
---|
| 638 | Node v = _graph.target(e); |
---|
| 639 | if ((*_level)[v] < level) { |
---|
| 640 | if (!_level->active(v) && v != _target) { |
---|
| 641 | _level->activate(v); |
---|
| 642 | } |
---|
| 643 | if (!_tolerance.less(rem, excess)) { |
---|
| 644 | _flow->set(e, (*_flow)[e] + excess); |
---|
| 645 | _excess->set(v, (*_excess)[v] + excess); |
---|
| 646 | excess = 0; |
---|
| 647 | goto no_more_push_2; |
---|
| 648 | } else { |
---|
| 649 | excess -= rem; |
---|
| 650 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 651 | _flow->set(e, (*_capacity)[e]); |
---|
| 652 | } |
---|
| 653 | } else if (new_level > (*_level)[v]) { |
---|
| 654 | new_level = (*_level)[v]; |
---|
| 655 | } |
---|
| 656 | } |
---|
| 657 | |
---|
| 658 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 659 | Value rem = (*_flow)[e]; |
---|
| 660 | if (!_tolerance.positive(rem)) continue; |
---|
| 661 | Node v = _graph.source(e); |
---|
| 662 | if ((*_level)[v] < level) { |
---|
| 663 | if (!_level->active(v) && v != _target) { |
---|
| 664 | _level->activate(v); |
---|
| 665 | } |
---|
| 666 | if (!_tolerance.less(rem, excess)) { |
---|
| 667 | _flow->set(e, (*_flow)[e] - excess); |
---|
| 668 | _excess->set(v, (*_excess)[v] + excess); |
---|
| 669 | excess = 0; |
---|
| 670 | goto no_more_push_2; |
---|
| 671 | } else { |
---|
| 672 | excess -= rem; |
---|
| 673 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 674 | _flow->set(e, 0); |
---|
| 675 | } |
---|
| 676 | } else if (new_level > (*_level)[v]) { |
---|
| 677 | new_level = (*_level)[v]; |
---|
| 678 | } |
---|
| 679 | } |
---|
| 680 | |
---|
| 681 | no_more_push_2: |
---|
| 682 | |
---|
| 683 | _excess->set(n, excess); |
---|
| 684 | |
---|
| 685 | if (excess != 0) { |
---|
| 686 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 687 | _level->liftActiveOn(level, new_level + 1); |
---|
| 688 | } else { |
---|
| 689 | _level->liftActiveToTop(level); |
---|
| 690 | } |
---|
| 691 | if (_level->emptyLevel(level)) { |
---|
| 692 | _level->liftToTop(level); |
---|
| 693 | } |
---|
| 694 | } else { |
---|
| 695 | _level->deactivate(n); |
---|
| 696 | } |
---|
| 697 | |
---|
| 698 | while (level >= 0 && _level->activeFree(level)) { |
---|
| 699 | --level; |
---|
| 700 | } |
---|
| 701 | if (level == -1) { |
---|
| 702 | n = _level->highestActive(); |
---|
| 703 | level = _level->highestActiveLevel(); |
---|
| 704 | } else { |
---|
| 705 | n = _level->activeOn(level); |
---|
| 706 | } |
---|
| 707 | --num; |
---|
| 708 | } |
---|
| 709 | } |
---|
| 710 | } |
---|
| 711 | |
---|
| 712 | /// \brief Starts the second phase of the preflow algorithm. |
---|
| 713 | /// |
---|
| 714 | /// The preflow algorithm consists of two phases, this method runs |
---|
| 715 | /// the second phase. After calling \ref init() and \ref |
---|
| 716 | /// startFirstPhase() and then \ref startSecondPhase(), \ref |
---|
| 717 | /// flowMap() return a maximum flow, \ref flowValue() returns the |
---|
| 718 | /// value of a maximum flow, \ref minCut() returns a minimum cut |
---|
| 719 | /// \pre The \ref init() and startFirstPhase() functions should be |
---|
| 720 | /// called before. |
---|
| 721 | void startSecondPhase() { |
---|
| 722 | _phase = false; |
---|
| 723 | |
---|
| 724 | typename Digraph::template NodeMap<bool> reached(_graph); |
---|
| 725 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
| 726 | reached.set(n, (*_level)[n] < _level->maxLevel()); |
---|
| 727 | } |
---|
| 728 | |
---|
| 729 | _level->initStart(); |
---|
| 730 | _level->initAddItem(_source); |
---|
| 731 | |
---|
| 732 | std::vector<Node> queue; |
---|
| 733 | queue.push_back(_source); |
---|
| 734 | reached.set(_source, true); |
---|
| 735 | |
---|
| 736 | while (!queue.empty()) { |
---|
| 737 | _level->initNewLevel(); |
---|
| 738 | std::vector<Node> nqueue; |
---|
| 739 | for (int i = 0; i < int(queue.size()); ++i) { |
---|
| 740 | Node n = queue[i]; |
---|
| 741 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 742 | Node v = _graph.target(e); |
---|
| 743 | if (!reached[v] && _tolerance.positive((*_flow)[e])) { |
---|
| 744 | reached.set(v, true); |
---|
| 745 | _level->initAddItem(v); |
---|
| 746 | nqueue.push_back(v); |
---|
| 747 | } |
---|
| 748 | } |
---|
| 749 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 750 | Node u = _graph.source(e); |
---|
| 751 | if (!reached[u] && |
---|
| 752 | _tolerance.positive((*_capacity)[e] - (*_flow)[e])) { |
---|
| 753 | reached.set(u, true); |
---|
| 754 | _level->initAddItem(u); |
---|
| 755 | nqueue.push_back(u); |
---|
| 756 | } |
---|
| 757 | } |
---|
| 758 | } |
---|
| 759 | queue.swap(nqueue); |
---|
| 760 | } |
---|
| 761 | _level->initFinish(); |
---|
| 762 | |
---|
| 763 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
| 764 | if (!reached[n]) { |
---|
| 765 | _level->dirtyTopButOne(n); |
---|
| 766 | } else if ((*_excess)[n] > 0 && _target != n) { |
---|
| 767 | _level->activate(n); |
---|
| 768 | } |
---|
| 769 | } |
---|
| 770 | |
---|
| 771 | Node n; |
---|
| 772 | while ((n = _level->highestActive()) != INVALID) { |
---|
| 773 | Value excess = (*_excess)[n]; |
---|
| 774 | int level = _level->highestActiveLevel(); |
---|
| 775 | int new_level = _level->maxLevel(); |
---|
| 776 | |
---|
| 777 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 778 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
| 779 | if (!_tolerance.positive(rem)) continue; |
---|
| 780 | Node v = _graph.target(e); |
---|
| 781 | if ((*_level)[v] < level) { |
---|
| 782 | if (!_level->active(v) && v != _source) { |
---|
| 783 | _level->activate(v); |
---|
| 784 | } |
---|
| 785 | if (!_tolerance.less(rem, excess)) { |
---|
| 786 | _flow->set(e, (*_flow)[e] + excess); |
---|
| 787 | _excess->set(v, (*_excess)[v] + excess); |
---|
| 788 | excess = 0; |
---|
| 789 | goto no_more_push; |
---|
| 790 | } else { |
---|
| 791 | excess -= rem; |
---|
| 792 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 793 | _flow->set(e, (*_capacity)[e]); |
---|
| 794 | } |
---|
| 795 | } else if (new_level > (*_level)[v]) { |
---|
| 796 | new_level = (*_level)[v]; |
---|
| 797 | } |
---|
| 798 | } |
---|
| 799 | |
---|
| 800 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 801 | Value rem = (*_flow)[e]; |
---|
| 802 | if (!_tolerance.positive(rem)) continue; |
---|
| 803 | Node v = _graph.source(e); |
---|
| 804 | if ((*_level)[v] < level) { |
---|
| 805 | if (!_level->active(v) && v != _source) { |
---|
| 806 | _level->activate(v); |
---|
| 807 | } |
---|
| 808 | if (!_tolerance.less(rem, excess)) { |
---|
| 809 | _flow->set(e, (*_flow)[e] - excess); |
---|
| 810 | _excess->set(v, (*_excess)[v] + excess); |
---|
| 811 | excess = 0; |
---|
| 812 | goto no_more_push; |
---|
| 813 | } else { |
---|
| 814 | excess -= rem; |
---|
| 815 | _excess->set(v, (*_excess)[v] + rem); |
---|
| 816 | _flow->set(e, 0); |
---|
| 817 | } |
---|
| 818 | } else if (new_level > (*_level)[v]) { |
---|
| 819 | new_level = (*_level)[v]; |
---|
| 820 | } |
---|
| 821 | } |
---|
| 822 | |
---|
| 823 | no_more_push: |
---|
| 824 | |
---|
| 825 | _excess->set(n, excess); |
---|
| 826 | |
---|
| 827 | if (excess != 0) { |
---|
| 828 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 829 | _level->liftHighestActive(new_level + 1); |
---|
| 830 | } else { |
---|
| 831 | // Calculation error |
---|
| 832 | _level->liftHighestActiveToTop(); |
---|
| 833 | } |
---|
| 834 | if (_level->emptyLevel(level)) { |
---|
| 835 | // Calculation error |
---|
| 836 | _level->liftToTop(level); |
---|
| 837 | } |
---|
| 838 | } else { |
---|
| 839 | _level->deactivate(n); |
---|
| 840 | } |
---|
| 841 | |
---|
| 842 | } |
---|
| 843 | } |
---|
| 844 | |
---|
| 845 | /// \brief Runs the preflow algorithm. |
---|
| 846 | /// |
---|
| 847 | /// Runs the preflow algorithm. |
---|
| 848 | /// \note pf.run() is just a shortcut of the following code. |
---|
| 849 | /// \code |
---|
| 850 | /// pf.init(); |
---|
| 851 | /// pf.startFirstPhase(); |
---|
| 852 | /// pf.startSecondPhase(); |
---|
| 853 | /// \endcode |
---|
| 854 | void run() { |
---|
| 855 | init(); |
---|
| 856 | startFirstPhase(); |
---|
| 857 | startSecondPhase(); |
---|
| 858 | } |
---|
| 859 | |
---|
| 860 | /// \brief Runs the preflow algorithm to compute the minimum cut. |
---|
| 861 | /// |
---|
| 862 | /// Runs the preflow algorithm to compute the minimum cut. |
---|
| 863 | /// \note pf.runMinCut() is just a shortcut of the following code. |
---|
| 864 | /// \code |
---|
| 865 | /// pf.init(); |
---|
| 866 | /// pf.startFirstPhase(); |
---|
| 867 | /// \endcode |
---|
| 868 | void runMinCut() { |
---|
| 869 | init(); |
---|
| 870 | startFirstPhase(); |
---|
| 871 | } |
---|
| 872 | |
---|
| 873 | /// @} |
---|
| 874 | |
---|
| 875 | /// \name Query Functions |
---|
| 876 | /// The result of the %Preflow algorithm can be obtained using these |
---|
| 877 | /// functions.\n |
---|
| 878 | /// Before the use of these functions, |
---|
| 879 | /// either run() or start() must be called. |
---|
| 880 | |
---|
| 881 | ///@{ |
---|
| 882 | |
---|
| 883 | /// \brief Returns the value of the maximum flow. |
---|
| 884 | /// |
---|
| 885 | /// Returns the value of the maximum flow by returning the excess |
---|
| 886 | /// of the target node \c t. This value equals to the value of |
---|
| 887 | /// the maximum flow already after the first phase. |
---|
| 888 | Value flowValue() const { |
---|
| 889 | return (*_excess)[_target]; |
---|
| 890 | } |
---|
| 891 | |
---|
| 892 | /// \brief Returns true when the node is on the source side of minimum cut. |
---|
| 893 | /// |
---|
| 894 | /// Returns true when the node is on the source side of minimum |
---|
| 895 | /// cut. This method can be called both after running \ref |
---|
| 896 | /// startFirstPhase() and \ref startSecondPhase(). |
---|
| 897 | bool minCut(const Node& node) const { |
---|
| 898 | return ((*_level)[node] == _level->maxLevel()) == _phase; |
---|
| 899 | } |
---|
| 900 | |
---|
| 901 | /// \brief Returns a minimum value cut. |
---|
| 902 | /// |
---|
| 903 | /// Sets the \c cutMap to the characteristic vector of a minimum value |
---|
| 904 | /// cut. This method can be called both after running \ref |
---|
| 905 | /// startFirstPhase() and \ref startSecondPhase(). The result after second |
---|
| 906 | /// phase could be changed slightly if inexact computation is used. |
---|
| 907 | /// \pre The \c cutMap should be a bool-valued node-map. |
---|
| 908 | template <typename CutMap> |
---|
| 909 | void minCutMap(CutMap& cutMap) const { |
---|
| 910 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
| 911 | cutMap.set(n, minCut(n)); |
---|
| 912 | } |
---|
| 913 | } |
---|
| 914 | |
---|
| 915 | /// \brief Returns the flow on the arc. |
---|
| 916 | /// |
---|
| 917 | /// Sets the \c flowMap to the flow on the arcs. This method can |
---|
| 918 | /// be called after the second phase of algorithm. |
---|
| 919 | Value flow(const Arc& arc) const { |
---|
| 920 | return (*_flow)[arc]; |
---|
| 921 | } |
---|
| 922 | |
---|
| 923 | /// @} |
---|
| 924 | }; |
---|
| 925 | } |
---|
| 926 | |
---|
| 927 | #endif |
---|