lemon/preflow.h
author Alpar Juttner <alpar@cs.elte.hu>
Tue, 06 Apr 2010 06:52:48 +0200
branch1.2
changeset 968 77704bf2a4ae
parent 891 75e6020b19b1
child 985 f63fd24c0aea
child 1107 2b6bffe0e7e8
permissions -rw-r--r--
Merge bugfix #364 to branch 1.2
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/* -*- mode: C++; indent-tabs-mode: nil; -*-
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 *
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 * This file is a part of LEMON, a generic C++ optimization library.
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 *
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 * Copyright (C) 2003-2010
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 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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 *
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 * Permission to use, modify and distribute this software is granted
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 * provided that this copyright notice appears in all copies. For
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 * precise terms see the accompanying LICENSE file.
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 *
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 * This software is provided "AS IS" with no warranty of any kind,
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 * express or implied, and with no claim as to its suitability for any
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 * purpose.
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 *
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 */
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#ifndef LEMON_PREFLOW_H
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#define LEMON_PREFLOW_H
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#include <lemon/tolerance.h>
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#include <lemon/elevator.h>
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/// \file
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/// \ingroup max_flow
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/// \brief Implementation of the preflow algorithm.
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namespace lemon {
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  /// \brief Default traits class of Preflow class.
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  ///
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  /// Default traits class of Preflow class.
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  /// \tparam GR Digraph type.
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  /// \tparam CAP Capacity map type.
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  template <typename GR, typename CAP>
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  struct PreflowDefaultTraits {
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    /// \brief The type of the digraph the algorithm runs on.
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    typedef GR Digraph;
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    /// \brief The type of the map that stores the arc capacities.
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    ///
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    /// The type of the map that stores the arc capacities.
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    /// It must meet the \ref concepts::ReadMap "ReadMap" concept.
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    typedef CAP CapacityMap;
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    /// \brief The type of the flow values.
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    typedef typename CapacityMap::Value Value;
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    /// \brief The type of the map that stores the flow values.
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    ///
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    /// The type of the map that stores the flow values.
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    /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
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#ifdef DOXYGEN
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    typedef GR::ArcMap<Value> FlowMap;
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#else
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    typedef typename Digraph::template ArcMap<Value> FlowMap;
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#endif
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    /// \brief Instantiates a FlowMap.
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    ///
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    /// This function instantiates a \ref FlowMap.
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    /// \param digraph The digraph for which we would like to define
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    /// the flow map.
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    static FlowMap* createFlowMap(const Digraph& digraph) {
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      return new FlowMap(digraph);
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    }
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    /// \brief The elevator type used by Preflow algorithm.
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    ///
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    /// The elevator type used by Preflow algorithm.
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    ///
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    /// \sa Elevator, LinkedElevator
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#ifdef DOXYGEN
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    typedef lemon::Elevator<GR, GR::Node> Elevator;
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#else
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    typedef lemon::Elevator<Digraph, typename Digraph::Node> Elevator;
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#endif
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    /// \brief Instantiates an Elevator.
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    ///
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    /// This function instantiates an \ref Elevator.
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    /// \param digraph The digraph for which we would like to define
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    /// the elevator.
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    /// \param max_level The maximum level of the elevator.
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    static Elevator* createElevator(const Digraph& digraph, int max_level) {
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      return new Elevator(digraph, max_level);
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    }
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    /// \brief The tolerance used by the algorithm
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    ///
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    /// The tolerance used by the algorithm to handle inexact computation.
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    typedef lemon::Tolerance<Value> Tolerance;
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  };
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  /// \ingroup max_flow
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  ///
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  /// \brief %Preflow algorithm class.
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  ///
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  /// This class provides an implementation of Goldberg-Tarjan's \e preflow
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  /// \e push-relabel algorithm producing a \ref max_flow
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  /// "flow of maximum value" in a digraph \ref clrs01algorithms,
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  /// \ref amo93networkflows, \ref goldberg88newapproach.
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  /// The preflow algorithms are the fastest known maximum
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  /// flow algorithms. The current implementation uses a mixture of the
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  /// \e "highest label" and the \e "bound decrease" heuristics.
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  /// The worst case time complexity of the algorithm is \f$O(n^2\sqrt{e})\f$.
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  ///
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  /// The algorithm consists of two phases. After the first phase
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  /// the maximum flow value and the minimum cut is obtained. The
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  /// second phase constructs a feasible maximum flow on each arc.
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  ///
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  /// \warning This implementation cannot handle infinite or very large
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  /// capacities (e.g. the maximum value of \c CAP::Value).
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  ///
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  /// \tparam GR The type of the digraph the algorithm runs on.
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  /// \tparam CAP The type of the capacity map. The default map
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  /// type is \ref concepts::Digraph::ArcMap "GR::ArcMap<int>".
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  /// \tparam TR The traits class that defines various types used by the
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  /// algorithm. By default, it is \ref PreflowDefaultTraits
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  /// "PreflowDefaultTraits<GR, CAP>".
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  /// In most cases, this parameter should not be set directly,
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  /// consider to use the named template parameters instead.
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#ifdef DOXYGEN
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  template <typename GR, typename CAP, typename TR>
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#else
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  template <typename GR,
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            typename CAP = typename GR::template ArcMap<int>,
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            typename TR = PreflowDefaultTraits<GR, CAP> >
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#endif
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  class Preflow {
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  public:
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    ///The \ref PreflowDefaultTraits "traits class" of the algorithm.
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    typedef TR Traits;
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    ///The type of the digraph the algorithm runs on.
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    typedef typename Traits::Digraph Digraph;
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    ///The type of the capacity map.
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    typedef typename Traits::CapacityMap CapacityMap;
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    ///The type of the flow values.
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    typedef typename Traits::Value Value;
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    ///The type of the flow map.
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    typedef typename Traits::FlowMap FlowMap;
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    ///The type of the elevator.
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    typedef typename Traits::Elevator Elevator;
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    ///The type of the tolerance.
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    typedef typename Traits::Tolerance Tolerance;
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  private:
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    TEMPLATE_DIGRAPH_TYPEDEFS(Digraph);
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    const Digraph& _graph;
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    const CapacityMap* _capacity;
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    int _node_num;
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    Node _source, _target;
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    FlowMap* _flow;
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    bool _local_flow;
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    Elevator* _level;
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    bool _local_level;
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    typedef typename Digraph::template NodeMap<Value> ExcessMap;
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    ExcessMap* _excess;
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    Tolerance _tolerance;
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    bool _phase;
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    void createStructures() {
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      _node_num = countNodes(_graph);
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      if (!_flow) {
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        _flow = Traits::createFlowMap(_graph);
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        _local_flow = true;
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      }
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      if (!_level) {
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        _level = Traits::createElevator(_graph, _node_num);
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        _local_level = true;
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      }
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      if (!_excess) {
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        _excess = new ExcessMap(_graph);
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      }
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    }
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    void destroyStructures() {
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      if (_local_flow) {
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        delete _flow;
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      }
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      if (_local_level) {
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        delete _level;
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      }
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      if (_excess) {
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        delete _excess;
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      }
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    }
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  public:
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    typedef Preflow Create;
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    ///\name Named Template Parameters
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    ///@{
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    template <typename T>
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    struct SetFlowMapTraits : public Traits {
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      typedef T FlowMap;
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      static FlowMap *createFlowMap(const Digraph&) {
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        LEMON_ASSERT(false, "FlowMap is not initialized");
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        return 0; // ignore warnings
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      }
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    };
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    /// \brief \ref named-templ-param "Named parameter" for setting
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    /// FlowMap type
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    ///
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    /// \ref named-templ-param "Named parameter" for setting FlowMap
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    /// type.
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    template <typename T>
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    struct SetFlowMap
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      : public Preflow<Digraph, CapacityMap, SetFlowMapTraits<T> > {
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      typedef Preflow<Digraph, CapacityMap,
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                      SetFlowMapTraits<T> > Create;
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    };
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    template <typename T>
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    struct SetElevatorTraits : public Traits {
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      typedef T Elevator;
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      static Elevator *createElevator(const Digraph&, int) {
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        LEMON_ASSERT(false, "Elevator is not initialized");
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        return 0; // ignore warnings
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      }
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    };
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    /// \brief \ref named-templ-param "Named parameter" for setting
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    /// Elevator type
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    ///
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    /// \ref named-templ-param "Named parameter" for setting Elevator
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    /// type. If this named parameter is used, then an external
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    /// elevator object must be passed to the algorithm using the
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    /// \ref elevator(Elevator&) "elevator()" function before calling
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    /// \ref run() or \ref init().
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    /// \sa SetStandardElevator
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    template <typename T>
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    struct SetElevator
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      : public Preflow<Digraph, CapacityMap, SetElevatorTraits<T> > {
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      typedef Preflow<Digraph, CapacityMap,
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                      SetElevatorTraits<T> > Create;
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    };
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    template <typename T>
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    struct SetStandardElevatorTraits : public Traits {
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      typedef T Elevator;
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      static Elevator *createElevator(const Digraph& digraph, int max_level) {
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        return new Elevator(digraph, max_level);
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      }
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    };
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    /// \brief \ref named-templ-param "Named parameter" for setting
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    /// Elevator type with automatic allocation
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    ///
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    /// \ref named-templ-param "Named parameter" for setting Elevator
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    /// type with automatic allocation.
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    /// The Elevator should have standard constructor interface to be
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    /// able to automatically created by the algorithm (i.e. the
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    /// digraph and the maximum level should be passed to it).
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    /// However, an external elevator object could also be passed to the
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    /// algorithm with the \ref elevator(Elevator&) "elevator()" function
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    /// before calling \ref run() or \ref init().
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    /// \sa SetElevator
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    template <typename T>
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    struct SetStandardElevator
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      : public Preflow<Digraph, CapacityMap,
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                       SetStandardElevatorTraits<T> > {
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      typedef Preflow<Digraph, CapacityMap,
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                      SetStandardElevatorTraits<T> > Create;
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    };
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    /// @}
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  protected:
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    Preflow() {}
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  public:
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    /// \brief The constructor of the class.
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    ///
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    /// The constructor of the class.
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    /// \param digraph The digraph the algorithm runs on.
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    /// \param capacity The capacity of the arcs.
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    /// \param source The source node.
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    /// \param target The target node.
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    Preflow(const Digraph& digraph, const CapacityMap& capacity,
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            Node source, Node target)
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      : _graph(digraph), _capacity(&capacity),
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        _node_num(0), _source(source), _target(target),
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        _flow(0), _local_flow(false),
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        _level(0), _local_level(false),
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        _excess(0), _tolerance(), _phase() {}
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    /// \brief Destructor.
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    ///
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    /// Destructor.
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    ~Preflow() {
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      destroyStructures();
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    }
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    /// \brief Sets the capacity map.
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    ///
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    /// Sets the capacity map.
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    /// \return <tt>(*this)</tt>
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    Preflow& capacityMap(const CapacityMap& map) {
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      _capacity = &map;
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      return *this;
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    }
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    /// \brief Sets the flow map.
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    ///
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    /// Sets the flow map.
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    /// If you don't use this function before calling \ref run() or
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    /// \ref init(), an instance will be allocated automatically.
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    /// The destructor deallocates this automatically allocated map,
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    /// of course.
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    /// \return <tt>(*this)</tt>
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    Preflow& flowMap(FlowMap& map) {
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      if (_local_flow) {
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        delete _flow;
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        _local_flow = false;
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      }
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      _flow = &map;
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      return *this;
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    }
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    /// \brief Sets the source node.
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    ///
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    /// Sets the source node.
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    /// \return <tt>(*this)</tt>
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    Preflow& source(const Node& node) {
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      _source = node;
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      return *this;
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    }
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    /// \brief Sets the target node.
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    ///
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    /// Sets the target node.
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    /// \return <tt>(*this)</tt>
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    Preflow& target(const Node& node) {
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      _target = node;
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      return *this;
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    }
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    /// \brief Sets the elevator used by algorithm.
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    ///
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    /// Sets the elevator used by algorithm.
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    /// If you don't use this function before calling \ref run() or
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    /// \ref init(), an instance will be allocated automatically.
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    /// The destructor deallocates this automatically allocated elevator,
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    /// of course.
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    /// \return <tt>(*this)</tt>
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    Preflow& elevator(Elevator& elevator) {
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      if (_local_level) {
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        delete _level;
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        _local_level = false;
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      }
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      _level = &elevator;
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      return *this;
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    }
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    /// \brief Returns a const reference to the elevator.
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    ///
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    /// Returns a const reference to the elevator.
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    ///
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    /// \pre Either \ref run() or \ref init() must be called before
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    /// using this function.
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    const Elevator& elevator() const {
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      return *_level;
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    }
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    /// \brief Sets the tolerance used by the algorithm.
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    ///
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    /// Sets the tolerance object used by the algorithm.
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    /// \return <tt>(*this)</tt>
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    Preflow& tolerance(const Tolerance& tolerance) {
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      _tolerance = tolerance;
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      return *this;
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    }
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    /// \brief Returns a const reference to the tolerance.
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    ///
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    /// Returns a const reference to the tolerance object used by
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    /// the algorithm.
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    const Tolerance& tolerance() const {
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      return _tolerance;
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    }
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    /// \name Execution Control
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    /// The simplest way to execute the preflow algorithm is to use
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    /// \ref run() or \ref runMinCut().\n
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    /// If you need better control on the initial solution or the execution,
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    /// you have to call one of the \ref init() functions first, then
kpeter@408
   412
    /// \ref startFirstPhase() and if you need it \ref startSecondPhase().
alpar@404
   413
alpar@404
   414
    ///@{
alpar@404
   415
alpar@404
   416
    /// \brief Initializes the internal data structures.
alpar@404
   417
    ///
kpeter@408
   418
    /// Initializes the internal data structures and sets the initial
kpeter@408
   419
    /// flow to zero on each arc.
alpar@404
   420
    void init() {
alpar@404
   421
      createStructures();
alpar@404
   422
alpar@404
   423
      _phase = true;
alpar@404
   424
      for (NodeIt n(_graph); n != INVALID; ++n) {
kpeter@628
   425
        (*_excess)[n] = 0;
alpar@404
   426
      }
alpar@404
   427
alpar@404
   428
      for (ArcIt e(_graph); e != INVALID; ++e) {
alpar@404
   429
        _flow->set(e, 0);
alpar@404
   430
      }
alpar@404
   431
alpar@404
   432
      typename Digraph::template NodeMap<bool> reached(_graph, false);
alpar@404
   433
alpar@404
   434
      _level->initStart();
alpar@404
   435
      _level->initAddItem(_target);
alpar@404
   436
alpar@404
   437
      std::vector<Node> queue;
kpeter@628
   438
      reached[_source] = true;
alpar@404
   439
alpar@404
   440
      queue.push_back(_target);
kpeter@628
   441
      reached[_target] = true;
alpar@404
   442
      while (!queue.empty()) {
alpar@404
   443
        _level->initNewLevel();
alpar@404
   444
        std::vector<Node> nqueue;
alpar@404
   445
        for (int i = 0; i < int(queue.size()); ++i) {
alpar@404
   446
          Node n = queue[i];
alpar@404
   447
          for (InArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   448
            Node u = _graph.source(e);
alpar@404
   449
            if (!reached[u] && _tolerance.positive((*_capacity)[e])) {
kpeter@628
   450
              reached[u] = true;
alpar@404
   451
              _level->initAddItem(u);
alpar@404
   452
              nqueue.push_back(u);
alpar@404
   453
            }
alpar@404
   454
          }
alpar@404
   455
        }
alpar@404
   456
        queue.swap(nqueue);
alpar@404
   457
      }
alpar@404
   458
      _level->initFinish();
alpar@404
   459
alpar@404
   460
      for (OutArcIt e(_graph, _source); e != INVALID; ++e) {
alpar@404
   461
        if (_tolerance.positive((*_capacity)[e])) {
alpar@404
   462
          Node u = _graph.target(e);
alpar@404
   463
          if ((*_level)[u] == _level->maxLevel()) continue;
alpar@404
   464
          _flow->set(e, (*_capacity)[e]);
kpeter@628
   465
          (*_excess)[u] += (*_capacity)[e];
alpar@404
   466
          if (u != _target && !_level->active(u)) {
alpar@404
   467
            _level->activate(u);
alpar@404
   468
          }
alpar@404
   469
        }
alpar@404
   470
      }
alpar@404
   471
    }
alpar@404
   472
kpeter@408
   473
    /// \brief Initializes the internal data structures using the
kpeter@408
   474
    /// given flow map.
alpar@404
   475
    ///
alpar@404
   476
    /// Initializes the internal data structures and sets the initial
alpar@404
   477
    /// flow to the given \c flowMap. The \c flowMap should contain a
kpeter@408
   478
    /// flow or at least a preflow, i.e. at each node excluding the
kpeter@408
   479
    /// source node the incoming flow should greater or equal to the
alpar@404
   480
    /// outgoing flow.
kpeter@408
   481
    /// \return \c false if the given \c flowMap is not a preflow.
alpar@404
   482
    template <typename FlowMap>
kpeter@407
   483
    bool init(const FlowMap& flowMap) {
alpar@404
   484
      createStructures();
alpar@404
   485
alpar@404
   486
      for (ArcIt e(_graph); e != INVALID; ++e) {
alpar@404
   487
        _flow->set(e, flowMap[e]);
alpar@404
   488
      }
alpar@404
   489
alpar@404
   490
      for (NodeIt n(_graph); n != INVALID; ++n) {
kpeter@688
   491
        Value excess = 0;
alpar@404
   492
        for (InArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   493
          excess += (*_flow)[e];
alpar@404
   494
        }
alpar@404
   495
        for (OutArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   496
          excess -= (*_flow)[e];
alpar@404
   497
        }
alpar@404
   498
        if (excess < 0 && n != _source) return false;
kpeter@628
   499
        (*_excess)[n] = excess;
alpar@404
   500
      }
alpar@404
   501
alpar@404
   502
      typename Digraph::template NodeMap<bool> reached(_graph, false);
alpar@404
   503
alpar@404
   504
      _level->initStart();
alpar@404
   505
      _level->initAddItem(_target);
alpar@404
   506
alpar@404
   507
      std::vector<Node> queue;
kpeter@628
   508
      reached[_source] = true;
alpar@404
   509
alpar@404
   510
      queue.push_back(_target);
kpeter@628
   511
      reached[_target] = true;
alpar@404
   512
      while (!queue.empty()) {
alpar@404
   513
        _level->initNewLevel();
alpar@404
   514
        std::vector<Node> nqueue;
alpar@404
   515
        for (int i = 0; i < int(queue.size()); ++i) {
alpar@404
   516
          Node n = queue[i];
alpar@404
   517
          for (InArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   518
            Node u = _graph.source(e);
alpar@404
   519
            if (!reached[u] &&
alpar@404
   520
                _tolerance.positive((*_capacity)[e] - (*_flow)[e])) {
kpeter@628
   521
              reached[u] = true;
alpar@404
   522
              _level->initAddItem(u);
alpar@404
   523
              nqueue.push_back(u);
alpar@404
   524
            }
alpar@404
   525
          }
alpar@404
   526
          for (OutArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   527
            Node v = _graph.target(e);
alpar@404
   528
            if (!reached[v] && _tolerance.positive((*_flow)[e])) {
kpeter@628
   529
              reached[v] = true;
alpar@404
   530
              _level->initAddItem(v);
alpar@404
   531
              nqueue.push_back(v);
alpar@404
   532
            }
alpar@404
   533
          }
alpar@404
   534
        }
alpar@404
   535
        queue.swap(nqueue);
alpar@404
   536
      }
alpar@404
   537
      _level->initFinish();
alpar@404
   538
alpar@404
   539
      for (OutArcIt e(_graph, _source); e != INVALID; ++e) {
kpeter@688
   540
        Value rem = (*_capacity)[e] - (*_flow)[e];
alpar@404
   541
        if (_tolerance.positive(rem)) {
alpar@404
   542
          Node u = _graph.target(e);
alpar@404
   543
          if ((*_level)[u] == _level->maxLevel()) continue;
alpar@404
   544
          _flow->set(e, (*_capacity)[e]);
kpeter@628
   545
          (*_excess)[u] += rem;
alpar@404
   546
          if (u != _target && !_level->active(u)) {
alpar@404
   547
            _level->activate(u);
alpar@404
   548
          }
alpar@404
   549
        }
alpar@404
   550
      }
alpar@404
   551
      for (InArcIt e(_graph, _source); e != INVALID; ++e) {
kpeter@688
   552
        Value rem = (*_flow)[e];
alpar@404
   553
        if (_tolerance.positive(rem)) {
alpar@404
   554
          Node v = _graph.source(e);
alpar@404
   555
          if ((*_level)[v] == _level->maxLevel()) continue;
alpar@404
   556
          _flow->set(e, 0);
kpeter@628
   557
          (*_excess)[v] += rem;
alpar@404
   558
          if (v != _target && !_level->active(v)) {
alpar@404
   559
            _level->activate(v);
alpar@404
   560
          }
alpar@404
   561
        }
alpar@404
   562
      }
alpar@404
   563
      return true;
alpar@404
   564
    }
alpar@404
   565
alpar@404
   566
    /// \brief Starts the first phase of the preflow algorithm.
alpar@404
   567
    ///
alpar@404
   568
    /// The preflow algorithm consists of two phases, this method runs
alpar@404
   569
    /// the first phase. After the first phase the maximum flow value
alpar@404
   570
    /// and a minimum value cut can already be computed, although a
alpar@404
   571
    /// maximum flow is not yet obtained. So after calling this method
alpar@404
   572
    /// \ref flowValue() returns the value of a maximum flow and \ref
alpar@404
   573
    /// minCut() returns a minimum cut.
kpeter@408
   574
    /// \pre One of the \ref init() functions must be called before
kpeter@408
   575
    /// using this function.
alpar@404
   576
    void startFirstPhase() {
alpar@404
   577
      _phase = true;
alpar@404
   578
alpar@404
   579
      Node n = _level->highestActive();
alpar@404
   580
      int level = _level->highestActiveLevel();
alpar@404
   581
      while (n != INVALID) {
alpar@404
   582
        int num = _node_num;
alpar@404
   583
alpar@404
   584
        while (num > 0 && n != INVALID) {
kpeter@688
   585
          Value excess = (*_excess)[n];
alpar@404
   586
          int new_level = _level->maxLevel();
alpar@404
   587
alpar@404
   588
          for (OutArcIt e(_graph, n); e != INVALID; ++e) {
kpeter@688
   589
            Value rem = (*_capacity)[e] - (*_flow)[e];
alpar@404
   590
            if (!_tolerance.positive(rem)) continue;
alpar@404
   591
            Node v = _graph.target(e);
alpar@404
   592
            if ((*_level)[v] < level) {
alpar@404
   593
              if (!_level->active(v) && v != _target) {
alpar@404
   594
                _level->activate(v);
alpar@404
   595
              }
alpar@404
   596
              if (!_tolerance.less(rem, excess)) {
alpar@404
   597
                _flow->set(e, (*_flow)[e] + excess);
kpeter@628
   598
                (*_excess)[v] += excess;
alpar@404
   599
                excess = 0;
alpar@404
   600
                goto no_more_push_1;
alpar@404
   601
              } else {
alpar@404
   602
                excess -= rem;
kpeter@628
   603
                (*_excess)[v] += rem;
alpar@404
   604
                _flow->set(e, (*_capacity)[e]);
alpar@404
   605
              }
alpar@404
   606
            } else if (new_level > (*_level)[v]) {
alpar@404
   607
              new_level = (*_level)[v];
alpar@404
   608
            }
alpar@404
   609
          }
alpar@404
   610
alpar@404
   611
          for (InArcIt e(_graph, n); e != INVALID; ++e) {
kpeter@688
   612
            Value rem = (*_flow)[e];
alpar@404
   613
            if (!_tolerance.positive(rem)) continue;
alpar@404
   614
            Node v = _graph.source(e);
alpar@404
   615
            if ((*_level)[v] < level) {
alpar@404
   616
              if (!_level->active(v) && v != _target) {
alpar@404
   617
                _level->activate(v);
alpar@404
   618
              }
alpar@404
   619
              if (!_tolerance.less(rem, excess)) {
alpar@404
   620
                _flow->set(e, (*_flow)[e] - excess);
kpeter@628
   621
                (*_excess)[v] += excess;
alpar@404
   622
                excess = 0;
alpar@404
   623
                goto no_more_push_1;
alpar@404
   624
              } else {
alpar@404
   625
                excess -= rem;
kpeter@628
   626
                (*_excess)[v] += rem;
alpar@404
   627
                _flow->set(e, 0);
alpar@404
   628
              }
alpar@404
   629
            } else if (new_level > (*_level)[v]) {
alpar@404
   630
              new_level = (*_level)[v];
alpar@404
   631
            }
alpar@404
   632
          }
alpar@404
   633
alpar@404
   634
        no_more_push_1:
alpar@404
   635
kpeter@628
   636
          (*_excess)[n] = excess;
alpar@404
   637
alpar@404
   638
          if (excess != 0) {
alpar@404
   639
            if (new_level + 1 < _level->maxLevel()) {
alpar@404
   640
              _level->liftHighestActive(new_level + 1);
alpar@404
   641
            } else {
alpar@404
   642
              _level->liftHighestActiveToTop();
alpar@404
   643
            }
alpar@404
   644
            if (_level->emptyLevel(level)) {
alpar@404
   645
              _level->liftToTop(level);
alpar@404
   646
            }
alpar@404
   647
          } else {
alpar@404
   648
            _level->deactivate(n);
alpar@404
   649
          }
alpar@404
   650
alpar@404
   651
          n = _level->highestActive();
alpar@404
   652
          level = _level->highestActiveLevel();
alpar@404
   653
          --num;
alpar@404
   654
        }
alpar@404
   655
alpar@404
   656
        num = _node_num * 20;
alpar@404
   657
        while (num > 0 && n != INVALID) {
kpeter@688
   658
          Value excess = (*_excess)[n];
alpar@404
   659
          int new_level = _level->maxLevel();
alpar@404
   660
alpar@404
   661
          for (OutArcIt e(_graph, n); e != INVALID; ++e) {
kpeter@688
   662
            Value rem = (*_capacity)[e] - (*_flow)[e];
alpar@404
   663
            if (!_tolerance.positive(rem)) continue;
alpar@404
   664
            Node v = _graph.target(e);
alpar@404
   665
            if ((*_level)[v] < level) {
alpar@404
   666
              if (!_level->active(v) && v != _target) {
alpar@404
   667
                _level->activate(v);
alpar@404
   668
              }
alpar@404
   669
              if (!_tolerance.less(rem, excess)) {
alpar@404
   670
                _flow->set(e, (*_flow)[e] + excess);
kpeter@628
   671
                (*_excess)[v] += excess;
alpar@404
   672
                excess = 0;
alpar@404
   673
                goto no_more_push_2;
alpar@404
   674
              } else {
alpar@404
   675
                excess -= rem;
kpeter@628
   676
                (*_excess)[v] += rem;
alpar@404
   677
                _flow->set(e, (*_capacity)[e]);
alpar@404
   678
              }
alpar@404
   679
            } else if (new_level > (*_level)[v]) {
alpar@404
   680
              new_level = (*_level)[v];
alpar@404
   681
            }
alpar@404
   682
          }
alpar@404
   683
alpar@404
   684
          for (InArcIt e(_graph, n); e != INVALID; ++e) {
kpeter@688
   685
            Value rem = (*_flow)[e];
alpar@404
   686
            if (!_tolerance.positive(rem)) continue;
alpar@404
   687
            Node v = _graph.source(e);
alpar@404
   688
            if ((*_level)[v] < level) {
alpar@404
   689
              if (!_level->active(v) && v != _target) {
alpar@404
   690
                _level->activate(v);
alpar@404
   691
              }
alpar@404
   692
              if (!_tolerance.less(rem, excess)) {
alpar@404
   693
                _flow->set(e, (*_flow)[e] - excess);
kpeter@628
   694
                (*_excess)[v] += excess;
alpar@404
   695
                excess = 0;
alpar@404
   696
                goto no_more_push_2;
alpar@404
   697
              } else {
alpar@404
   698
                excess -= rem;
kpeter@628
   699
                (*_excess)[v] += rem;
alpar@404
   700
                _flow->set(e, 0);
alpar@404
   701
              }
alpar@404
   702
            } else if (new_level > (*_level)[v]) {
alpar@404
   703
              new_level = (*_level)[v];
alpar@404
   704
            }
alpar@404
   705
          }
alpar@404
   706
alpar@404
   707
        no_more_push_2:
alpar@404
   708
kpeter@628
   709
          (*_excess)[n] = excess;
alpar@404
   710
alpar@404
   711
          if (excess != 0) {
alpar@404
   712
            if (new_level + 1 < _level->maxLevel()) {
alpar@404
   713
              _level->liftActiveOn(level, new_level + 1);
alpar@404
   714
            } else {
alpar@404
   715
              _level->liftActiveToTop(level);
alpar@404
   716
            }
alpar@404
   717
            if (_level->emptyLevel(level)) {
alpar@404
   718
              _level->liftToTop(level);
alpar@404
   719
            }
alpar@404
   720
          } else {
alpar@404
   721
            _level->deactivate(n);
alpar@404
   722
          }
alpar@404
   723
alpar@404
   724
          while (level >= 0 && _level->activeFree(level)) {
alpar@404
   725
            --level;
alpar@404
   726
          }
alpar@404
   727
          if (level == -1) {
alpar@404
   728
            n = _level->highestActive();
alpar@404
   729
            level = _level->highestActiveLevel();
alpar@404
   730
          } else {
alpar@404
   731
            n = _level->activeOn(level);
alpar@404
   732
          }
alpar@404
   733
          --num;
alpar@404
   734
        }
alpar@404
   735
      }
alpar@404
   736
    }
alpar@404
   737
alpar@404
   738
    /// \brief Starts the second phase of the preflow algorithm.
alpar@404
   739
    ///
alpar@404
   740
    /// The preflow algorithm consists of two phases, this method runs
kpeter@408
   741
    /// the second phase. After calling one of the \ref init() functions
kpeter@408
   742
    /// and \ref startFirstPhase() and then \ref startSecondPhase(),
kpeter@408
   743
    /// \ref flowMap() returns a maximum flow, \ref flowValue() returns the
alpar@404
   744
    /// value of a maximum flow, \ref minCut() returns a minimum cut
kpeter@408
   745
    /// \pre One of the \ref init() functions and \ref startFirstPhase()
kpeter@408
   746
    /// must be called before using this function.
alpar@404
   747
    void startSecondPhase() {
alpar@404
   748
      _phase = false;
alpar@404
   749
alpar@404
   750
      typename Digraph::template NodeMap<bool> reached(_graph);
alpar@404
   751
      for (NodeIt n(_graph); n != INVALID; ++n) {
kpeter@628
   752
        reached[n] = (*_level)[n] < _level->maxLevel();
alpar@404
   753
      }
alpar@404
   754
alpar@404
   755
      _level->initStart();
alpar@404
   756
      _level->initAddItem(_source);
alpar@404
   757
alpar@404
   758
      std::vector<Node> queue;
alpar@404
   759
      queue.push_back(_source);
kpeter@628
   760
      reached[_source] = true;
alpar@404
   761
alpar@404
   762
      while (!queue.empty()) {
alpar@404
   763
        _level->initNewLevel();
alpar@404
   764
        std::vector<Node> nqueue;
alpar@404
   765
        for (int i = 0; i < int(queue.size()); ++i) {
alpar@404
   766
          Node n = queue[i];
alpar@404
   767
          for (OutArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   768
            Node v = _graph.target(e);
alpar@404
   769
            if (!reached[v] && _tolerance.positive((*_flow)[e])) {
kpeter@628
   770
              reached[v] = true;
alpar@404
   771
              _level->initAddItem(v);
alpar@404
   772
              nqueue.push_back(v);
alpar@404
   773
            }
alpar@404
   774
          }
alpar@404
   775
          for (InArcIt e(_graph, n); e != INVALID; ++e) {
alpar@404
   776
            Node u = _graph.source(e);
alpar@404
   777
            if (!reached[u] &&
alpar@404
   778
                _tolerance.positive((*_capacity)[e] - (*_flow)[e])) {
kpeter@628
   779
              reached[u] = true;
alpar@404
   780
              _level->initAddItem(u);
alpar@404
   781
              nqueue.push_back(u);
alpar@404
   782
            }
alpar@404
   783
          }
alpar@404
   784
        }
alpar@404
   785
        queue.swap(nqueue);
alpar@404
   786
      }
alpar@404
   787
      _level->initFinish();
alpar@404
   788
alpar@404
   789
      for (NodeIt n(_graph); n != INVALID; ++n) {
alpar@404
   790
        if (!reached[n]) {
alpar@404
   791
          _level->dirtyTopButOne(n);
alpar@404
   792
        } else if ((*_excess)[n] > 0 && _target != n) {
alpar@404
   793
          _level->activate(n);
alpar@404
   794
        }
alpar@404
   795
      }
alpar@404
   796
alpar@404
   797
      Node n;
alpar@404
   798
      while ((n = _level->highestActive()) != INVALID) {
kpeter@688
   799
        Value excess = (*_excess)[n];
alpar@404
   800
        int level = _level->highestActiveLevel();
alpar@404
   801
        int new_level = _level->maxLevel();
alpar@404
   802
alpar@404
   803
        for (OutArcIt e(_graph, n); e != INVALID; ++e) {
kpeter@688
   804
          Value rem = (*_capacity)[e] - (*_flow)[e];
alpar@404
   805
          if (!_tolerance.positive(rem)) continue;
alpar@404
   806
          Node v = _graph.target(e);
alpar@404
   807
          if ((*_level)[v] < level) {
alpar@404
   808
            if (!_level->active(v) && v != _source) {
alpar@404
   809
              _level->activate(v);
alpar@404
   810
            }
alpar@404
   811
            if (!_tolerance.less(rem, excess)) {
alpar@404
   812
              _flow->set(e, (*_flow)[e] + excess);
kpeter@628
   813
              (*_excess)[v] += excess;
alpar@404
   814
              excess = 0;
alpar@404
   815
              goto no_more_push;
alpar@404
   816
            } else {
alpar@404
   817
              excess -= rem;
kpeter@628
   818
              (*_excess)[v] += rem;
alpar@404
   819
              _flow->set(e, (*_capacity)[e]);
alpar@404
   820
            }
alpar@404
   821
          } else if (new_level > (*_level)[v]) {
alpar@404
   822
            new_level = (*_level)[v];
alpar@404
   823
          }
alpar@404
   824
        }
alpar@404
   825
alpar@404
   826
        for (InArcIt e(_graph, n); e != INVALID; ++e) {
kpeter@688
   827
          Value rem = (*_flow)[e];
alpar@404
   828
          if (!_tolerance.positive(rem)) continue;
alpar@404
   829
          Node v = _graph.source(e);
alpar@404
   830
          if ((*_level)[v] < level) {
alpar@404
   831
            if (!_level->active(v) && v != _source) {
alpar@404
   832
              _level->activate(v);
alpar@404
   833
            }
alpar@404
   834
            if (!_tolerance.less(rem, excess)) {
alpar@404
   835
              _flow->set(e, (*_flow)[e] - excess);
kpeter@628
   836
              (*_excess)[v] += excess;
alpar@404
   837
              excess = 0;
alpar@404
   838
              goto no_more_push;
alpar@404
   839
            } else {
alpar@404
   840
              excess -= rem;
kpeter@628
   841
              (*_excess)[v] += rem;
alpar@404
   842
              _flow->set(e, 0);
alpar@404
   843
            }
alpar@404
   844
          } else if (new_level > (*_level)[v]) {
alpar@404
   845
            new_level = (*_level)[v];
alpar@404
   846
          }
alpar@404
   847
        }
alpar@404
   848
alpar@404
   849
      no_more_push:
alpar@404
   850
kpeter@628
   851
        (*_excess)[n] = excess;
alpar@404
   852
alpar@404
   853
        if (excess != 0) {
alpar@404
   854
          if (new_level + 1 < _level->maxLevel()) {
alpar@404
   855
            _level->liftHighestActive(new_level + 1);
alpar@404
   856
          } else {
alpar@404
   857
            // Calculation error
alpar@404
   858
            _level->liftHighestActiveToTop();
alpar@404
   859
          }
alpar@404
   860
          if (_level->emptyLevel(level)) {
alpar@404
   861
            // Calculation error
alpar@404
   862
            _level->liftToTop(level);
alpar@404
   863
          }
alpar@404
   864
        } else {
alpar@404
   865
          _level->deactivate(n);
alpar@404
   866
        }
alpar@404
   867
alpar@404
   868
      }
alpar@404
   869
    }
alpar@404
   870
alpar@404
   871
    /// \brief Runs the preflow algorithm.
alpar@404
   872
    ///
alpar@404
   873
    /// Runs the preflow algorithm.
alpar@404
   874
    /// \note pf.run() is just a shortcut of the following code.
alpar@404
   875
    /// \code
alpar@404
   876
    ///   pf.init();
alpar@404
   877
    ///   pf.startFirstPhase();
alpar@404
   878
    ///   pf.startSecondPhase();
alpar@404
   879
    /// \endcode
alpar@404
   880
    void run() {
alpar@404
   881
      init();
alpar@404
   882
      startFirstPhase();
alpar@404
   883
      startSecondPhase();
alpar@404
   884
    }
alpar@404
   885
alpar@404
   886
    /// \brief Runs the preflow algorithm to compute the minimum cut.
alpar@404
   887
    ///
alpar@404
   888
    /// Runs the preflow algorithm to compute the minimum cut.
alpar@404
   889
    /// \note pf.runMinCut() is just a shortcut of the following code.
alpar@404
   890
    /// \code
alpar@404
   891
    ///   pf.init();
alpar@404
   892
    ///   pf.startFirstPhase();
alpar@404
   893
    /// \endcode
alpar@404
   894
    void runMinCut() {
alpar@404
   895
      init();
alpar@404
   896
      startFirstPhase();
alpar@404
   897
    }
alpar@404
   898
alpar@404
   899
    /// @}
alpar@404
   900
alpar@404
   901
    /// \name Query Functions
kpeter@408
   902
    /// The results of the preflow algorithm can be obtained using these
alpar@404
   903
    /// functions.\n
kpeter@408
   904
    /// Either one of the \ref run() "run*()" functions or one of the
kpeter@408
   905
    /// \ref startFirstPhase() "start*()" functions should be called
kpeter@408
   906
    /// before using them.
alpar@404
   907
alpar@404
   908
    ///@{
alpar@404
   909
alpar@404
   910
    /// \brief Returns the value of the maximum flow.
alpar@404
   911
    ///
alpar@404
   912
    /// Returns the value of the maximum flow by returning the excess
kpeter@408
   913
    /// of the target node. This value equals to the value of
kpeter@408
   914
    /// the maximum flow already after the first phase of the algorithm.
kpeter@408
   915
    ///
kpeter@408
   916
    /// \pre Either \ref run() or \ref init() must be called before
kpeter@408
   917
    /// using this function.
kpeter@688
   918
    Value flowValue() const {
alpar@404
   919
      return (*_excess)[_target];
alpar@404
   920
    }
alpar@404
   921
kpeter@688
   922
    /// \brief Returns the flow value on the given arc.
alpar@404
   923
    ///
kpeter@688
   924
    /// Returns the flow value on the given arc. This method can
kpeter@408
   925
    /// be called after the second phase of the algorithm.
kpeter@408
   926
    ///
kpeter@408
   927
    /// \pre Either \ref run() or \ref init() must be called before
kpeter@408
   928
    /// using this function.
kpeter@688
   929
    Value flow(const Arc& arc) const {
kpeter@408
   930
      return (*_flow)[arc];
kpeter@408
   931
    }
kpeter@408
   932
kpeter@408
   933
    /// \brief Returns a const reference to the flow map.
kpeter@408
   934
    ///
kpeter@408
   935
    /// Returns a const reference to the arc map storing the found flow.
kpeter@408
   936
    /// This method can be called after the second phase of the algorithm.
kpeter@408
   937
    ///
kpeter@408
   938
    /// \pre Either \ref run() or \ref init() must be called before
kpeter@408
   939
    /// using this function.
kpeter@437
   940
    const FlowMap& flowMap() const {
kpeter@408
   941
      return *_flow;
kpeter@408
   942
    }
kpeter@408
   943
kpeter@408
   944
    /// \brief Returns \c true when the node is on the source side of the
kpeter@408
   945
    /// minimum cut.
kpeter@408
   946
    ///
kpeter@408
   947
    /// Returns true when the node is on the source side of the found
kpeter@408
   948
    /// minimum cut. This method can be called both after running \ref
alpar@404
   949
    /// startFirstPhase() and \ref startSecondPhase().
kpeter@408
   950
    ///
kpeter@408
   951
    /// \pre Either \ref run() or \ref init() must be called before
kpeter@408
   952
    /// using this function.
alpar@404
   953
    bool minCut(const Node& node) const {
alpar@404
   954
      return ((*_level)[node] == _level->maxLevel()) == _phase;
alpar@404
   955
    }
alpar@404
   956
kpeter@408
   957
    /// \brief Gives back a minimum value cut.
alpar@404
   958
    ///
kpeter@408
   959
    /// Sets \c cutMap to the characteristic vector of a minimum value
kpeter@408
   960
    /// cut. \c cutMap should be a \ref concepts::WriteMap "writable"
kpeter@408
   961
    /// node map with \c bool (or convertible) value type.
kpeter@408
   962
    ///
kpeter@408
   963
    /// This method can be called both after running \ref startFirstPhase()
kpeter@408
   964
    /// and \ref startSecondPhase(). The result after the second phase
kpeter@408
   965
    /// could be slightly different if inexact computation is used.
kpeter@408
   966
    ///
kpeter@408
   967
    /// \note This function calls \ref minCut() for each node, so it runs in
kpeter@606
   968
    /// O(n) time.
kpeter@408
   969
    ///
kpeter@408
   970
    /// \pre Either \ref run() or \ref init() must be called before
kpeter@408
   971
    /// using this function.
alpar@404
   972
    template <typename CutMap>
alpar@404
   973
    void minCutMap(CutMap& cutMap) const {
alpar@404
   974
      for (NodeIt n(_graph); n != INVALID; ++n) {
alpar@404
   975
        cutMap.set(n, minCut(n));
alpar@404
   976
      }
alpar@404
   977
    }
alpar@404
   978
alpar@404
   979
    /// @}
alpar@404
   980
  };
alpar@404
   981
}
alpar@404
   982
alpar@404
   983
#endif