[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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[1084] | 5 | * Copyright (C) 2003-2011 |
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[404] | 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/tolerance.h> |
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| 23 | #include <lemon/elevator.h> |
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| 24 | |
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| 25 | /// \file |
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| 26 | /// \ingroup max_flow |
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| 27 | /// \brief Implementation of the preflow algorithm. |
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| 28 | |
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| 29 | namespace lemon { |
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| 30 | |
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| 31 | /// \brief Default traits class of Preflow class. |
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| 32 | /// |
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| 33 | /// Default traits class of Preflow class. |
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[525] | 34 | /// \tparam GR Digraph type. |
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[606] | 35 | /// \tparam CAP Capacity map type. |
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| 36 | template <typename GR, typename CAP> |
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[404] | 37 | struct PreflowDefaultTraits { |
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| 38 | |
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[408] | 39 | /// \brief The type of the digraph the algorithm runs on. |
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[525] | 40 | typedef GR Digraph; |
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[404] | 41 | |
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| 42 | /// \brief The type of the map that stores the arc capacities. |
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| 43 | /// |
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| 44 | /// The type of the map that stores the arc capacities. |
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| 45 | /// It must meet the \ref concepts::ReadMap "ReadMap" concept. |
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[606] | 46 | typedef CAP CapacityMap; |
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[404] | 47 | |
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[408] | 48 | /// \brief The type of the flow values. |
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[688] | 49 | typedef typename CapacityMap::Value Value; |
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[404] | 50 | |
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[408] | 51 | /// \brief The type of the map that stores the flow values. |
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[404] | 52 | /// |
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[408] | 53 | /// The type of the map that stores the flow values. |
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[404] | 54 | /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
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[760] | 55 | #ifdef DOXYGEN |
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| 56 | typedef GR::ArcMap<Value> FlowMap; |
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| 57 | #else |
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[688] | 58 | typedef typename Digraph::template ArcMap<Value> FlowMap; |
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[760] | 59 | #endif |
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[404] | 60 | |
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| 61 | /// \brief Instantiates a FlowMap. |
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| 62 | /// |
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| 63 | /// This function instantiates a \ref FlowMap. |
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[657] | 64 | /// \param digraph The digraph for which we would like to define |
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[404] | 65 | /// the flow map. |
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| 66 | static FlowMap* createFlowMap(const Digraph& digraph) { |
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| 67 | return new FlowMap(digraph); |
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| 68 | } |
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| 69 | |
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[408] | 70 | /// \brief The elevator type used by Preflow algorithm. |
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[404] | 71 | /// |
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| 72 | /// The elevator type used by Preflow algorithm. |
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| 73 | /// |
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[760] | 74 | /// \sa Elevator, LinkedElevator |
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| 75 | #ifdef DOXYGEN |
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| 76 | typedef lemon::Elevator<GR, GR::Node> Elevator; |
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| 77 | #else |
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| 78 | typedef lemon::Elevator<Digraph, typename Digraph::Node> Elevator; |
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| 79 | #endif |
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[404] | 80 | |
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| 81 | /// \brief Instantiates an Elevator. |
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| 82 | /// |
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[408] | 83 | /// This function instantiates an \ref Elevator. |
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[657] | 84 | /// \param digraph The digraph for which we would like to define |
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[404] | 85 | /// the elevator. |
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| 86 | /// \param max_level The maximum level of the elevator. |
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| 87 | static Elevator* createElevator(const Digraph& digraph, int max_level) { |
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| 88 | return new Elevator(digraph, max_level); |
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| 89 | } |
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| 90 | |
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| 91 | /// \brief The tolerance used by the algorithm |
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| 92 | /// |
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| 93 | /// The tolerance used by the algorithm to handle inexact computation. |
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[688] | 94 | typedef lemon::Tolerance<Value> Tolerance; |
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[404] | 95 | |
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| 96 | }; |
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| 97 | |
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| 98 | |
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| 99 | /// \ingroup max_flow |
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| 100 | /// |
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[408] | 101 | /// \brief %Preflow algorithm class. |
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[404] | 102 | /// |
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[408] | 103 | /// This class provides an implementation of Goldberg-Tarjan's \e preflow |
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[606] | 104 | /// \e push-relabel algorithm producing a \ref max_flow |
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[802] | 105 | /// "flow of maximum value" in a digraph \ref clrs01algorithms, |
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| 106 | /// \ref amo93networkflows, \ref goldberg88newapproach. |
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[606] | 107 | /// The preflow algorithms are the fastest known maximum |
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[736] | 108 | /// flow algorithms. The current implementation uses a mixture of the |
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[404] | 109 | /// \e "highest label" and the \e "bound decrease" heuristics. |
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| 110 | /// The worst case time complexity of the algorithm is \f$O(n^2\sqrt{e})\f$. |
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| 111 | /// |
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[408] | 112 | /// The algorithm consists of two phases. After the first phase |
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| 113 | /// the maximum flow value and the minimum cut is obtained. The |
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| 114 | /// second phase constructs a feasible maximum flow on each arc. |
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[404] | 115 | /// |
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[889] | 116 | /// \warning This implementation cannot handle infinite or very large |
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| 117 | /// capacities (e.g. the maximum value of \c CAP::Value). |
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| 118 | /// |
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[525] | 119 | /// \tparam GR The type of the digraph the algorithm runs on. |
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[606] | 120 | /// \tparam CAP The type of the capacity map. The default map |
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[525] | 121 | /// type is \ref concepts::Digraph::ArcMap "GR::ArcMap<int>". |
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[891] | 122 | /// \tparam TR The traits class that defines various types used by the |
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| 123 | /// algorithm. By default, it is \ref PreflowDefaultTraits |
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| 124 | /// "PreflowDefaultTraits<GR, CAP>". |
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| 125 | /// In most cases, this parameter should not be set directly, |
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| 126 | /// consider to use the named template parameters instead. |
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[404] | 127 | #ifdef DOXYGEN |
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[606] | 128 | template <typename GR, typename CAP, typename TR> |
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[404] | 129 | #else |
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[525] | 130 | template <typename GR, |
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[606] | 131 | typename CAP = typename GR::template ArcMap<int>, |
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| 132 | typename TR = PreflowDefaultTraits<GR, CAP> > |
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[404] | 133 | #endif |
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| 134 | class Preflow { |
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| 135 | public: |
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| 136 | |
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[408] | 137 | ///The \ref PreflowDefaultTraits "traits class" of the algorithm. |
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[525] | 138 | typedef TR Traits; |
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[408] | 139 | ///The type of the digraph the algorithm runs on. |
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[404] | 140 | typedef typename Traits::Digraph Digraph; |
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[408] | 141 | ///The type of the capacity map. |
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[404] | 142 | typedef typename Traits::CapacityMap CapacityMap; |
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[408] | 143 | ///The type of the flow values. |
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[688] | 144 | typedef typename Traits::Value Value; |
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[404] | 145 | |
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[408] | 146 | ///The type of the flow map. |
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[404] | 147 | typedef typename Traits::FlowMap FlowMap; |
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[408] | 148 | ///The type of the elevator. |
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[404] | 149 | typedef typename Traits::Elevator Elevator; |
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[408] | 150 | ///The type of the tolerance. |
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[404] | 151 | typedef typename Traits::Tolerance Tolerance; |
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| 152 | |
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| 153 | private: |
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| 154 | |
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| 155 | TEMPLATE_DIGRAPH_TYPEDEFS(Digraph); |
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| 156 | |
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| 157 | const Digraph& _graph; |
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| 158 | const CapacityMap* _capacity; |
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| 159 | |
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| 160 | int _node_num; |
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| 161 | |
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| 162 | Node _source, _target; |
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| 163 | |
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| 164 | FlowMap* _flow; |
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| 165 | bool _local_flow; |
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| 166 | |
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| 167 | Elevator* _level; |
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| 168 | bool _local_level; |
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| 169 | |
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[688] | 170 | typedef typename Digraph::template NodeMap<Value> ExcessMap; |
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[404] | 171 | ExcessMap* _excess; |
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| 172 | |
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| 173 | Tolerance _tolerance; |
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| 174 | |
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| 175 | bool _phase; |
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| 176 | |
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| 177 | |
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| 178 | void createStructures() { |
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| 179 | _node_num = countNodes(_graph); |
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| 180 | |
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| 181 | if (!_flow) { |
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| 182 | _flow = Traits::createFlowMap(_graph); |
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| 183 | _local_flow = true; |
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| 184 | } |
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| 185 | if (!_level) { |
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| 186 | _level = Traits::createElevator(_graph, _node_num); |
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| 187 | _local_level = true; |
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| 188 | } |
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| 189 | if (!_excess) { |
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| 190 | _excess = new ExcessMap(_graph); |
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| 191 | } |
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| 192 | } |
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| 193 | |
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| 194 | void destroyStructures() { |
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| 195 | if (_local_flow) { |
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| 196 | delete _flow; |
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| 197 | } |
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| 198 | if (_local_level) { |
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| 199 | delete _level; |
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| 200 | } |
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| 201 | if (_excess) { |
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| 202 | delete _excess; |
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| 203 | } |
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| 204 | } |
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| 205 | |
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| 206 | public: |
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| 207 | |
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| 208 | typedef Preflow Create; |
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| 209 | |
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[408] | 210 | ///\name Named Template Parameters |
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[404] | 211 | |
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| 212 | ///@{ |
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| 213 | |
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[606] | 214 | template <typename T> |
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[406] | 215 | struct SetFlowMapTraits : public Traits { |
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[606] | 216 | typedef T FlowMap; |
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[404] | 217 | static FlowMap *createFlowMap(const Digraph&) { |
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[405] | 218 | LEMON_ASSERT(false, "FlowMap is not initialized"); |
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| 219 | return 0; // ignore warnings |
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[404] | 220 | } |
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| 221 | }; |
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| 222 | |
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| 223 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 224 | /// FlowMap type |
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| 225 | /// |
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| 226 | /// \ref named-templ-param "Named parameter" for setting FlowMap |
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[408] | 227 | /// type. |
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[606] | 228 | template <typename T> |
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[406] | 229 | struct SetFlowMap |
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[606] | 230 | : public Preflow<Digraph, CapacityMap, SetFlowMapTraits<T> > { |
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[404] | 231 | typedef Preflow<Digraph, CapacityMap, |
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[606] | 232 | SetFlowMapTraits<T> > Create; |
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[404] | 233 | }; |
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| 234 | |
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[606] | 235 | template <typename T> |
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[406] | 236 | struct SetElevatorTraits : public Traits { |
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[606] | 237 | typedef T Elevator; |
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[404] | 238 | static Elevator *createElevator(const Digraph&, int) { |
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[405] | 239 | LEMON_ASSERT(false, "Elevator is not initialized"); |
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| 240 | return 0; // ignore warnings |
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[404] | 241 | } |
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| 242 | }; |
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| 243 | |
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| 244 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 245 | /// Elevator type |
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| 246 | /// |
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| 247 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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[408] | 248 | /// type. If this named parameter is used, then an external |
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| 249 | /// elevator object must be passed to the algorithm using the |
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| 250 | /// \ref elevator(Elevator&) "elevator()" function before calling |
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| 251 | /// \ref run() or \ref init(). |
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| 252 | /// \sa SetStandardElevator |
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[606] | 253 | template <typename T> |
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[406] | 254 | struct SetElevator |
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[606] | 255 | : public Preflow<Digraph, CapacityMap, SetElevatorTraits<T> > { |
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[404] | 256 | typedef Preflow<Digraph, CapacityMap, |
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[606] | 257 | SetElevatorTraits<T> > Create; |
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[404] | 258 | }; |
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| 259 | |
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[606] | 260 | template <typename T> |
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[406] | 261 | struct SetStandardElevatorTraits : public Traits { |
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[606] | 262 | typedef T Elevator; |
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[404] | 263 | static Elevator *createElevator(const Digraph& digraph, int max_level) { |
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| 264 | return new Elevator(digraph, max_level); |
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| 265 | } |
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| 266 | }; |
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| 267 | |
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| 268 | /// \brief \ref named-templ-param "Named parameter" for setting |
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[408] | 269 | /// Elevator type with automatic allocation |
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[404] | 270 | /// |
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| 271 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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[408] | 272 | /// type with automatic allocation. |
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| 273 | /// The Elevator should have standard constructor interface to be |
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| 274 | /// able to automatically created by the algorithm (i.e. the |
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| 275 | /// digraph and the maximum level should be passed to it). |
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[833] | 276 | /// However, an external elevator object could also be passed to the |
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[408] | 277 | /// algorithm with the \ref elevator(Elevator&) "elevator()" function |
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| 278 | /// before calling \ref run() or \ref init(). |
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| 279 | /// \sa SetElevator |
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[606] | 280 | template <typename T> |
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[406] | 281 | struct SetStandardElevator |
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[404] | 282 | : public Preflow<Digraph, CapacityMap, |
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[606] | 283 | SetStandardElevatorTraits<T> > { |
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[404] | 284 | typedef Preflow<Digraph, CapacityMap, |
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[606] | 285 | SetStandardElevatorTraits<T> > Create; |
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[404] | 286 | }; |
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| 287 | |
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| 288 | /// @} |
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| 289 | |
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| 290 | protected: |
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| 291 | |
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| 292 | Preflow() {} |
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| 293 | |
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| 294 | public: |
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| 295 | |
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| 296 | |
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| 297 | /// \brief The constructor of the class. |
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| 298 | /// |
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| 299 | /// The constructor of the class. |
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| 300 | /// \param digraph The digraph the algorithm runs on. |
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| 301 | /// \param capacity The capacity of the arcs. |
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| 302 | /// \param source The source node. |
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| 303 | /// \param target The target node. |
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| 304 | Preflow(const Digraph& digraph, const CapacityMap& capacity, |
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[408] | 305 | Node source, Node target) |
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[404] | 306 | : _graph(digraph), _capacity(&capacity), |
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| 307 | _node_num(0), _source(source), _target(target), |
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| 308 | _flow(0), _local_flow(false), |
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| 309 | _level(0), _local_level(false), |
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| 310 | _excess(0), _tolerance(), _phase() {} |
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| 311 | |
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[408] | 312 | /// \brief Destructor. |
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[404] | 313 | /// |
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| 314 | /// Destructor. |
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| 315 | ~Preflow() { |
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| 316 | destroyStructures(); |
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| 317 | } |
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| 318 | |
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| 319 | /// \brief Sets the capacity map. |
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| 320 | /// |
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| 321 | /// Sets the capacity map. |
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[408] | 322 | /// \return <tt>(*this)</tt> |
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[404] | 323 | Preflow& capacityMap(const CapacityMap& map) { |
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| 324 | _capacity = ↦ |
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| 325 | return *this; |
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| 326 | } |
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| 327 | |
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| 328 | /// \brief Sets the flow map. |
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| 329 | /// |
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| 330 | /// Sets the flow map. |
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[408] | 331 | /// If you don't use this function before calling \ref run() or |
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| 332 | /// \ref init(), an instance will be allocated automatically. |
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| 333 | /// The destructor deallocates this automatically allocated map, |
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| 334 | /// of course. |
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| 335 | /// \return <tt>(*this)</tt> |
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[404] | 336 | Preflow& flowMap(FlowMap& map) { |
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| 337 | if (_local_flow) { |
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| 338 | delete _flow; |
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| 339 | _local_flow = false; |
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| 340 | } |
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| 341 | _flow = ↦ |
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| 342 | return *this; |
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| 343 | } |
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| 344 | |
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[408] | 345 | /// \brief Sets the source node. |
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[404] | 346 | /// |
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[408] | 347 | /// Sets the source node. |
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| 348 | /// \return <tt>(*this)</tt> |
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| 349 | Preflow& source(const Node& node) { |
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| 350 | _source = node; |
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| 351 | return *this; |
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[404] | 352 | } |
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| 353 | |
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[408] | 354 | /// \brief Sets the target node. |
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[404] | 355 | /// |
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[408] | 356 | /// Sets the target node. |
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| 357 | /// \return <tt>(*this)</tt> |
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| 358 | Preflow& target(const Node& node) { |
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| 359 | _target = node; |
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| 360 | return *this; |
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| 361 | } |
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| 362 | |
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| 363 | /// \brief Sets the elevator used by algorithm. |
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| 364 | /// |
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| 365 | /// Sets the elevator used by algorithm. |
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| 366 | /// If you don't use this function before calling \ref run() or |
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| 367 | /// \ref init(), an instance will be allocated automatically. |
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| 368 | /// The destructor deallocates this automatically allocated elevator, |
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| 369 | /// of course. |
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| 370 | /// \return <tt>(*this)</tt> |
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[404] | 371 | Preflow& elevator(Elevator& elevator) { |
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| 372 | if (_local_level) { |
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| 373 | delete _level; |
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| 374 | _local_level = false; |
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| 375 | } |
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| 376 | _level = &elevator; |
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| 377 | return *this; |
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| 378 | } |
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| 379 | |
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[408] | 380 | /// \brief Returns a const reference to the elevator. |
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[404] | 381 | /// |
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[408] | 382 | /// Returns a const reference to the elevator. |
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| 383 | /// |
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| 384 | /// \pre Either \ref run() or \ref init() must be called before |
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| 385 | /// using this function. |
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[437] | 386 | const Elevator& elevator() const { |
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[404] | 387 | return *_level; |
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| 388 | } |
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| 389 | |
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[736] | 390 | /// \brief Sets the tolerance used by the algorithm. |
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[404] | 391 | /// |
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[736] | 392 | /// Sets the tolerance object used by the algorithm. |
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| 393 | /// \return <tt>(*this)</tt> |
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[735] | 394 | Preflow& tolerance(const Tolerance& tolerance) { |
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[404] | 395 | _tolerance = tolerance; |
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| 396 | return *this; |
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| 397 | } |
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| 398 | |
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[408] | 399 | /// \brief Returns a const reference to the tolerance. |
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[404] | 400 | /// |
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[736] | 401 | /// Returns a const reference to the tolerance object used by |
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| 402 | /// the algorithm. |
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[404] | 403 | const Tolerance& tolerance() const { |
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[735] | 404 | return _tolerance; |
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[404] | 405 | } |
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| 406 | |
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[408] | 407 | /// \name Execution Control |
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| 408 | /// The simplest way to execute the preflow algorithm is to use |
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| 409 | /// \ref run() or \ref runMinCut().\n |
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[760] | 410 | /// If you need better control on the initial solution or the execution, |
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| 411 | /// you have to call one of the \ref init() functions first, then |
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[408] | 412 | /// \ref startFirstPhase() and if you need it \ref startSecondPhase(). |
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[404] | 413 | |
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| 414 | ///@{ |
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| 415 | |
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| 416 | /// \brief Initializes the internal data structures. |
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| 417 | /// |
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[408] | 418 | /// Initializes the internal data structures and sets the initial |
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| 419 | /// flow to zero on each arc. |
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[404] | 420 | void init() { |
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| 421 | createStructures(); |
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| 422 | |
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| 423 | _phase = true; |
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| 424 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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[628] | 425 | (*_excess)[n] = 0; |
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[404] | 426 | } |
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| 427 | |
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| 428 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 429 | _flow->set(e, 0); |
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| 430 | } |
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| 431 | |
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| 432 | typename Digraph::template NodeMap<bool> reached(_graph, false); |
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| 433 | |
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| 434 | _level->initStart(); |
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| 435 | _level->initAddItem(_target); |
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| 436 | |
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| 437 | std::vector<Node> queue; |
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[628] | 438 | reached[_source] = true; |
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[404] | 439 | |
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| 440 | queue.push_back(_target); |
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[628] | 441 | reached[_target] = true; |
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[404] | 442 | while (!queue.empty()) { |
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| 443 | _level->initNewLevel(); |
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| 444 | std::vector<Node> nqueue; |
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| 445 | for (int i = 0; i < int(queue.size()); ++i) { |
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| 446 | Node n = queue[i]; |
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| 447 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
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| 448 | Node u = _graph.source(e); |
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| 449 | if (!reached[u] && _tolerance.positive((*_capacity)[e])) { |
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[628] | 450 | reached[u] = true; |
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[404] | 451 | _level->initAddItem(u); |
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| 452 | nqueue.push_back(u); |
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| 453 | } |
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| 454 | } |
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| 455 | } |
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| 456 | queue.swap(nqueue); |
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| 457 | } |
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| 458 | _level->initFinish(); |
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| 459 | |
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| 460 | for (OutArcIt e(_graph, _source); e != INVALID; ++e) { |
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| 461 | if (_tolerance.positive((*_capacity)[e])) { |
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| 462 | Node u = _graph.target(e); |
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| 463 | if ((*_level)[u] == _level->maxLevel()) continue; |
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| 464 | _flow->set(e, (*_capacity)[e]); |
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[628] | 465 | (*_excess)[u] += (*_capacity)[e]; |
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[404] | 466 | if (u != _target && !_level->active(u)) { |
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| 467 | _level->activate(u); |
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| 468 | } |
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| 469 | } |
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| 470 | } |
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| 471 | } |
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| 472 | |
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[408] | 473 | /// \brief Initializes the internal data structures using the |
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| 474 | /// given flow map. |
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[404] | 475 | /// |
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| 476 | /// Initializes the internal data structures and sets the initial |
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| 477 | /// flow to the given \c flowMap. The \c flowMap should contain a |
---|
[408] | 478 | /// flow or at least a preflow, i.e. at each node excluding the |
---|
| 479 | /// source node the incoming flow should greater or equal to the |
---|
[404] | 480 | /// outgoing flow. |
---|
[408] | 481 | /// \return \c false if the given \c flowMap is not a preflow. |
---|
[404] | 482 | template <typename FlowMap> |
---|
[407] | 483 | bool init(const FlowMap& flowMap) { |
---|
[404] | 484 | createStructures(); |
---|
| 485 | |
---|
| 486 | for (ArcIt e(_graph); e != INVALID; ++e) { |
---|
| 487 | _flow->set(e, flowMap[e]); |
---|
| 488 | } |
---|
| 489 | |
---|
| 490 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
[688] | 491 | Value excess = 0; |
---|
[404] | 492 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 493 | excess += (*_flow)[e]; |
---|
| 494 | } |
---|
| 495 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 496 | excess -= (*_flow)[e]; |
---|
| 497 | } |
---|
| 498 | if (excess < 0 && n != _source) return false; |
---|
[628] | 499 | (*_excess)[n] = excess; |
---|
[404] | 500 | } |
---|
| 501 | |
---|
| 502 | typename Digraph::template NodeMap<bool> reached(_graph, false); |
---|
| 503 | |
---|
| 504 | _level->initStart(); |
---|
| 505 | _level->initAddItem(_target); |
---|
| 506 | |
---|
| 507 | std::vector<Node> queue; |
---|
[628] | 508 | reached[_source] = true; |
---|
[404] | 509 | |
---|
| 510 | queue.push_back(_target); |
---|
[628] | 511 | reached[_target] = true; |
---|
[404] | 512 | while (!queue.empty()) { |
---|
| 513 | _level->initNewLevel(); |
---|
| 514 | std::vector<Node> nqueue; |
---|
| 515 | for (int i = 0; i < int(queue.size()); ++i) { |
---|
| 516 | Node n = queue[i]; |
---|
| 517 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 518 | Node u = _graph.source(e); |
---|
| 519 | if (!reached[u] && |
---|
| 520 | _tolerance.positive((*_capacity)[e] - (*_flow)[e])) { |
---|
[628] | 521 | reached[u] = true; |
---|
[404] | 522 | _level->initAddItem(u); |
---|
| 523 | nqueue.push_back(u); |
---|
| 524 | } |
---|
| 525 | } |
---|
| 526 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 527 | Node v = _graph.target(e); |
---|
| 528 | if (!reached[v] && _tolerance.positive((*_flow)[e])) { |
---|
[628] | 529 | reached[v] = true; |
---|
[404] | 530 | _level->initAddItem(v); |
---|
| 531 | nqueue.push_back(v); |
---|
| 532 | } |
---|
| 533 | } |
---|
| 534 | } |
---|
| 535 | queue.swap(nqueue); |
---|
| 536 | } |
---|
| 537 | _level->initFinish(); |
---|
| 538 | |
---|
| 539 | for (OutArcIt e(_graph, _source); e != INVALID; ++e) { |
---|
[688] | 540 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[404] | 541 | if (_tolerance.positive(rem)) { |
---|
| 542 | Node u = _graph.target(e); |
---|
| 543 | if ((*_level)[u] == _level->maxLevel()) continue; |
---|
| 544 | _flow->set(e, (*_capacity)[e]); |
---|
[628] | 545 | (*_excess)[u] += rem; |
---|
[404] | 546 | } |
---|
| 547 | } |
---|
| 548 | for (InArcIt e(_graph, _source); e != INVALID; ++e) { |
---|
[688] | 549 | Value rem = (*_flow)[e]; |
---|
[404] | 550 | if (_tolerance.positive(rem)) { |
---|
| 551 | Node v = _graph.source(e); |
---|
| 552 | if ((*_level)[v] == _level->maxLevel()) continue; |
---|
| 553 | _flow->set(e, 0); |
---|
[628] | 554 | (*_excess)[v] += rem; |
---|
[404] | 555 | } |
---|
| 556 | } |
---|
[1084] | 557 | for (NodeIt n(_graph); n != INVALID; ++n) |
---|
[1027] | 558 | if(n!=_source && n!=_target && _tolerance.positive((*_excess)[n])) |
---|
| 559 | _level->activate(n); |
---|
[1084] | 560 | |
---|
[404] | 561 | return true; |
---|
| 562 | } |
---|
| 563 | |
---|
| 564 | /// \brief Starts the first phase of the preflow algorithm. |
---|
| 565 | /// |
---|
| 566 | /// The preflow algorithm consists of two phases, this method runs |
---|
| 567 | /// the first phase. After the first phase the maximum flow value |
---|
| 568 | /// and a minimum value cut can already be computed, although a |
---|
| 569 | /// maximum flow is not yet obtained. So after calling this method |
---|
| 570 | /// \ref flowValue() returns the value of a maximum flow and \ref |
---|
| 571 | /// minCut() returns a minimum cut. |
---|
[408] | 572 | /// \pre One of the \ref init() functions must be called before |
---|
| 573 | /// using this function. |
---|
[404] | 574 | void startFirstPhase() { |
---|
| 575 | _phase = true; |
---|
| 576 | |
---|
[982] | 577 | while (true) { |
---|
[404] | 578 | int num = _node_num; |
---|
| 579 | |
---|
[982] | 580 | Node n = INVALID; |
---|
| 581 | int level = -1; |
---|
| 582 | |
---|
| 583 | while (num > 0) { |
---|
| 584 | n = _level->highestActive(); |
---|
| 585 | if (n == INVALID) goto first_phase_done; |
---|
| 586 | level = _level->highestActiveLevel(); |
---|
| 587 | --num; |
---|
[1084] | 588 | |
---|
[688] | 589 | Value excess = (*_excess)[n]; |
---|
[404] | 590 | int new_level = _level->maxLevel(); |
---|
| 591 | |
---|
| 592 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[688] | 593 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[404] | 594 | if (!_tolerance.positive(rem)) continue; |
---|
| 595 | Node v = _graph.target(e); |
---|
| 596 | if ((*_level)[v] < level) { |
---|
| 597 | if (!_level->active(v) && v != _target) { |
---|
| 598 | _level->activate(v); |
---|
| 599 | } |
---|
| 600 | if (!_tolerance.less(rem, excess)) { |
---|
| 601 | _flow->set(e, (*_flow)[e] + excess); |
---|
[628] | 602 | (*_excess)[v] += excess; |
---|
[404] | 603 | excess = 0; |
---|
| 604 | goto no_more_push_1; |
---|
| 605 | } else { |
---|
| 606 | excess -= rem; |
---|
[628] | 607 | (*_excess)[v] += rem; |
---|
[404] | 608 | _flow->set(e, (*_capacity)[e]); |
---|
| 609 | } |
---|
| 610 | } else if (new_level > (*_level)[v]) { |
---|
| 611 | new_level = (*_level)[v]; |
---|
| 612 | } |
---|
| 613 | } |
---|
| 614 | |
---|
| 615 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[688] | 616 | Value rem = (*_flow)[e]; |
---|
[404] | 617 | if (!_tolerance.positive(rem)) continue; |
---|
| 618 | Node v = _graph.source(e); |
---|
| 619 | if ((*_level)[v] < level) { |
---|
| 620 | if (!_level->active(v) && v != _target) { |
---|
| 621 | _level->activate(v); |
---|
| 622 | } |
---|
| 623 | if (!_tolerance.less(rem, excess)) { |
---|
| 624 | _flow->set(e, (*_flow)[e] - excess); |
---|
[628] | 625 | (*_excess)[v] += excess; |
---|
[404] | 626 | excess = 0; |
---|
| 627 | goto no_more_push_1; |
---|
| 628 | } else { |
---|
| 629 | excess -= rem; |
---|
[628] | 630 | (*_excess)[v] += rem; |
---|
[404] | 631 | _flow->set(e, 0); |
---|
| 632 | } |
---|
| 633 | } else if (new_level > (*_level)[v]) { |
---|
| 634 | new_level = (*_level)[v]; |
---|
| 635 | } |
---|
| 636 | } |
---|
| 637 | |
---|
| 638 | no_more_push_1: |
---|
| 639 | |
---|
[628] | 640 | (*_excess)[n] = excess; |
---|
[404] | 641 | |
---|
| 642 | if (excess != 0) { |
---|
| 643 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 644 | _level->liftHighestActive(new_level + 1); |
---|
| 645 | } else { |
---|
| 646 | _level->liftHighestActiveToTop(); |
---|
| 647 | } |
---|
| 648 | if (_level->emptyLevel(level)) { |
---|
| 649 | _level->liftToTop(level); |
---|
| 650 | } |
---|
| 651 | } else { |
---|
| 652 | _level->deactivate(n); |
---|
| 653 | } |
---|
| 654 | } |
---|
| 655 | |
---|
| 656 | num = _node_num * 20; |
---|
[982] | 657 | while (num > 0) { |
---|
| 658 | while (level >= 0 && _level->activeFree(level)) { |
---|
| 659 | --level; |
---|
| 660 | } |
---|
| 661 | if (level == -1) { |
---|
| 662 | n = _level->highestActive(); |
---|
| 663 | level = _level->highestActiveLevel(); |
---|
| 664 | if (n == INVALID) goto first_phase_done; |
---|
| 665 | } else { |
---|
| 666 | n = _level->activeOn(level); |
---|
| 667 | } |
---|
| 668 | --num; |
---|
| 669 | |
---|
[688] | 670 | Value excess = (*_excess)[n]; |
---|
[404] | 671 | int new_level = _level->maxLevel(); |
---|
| 672 | |
---|
| 673 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[688] | 674 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[404] | 675 | if (!_tolerance.positive(rem)) continue; |
---|
| 676 | Node v = _graph.target(e); |
---|
| 677 | if ((*_level)[v] < level) { |
---|
| 678 | if (!_level->active(v) && v != _target) { |
---|
| 679 | _level->activate(v); |
---|
| 680 | } |
---|
| 681 | if (!_tolerance.less(rem, excess)) { |
---|
| 682 | _flow->set(e, (*_flow)[e] + excess); |
---|
[628] | 683 | (*_excess)[v] += excess; |
---|
[404] | 684 | excess = 0; |
---|
| 685 | goto no_more_push_2; |
---|
| 686 | } else { |
---|
| 687 | excess -= rem; |
---|
[628] | 688 | (*_excess)[v] += rem; |
---|
[404] | 689 | _flow->set(e, (*_capacity)[e]); |
---|
| 690 | } |
---|
| 691 | } else if (new_level > (*_level)[v]) { |
---|
| 692 | new_level = (*_level)[v]; |
---|
| 693 | } |
---|
| 694 | } |
---|
| 695 | |
---|
| 696 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[688] | 697 | Value rem = (*_flow)[e]; |
---|
[404] | 698 | if (!_tolerance.positive(rem)) continue; |
---|
| 699 | Node v = _graph.source(e); |
---|
| 700 | if ((*_level)[v] < level) { |
---|
| 701 | if (!_level->active(v) && v != _target) { |
---|
| 702 | _level->activate(v); |
---|
| 703 | } |
---|
| 704 | if (!_tolerance.less(rem, excess)) { |
---|
| 705 | _flow->set(e, (*_flow)[e] - excess); |
---|
[628] | 706 | (*_excess)[v] += excess; |
---|
[404] | 707 | excess = 0; |
---|
| 708 | goto no_more_push_2; |
---|
| 709 | } else { |
---|
| 710 | excess -= rem; |
---|
[628] | 711 | (*_excess)[v] += rem; |
---|
[404] | 712 | _flow->set(e, 0); |
---|
| 713 | } |
---|
| 714 | } else if (new_level > (*_level)[v]) { |
---|
| 715 | new_level = (*_level)[v]; |
---|
| 716 | } |
---|
| 717 | } |
---|
| 718 | |
---|
| 719 | no_more_push_2: |
---|
| 720 | |
---|
[628] | 721 | (*_excess)[n] = excess; |
---|
[404] | 722 | |
---|
| 723 | if (excess != 0) { |
---|
| 724 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 725 | _level->liftActiveOn(level, new_level + 1); |
---|
| 726 | } else { |
---|
| 727 | _level->liftActiveToTop(level); |
---|
| 728 | } |
---|
| 729 | if (_level->emptyLevel(level)) { |
---|
| 730 | _level->liftToTop(level); |
---|
| 731 | } |
---|
| 732 | } else { |
---|
| 733 | _level->deactivate(n); |
---|
| 734 | } |
---|
| 735 | } |
---|
| 736 | } |
---|
[982] | 737 | first_phase_done:; |
---|
[404] | 738 | } |
---|
| 739 | |
---|
| 740 | /// \brief Starts the second phase of the preflow algorithm. |
---|
| 741 | /// |
---|
| 742 | /// The preflow algorithm consists of two phases, this method runs |
---|
[408] | 743 | /// the second phase. After calling one of the \ref init() functions |
---|
| 744 | /// and \ref startFirstPhase() and then \ref startSecondPhase(), |
---|
| 745 | /// \ref flowMap() returns a maximum flow, \ref flowValue() returns the |
---|
[404] | 746 | /// value of a maximum flow, \ref minCut() returns a minimum cut |
---|
[408] | 747 | /// \pre One of the \ref init() functions and \ref startFirstPhase() |
---|
| 748 | /// must be called before using this function. |
---|
[404] | 749 | void startSecondPhase() { |
---|
| 750 | _phase = false; |
---|
| 751 | |
---|
| 752 | typename Digraph::template NodeMap<bool> reached(_graph); |
---|
| 753 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
[628] | 754 | reached[n] = (*_level)[n] < _level->maxLevel(); |
---|
[404] | 755 | } |
---|
| 756 | |
---|
| 757 | _level->initStart(); |
---|
| 758 | _level->initAddItem(_source); |
---|
| 759 | |
---|
| 760 | std::vector<Node> queue; |
---|
| 761 | queue.push_back(_source); |
---|
[628] | 762 | reached[_source] = true; |
---|
[404] | 763 | |
---|
| 764 | while (!queue.empty()) { |
---|
| 765 | _level->initNewLevel(); |
---|
| 766 | std::vector<Node> nqueue; |
---|
| 767 | for (int i = 0; i < int(queue.size()); ++i) { |
---|
| 768 | Node n = queue[i]; |
---|
| 769 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 770 | Node v = _graph.target(e); |
---|
| 771 | if (!reached[v] && _tolerance.positive((*_flow)[e])) { |
---|
[628] | 772 | reached[v] = true; |
---|
[404] | 773 | _level->initAddItem(v); |
---|
| 774 | nqueue.push_back(v); |
---|
| 775 | } |
---|
| 776 | } |
---|
| 777 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 778 | Node u = _graph.source(e); |
---|
| 779 | if (!reached[u] && |
---|
| 780 | _tolerance.positive((*_capacity)[e] - (*_flow)[e])) { |
---|
[628] | 781 | reached[u] = true; |
---|
[404] | 782 | _level->initAddItem(u); |
---|
| 783 | nqueue.push_back(u); |
---|
| 784 | } |
---|
| 785 | } |
---|
| 786 | } |
---|
| 787 | queue.swap(nqueue); |
---|
| 788 | } |
---|
| 789 | _level->initFinish(); |
---|
| 790 | |
---|
| 791 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
| 792 | if (!reached[n]) { |
---|
| 793 | _level->dirtyTopButOne(n); |
---|
| 794 | } else if ((*_excess)[n] > 0 && _target != n) { |
---|
| 795 | _level->activate(n); |
---|
| 796 | } |
---|
| 797 | } |
---|
| 798 | |
---|
| 799 | Node n; |
---|
| 800 | while ((n = _level->highestActive()) != INVALID) { |
---|
[688] | 801 | Value excess = (*_excess)[n]; |
---|
[404] | 802 | int level = _level->highestActiveLevel(); |
---|
| 803 | int new_level = _level->maxLevel(); |
---|
| 804 | |
---|
| 805 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[688] | 806 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[404] | 807 | if (!_tolerance.positive(rem)) continue; |
---|
| 808 | Node v = _graph.target(e); |
---|
| 809 | if ((*_level)[v] < level) { |
---|
| 810 | if (!_level->active(v) && v != _source) { |
---|
| 811 | _level->activate(v); |
---|
| 812 | } |
---|
| 813 | if (!_tolerance.less(rem, excess)) { |
---|
| 814 | _flow->set(e, (*_flow)[e] + excess); |
---|
[628] | 815 | (*_excess)[v] += excess; |
---|
[404] | 816 | excess = 0; |
---|
| 817 | goto no_more_push; |
---|
| 818 | } else { |
---|
| 819 | excess -= rem; |
---|
[628] | 820 | (*_excess)[v] += rem; |
---|
[404] | 821 | _flow->set(e, (*_capacity)[e]); |
---|
| 822 | } |
---|
| 823 | } else if (new_level > (*_level)[v]) { |
---|
| 824 | new_level = (*_level)[v]; |
---|
| 825 | } |
---|
| 826 | } |
---|
| 827 | |
---|
| 828 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[688] | 829 | Value rem = (*_flow)[e]; |
---|
[404] | 830 | if (!_tolerance.positive(rem)) continue; |
---|
| 831 | Node v = _graph.source(e); |
---|
| 832 | if ((*_level)[v] < level) { |
---|
| 833 | if (!_level->active(v) && v != _source) { |
---|
| 834 | _level->activate(v); |
---|
| 835 | } |
---|
| 836 | if (!_tolerance.less(rem, excess)) { |
---|
| 837 | _flow->set(e, (*_flow)[e] - excess); |
---|
[628] | 838 | (*_excess)[v] += excess; |
---|
[404] | 839 | excess = 0; |
---|
| 840 | goto no_more_push; |
---|
| 841 | } else { |
---|
| 842 | excess -= rem; |
---|
[628] | 843 | (*_excess)[v] += rem; |
---|
[404] | 844 | _flow->set(e, 0); |
---|
| 845 | } |
---|
| 846 | } else if (new_level > (*_level)[v]) { |
---|
| 847 | new_level = (*_level)[v]; |
---|
| 848 | } |
---|
| 849 | } |
---|
| 850 | |
---|
| 851 | no_more_push: |
---|
| 852 | |
---|
[628] | 853 | (*_excess)[n] = excess; |
---|
[404] | 854 | |
---|
| 855 | if (excess != 0) { |
---|
| 856 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 857 | _level->liftHighestActive(new_level + 1); |
---|
| 858 | } else { |
---|
| 859 | // Calculation error |
---|
| 860 | _level->liftHighestActiveToTop(); |
---|
| 861 | } |
---|
| 862 | if (_level->emptyLevel(level)) { |
---|
| 863 | // Calculation error |
---|
| 864 | _level->liftToTop(level); |
---|
| 865 | } |
---|
| 866 | } else { |
---|
| 867 | _level->deactivate(n); |
---|
| 868 | } |
---|
| 869 | |
---|
| 870 | } |
---|
| 871 | } |
---|
| 872 | |
---|
| 873 | /// \brief Runs the preflow algorithm. |
---|
| 874 | /// |
---|
| 875 | /// Runs the preflow algorithm. |
---|
| 876 | /// \note pf.run() is just a shortcut of the following code. |
---|
| 877 | /// \code |
---|
| 878 | /// pf.init(); |
---|
| 879 | /// pf.startFirstPhase(); |
---|
| 880 | /// pf.startSecondPhase(); |
---|
| 881 | /// \endcode |
---|
| 882 | void run() { |
---|
| 883 | init(); |
---|
| 884 | startFirstPhase(); |
---|
| 885 | startSecondPhase(); |
---|
| 886 | } |
---|
| 887 | |
---|
| 888 | /// \brief Runs the preflow algorithm to compute the minimum cut. |
---|
| 889 | /// |
---|
| 890 | /// Runs the preflow algorithm to compute the minimum cut. |
---|
| 891 | /// \note pf.runMinCut() is just a shortcut of the following code. |
---|
| 892 | /// \code |
---|
| 893 | /// pf.init(); |
---|
| 894 | /// pf.startFirstPhase(); |
---|
| 895 | /// \endcode |
---|
| 896 | void runMinCut() { |
---|
| 897 | init(); |
---|
| 898 | startFirstPhase(); |
---|
| 899 | } |
---|
| 900 | |
---|
| 901 | /// @} |
---|
| 902 | |
---|
| 903 | /// \name Query Functions |
---|
[408] | 904 | /// The results of the preflow algorithm can be obtained using these |
---|
[404] | 905 | /// functions.\n |
---|
[408] | 906 | /// Either one of the \ref run() "run*()" functions or one of the |
---|
| 907 | /// \ref startFirstPhase() "start*()" functions should be called |
---|
| 908 | /// before using them. |
---|
[404] | 909 | |
---|
| 910 | ///@{ |
---|
| 911 | |
---|
| 912 | /// \brief Returns the value of the maximum flow. |
---|
| 913 | /// |
---|
| 914 | /// Returns the value of the maximum flow by returning the excess |
---|
[408] | 915 | /// of the target node. This value equals to the value of |
---|
| 916 | /// the maximum flow already after the first phase of the algorithm. |
---|
| 917 | /// |
---|
| 918 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 919 | /// using this function. |
---|
[688] | 920 | Value flowValue() const { |
---|
[404] | 921 | return (*_excess)[_target]; |
---|
| 922 | } |
---|
| 923 | |
---|
[688] | 924 | /// \brief Returns the flow value on the given arc. |
---|
[404] | 925 | /// |
---|
[688] | 926 | /// Returns the flow value on the given arc. This method can |
---|
[408] | 927 | /// be called after the second phase of the algorithm. |
---|
| 928 | /// |
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| 929 | /// \pre Either \ref run() or \ref init() must be called before |
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| 930 | /// using this function. |
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[688] | 931 | Value flow(const Arc& arc) const { |
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[408] | 932 | return (*_flow)[arc]; |
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| 933 | } |
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| 934 | |
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| 935 | /// \brief Returns a const reference to the flow map. |
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| 936 | /// |
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| 937 | /// Returns a const reference to the arc map storing the found flow. |
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| 938 | /// This method can be called after the second phase of the algorithm. |
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| 939 | /// |
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| 940 | /// \pre Either \ref run() or \ref init() must be called before |
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| 941 | /// using this function. |
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[437] | 942 | const FlowMap& flowMap() const { |
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[408] | 943 | return *_flow; |
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| 944 | } |
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| 945 | |
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| 946 | /// \brief Returns \c true when the node is on the source side of the |
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| 947 | /// minimum cut. |
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| 948 | /// |
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| 949 | /// Returns true when the node is on the source side of the found |
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| 950 | /// minimum cut. This method can be called both after running \ref |
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[404] | 951 | /// startFirstPhase() and \ref startSecondPhase(). |
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[408] | 952 | /// |
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| 953 | /// \pre Either \ref run() or \ref init() must be called before |
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| 954 | /// using this function. |
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[404] | 955 | bool minCut(const Node& node) const { |
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| 956 | return ((*_level)[node] == _level->maxLevel()) == _phase; |
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| 957 | } |
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| 958 | |
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[408] | 959 | /// \brief Gives back a minimum value cut. |
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[404] | 960 | /// |
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[408] | 961 | /// Sets \c cutMap to the characteristic vector of a minimum value |
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| 962 | /// cut. \c cutMap should be a \ref concepts::WriteMap "writable" |
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| 963 | /// node map with \c bool (or convertible) value type. |
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| 964 | /// |
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| 965 | /// This method can be called both after running \ref startFirstPhase() |
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| 966 | /// and \ref startSecondPhase(). The result after the second phase |
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| 967 | /// could be slightly different if inexact computation is used. |
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| 968 | /// |
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| 969 | /// \note This function calls \ref minCut() for each node, so it runs in |
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[606] | 970 | /// O(n) time. |
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[408] | 971 | /// |
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| 972 | /// \pre Either \ref run() or \ref init() must be called before |
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| 973 | /// using this function. |
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[404] | 974 | template <typename CutMap> |
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| 975 | void minCutMap(CutMap& cutMap) const { |
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| 976 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 977 | cutMap.set(n, minCut(n)); |
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| 978 | } |
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| 979 | } |
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| 980 | |
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| 981 | /// @} |
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| 982 | }; |
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| 983 | } |
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| 984 | |
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| 985 | #endif |
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