[389] | 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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[440] | 5 | * Copyright (C) 2003-2009 |
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[389] | 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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[503] | 34 | /// \tparam GR Digraph type. |
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[559] | 35 | /// \tparam CAP Capacity map type. |
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| 36 | template <typename GR, typename CAP> |
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[389] | 37 | struct PreflowDefaultTraits { |
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| 38 | |
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[393] | 39 | /// \brief The type of the digraph the algorithm runs on. |
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[503] | 40 | typedef GR Digraph; |
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[389] | 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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[559] | 46 | typedef CAP CapacityMap; |
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[389] | 47 | |
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[393] | 48 | /// \brief The type of the flow values. |
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[641] | 49 | typedef typename CapacityMap::Value Value; |
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[389] | 50 | |
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[393] | 51 | /// \brief The type of the map that stores the flow values. |
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[389] | 52 | /// |
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[393] | 53 | /// The type of the map that stores the flow values. |
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[389] | 54 | /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
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[713] | 55 | #ifdef DOXYGEN |
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| 56 | typedef GR::ArcMap<Value> FlowMap; |
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| 57 | #else |
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[641] | 58 | typedef typename Digraph::template ArcMap<Value> FlowMap; |
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[713] | 59 | #endif |
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[389] | 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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[610] | 64 | /// \param digraph The digraph for which we would like to define |
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[389] | 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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[393] | 70 | /// \brief The elevator type used by Preflow algorithm. |
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[389] | 71 | /// |
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| 72 | /// The elevator type used by Preflow algorithm. |
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| 73 | /// |
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[713] | 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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[389] | 80 | |
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| 81 | /// \brief Instantiates an Elevator. |
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| 82 | /// |
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[393] | 83 | /// This function instantiates an \ref Elevator. |
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[610] | 84 | /// \param digraph The digraph for which we would like to define |
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[389] | 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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[641] | 94 | typedef lemon::Tolerance<Value> Tolerance; |
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[389] | 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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[393] | 101 | /// \brief %Preflow algorithm class. |
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[389] | 102 | /// |
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[393] | 103 | /// This class provides an implementation of Goldberg-Tarjan's \e preflow |
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[559] | 104 | /// \e push-relabel algorithm producing a \ref max_flow |
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| 105 | /// "flow of maximum value" in a digraph. |
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| 106 | /// The preflow algorithms are the fastest known maximum |
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[689] | 107 | /// flow algorithms. The current implementation uses a mixture of the |
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[389] | 108 | /// \e "highest label" and the \e "bound decrease" heuristics. |
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| 109 | /// The worst case time complexity of the algorithm is \f$O(n^2\sqrt{e})\f$. |
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| 110 | /// |
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[393] | 111 | /// The algorithm consists of two phases. After the first phase |
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| 112 | /// the maximum flow value and the minimum cut is obtained. The |
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| 113 | /// second phase constructs a feasible maximum flow on each arc. |
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[389] | 114 | /// |
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[503] | 115 | /// \tparam GR The type of the digraph the algorithm runs on. |
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[559] | 116 | /// \tparam CAP The type of the capacity map. The default map |
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[503] | 117 | /// type is \ref concepts::Digraph::ArcMap "GR::ArcMap<int>". |
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[389] | 118 | #ifdef DOXYGEN |
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[559] | 119 | template <typename GR, typename CAP, typename TR> |
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[389] | 120 | #else |
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[503] | 121 | template <typename GR, |
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[559] | 122 | typename CAP = typename GR::template ArcMap<int>, |
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| 123 | typename TR = PreflowDefaultTraits<GR, CAP> > |
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[389] | 124 | #endif |
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| 125 | class Preflow { |
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| 126 | public: |
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| 127 | |
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[393] | 128 | ///The \ref PreflowDefaultTraits "traits class" of the algorithm. |
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[503] | 129 | typedef TR Traits; |
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[393] | 130 | ///The type of the digraph the algorithm runs on. |
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[389] | 131 | typedef typename Traits::Digraph Digraph; |
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[393] | 132 | ///The type of the capacity map. |
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[389] | 133 | typedef typename Traits::CapacityMap CapacityMap; |
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[393] | 134 | ///The type of the flow values. |
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[641] | 135 | typedef typename Traits::Value Value; |
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[389] | 136 | |
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[393] | 137 | ///The type of the flow map. |
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[389] | 138 | typedef typename Traits::FlowMap FlowMap; |
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[393] | 139 | ///The type of the elevator. |
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[389] | 140 | typedef typename Traits::Elevator Elevator; |
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[393] | 141 | ///The type of the tolerance. |
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[389] | 142 | typedef typename Traits::Tolerance Tolerance; |
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| 143 | |
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| 144 | private: |
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| 145 | |
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| 146 | TEMPLATE_DIGRAPH_TYPEDEFS(Digraph); |
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| 147 | |
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| 148 | const Digraph& _graph; |
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| 149 | const CapacityMap* _capacity; |
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| 150 | |
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| 151 | int _node_num; |
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| 152 | |
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| 153 | Node _source, _target; |
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| 154 | |
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| 155 | FlowMap* _flow; |
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| 156 | bool _local_flow; |
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| 157 | |
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| 158 | Elevator* _level; |
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| 159 | bool _local_level; |
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| 160 | |
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[641] | 161 | typedef typename Digraph::template NodeMap<Value> ExcessMap; |
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[389] | 162 | ExcessMap* _excess; |
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| 163 | |
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| 164 | Tolerance _tolerance; |
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| 165 | |
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| 166 | bool _phase; |
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| 167 | |
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| 168 | |
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| 169 | void createStructures() { |
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| 170 | _node_num = countNodes(_graph); |
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| 171 | |
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| 172 | if (!_flow) { |
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| 173 | _flow = Traits::createFlowMap(_graph); |
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| 174 | _local_flow = true; |
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| 175 | } |
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| 176 | if (!_level) { |
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| 177 | _level = Traits::createElevator(_graph, _node_num); |
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| 178 | _local_level = true; |
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| 179 | } |
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| 180 | if (!_excess) { |
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| 181 | _excess = new ExcessMap(_graph); |
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| 182 | } |
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| 183 | } |
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| 184 | |
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| 185 | void destroyStructures() { |
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| 186 | if (_local_flow) { |
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| 187 | delete _flow; |
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| 188 | } |
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| 189 | if (_local_level) { |
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| 190 | delete _level; |
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| 191 | } |
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| 192 | if (_excess) { |
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| 193 | delete _excess; |
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| 194 | } |
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| 195 | } |
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| 196 | |
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| 197 | public: |
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| 198 | |
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| 199 | typedef Preflow Create; |
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| 200 | |
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[393] | 201 | ///\name Named Template Parameters |
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[389] | 202 | |
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| 203 | ///@{ |
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| 204 | |
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[559] | 205 | template <typename T> |
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[391] | 206 | struct SetFlowMapTraits : public Traits { |
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[559] | 207 | typedef T FlowMap; |
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[389] | 208 | static FlowMap *createFlowMap(const Digraph&) { |
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[390] | 209 | LEMON_ASSERT(false, "FlowMap is not initialized"); |
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| 210 | return 0; // ignore warnings |
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[389] | 211 | } |
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| 212 | }; |
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| 213 | |
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| 214 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 215 | /// FlowMap type |
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| 216 | /// |
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| 217 | /// \ref named-templ-param "Named parameter" for setting FlowMap |
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[393] | 218 | /// type. |
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[559] | 219 | template <typename T> |
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[391] | 220 | struct SetFlowMap |
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[559] | 221 | : public Preflow<Digraph, CapacityMap, SetFlowMapTraits<T> > { |
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[389] | 222 | typedef Preflow<Digraph, CapacityMap, |
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[559] | 223 | SetFlowMapTraits<T> > Create; |
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[389] | 224 | }; |
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| 225 | |
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[559] | 226 | template <typename T> |
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[391] | 227 | struct SetElevatorTraits : public Traits { |
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[559] | 228 | typedef T Elevator; |
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[389] | 229 | static Elevator *createElevator(const Digraph&, int) { |
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[390] | 230 | LEMON_ASSERT(false, "Elevator is not initialized"); |
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| 231 | return 0; // ignore warnings |
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[389] | 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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[393] | 239 | /// type. If this named parameter is used, then an external |
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| 240 | /// elevator object must be passed to the algorithm using the |
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| 241 | /// \ref elevator(Elevator&) "elevator()" function before calling |
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| 242 | /// \ref run() or \ref init(). |
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| 243 | /// \sa SetStandardElevator |
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[559] | 244 | template <typename T> |
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[391] | 245 | struct SetElevator |
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[559] | 246 | : public Preflow<Digraph, CapacityMap, SetElevatorTraits<T> > { |
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[389] | 247 | typedef Preflow<Digraph, CapacityMap, |
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[559] | 248 | SetElevatorTraits<T> > Create; |
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[389] | 249 | }; |
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| 250 | |
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[559] | 251 | template <typename T> |
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[391] | 252 | struct SetStandardElevatorTraits : public Traits { |
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[559] | 253 | typedef T Elevator; |
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[389] | 254 | static Elevator *createElevator(const Digraph& digraph, int max_level) { |
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| 255 | return new Elevator(digraph, max_level); |
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| 256 | } |
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| 257 | }; |
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| 258 | |
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| 259 | /// \brief \ref named-templ-param "Named parameter" for setting |
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[393] | 260 | /// Elevator type with automatic allocation |
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[389] | 261 | /// |
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| 262 | /// \ref named-templ-param "Named parameter" for setting Elevator |
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[393] | 263 | /// type with automatic allocation. |
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| 264 | /// The Elevator should have standard constructor interface to be |
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| 265 | /// able to automatically created by the algorithm (i.e. the |
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| 266 | /// digraph and the maximum level should be passed to it). |
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[786] | 267 | /// However, an external elevator object could also be passed to the |
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[393] | 268 | /// algorithm with the \ref elevator(Elevator&) "elevator()" function |
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| 269 | /// before calling \ref run() or \ref init(). |
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| 270 | /// \sa SetElevator |
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[559] | 271 | template <typename T> |
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[391] | 272 | struct SetStandardElevator |
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[389] | 273 | : public Preflow<Digraph, CapacityMap, |
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[559] | 274 | SetStandardElevatorTraits<T> > { |
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[389] | 275 | typedef Preflow<Digraph, CapacityMap, |
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[559] | 276 | SetStandardElevatorTraits<T> > Create; |
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[389] | 277 | }; |
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| 278 | |
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| 279 | /// @} |
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| 280 | |
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| 281 | protected: |
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| 282 | |
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| 283 | Preflow() {} |
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| 284 | |
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| 285 | public: |
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| 286 | |
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| 287 | |
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| 288 | /// \brief The constructor of the class. |
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| 289 | /// |
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| 290 | /// The constructor of the class. |
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| 291 | /// \param digraph The digraph the algorithm runs on. |
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| 292 | /// \param capacity The capacity of the arcs. |
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| 293 | /// \param source The source node. |
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| 294 | /// \param target The target node. |
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| 295 | Preflow(const Digraph& digraph, const CapacityMap& capacity, |
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[393] | 296 | Node source, Node target) |
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[389] | 297 | : _graph(digraph), _capacity(&capacity), |
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| 298 | _node_num(0), _source(source), _target(target), |
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| 299 | _flow(0), _local_flow(false), |
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| 300 | _level(0), _local_level(false), |
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| 301 | _excess(0), _tolerance(), _phase() {} |
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| 302 | |
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[393] | 303 | /// \brief Destructor. |
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[389] | 304 | /// |
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| 305 | /// Destructor. |
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| 306 | ~Preflow() { |
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| 307 | destroyStructures(); |
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| 308 | } |
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| 309 | |
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| 310 | /// \brief Sets the capacity map. |
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| 311 | /// |
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| 312 | /// Sets the capacity map. |
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[393] | 313 | /// \return <tt>(*this)</tt> |
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[389] | 314 | Preflow& capacityMap(const CapacityMap& map) { |
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| 315 | _capacity = ↦ |
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| 316 | return *this; |
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| 317 | } |
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| 318 | |
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| 319 | /// \brief Sets the flow map. |
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| 320 | /// |
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| 321 | /// Sets the flow map. |
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[393] | 322 | /// If you don't use this function before calling \ref run() or |
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| 323 | /// \ref init(), an instance will be allocated automatically. |
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| 324 | /// The destructor deallocates this automatically allocated map, |
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| 325 | /// of course. |
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| 326 | /// \return <tt>(*this)</tt> |
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[389] | 327 | Preflow& flowMap(FlowMap& map) { |
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| 328 | if (_local_flow) { |
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| 329 | delete _flow; |
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| 330 | _local_flow = false; |
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| 331 | } |
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| 332 | _flow = ↦ |
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| 333 | return *this; |
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| 334 | } |
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| 335 | |
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[393] | 336 | /// \brief Sets the source node. |
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[389] | 337 | /// |
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[393] | 338 | /// Sets the source node. |
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| 339 | /// \return <tt>(*this)</tt> |
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| 340 | Preflow& source(const Node& node) { |
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| 341 | _source = node; |
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| 342 | return *this; |
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[389] | 343 | } |
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| 344 | |
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[393] | 345 | /// \brief Sets the target node. |
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[389] | 346 | /// |
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[393] | 347 | /// Sets the target node. |
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| 348 | /// \return <tt>(*this)</tt> |
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| 349 | Preflow& target(const Node& node) { |
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| 350 | _target = node; |
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| 351 | return *this; |
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| 352 | } |
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| 353 | |
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| 354 | /// \brief Sets the elevator used by algorithm. |
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| 355 | /// |
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| 356 | /// Sets the elevator used by algorithm. |
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| 357 | /// If you don't use this function before calling \ref run() or |
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| 358 | /// \ref init(), an instance will be allocated automatically. |
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| 359 | /// The destructor deallocates this automatically allocated elevator, |
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| 360 | /// of course. |
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| 361 | /// \return <tt>(*this)</tt> |
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[389] | 362 | Preflow& elevator(Elevator& elevator) { |
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| 363 | if (_local_level) { |
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| 364 | delete _level; |
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| 365 | _local_level = false; |
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| 366 | } |
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| 367 | _level = &elevator; |
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| 368 | return *this; |
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| 369 | } |
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| 370 | |
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[393] | 371 | /// \brief Returns a const reference to the elevator. |
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[389] | 372 | /// |
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[393] | 373 | /// Returns a const reference to the elevator. |
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| 374 | /// |
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| 375 | /// \pre Either \ref run() or \ref init() must be called before |
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| 376 | /// using this function. |
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[420] | 377 | const Elevator& elevator() const { |
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[389] | 378 | return *_level; |
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| 379 | } |
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| 380 | |
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[689] | 381 | /// \brief Sets the tolerance used by the algorithm. |
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[389] | 382 | /// |
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[689] | 383 | /// Sets the tolerance object used by the algorithm. |
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| 384 | /// \return <tt>(*this)</tt> |
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[688] | 385 | Preflow& tolerance(const Tolerance& tolerance) { |
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[389] | 386 | _tolerance = tolerance; |
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| 387 | return *this; |
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| 388 | } |
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| 389 | |
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[393] | 390 | /// \brief Returns a const reference to the tolerance. |
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[389] | 391 | /// |
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[689] | 392 | /// Returns a const reference to the tolerance object used by |
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| 393 | /// the algorithm. |
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[389] | 394 | const Tolerance& tolerance() const { |
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[688] | 395 | return _tolerance; |
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[389] | 396 | } |
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| 397 | |
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[393] | 398 | /// \name Execution Control |
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| 399 | /// The simplest way to execute the preflow algorithm is to use |
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| 400 | /// \ref run() or \ref runMinCut().\n |
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[713] | 401 | /// If you need better control on the initial solution or the execution, |
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| 402 | /// you have to call one of the \ref init() functions first, then |
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[393] | 403 | /// \ref startFirstPhase() and if you need it \ref startSecondPhase(). |
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[389] | 404 | |
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| 405 | ///@{ |
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| 406 | |
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| 407 | /// \brief Initializes the internal data structures. |
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| 408 | /// |
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[393] | 409 | /// Initializes the internal data structures and sets the initial |
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| 410 | /// flow to zero on each arc. |
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[389] | 411 | void init() { |
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| 412 | createStructures(); |
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| 413 | |
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| 414 | _phase = true; |
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| 415 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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[581] | 416 | (*_excess)[n] = 0; |
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[389] | 417 | } |
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| 418 | |
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| 419 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 420 | _flow->set(e, 0); |
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| 421 | } |
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| 422 | |
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| 423 | typename Digraph::template NodeMap<bool> reached(_graph, false); |
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| 424 | |
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| 425 | _level->initStart(); |
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| 426 | _level->initAddItem(_target); |
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| 427 | |
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| 428 | std::vector<Node> queue; |
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[581] | 429 | reached[_source] = true; |
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[389] | 430 | |
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| 431 | queue.push_back(_target); |
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[581] | 432 | reached[_target] = true; |
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[389] | 433 | while (!queue.empty()) { |
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| 434 | _level->initNewLevel(); |
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| 435 | std::vector<Node> nqueue; |
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| 436 | for (int i = 0; i < int(queue.size()); ++i) { |
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| 437 | Node n = queue[i]; |
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| 438 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
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| 439 | Node u = _graph.source(e); |
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| 440 | if (!reached[u] && _tolerance.positive((*_capacity)[e])) { |
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[581] | 441 | reached[u] = true; |
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[389] | 442 | _level->initAddItem(u); |
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| 443 | nqueue.push_back(u); |
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| 444 | } |
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| 445 | } |
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| 446 | } |
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| 447 | queue.swap(nqueue); |
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| 448 | } |
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| 449 | _level->initFinish(); |
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| 450 | |
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| 451 | for (OutArcIt e(_graph, _source); e != INVALID; ++e) { |
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| 452 | if (_tolerance.positive((*_capacity)[e])) { |
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| 453 | Node u = _graph.target(e); |
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| 454 | if ((*_level)[u] == _level->maxLevel()) continue; |
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| 455 | _flow->set(e, (*_capacity)[e]); |
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[581] | 456 | (*_excess)[u] += (*_capacity)[e]; |
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[389] | 457 | if (u != _target && !_level->active(u)) { |
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| 458 | _level->activate(u); |
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| 459 | } |
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| 460 | } |
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| 461 | } |
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| 462 | } |
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| 463 | |
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[393] | 464 | /// \brief Initializes the internal data structures using the |
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| 465 | /// given flow map. |
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[389] | 466 | /// |
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| 467 | /// Initializes the internal data structures and sets the initial |
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| 468 | /// flow to the given \c flowMap. The \c flowMap should contain a |
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[393] | 469 | /// flow or at least a preflow, i.e. at each node excluding the |
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| 470 | /// source node the incoming flow should greater or equal to the |
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[389] | 471 | /// outgoing flow. |
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[393] | 472 | /// \return \c false if the given \c flowMap is not a preflow. |
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[389] | 473 | template <typename FlowMap> |
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[392] | 474 | bool init(const FlowMap& flowMap) { |
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[389] | 475 | createStructures(); |
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| 476 | |
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| 477 | for (ArcIt e(_graph); e != INVALID; ++e) { |
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| 478 | _flow->set(e, flowMap[e]); |
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| 479 | } |
---|
| 480 | |
---|
| 481 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
[641] | 482 | Value excess = 0; |
---|
[389] | 483 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 484 | excess += (*_flow)[e]; |
---|
| 485 | } |
---|
| 486 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 487 | excess -= (*_flow)[e]; |
---|
| 488 | } |
---|
| 489 | if (excess < 0 && n != _source) return false; |
---|
[581] | 490 | (*_excess)[n] = excess; |
---|
[389] | 491 | } |
---|
| 492 | |
---|
| 493 | typename Digraph::template NodeMap<bool> reached(_graph, false); |
---|
| 494 | |
---|
| 495 | _level->initStart(); |
---|
| 496 | _level->initAddItem(_target); |
---|
| 497 | |
---|
| 498 | std::vector<Node> queue; |
---|
[581] | 499 | reached[_source] = true; |
---|
[389] | 500 | |
---|
| 501 | queue.push_back(_target); |
---|
[581] | 502 | reached[_target] = true; |
---|
[389] | 503 | while (!queue.empty()) { |
---|
| 504 | _level->initNewLevel(); |
---|
| 505 | std::vector<Node> nqueue; |
---|
| 506 | for (int i = 0; i < int(queue.size()); ++i) { |
---|
| 507 | Node n = queue[i]; |
---|
| 508 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 509 | Node u = _graph.source(e); |
---|
| 510 | if (!reached[u] && |
---|
| 511 | _tolerance.positive((*_capacity)[e] - (*_flow)[e])) { |
---|
[581] | 512 | reached[u] = true; |
---|
[389] | 513 | _level->initAddItem(u); |
---|
| 514 | nqueue.push_back(u); |
---|
| 515 | } |
---|
| 516 | } |
---|
| 517 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 518 | Node v = _graph.target(e); |
---|
| 519 | if (!reached[v] && _tolerance.positive((*_flow)[e])) { |
---|
[581] | 520 | reached[v] = true; |
---|
[389] | 521 | _level->initAddItem(v); |
---|
| 522 | nqueue.push_back(v); |
---|
| 523 | } |
---|
| 524 | } |
---|
| 525 | } |
---|
| 526 | queue.swap(nqueue); |
---|
| 527 | } |
---|
| 528 | _level->initFinish(); |
---|
| 529 | |
---|
| 530 | for (OutArcIt e(_graph, _source); e != INVALID; ++e) { |
---|
[641] | 531 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[389] | 532 | if (_tolerance.positive(rem)) { |
---|
| 533 | Node u = _graph.target(e); |
---|
| 534 | if ((*_level)[u] == _level->maxLevel()) continue; |
---|
| 535 | _flow->set(e, (*_capacity)[e]); |
---|
[581] | 536 | (*_excess)[u] += rem; |
---|
[389] | 537 | if (u != _target && !_level->active(u)) { |
---|
| 538 | _level->activate(u); |
---|
| 539 | } |
---|
| 540 | } |
---|
| 541 | } |
---|
| 542 | for (InArcIt e(_graph, _source); e != INVALID; ++e) { |
---|
[641] | 543 | Value rem = (*_flow)[e]; |
---|
[389] | 544 | if (_tolerance.positive(rem)) { |
---|
| 545 | Node v = _graph.source(e); |
---|
| 546 | if ((*_level)[v] == _level->maxLevel()) continue; |
---|
| 547 | _flow->set(e, 0); |
---|
[581] | 548 | (*_excess)[v] += rem; |
---|
[389] | 549 | if (v != _target && !_level->active(v)) { |
---|
| 550 | _level->activate(v); |
---|
| 551 | } |
---|
| 552 | } |
---|
| 553 | } |
---|
| 554 | return true; |
---|
| 555 | } |
---|
| 556 | |
---|
| 557 | /// \brief Starts the first phase of the preflow algorithm. |
---|
| 558 | /// |
---|
| 559 | /// The preflow algorithm consists of two phases, this method runs |
---|
| 560 | /// the first phase. After the first phase the maximum flow value |
---|
| 561 | /// and a minimum value cut can already be computed, although a |
---|
| 562 | /// maximum flow is not yet obtained. So after calling this method |
---|
| 563 | /// \ref flowValue() returns the value of a maximum flow and \ref |
---|
| 564 | /// minCut() returns a minimum cut. |
---|
[393] | 565 | /// \pre One of the \ref init() functions must be called before |
---|
| 566 | /// using this function. |
---|
[389] | 567 | void startFirstPhase() { |
---|
| 568 | _phase = true; |
---|
| 569 | |
---|
| 570 | Node n = _level->highestActive(); |
---|
| 571 | int level = _level->highestActiveLevel(); |
---|
| 572 | while (n != INVALID) { |
---|
| 573 | int num = _node_num; |
---|
| 574 | |
---|
| 575 | while (num > 0 && n != INVALID) { |
---|
[641] | 576 | Value excess = (*_excess)[n]; |
---|
[389] | 577 | int new_level = _level->maxLevel(); |
---|
| 578 | |
---|
| 579 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[641] | 580 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[389] | 581 | if (!_tolerance.positive(rem)) continue; |
---|
| 582 | Node v = _graph.target(e); |
---|
| 583 | if ((*_level)[v] < level) { |
---|
| 584 | if (!_level->active(v) && v != _target) { |
---|
| 585 | _level->activate(v); |
---|
| 586 | } |
---|
| 587 | if (!_tolerance.less(rem, excess)) { |
---|
| 588 | _flow->set(e, (*_flow)[e] + excess); |
---|
[581] | 589 | (*_excess)[v] += excess; |
---|
[389] | 590 | excess = 0; |
---|
| 591 | goto no_more_push_1; |
---|
| 592 | } else { |
---|
| 593 | excess -= rem; |
---|
[581] | 594 | (*_excess)[v] += rem; |
---|
[389] | 595 | _flow->set(e, (*_capacity)[e]); |
---|
| 596 | } |
---|
| 597 | } else if (new_level > (*_level)[v]) { |
---|
| 598 | new_level = (*_level)[v]; |
---|
| 599 | } |
---|
| 600 | } |
---|
| 601 | |
---|
| 602 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[641] | 603 | Value rem = (*_flow)[e]; |
---|
[389] | 604 | if (!_tolerance.positive(rem)) continue; |
---|
| 605 | Node v = _graph.source(e); |
---|
| 606 | if ((*_level)[v] < level) { |
---|
| 607 | if (!_level->active(v) && v != _target) { |
---|
| 608 | _level->activate(v); |
---|
| 609 | } |
---|
| 610 | if (!_tolerance.less(rem, excess)) { |
---|
| 611 | _flow->set(e, (*_flow)[e] - excess); |
---|
[581] | 612 | (*_excess)[v] += excess; |
---|
[389] | 613 | excess = 0; |
---|
| 614 | goto no_more_push_1; |
---|
| 615 | } else { |
---|
| 616 | excess -= rem; |
---|
[581] | 617 | (*_excess)[v] += rem; |
---|
[389] | 618 | _flow->set(e, 0); |
---|
| 619 | } |
---|
| 620 | } else if (new_level > (*_level)[v]) { |
---|
| 621 | new_level = (*_level)[v]; |
---|
| 622 | } |
---|
| 623 | } |
---|
| 624 | |
---|
| 625 | no_more_push_1: |
---|
| 626 | |
---|
[581] | 627 | (*_excess)[n] = excess; |
---|
[389] | 628 | |
---|
| 629 | if (excess != 0) { |
---|
| 630 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 631 | _level->liftHighestActive(new_level + 1); |
---|
| 632 | } else { |
---|
| 633 | _level->liftHighestActiveToTop(); |
---|
| 634 | } |
---|
| 635 | if (_level->emptyLevel(level)) { |
---|
| 636 | _level->liftToTop(level); |
---|
| 637 | } |
---|
| 638 | } else { |
---|
| 639 | _level->deactivate(n); |
---|
| 640 | } |
---|
| 641 | |
---|
| 642 | n = _level->highestActive(); |
---|
| 643 | level = _level->highestActiveLevel(); |
---|
| 644 | --num; |
---|
| 645 | } |
---|
| 646 | |
---|
| 647 | num = _node_num * 20; |
---|
| 648 | while (num > 0 && n != INVALID) { |
---|
[641] | 649 | Value excess = (*_excess)[n]; |
---|
[389] | 650 | int new_level = _level->maxLevel(); |
---|
| 651 | |
---|
| 652 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[641] | 653 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[389] | 654 | if (!_tolerance.positive(rem)) continue; |
---|
| 655 | Node v = _graph.target(e); |
---|
| 656 | if ((*_level)[v] < level) { |
---|
| 657 | if (!_level->active(v) && v != _target) { |
---|
| 658 | _level->activate(v); |
---|
| 659 | } |
---|
| 660 | if (!_tolerance.less(rem, excess)) { |
---|
| 661 | _flow->set(e, (*_flow)[e] + excess); |
---|
[581] | 662 | (*_excess)[v] += excess; |
---|
[389] | 663 | excess = 0; |
---|
| 664 | goto no_more_push_2; |
---|
| 665 | } else { |
---|
| 666 | excess -= rem; |
---|
[581] | 667 | (*_excess)[v] += rem; |
---|
[389] | 668 | _flow->set(e, (*_capacity)[e]); |
---|
| 669 | } |
---|
| 670 | } else if (new_level > (*_level)[v]) { |
---|
| 671 | new_level = (*_level)[v]; |
---|
| 672 | } |
---|
| 673 | } |
---|
| 674 | |
---|
| 675 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[641] | 676 | Value rem = (*_flow)[e]; |
---|
[389] | 677 | if (!_tolerance.positive(rem)) continue; |
---|
| 678 | Node v = _graph.source(e); |
---|
| 679 | if ((*_level)[v] < level) { |
---|
| 680 | if (!_level->active(v) && v != _target) { |
---|
| 681 | _level->activate(v); |
---|
| 682 | } |
---|
| 683 | if (!_tolerance.less(rem, excess)) { |
---|
| 684 | _flow->set(e, (*_flow)[e] - excess); |
---|
[581] | 685 | (*_excess)[v] += excess; |
---|
[389] | 686 | excess = 0; |
---|
| 687 | goto no_more_push_2; |
---|
| 688 | } else { |
---|
| 689 | excess -= rem; |
---|
[581] | 690 | (*_excess)[v] += rem; |
---|
[389] | 691 | _flow->set(e, 0); |
---|
| 692 | } |
---|
| 693 | } else if (new_level > (*_level)[v]) { |
---|
| 694 | new_level = (*_level)[v]; |
---|
| 695 | } |
---|
| 696 | } |
---|
| 697 | |
---|
| 698 | no_more_push_2: |
---|
| 699 | |
---|
[581] | 700 | (*_excess)[n] = excess; |
---|
[389] | 701 | |
---|
| 702 | if (excess != 0) { |
---|
| 703 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 704 | _level->liftActiveOn(level, new_level + 1); |
---|
| 705 | } else { |
---|
| 706 | _level->liftActiveToTop(level); |
---|
| 707 | } |
---|
| 708 | if (_level->emptyLevel(level)) { |
---|
| 709 | _level->liftToTop(level); |
---|
| 710 | } |
---|
| 711 | } else { |
---|
| 712 | _level->deactivate(n); |
---|
| 713 | } |
---|
| 714 | |
---|
| 715 | while (level >= 0 && _level->activeFree(level)) { |
---|
| 716 | --level; |
---|
| 717 | } |
---|
| 718 | if (level == -1) { |
---|
| 719 | n = _level->highestActive(); |
---|
| 720 | level = _level->highestActiveLevel(); |
---|
| 721 | } else { |
---|
| 722 | n = _level->activeOn(level); |
---|
| 723 | } |
---|
| 724 | --num; |
---|
| 725 | } |
---|
| 726 | } |
---|
| 727 | } |
---|
| 728 | |
---|
| 729 | /// \brief Starts the second phase of the preflow algorithm. |
---|
| 730 | /// |
---|
| 731 | /// The preflow algorithm consists of two phases, this method runs |
---|
[393] | 732 | /// the second phase. After calling one of the \ref init() functions |
---|
| 733 | /// and \ref startFirstPhase() and then \ref startSecondPhase(), |
---|
| 734 | /// \ref flowMap() returns a maximum flow, \ref flowValue() returns the |
---|
[389] | 735 | /// value of a maximum flow, \ref minCut() returns a minimum cut |
---|
[393] | 736 | /// \pre One of the \ref init() functions and \ref startFirstPhase() |
---|
| 737 | /// must be called before using this function. |
---|
[389] | 738 | void startSecondPhase() { |
---|
| 739 | _phase = false; |
---|
| 740 | |
---|
| 741 | typename Digraph::template NodeMap<bool> reached(_graph); |
---|
| 742 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
[581] | 743 | reached[n] = (*_level)[n] < _level->maxLevel(); |
---|
[389] | 744 | } |
---|
| 745 | |
---|
| 746 | _level->initStart(); |
---|
| 747 | _level->initAddItem(_source); |
---|
| 748 | |
---|
| 749 | std::vector<Node> queue; |
---|
| 750 | queue.push_back(_source); |
---|
[581] | 751 | reached[_source] = true; |
---|
[389] | 752 | |
---|
| 753 | while (!queue.empty()) { |
---|
| 754 | _level->initNewLevel(); |
---|
| 755 | std::vector<Node> nqueue; |
---|
| 756 | for (int i = 0; i < int(queue.size()); ++i) { |
---|
| 757 | Node n = queue[i]; |
---|
| 758 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 759 | Node v = _graph.target(e); |
---|
| 760 | if (!reached[v] && _tolerance.positive((*_flow)[e])) { |
---|
[581] | 761 | reached[v] = true; |
---|
[389] | 762 | _level->initAddItem(v); |
---|
| 763 | nqueue.push_back(v); |
---|
| 764 | } |
---|
| 765 | } |
---|
| 766 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
| 767 | Node u = _graph.source(e); |
---|
| 768 | if (!reached[u] && |
---|
| 769 | _tolerance.positive((*_capacity)[e] - (*_flow)[e])) { |
---|
[581] | 770 | reached[u] = true; |
---|
[389] | 771 | _level->initAddItem(u); |
---|
| 772 | nqueue.push_back(u); |
---|
| 773 | } |
---|
| 774 | } |
---|
| 775 | } |
---|
| 776 | queue.swap(nqueue); |
---|
| 777 | } |
---|
| 778 | _level->initFinish(); |
---|
| 779 | |
---|
| 780 | for (NodeIt n(_graph); n != INVALID; ++n) { |
---|
| 781 | if (!reached[n]) { |
---|
| 782 | _level->dirtyTopButOne(n); |
---|
| 783 | } else if ((*_excess)[n] > 0 && _target != n) { |
---|
| 784 | _level->activate(n); |
---|
| 785 | } |
---|
| 786 | } |
---|
| 787 | |
---|
| 788 | Node n; |
---|
| 789 | while ((n = _level->highestActive()) != INVALID) { |
---|
[641] | 790 | Value excess = (*_excess)[n]; |
---|
[389] | 791 | int level = _level->highestActiveLevel(); |
---|
| 792 | int new_level = _level->maxLevel(); |
---|
| 793 | |
---|
| 794 | for (OutArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[641] | 795 | Value rem = (*_capacity)[e] - (*_flow)[e]; |
---|
[389] | 796 | if (!_tolerance.positive(rem)) continue; |
---|
| 797 | Node v = _graph.target(e); |
---|
| 798 | if ((*_level)[v] < level) { |
---|
| 799 | if (!_level->active(v) && v != _source) { |
---|
| 800 | _level->activate(v); |
---|
| 801 | } |
---|
| 802 | if (!_tolerance.less(rem, excess)) { |
---|
| 803 | _flow->set(e, (*_flow)[e] + excess); |
---|
[581] | 804 | (*_excess)[v] += excess; |
---|
[389] | 805 | excess = 0; |
---|
| 806 | goto no_more_push; |
---|
| 807 | } else { |
---|
| 808 | excess -= rem; |
---|
[581] | 809 | (*_excess)[v] += rem; |
---|
[389] | 810 | _flow->set(e, (*_capacity)[e]); |
---|
| 811 | } |
---|
| 812 | } else if (new_level > (*_level)[v]) { |
---|
| 813 | new_level = (*_level)[v]; |
---|
| 814 | } |
---|
| 815 | } |
---|
| 816 | |
---|
| 817 | for (InArcIt e(_graph, n); e != INVALID; ++e) { |
---|
[641] | 818 | Value rem = (*_flow)[e]; |
---|
[389] | 819 | if (!_tolerance.positive(rem)) continue; |
---|
| 820 | Node v = _graph.source(e); |
---|
| 821 | if ((*_level)[v] < level) { |
---|
| 822 | if (!_level->active(v) && v != _source) { |
---|
| 823 | _level->activate(v); |
---|
| 824 | } |
---|
| 825 | if (!_tolerance.less(rem, excess)) { |
---|
| 826 | _flow->set(e, (*_flow)[e] - excess); |
---|
[581] | 827 | (*_excess)[v] += excess; |
---|
[389] | 828 | excess = 0; |
---|
| 829 | goto no_more_push; |
---|
| 830 | } else { |
---|
| 831 | excess -= rem; |
---|
[581] | 832 | (*_excess)[v] += rem; |
---|
[389] | 833 | _flow->set(e, 0); |
---|
| 834 | } |
---|
| 835 | } else if (new_level > (*_level)[v]) { |
---|
| 836 | new_level = (*_level)[v]; |
---|
| 837 | } |
---|
| 838 | } |
---|
| 839 | |
---|
| 840 | no_more_push: |
---|
| 841 | |
---|
[581] | 842 | (*_excess)[n] = excess; |
---|
[389] | 843 | |
---|
| 844 | if (excess != 0) { |
---|
| 845 | if (new_level + 1 < _level->maxLevel()) { |
---|
| 846 | _level->liftHighestActive(new_level + 1); |
---|
| 847 | } else { |
---|
| 848 | // Calculation error |
---|
| 849 | _level->liftHighestActiveToTop(); |
---|
| 850 | } |
---|
| 851 | if (_level->emptyLevel(level)) { |
---|
| 852 | // Calculation error |
---|
| 853 | _level->liftToTop(level); |
---|
| 854 | } |
---|
| 855 | } else { |
---|
| 856 | _level->deactivate(n); |
---|
| 857 | } |
---|
| 858 | |
---|
| 859 | } |
---|
| 860 | } |
---|
| 861 | |
---|
| 862 | /// \brief Runs the preflow algorithm. |
---|
| 863 | /// |
---|
| 864 | /// Runs the preflow algorithm. |
---|
| 865 | /// \note pf.run() is just a shortcut of the following code. |
---|
| 866 | /// \code |
---|
| 867 | /// pf.init(); |
---|
| 868 | /// pf.startFirstPhase(); |
---|
| 869 | /// pf.startSecondPhase(); |
---|
| 870 | /// \endcode |
---|
| 871 | void run() { |
---|
| 872 | init(); |
---|
| 873 | startFirstPhase(); |
---|
| 874 | startSecondPhase(); |
---|
| 875 | } |
---|
| 876 | |
---|
| 877 | /// \brief Runs the preflow algorithm to compute the minimum cut. |
---|
| 878 | /// |
---|
| 879 | /// Runs the preflow algorithm to compute the minimum cut. |
---|
| 880 | /// \note pf.runMinCut() is just a shortcut of the following code. |
---|
| 881 | /// \code |
---|
| 882 | /// pf.init(); |
---|
| 883 | /// pf.startFirstPhase(); |
---|
| 884 | /// \endcode |
---|
| 885 | void runMinCut() { |
---|
| 886 | init(); |
---|
| 887 | startFirstPhase(); |
---|
| 888 | } |
---|
| 889 | |
---|
| 890 | /// @} |
---|
| 891 | |
---|
| 892 | /// \name Query Functions |
---|
[393] | 893 | /// The results of the preflow algorithm can be obtained using these |
---|
[389] | 894 | /// functions.\n |
---|
[393] | 895 | /// Either one of the \ref run() "run*()" functions or one of the |
---|
| 896 | /// \ref startFirstPhase() "start*()" functions should be called |
---|
| 897 | /// before using them. |
---|
[389] | 898 | |
---|
| 899 | ///@{ |
---|
| 900 | |
---|
| 901 | /// \brief Returns the value of the maximum flow. |
---|
| 902 | /// |
---|
| 903 | /// Returns the value of the maximum flow by returning the excess |
---|
[393] | 904 | /// of the target node. This value equals to the value of |
---|
| 905 | /// the maximum flow already after the first phase of the algorithm. |
---|
| 906 | /// |
---|
| 907 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 908 | /// using this function. |
---|
[641] | 909 | Value flowValue() const { |
---|
[389] | 910 | return (*_excess)[_target]; |
---|
| 911 | } |
---|
| 912 | |
---|
[641] | 913 | /// \brief Returns the flow value on the given arc. |
---|
[389] | 914 | /// |
---|
[641] | 915 | /// Returns the flow value on the given arc. This method can |
---|
[393] | 916 | /// be called after the second phase of the algorithm. |
---|
| 917 | /// |
---|
| 918 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 919 | /// using this function. |
---|
[641] | 920 | Value flow(const Arc& arc) const { |
---|
[393] | 921 | return (*_flow)[arc]; |
---|
| 922 | } |
---|
| 923 | |
---|
| 924 | /// \brief Returns a const reference to the flow map. |
---|
| 925 | /// |
---|
| 926 | /// Returns a const reference to the arc map storing the found flow. |
---|
| 927 | /// This method can be called after the second phase of the algorithm. |
---|
| 928 | /// |
---|
| 929 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 930 | /// using this function. |
---|
[420] | 931 | const FlowMap& flowMap() const { |
---|
[393] | 932 | return *_flow; |
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| 933 | } |
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| 934 | |
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| 935 | /// \brief Returns \c true when the node is on the source side of the |
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| 936 | /// minimum cut. |
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| 937 | /// |
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| 938 | /// Returns true when the node is on the source side of the found |
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| 939 | /// minimum cut. This method can be called both after running \ref |
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[389] | 940 | /// startFirstPhase() and \ref startSecondPhase(). |
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[393] | 941 | /// |
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| 942 | /// \pre Either \ref run() or \ref init() must be called before |
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| 943 | /// using this function. |
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[389] | 944 | bool minCut(const Node& node) const { |
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| 945 | return ((*_level)[node] == _level->maxLevel()) == _phase; |
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| 946 | } |
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| 947 | |
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[393] | 948 | /// \brief Gives back a minimum value cut. |
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[389] | 949 | /// |
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[393] | 950 | /// Sets \c cutMap to the characteristic vector of a minimum value |
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| 951 | /// cut. \c cutMap should be a \ref concepts::WriteMap "writable" |
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| 952 | /// node map with \c bool (or convertible) value type. |
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| 953 | /// |
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| 954 | /// This method can be called both after running \ref startFirstPhase() |
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| 955 | /// and \ref startSecondPhase(). The result after the second phase |
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| 956 | /// could be slightly different if inexact computation is used. |
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| 957 | /// |
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| 958 | /// \note This function calls \ref minCut() for each node, so it runs in |
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[559] | 959 | /// O(n) time. |
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[393] | 960 | /// |
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| 961 | /// \pre Either \ref run() or \ref init() must be called before |
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| 962 | /// using this function. |
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[389] | 963 | template <typename CutMap> |
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| 964 | void minCutMap(CutMap& cutMap) const { |
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| 965 | for (NodeIt n(_graph); n != INVALID; ++n) { |
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| 966 | cutMap.set(n, minCut(n)); |
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| 967 | } |
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| 968 | } |
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| 969 | |
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| 970 | /// @} |
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| 971 | }; |
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| 972 | } |
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| 973 | |
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| 974 | #endif |
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