src/hugo/preflow.h
author marci
Mon, 20 Sep 2004 17:53:33 +0000
changeset 890 3a48bc350e0f
parent 851 209c9d53e195
child 906 17f31d280385
permissions -rw-r--r--
Specialized ConstMap for defining constant maps at compile time, by klao.
Time comparision of the generic and specialized maps.
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// -*- C++ -*-
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#ifndef HUGO_PREFLOW_H
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#define HUGO_PREFLOW_H
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#include <vector>
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#include <queue>
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#include <hugo/invalid.h>
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#include <hugo/maps.h>
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/// \file
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/// \ingroup flowalgs
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/// Implementation of the preflow algorithm.
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namespace hugo {
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  /// \addtogroup flowalgs
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  /// @{                                                   
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  ///%Preflow algorithms class.
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  ///This class provides an implementation of the \e preflow \e
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  ///algorithm producing a flow of maximum value in a directed
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  ///graph. The preflow algorithms are the fastest max flow algorithms
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  ///up to now. The \e source node, the \e target node, the \e
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  ///capacity of the edges and the \e starting \e flow value of the
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  ///edges should be passed to the algorithm through the
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  ///constructor. It is possible to change these quantities using the
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  ///functions \ref setSource, \ref setTarget, \ref setCap and \ref
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  ///setFlow.
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  ///
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  ///After running \ref phase1() or \ref preflow(), the actual flow
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  ///value can be obtained by calling \ref flowValue(). The minimum
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  ///value cut can be written into a <tt>bool</tt> node map by
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  ///calling \ref minCut(). (\ref minMinCut() and \ref maxMinCut() writes
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  ///the inclusionwise minimum and maximum of the minimum value cuts,
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  ///resp.)
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  ///
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  ///\param Graph The directed graph type the algorithm runs on.
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  ///\param Num The number type of the capacities and the flow values.
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  ///\param CapMap The capacity map type.
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  ///\param FlowMap The flow map type.
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  ///
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  ///\author Jacint Szabo 
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  template <typename Graph, typename Num,
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	    typename CapMap=typename Graph::template EdgeMap<Num>,
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            typename FlowMap=typename Graph::template EdgeMap<Num> >
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  class Preflow {
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  protected:
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    typedef typename Graph::Node Node;
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    typedef typename Graph::NodeIt NodeIt;
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    typedef typename Graph::EdgeIt EdgeIt;
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    typedef typename Graph::OutEdgeIt OutEdgeIt;
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    typedef typename Graph::InEdgeIt InEdgeIt;
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    typedef typename Graph::template NodeMap<Node> NNMap;
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    typedef typename std::vector<Node> VecNode;
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    const Graph* g;
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    Node s;
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    Node t;
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    const CapMap* capacity;
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    FlowMap* flow;
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    int n;      //the number of nodes of G
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    typename Graph::template NodeMap<int> level;  
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    typename Graph::template NodeMap<Num> excess;
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    // constants used for heuristics
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    static const int H0=20;
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    static const int H1=1;
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    public:
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    ///Indicates the property of the starting flow map.
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    ///Indicates the property of the starting flow map. The meanings are as follows:
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    ///- \c ZERO_FLOW: constant zero flow
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    ///- \c GEN_FLOW: any flow, i.e. the sum of the in-flows equals to
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    ///the sum of the out-flows in every node except the \e source and
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    ///the \e target.
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    ///- \c PRE_FLOW: any preflow, i.e. the sum of the in-flows is at 
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    ///least the sum of the out-flows in every node except the \e source.
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    ///- \c NO_FLOW: indicates an unspecified edge map. \ref flow will be 
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    ///set to the constant zero flow in the beginning of the algorithm in this case.
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    ///
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    enum FlowEnum{
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      NO_FLOW,
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      ZERO_FLOW,
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      GEN_FLOW,
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      PRE_FLOW
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    };
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    ///Indicates the state of the preflow algorithm.
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    ///Indicates the state of the preflow algorithm. The meanings are as follows:
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    ///- \c AFTER_NOTHING: before running the algorithm or at an unspecified state.
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    ///- \c AFTER_PREFLOW_PHASE_1: right after running \c phase1
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    ///- \c AFTER_PREFLOW_PHASE_2: after running \ref phase2()
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    ///
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    enum StatusEnum {
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      AFTER_NOTHING,
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      AFTER_PREFLOW_PHASE_1,      
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      AFTER_PREFLOW_PHASE_2
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    };
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    protected: 
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      FlowEnum flow_prop;
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    StatusEnum status; // Do not needle this flag only if necessary.
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  public: 
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    ///The constructor of the class.
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    ///The constructor of the class. 
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    ///\param _G The directed graph the algorithm runs on. 
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    ///\param _s The source node.
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    ///\param _t The target node.
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    ///\param _capacity The capacity of the edges. 
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    ///\param _flow The flow of the edges. 
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    ///Except the graph, all of these parameters can be reset by
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    ///calling \ref setSource, \ref setTarget, \ref setCap and \ref
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    ///setFlow, resp.
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      Preflow(const Graph& _G, Node _s, Node _t, 
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	      const CapMap& _capacity, FlowMap& _flow) :
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	g(&_G), s(_s), t(_t), capacity(&_capacity),
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	flow(&_flow), n(_G.nodeNum()), level(_G), excess(_G,0), 
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	flow_prop(NO_FLOW), status(AFTER_NOTHING) { }
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    ///Runs the preflow algorithm.  
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    ///Runs the preflow algorithm.
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    ///
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    void run() {
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      phase1(flow_prop);
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      phase2();
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    }
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    ///Runs the preflow algorithm.  
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    ///Runs the preflow algorithm. 
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    ///\pre The starting flow map must be
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    /// - a constant zero flow if \c fp is \c ZERO_FLOW,
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    /// - an arbitrary flow if \c fp is \c GEN_FLOW,
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    /// - an arbitrary preflow if \c fp is \c PRE_FLOW,
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    /// - any map if \c fp is NO_FLOW.
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    ///If the starting flow map is a flow or a preflow then 
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    ///the algorithm terminates faster.
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    void run(FlowEnum fp) {
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      flow_prop=fp;
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      run();
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    }
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    ///Runs the first phase of the preflow algorithm.
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    ///The preflow algorithm consists of two phases, this method runs the
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    ///first phase. After the first phase the maximum flow value and a
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    ///minimum value cut can already be computed, though a maximum flow
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    ///is not yet obtained. So after calling this method \ref flowValue
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    ///and \ref minCut gives proper results.
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    ///\warning \ref minMinCut and \ref maxMinCut do not
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    ///give minimum value cuts unless calling \ref phase2.
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    ///\pre The starting flow must be
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    /// - a constant zero flow if \c fp is \c ZERO_FLOW,
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    /// - an arbitary flow if \c fp is \c GEN_FLOW,
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    /// - an arbitary preflow if \c fp is \c PRE_FLOW,
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    /// - any map if \c fp is NO_FLOW.
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    void phase1(FlowEnum fp)
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    {
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      flow_prop=fp;
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      phase1();
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    }
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    ///Runs the first phase of the preflow algorithm.
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    ///The preflow algorithm consists of two phases, this method runs the
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    ///first phase. After the first phase the maximum flow value and a
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    ///minimum value cut can already be computed, though a maximum flow
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    ///is not yet obtained. So after calling this method \ref flowValue
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    ///and \ref actMinCut gives proper results.
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    ///\warning \ref minCut, \ref minMinCut and \ref maxMinCut do not
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    ///give minimum value cuts unless calling \ref phase2.
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    void phase1()
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    {
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      int heur0=(int)(H0*n);  //time while running 'bound decrease'
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      int heur1=(int)(H1*n);  //time while running 'highest label'
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      int heur=heur1;         //starting time interval (#of relabels)
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      int numrelabel=0;
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      bool what_heur=1;
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      //It is 0 in case 'bound decrease' and 1 in case 'highest label'
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      bool end=false;
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      //Needed for 'bound decrease', true means no active 
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      //nodes are above bound b.
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      int k=n-2;  //bound on the highest level under n containing a node
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      int b=k;    //bound on the highest level under n of an active node
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      VecNode first(n, INVALID);
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      NNMap next(*g, INVALID);
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      NNMap left(*g, INVALID);
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      NNMap right(*g, INVALID);
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      VecNode level_list(n,INVALID);
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      //List of the nodes in level i<n, set to n.
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      preflowPreproc(first, next, level_list, left, right);
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      //Push/relabel on the highest level active nodes.
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      while ( true ) {
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	if ( b == 0 ) {
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	  if ( !what_heur && !end && k > 0 ) {
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	    b=k;
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	    end=true;
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	  } else break;
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	}
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	if ( first[b]==INVALID ) --b;
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	else {
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	  end=false;
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	  Node w=first[b];
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	  first[b]=next[w];
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	  int newlevel=push(w, next, first);
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	  if ( excess[w] > 0 ) relabel(w, newlevel, first, next, level_list, 
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				       left, right, b, k, what_heur);
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	  ++numrelabel;
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	  if ( numrelabel >= heur ) {
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	    numrelabel=0;
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	    if ( what_heur ) {
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	      what_heur=0;
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	      heur=heur0;
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	      end=false;
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	    } else {
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	      what_heur=1;
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	      heur=heur1;
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	      b=k;
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	    }
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	  }
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	}
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      }
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      flow_prop=PRE_FLOW;
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      status=AFTER_PREFLOW_PHASE_1;
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    }
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    // Heuristics:
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    //   2 phase
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    //   gap
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    //   list 'level_list' on the nodes on level i implemented by hand
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    //   stack 'active' on the active nodes on level i      
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    //   runs heuristic 'highest label' for H1*n relabels
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    //   runs heuristic 'bound decrease' for H0*n relabels, starts with 'highest label'
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    //   Parameters H0 and H1 are initialized to 20 and 1.
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    ///Runs the second phase of the preflow algorithm.
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    ///The preflow algorithm consists of two phases, this method runs
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    ///the second phase. After calling \ref phase1 and then
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    ///\ref phase2 the methods \ref flowValue, \ref minCut,
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    ///\ref minMinCut and \ref maxMinCut give proper results.
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    ///\pre \ref phase1 must be called before.
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    void phase2()
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    {
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      int k=n-2;  //bound on the highest level under n containing a node
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      int b=k;    //bound on the highest level under n of an active node
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      VecNode first(n, INVALID);
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      NNMap next(*g, INVALID); 
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      level.set(s,0);
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      std::queue<Node> bfs_queue;
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      bfs_queue.push(s);
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      while ( !bfs_queue.empty() ) {
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	Node v=bfs_queue.front();
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	bfs_queue.pop();
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	int l=level[v]+1;
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	for(InEdgeIt e(*g,v); e!=INVALID; ++e) {
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	  if ( (*capacity)[e] <= (*flow)[e] ) continue;
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	  Node u=g->tail(e);
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	  if ( level[u] >= n ) {
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	    bfs_queue.push(u);
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	    level.set(u, l);
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	    if ( excess[u] > 0 ) {
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	      next.set(u,first[l]);
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	      first[l]=u;
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	    }
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	  }
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	}
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	for(OutEdgeIt e(*g,v); e!=INVALID; ++e) {
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	  if ( 0 >= (*flow)[e] ) continue;
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	  Node u=g->head(e);
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	  if ( level[u] >= n ) {
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	    bfs_queue.push(u);
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	    level.set(u, l);
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	    if ( excess[u] > 0 ) {
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	      next.set(u,first[l]);
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	      first[l]=u;
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	    }
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	  }
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	}
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      }
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      b=n-2;
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      while ( true ) {
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	if ( b == 0 ) break;
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	if ( first[b]==INVALID ) --b;
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	else {
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	  Node w=first[b];
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	  first[b]=next[w];
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	  int newlevel=push(w,next, first);
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	  //relabel
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	  if ( excess[w] > 0 ) {
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	    level.set(w,++newlevel);
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	    next.set(w,first[newlevel]);
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	    first[newlevel]=w;
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	    b=newlevel;
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	  }
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	} 
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      } // while(true)
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      flow_prop=GEN_FLOW;
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      status=AFTER_PREFLOW_PHASE_2;
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    }
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    /// Returns the value of the maximum flow.
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    /// Returns the value of the maximum flow by returning the excess
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    /// of the target node \ref t. This value equals to the value of
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    /// the maximum flow already after running \ref phase1.
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    Num flowValue() const {
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      return excess[t];
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    }
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    ///Returns a minimum value cut.
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    ///Sets \c M to the characteristic vector of a minimum value
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    ///cut. This method can be called both after running \ref
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    ///phase1 and \ref phase2. It is much faster after
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    ///\ref phase1.  \pre M should be a bool-valued node-map. \pre
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    ///If \ref mincut is called after \ref phase2 then M should
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    ///be initialized to false.
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    template<typename _CutMap>
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    void minCut(_CutMap& M) const {
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      switch ( status ) {
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	case AFTER_PREFLOW_PHASE_1:
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	for(NodeIt v(*g); v!=INVALID; ++v) {
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	  if (level[v] < n) {
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	    M.set(v, false);
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	  } else {
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	    M.set(v, true);
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	  }
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	}
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	break;
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	case AFTER_PREFLOW_PHASE_2:
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	minMinCut(M);
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	break;
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	case AFTER_NOTHING:
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	break;
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      }
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    }
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   372
    ///Returns the inclusionwise minimum of the minimum value cuts.
jacint@836
   373
jacint@836
   374
    ///Sets \c M to the characteristic vector of the minimum value cut
jacint@836
   375
    ///which is inclusionwise minimum. It is computed by processing a
jacint@836
   376
    ///bfs from the source node \c s in the residual graph.  \pre M
jacint@836
   377
    ///should be a node map of bools initialized to false.  \pre \ref
jacint@836
   378
    ///phase2 should already be run.
jacint@836
   379
    template<typename _CutMap>
jacint@836
   380
    void minMinCut(_CutMap& M) const {
jacint@836
   381
jacint@836
   382
      std::queue<Node> queue;
jacint@836
   383
      M.set(s,true);
jacint@836
   384
      queue.push(s);
jacint@836
   385
      
jacint@836
   386
      while (!queue.empty()) {
jacint@836
   387
	Node w=queue.front();
jacint@836
   388
	queue.pop();
jacint@836
   389
	
jacint@836
   390
	for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
jacint@836
   391
	  Node v=g->head(e);
jacint@836
   392
	  if (!M[v] && (*flow)[e] < (*capacity)[e] ) {
jacint@836
   393
	    queue.push(v);
jacint@836
   394
	    M.set(v, true);
jacint@836
   395
	  }
jacint@836
   396
	}
jacint@836
   397
	
jacint@836
   398
	for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
jacint@836
   399
	  Node v=g->tail(e);
jacint@836
   400
	  if (!M[v] && (*flow)[e] > 0 ) {
jacint@836
   401
	    queue.push(v);
jacint@836
   402
	    M.set(v, true);
jacint@836
   403
	  }
jacint@836
   404
	}
jacint@836
   405
      }
jacint@836
   406
    }
jacint@836
   407
    
jacint@836
   408
    ///Returns the inclusionwise maximum of the minimum value cuts.
jacint@836
   409
jacint@836
   410
    ///Sets \c M to the characteristic vector of the minimum value cut
jacint@836
   411
    ///which is inclusionwise maximum. It is computed by processing a
jacint@836
   412
    ///backward bfs from the target node \c t in the residual graph.
jacint@836
   413
    ///\pre \ref phase2() or preflow() should already be run.
jacint@836
   414
    template<typename _CutMap>
jacint@836
   415
    void maxMinCut(_CutMap& M) const {
jacint@836
   416
jacint@836
   417
      for(NodeIt v(*g) ; v!=INVALID; ++v) M.set(v, true);
jacint@836
   418
jacint@836
   419
      std::queue<Node> queue;
jacint@836
   420
jacint@836
   421
      M.set(t,false);
jacint@836
   422
      queue.push(t);
jacint@836
   423
jacint@836
   424
      while (!queue.empty()) {
jacint@836
   425
        Node w=queue.front();
jacint@836
   426
	queue.pop();
jacint@836
   427
jacint@836
   428
	for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
jacint@836
   429
	  Node v=g->tail(e);
jacint@836
   430
	  if (M[v] && (*flow)[e] < (*capacity)[e] ) {
jacint@836
   431
	    queue.push(v);
jacint@836
   432
	    M.set(v, false);
jacint@836
   433
	  }
jacint@836
   434
	}
jacint@836
   435
jacint@836
   436
	for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
jacint@836
   437
	  Node v=g->head(e);
jacint@836
   438
	  if (M[v] && (*flow)[e] > 0 ) {
jacint@836
   439
	    queue.push(v);
jacint@836
   440
	    M.set(v, false);
jacint@836
   441
	  }
jacint@836
   442
	}
jacint@836
   443
      }
jacint@836
   444
    }
jacint@836
   445
jacint@836
   446
    ///Sets the source node to \c _s.
jacint@836
   447
jacint@836
   448
    ///Sets the source node to \c _s.
jacint@836
   449
    /// 
jacint@836
   450
    void setSource(Node _s) { 
jacint@836
   451
      s=_s; 
jacint@836
   452
      if ( flow_prop != ZERO_FLOW ) flow_prop=NO_FLOW;
jacint@836
   453
      status=AFTER_NOTHING; 
jacint@836
   454
    }
jacint@836
   455
jacint@836
   456
    ///Sets the target node to \c _t.
jacint@836
   457
jacint@836
   458
    ///Sets the target node to \c _t.
jacint@836
   459
    ///
jacint@836
   460
    void setTarget(Node _t) { 
jacint@836
   461
      t=_t; 
jacint@836
   462
      if ( flow_prop == GEN_FLOW ) flow_prop=PRE_FLOW;
jacint@836
   463
      status=AFTER_NOTHING; 
jacint@836
   464
    }
jacint@836
   465
jacint@836
   466
    /// Sets the edge map of the capacities to _cap.
jacint@836
   467
jacint@836
   468
    /// Sets the edge map of the capacities to _cap.
jacint@836
   469
    /// 
jacint@836
   470
    void setCap(const CapMap& _cap) { 
jacint@836
   471
      capacity=&_cap; 
jacint@836
   472
      status=AFTER_NOTHING; 
jacint@836
   473
    }
jacint@836
   474
jacint@836
   475
    /// Sets the edge map of the flows to _flow.
jacint@836
   476
jacint@836
   477
    /// Sets the edge map of the flows to _flow.
jacint@836
   478
    /// 
jacint@836
   479
    void setFlow(FlowMap& _flow) { 
jacint@836
   480
      flow=&_flow; 
jacint@836
   481
      flow_prop=NO_FLOW;
jacint@836
   482
      status=AFTER_NOTHING; 
jacint@836
   483
    }
jacint@836
   484
jacint@836
   485
jacint@836
   486
  private:
jacint@836
   487
jacint@836
   488
    int push(Node w, NNMap& next, VecNode& first) {
jacint@836
   489
jacint@836
   490
      int lev=level[w];
jacint@836
   491
      Num exc=excess[w];
jacint@836
   492
      int newlevel=n;       //bound on the next level of w
jacint@836
   493
jacint@836
   494
      for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
jacint@836
   495
	if ( (*flow)[e] >= (*capacity)[e] ) continue;
jacint@836
   496
	Node v=g->head(e);
jacint@836
   497
jacint@836
   498
	if( lev > level[v] ) { //Push is allowed now
jacint@836
   499
	  
jacint@836
   500
	  if ( excess[v]<=0 && v!=t && v!=s ) {
jacint@836
   501
	    next.set(v,first[level[v]]);
jacint@836
   502
	    first[level[v]]=v;
jacint@836
   503
	  }
jacint@836
   504
jacint@836
   505
	  Num cap=(*capacity)[e];
jacint@836
   506
	  Num flo=(*flow)[e];
jacint@836
   507
	  Num remcap=cap-flo;
jacint@836
   508
	  
jacint@836
   509
	  if ( remcap >= exc ) { //A nonsaturating push.
jacint@836
   510
	    
jacint@836
   511
	    flow->set(e, flo+exc);
jacint@836
   512
	    excess.set(v, excess[v]+exc);
jacint@836
   513
	    exc=0;
jacint@836
   514
	    break;
jacint@836
   515
jacint@836
   516
	  } else { //A saturating push.
jacint@836
   517
	    flow->set(e, cap);
jacint@836
   518
	    excess.set(v, excess[v]+remcap);
jacint@836
   519
	    exc-=remcap;
jacint@836
   520
	  }
jacint@836
   521
	} else if ( newlevel > level[v] ) newlevel = level[v];
jacint@836
   522
      } //for out edges wv
jacint@836
   523
jacint@836
   524
      if ( exc > 0 ) {
jacint@836
   525
	for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
jacint@836
   526
	  
jacint@836
   527
	  if( (*flow)[e] <= 0 ) continue;
jacint@836
   528
	  Node v=g->tail(e);
jacint@836
   529
jacint@836
   530
	  if( lev > level[v] ) { //Push is allowed now
jacint@836
   531
jacint@836
   532
	    if ( excess[v]<=0 && v!=t && v!=s ) {
jacint@836
   533
	      next.set(v,first[level[v]]);
jacint@836
   534
	      first[level[v]]=v;
jacint@836
   535
	    }
jacint@836
   536
jacint@836
   537
	    Num flo=(*flow)[e];
jacint@836
   538
jacint@836
   539
	    if ( flo >= exc ) { //A nonsaturating push.
jacint@836
   540
jacint@836
   541
	      flow->set(e, flo-exc);
jacint@836
   542
	      excess.set(v, excess[v]+exc);
jacint@836
   543
	      exc=0;
jacint@836
   544
	      break;
jacint@836
   545
	    } else {  //A saturating push.
jacint@836
   546
jacint@836
   547
	      excess.set(v, excess[v]+flo);
jacint@836
   548
	      exc-=flo;
jacint@836
   549
	      flow->set(e,0);
jacint@836
   550
	    }
jacint@836
   551
	  } else if ( newlevel > level[v] ) newlevel = level[v];
jacint@836
   552
	} //for in edges vw
jacint@836
   553
jacint@836
   554
      } // if w still has excess after the out edge for cycle
jacint@836
   555
jacint@836
   556
      excess.set(w, exc);
jacint@836
   557
      
jacint@836
   558
      return newlevel;
jacint@836
   559
    }
jacint@836
   560
    
jacint@836
   561
    
jacint@836
   562
    
jacint@836
   563
    void preflowPreproc(VecNode& first, NNMap& next, 
jacint@836
   564
			VecNode& level_list, NNMap& left, NNMap& right)
jacint@836
   565
    {
jacint@836
   566
      for(NodeIt v(*g); v!=INVALID; ++v) level.set(v,n);
jacint@836
   567
      std::queue<Node> bfs_queue;
jacint@836
   568
      
jacint@836
   569
      if ( flow_prop == GEN_FLOW || flow_prop == PRE_FLOW ) {
jacint@836
   570
	//Reverse_bfs from t in the residual graph,
jacint@836
   571
	//to find the starting level.
jacint@836
   572
	level.set(t,0);
jacint@836
   573
	bfs_queue.push(t);
jacint@836
   574
	
jacint@836
   575
	while ( !bfs_queue.empty() ) {
jacint@836
   576
	  
jacint@836
   577
	  Node v=bfs_queue.front();
jacint@836
   578
	  bfs_queue.pop();
jacint@836
   579
	  int l=level[v]+1;
jacint@836
   580
	  
jacint@836
   581
	  for(InEdgeIt e(*g,v) ; e!=INVALID; ++e) {
jacint@836
   582
	    if ( (*capacity)[e] <= (*flow)[e] ) continue;
jacint@836
   583
	    Node w=g->tail(e);
jacint@836
   584
	    if ( level[w] == n && w != s ) {
jacint@836
   585
	      bfs_queue.push(w);
jacint@836
   586
	      Node z=level_list[l];
jacint@836
   587
	      if ( z!=INVALID ) left.set(z,w);
jacint@836
   588
	      right.set(w,z);
jacint@836
   589
	      level_list[l]=w;
jacint@836
   590
	      level.set(w, l);
jacint@836
   591
	    }
jacint@836
   592
	  }
jacint@836
   593
	  
jacint@836
   594
	  for(OutEdgeIt e(*g,v) ; e!=INVALID; ++e) {
jacint@836
   595
	    if ( 0 >= (*flow)[e] ) continue;
jacint@836
   596
	    Node w=g->head(e);
jacint@836
   597
	    if ( level[w] == n && w != s ) {
jacint@836
   598
	      bfs_queue.push(w);
jacint@836
   599
	      Node z=level_list[l];
jacint@836
   600
	      if ( z!=INVALID ) left.set(z,w);
jacint@836
   601
	      right.set(w,z);
jacint@836
   602
	      level_list[l]=w;
jacint@836
   603
	      level.set(w, l);
jacint@836
   604
	    }
jacint@836
   605
	  }
jacint@836
   606
	} //while
jacint@836
   607
      } //if
jacint@836
   608
jacint@836
   609
jacint@836
   610
      switch (flow_prop) {
jacint@836
   611
	case NO_FLOW:  
jacint@836
   612
	for(EdgeIt e(*g); e!=INVALID; ++e) flow->set(e,0);
jacint@836
   613
	case ZERO_FLOW:
jacint@836
   614
	for(NodeIt v(*g); v!=INVALID; ++v) excess.set(v,0);
jacint@836
   615
	
jacint@836
   616
	//Reverse_bfs from t, to find the starting level.
jacint@836
   617
	level.set(t,0);
jacint@836
   618
	bfs_queue.push(t);
jacint@836
   619
	
jacint@836
   620
	while ( !bfs_queue.empty() ) {
jacint@836
   621
	  
jacint@836
   622
	  Node v=bfs_queue.front();
jacint@836
   623
	  bfs_queue.pop();
jacint@836
   624
	  int l=level[v]+1;
jacint@836
   625
	  
jacint@836
   626
	  for(InEdgeIt e(*g,v) ; e!=INVALID; ++e) {
jacint@836
   627
	    Node w=g->tail(e);
jacint@836
   628
	    if ( level[w] == n && w != s ) {
jacint@836
   629
	      bfs_queue.push(w);
jacint@836
   630
	      Node z=level_list[l];
jacint@836
   631
	      if ( z!=INVALID ) left.set(z,w);
jacint@836
   632
	      right.set(w,z);
jacint@836
   633
	      level_list[l]=w;
jacint@836
   634
	      level.set(w, l);
jacint@836
   635
	    }
jacint@836
   636
	  }
jacint@836
   637
	}
jacint@836
   638
	
jacint@836
   639
	//the starting flow
jacint@836
   640
	for(OutEdgeIt e(*g,s) ; e!=INVALID; ++e) {
jacint@836
   641
	  Num c=(*capacity)[e];
jacint@836
   642
	  if ( c <= 0 ) continue;
jacint@836
   643
	  Node w=g->head(e);
jacint@836
   644
	  if ( level[w] < n ) {
jacint@836
   645
	    if ( excess[w] <= 0 && w!=t ) { //putting into the stack
jacint@836
   646
	      next.set(w,first[level[w]]);
jacint@836
   647
	      first[level[w]]=w;
jacint@836
   648
	    }
jacint@836
   649
	    flow->set(e, c);
jacint@836
   650
	    excess.set(w, excess[w]+c);
jacint@836
   651
	  }
jacint@836
   652
	}
jacint@836
   653
	break;
jacint@836
   654
jacint@836
   655
	case GEN_FLOW:
jacint@836
   656
	for(NodeIt v(*g); v!=INVALID; ++v) excess.set(v,0);
jacint@836
   657
	{
jacint@836
   658
	  Num exc=0;
jacint@836
   659
	  for(InEdgeIt e(*g,t) ; e!=INVALID; ++e) exc+=(*flow)[e];
jacint@836
   660
	  for(OutEdgeIt e(*g,t) ; e!=INVALID; ++e) exc-=(*flow)[e];
jacint@836
   661
	  excess.set(t,exc);
jacint@836
   662
	}
jacint@836
   663
jacint@836
   664
	//the starting flow
jacint@836
   665
	for(OutEdgeIt e(*g,s); e!=INVALID; ++e)	{
jacint@836
   666
	  Num rem=(*capacity)[e]-(*flow)[e];
jacint@836
   667
	  if ( rem <= 0 ) continue;
jacint@836
   668
	  Node w=g->head(e);
jacint@836
   669
	  if ( level[w] < n ) {
jacint@836
   670
	    if ( excess[w] <= 0 && w!=t ) { //putting into the stack
jacint@836
   671
	      next.set(w,first[level[w]]);
jacint@836
   672
	      first[level[w]]=w;
jacint@836
   673
	    }   
jacint@836
   674
	    flow->set(e, (*capacity)[e]);
jacint@836
   675
	    excess.set(w, excess[w]+rem);
jacint@836
   676
	  }
jacint@836
   677
	}
jacint@836
   678
	
jacint@836
   679
	for(InEdgeIt e(*g,s); e!=INVALID; ++e) {
jacint@836
   680
	  if ( (*flow)[e] <= 0 ) continue;
jacint@836
   681
	  Node w=g->tail(e);
jacint@836
   682
	  if ( level[w] < n ) {
jacint@836
   683
	    if ( excess[w] <= 0 && w!=t ) {
jacint@836
   684
	      next.set(w,first[level[w]]);
jacint@836
   685
	      first[level[w]]=w;
jacint@836
   686
	    }  
jacint@836
   687
	    excess.set(w, excess[w]+(*flow)[e]);
jacint@836
   688
	    flow->set(e, 0);
jacint@836
   689
	  }
jacint@836
   690
	}
jacint@836
   691
	break;
jacint@836
   692
jacint@836
   693
	case PRE_FLOW:	
jacint@836
   694
	//the starting flow
jacint@836
   695
	for(OutEdgeIt e(*g,s) ; e!=INVALID; ++e) {
jacint@836
   696
	  Num rem=(*capacity)[e]-(*flow)[e];
jacint@836
   697
	  if ( rem <= 0 ) continue;
jacint@836
   698
	  Node w=g->head(e);
jacint@836
   699
	  if ( level[w] < n ) flow->set(e, (*capacity)[e]);
jacint@836
   700
	}
jacint@836
   701
	
jacint@836
   702
	for(InEdgeIt e(*g,s) ; e!=INVALID; ++e) {
jacint@836
   703
	  if ( (*flow)[e] <= 0 ) continue;
jacint@836
   704
	  Node w=g->tail(e);
jacint@836
   705
	  if ( level[w] < n ) flow->set(e, 0);
jacint@836
   706
	}
jacint@836
   707
	
jacint@836
   708
	//computing the excess
jacint@836
   709
	for(NodeIt w(*g); w!=INVALID; ++w) {
jacint@836
   710
	  Num exc=0;
jacint@836
   711
	  for(InEdgeIt e(*g,w); e!=INVALID; ++e) exc+=(*flow)[e];
jacint@836
   712
	  for(OutEdgeIt e(*g,w); e!=INVALID; ++e) exc-=(*flow)[e];
jacint@836
   713
	  excess.set(w,exc);
jacint@836
   714
	  
jacint@836
   715
	  //putting the active nodes into the stack
jacint@836
   716
	  int lev=level[w];
jacint@836
   717
	    if ( exc > 0 && lev < n && Node(w) != t ) {
jacint@836
   718
	      next.set(w,first[lev]);
jacint@836
   719
	      first[lev]=w;
jacint@836
   720
	    }
jacint@836
   721
	}
jacint@836
   722
	break;
jacint@836
   723
      } //switch
jacint@836
   724
    } //preflowPreproc
jacint@836
   725
jacint@836
   726
jacint@836
   727
    void relabel(Node w, int newlevel, VecNode& first, NNMap& next, 
jacint@836
   728
		 VecNode& level_list, NNMap& left,
jacint@836
   729
		 NNMap& right, int& b, int& k, bool what_heur )
jacint@836
   730
    {
jacint@836
   731
jacint@836
   732
      int lev=level[w];
jacint@836
   733
jacint@836
   734
      Node right_n=right[w];
jacint@836
   735
      Node left_n=left[w];
jacint@836
   736
jacint@836
   737
      //unlacing starts
jacint@836
   738
      if ( right_n!=INVALID ) {
jacint@836
   739
	if ( left_n!=INVALID ) {
jacint@836
   740
	  right.set(left_n, right_n);
jacint@836
   741
	  left.set(right_n, left_n);
jacint@836
   742
	} else {
jacint@836
   743
	  level_list[lev]=right_n;
jacint@836
   744
	  left.set(right_n, INVALID);
jacint@836
   745
	}
jacint@836
   746
      } else {
jacint@836
   747
	if ( left_n!=INVALID ) {
jacint@836
   748
	  right.set(left_n, INVALID);
jacint@836
   749
	} else {
jacint@836
   750
	  level_list[lev]=INVALID;
jacint@836
   751
	}
jacint@836
   752
      }
jacint@836
   753
      //unlacing ends
jacint@836
   754
jacint@836
   755
      if ( level_list[lev]==INVALID ) {
jacint@836
   756
jacint@836
   757
	//gapping starts
jacint@836
   758
	for (int i=lev; i!=k ; ) {
jacint@836
   759
	  Node v=level_list[++i];
jacint@836
   760
	  while ( v!=INVALID ) {
jacint@836
   761
	    level.set(v,n);
jacint@836
   762
	    v=right[v];
jacint@836
   763
	  }
jacint@836
   764
	  level_list[i]=INVALID;
jacint@836
   765
	  if ( !what_heur ) first[i]=INVALID;
jacint@836
   766
	}
jacint@836
   767
jacint@836
   768
	level.set(w,n);
jacint@836
   769
	b=lev-1;
jacint@836
   770
	k=b;
jacint@836
   771
	//gapping ends
jacint@836
   772
jacint@836
   773
      } else {
jacint@836
   774
jacint@836
   775
	if ( newlevel == n ) level.set(w,n);
jacint@836
   776
	else {
jacint@836
   777
	  level.set(w,++newlevel);
jacint@836
   778
	  next.set(w,first[newlevel]);
jacint@836
   779
	  first[newlevel]=w;
jacint@836
   780
	  if ( what_heur ) b=newlevel;
jacint@836
   781
	  if ( k < newlevel ) ++k;      //now k=newlevel
jacint@836
   782
	  Node z=level_list[newlevel];
jacint@836
   783
	  if ( z!=INVALID ) left.set(z,w);
jacint@836
   784
	  right.set(w,z);
jacint@836
   785
	  left.set(w,INVALID);
jacint@836
   786
	  level_list[newlevel]=w;
jacint@836
   787
	}
jacint@836
   788
      }
jacint@836
   789
    } //relabel
jacint@836
   790
jacint@836
   791
  }; 
jacint@836
   792
} //namespace hugo
jacint@836
   793
jacint@836
   794
#endif //HUGO_PREFLOW_H
jacint@836
   795
jacint@836
   796
jacint@836
   797
jacint@836
   798