COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/lemon/preflow.h @ 977:48962802d168

Last change on this file since 977:48962802d168 was 977:48962802d168, checked in by Mihaly Barasz, 15 years ago
  • enable_if imported from BOOST
  • count{Nodes,Edges} implemented via graph tags
  • some #include bugs fixed
File size: 21.5 KB
Line 
1/* -*- C++ -*-
2 * src/lemon/preflow.h - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Combinatorial Optimization Research Group, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17#ifndef LEMON_PREFLOW_H
18#define LEMON_PREFLOW_H
19
20#include <vector>
21#include <queue>
22
23#include <lemon/invalid.h>
24#include <lemon/maps.h>
25#include <lemon/graph_utils.h>
26
27/// \file
28/// \ingroup flowalgs
29/// Implementation of the preflow algorithm.
30
31namespace lemon {
32
33  /// \addtogroup flowalgs
34  /// @{                                                   
35
36  ///%Preflow algorithms class.
37
38  ///This class provides an implementation of the \e preflow \e
39  ///algorithm producing a flow of maximum value in a directed
40  ///graph. The preflow algorithms are the fastest max flow algorithms
41  ///up to now. The \e source node, the \e target node, the \e
42  ///capacity of the edges and the \e starting \e flow value of the
43  ///edges should be passed to the algorithm through the
44  ///constructor. It is possible to change these quantities using the
45  ///functions \ref setSource, \ref setTarget, \ref setCap and \ref
46  ///setFlow.
47  ///
48  ///After running \ref lemon::Preflow::phase1() "phase1()"
49  ///or \ref lemon::Preflow::run() "run()", the maximal flow
50  ///value can be obtained by calling \ref flowValue(). The minimum
51  ///value cut can be written into a <tt>bool</tt> node map by
52  ///calling \ref minCut(). (\ref minMinCut() and \ref maxMinCut() writes
53  ///the inclusionwise minimum and maximum of the minimum value cuts,
54  ///resp.)
55  ///
56  ///\param Graph The directed graph type the algorithm runs on.
57  ///\param Num The number type of the capacities and the flow values.
58  ///\param CapMap The capacity map type.
59  ///\param FlowMap The flow map type.
60  ///
61  ///\author Jacint Szabo
62  template <typename Graph, typename Num,
63            typename CapMap=typename Graph::template EdgeMap<Num>,
64            typename FlowMap=typename Graph::template EdgeMap<Num> >
65  class Preflow {
66  protected:
67    typedef typename Graph::Node Node;
68    typedef typename Graph::NodeIt NodeIt;
69    typedef typename Graph::EdgeIt EdgeIt;
70    typedef typename Graph::OutEdgeIt OutEdgeIt;
71    typedef typename Graph::InEdgeIt InEdgeIt;
72
73    typedef typename Graph::template NodeMap<Node> NNMap;
74    typedef typename std::vector<Node> VecNode;
75
76    const Graph* g;
77    Node s;
78    Node t;
79    const CapMap* capacity;
80    FlowMap* flow;
81    int n;      //the number of nodes of G
82   
83    typename Graph::template NodeMap<int> level; 
84    typename Graph::template NodeMap<Num> excess;
85
86    // constants used for heuristics
87    static const int H0=20;
88    static const int H1=1;
89
90    public:
91
92    ///Indicates the property of the starting flow map.
93
94    ///Indicates the property of the starting flow map. The meanings are as follows:
95    ///- \c ZERO_FLOW: constant zero flow
96    ///- \c GEN_FLOW: any flow, i.e. the sum of the in-flows equals to
97    ///the sum of the out-flows in every node except the \e source and
98    ///the \e target.
99    ///- \c PRE_FLOW: any preflow, i.e. the sum of the in-flows is at
100    ///least the sum of the out-flows in every node except the \e source.
101    ///- \c NO_FLOW: indicates an unspecified edge map. \c flow will be
102    ///set to the constant zero flow in the beginning of
103    ///the algorithm in this case.
104    ///
105    enum FlowEnum{
106      NO_FLOW,
107      ZERO_FLOW,
108      GEN_FLOW,
109      PRE_FLOW
110    };
111
112    ///Indicates the state of the preflow algorithm.
113
114    ///Indicates the state of the preflow algorithm. The meanings are as follows:
115    ///- \c AFTER_NOTHING: before running the algorithm or at an unspecified state.
116    ///- \c AFTER_PREFLOW_PHASE_1: right after running \c phase1
117    ///- \c AFTER_PREFLOW_PHASE_2: after running \ref phase2()
118    ///
119    enum StatusEnum {
120      AFTER_NOTHING,
121      AFTER_PREFLOW_PHASE_1,     
122      AFTER_PREFLOW_PHASE_2
123    };
124   
125    protected:
126      FlowEnum flow_prop;
127    StatusEnum status; // Do not needle this flag only if necessary.
128   
129  public:
130    ///The constructor of the class.
131
132    ///The constructor of the class.
133    ///\param _G The directed graph the algorithm runs on.
134    ///\param _s The source node.
135    ///\param _t The target node.
136    ///\param _capacity The capacity of the edges.
137    ///\param _flow The flow of the edges.
138    ///Except the graph, all of these parameters can be reset by
139    ///calling \ref setSource, \ref setTarget, \ref setCap and \ref
140    ///setFlow, resp.
141      Preflow(const Graph& _G, Node _s, Node _t,
142              const CapMap& _capacity, FlowMap& _flow) :
143        g(&_G), s(_s), t(_t), capacity(&_capacity),
144        flow(&_flow), n(countNodes(_G)), level(_G), excess(_G,0),
145        flow_prop(NO_FLOW), status(AFTER_NOTHING) { }
146
147
148                                                                             
149    ///Runs the preflow algorithm. 
150
151    ///Runs the preflow algorithm.
152    ///
153    void run() {
154      phase1(flow_prop);
155      phase2();
156    }
157   
158    ///Runs the preflow algorithm. 
159   
160    ///Runs the preflow algorithm.
161    ///\pre The starting flow map must be
162    /// - a constant zero flow if \c fp is \c ZERO_FLOW,
163    /// - an arbitrary flow if \c fp is \c GEN_FLOW,
164    /// - an arbitrary preflow if \c fp is \c PRE_FLOW,
165    /// - any map if \c fp is NO_FLOW.
166    ///If the starting flow map is a flow or a preflow then
167    ///the algorithm terminates faster.
168    void run(FlowEnum fp) {
169      flow_prop=fp;
170      run();
171    }
172     
173    ///Runs the first phase of the preflow algorithm.
174
175    ///The preflow algorithm consists of two phases, this method runs
176    ///the first phase. After the first phase the maximum flow value
177    ///and a minimum value cut can already be computed, though a
178    ///maximum flow is not yet obtained. So after calling this method
179    ///\ref flowValue returns the value of a maximum flow and \ref
180    ///minCut returns a minimum cut.     
181    ///\warning \ref minMinCut and \ref maxMinCut do not give minimum
182    ///value cuts unless calling \ref phase2. 
183    ///\pre The starting flow must be
184    ///- a constant zero flow if \c fp is \c ZERO_FLOW,
185    ///- an arbitary flow if \c fp is \c GEN_FLOW,
186    ///- an arbitary preflow if \c fp is \c PRE_FLOW,
187    ///- any map if \c fp is NO_FLOW.
188    void phase1(FlowEnum fp)
189    {
190      flow_prop=fp;
191      phase1();
192    }
193
194   
195    ///Runs the first phase of the preflow algorithm.
196
197    ///The preflow algorithm consists of two phases, this method runs
198    ///the first phase. After the first phase the maximum flow value
199    ///and a minimum value cut can already be computed, though a
200    ///maximum flow is not yet obtained. So after calling this method
201    ///\ref flowValue returns the value of a maximum flow and \ref
202    ///minCut returns a minimum cut.
203    ///\warning \ref minCut(), \ref minMinCut() and \ref maxMinCut() do not
204    ///give minimum value cuts unless calling \ref phase2().
205    void phase1()
206    {
207      int heur0=(int)(H0*n);  //time while running 'bound decrease'
208      int heur1=(int)(H1*n);  //time while running 'highest label'
209      int heur=heur1;         //starting time interval (#of relabels)
210      int numrelabel=0;
211
212      bool what_heur=1;
213      //It is 0 in case 'bound decrease' and 1 in case 'highest label'
214
215      bool end=false;
216      //Needed for 'bound decrease', true means no active
217      //nodes are above bound b.
218
219      int k=n-2;  //bound on the highest level under n containing a node
220      int b=k;    //bound on the highest level under n of an active node
221
222      VecNode first(n, INVALID);
223      NNMap next(*g, INVALID);
224
225      NNMap left(*g, INVALID);
226      NNMap right(*g, INVALID);
227      VecNode level_list(n,INVALID);
228      //List of the nodes in level i<n, set to n.
229
230      preflowPreproc(first, next, level_list, left, right);
231
232      //Push/relabel on the highest level active nodes.
233      while ( true ) {
234        if ( b == 0 ) {
235          if ( !what_heur && !end && k > 0 ) {
236            b=k;
237            end=true;
238          } else break;
239        }
240
241        if ( first[b]==INVALID ) --b;
242        else {
243          end=false;
244          Node w=first[b];
245          first[b]=next[w];
246          int newlevel=push(w, next, first);
247          if ( excess[w] > 0 ) relabel(w, newlevel, first, next, level_list,
248                                       left, right, b, k, what_heur);
249
250          ++numrelabel;
251          if ( numrelabel >= heur ) {
252            numrelabel=0;
253            if ( what_heur ) {
254              what_heur=0;
255              heur=heur0;
256              end=false;
257            } else {
258              what_heur=1;
259              heur=heur1;
260              b=k;
261            }
262          }
263        }
264      }
265      flow_prop=PRE_FLOW;
266      status=AFTER_PREFLOW_PHASE_1;
267    }
268    // Heuristics:
269    //   2 phase
270    //   gap
271    //   list 'level_list' on the nodes on level i implemented by hand
272    //   stack 'active' on the active nodes on level i     
273    //   runs heuristic 'highest label' for H1*n relabels
274    //   runs heuristic 'bound decrease' for H0*n relabels, starts with 'highest label'
275    //   Parameters H0 and H1 are initialized to 20 and 1.
276
277
278    ///Runs the second phase of the preflow algorithm.
279
280    ///The preflow algorithm consists of two phases, this method runs
281    ///the second phase. After calling \ref phase1 and then \ref
282    ///phase2, \ref flow contains a maximum flow, \ref flowValue
283    ///returns the value of a maximum flow, \ref minCut returns a
284    ///minimum cut, while the methods \ref minMinCut and \ref
285    ///maxMinCut return the inclusionwise minimum and maximum cuts of
286    ///minimum value, resp.  \pre \ref phase1 must be called before.
287    void phase2()
288    {
289
290      int k=n-2;  //bound on the highest level under n containing a node
291      int b=k;    //bound on the highest level under n of an active node
292
293   
294      VecNode first(n, INVALID);
295      NNMap next(*g, INVALID);
296      level.set(s,0);
297      std::queue<Node> bfs_queue;
298      bfs_queue.push(s);
299
300      while ( !bfs_queue.empty() ) {
301
302        Node v=bfs_queue.front();
303        bfs_queue.pop();
304        int l=level[v]+1;
305
306        for(InEdgeIt e(*g,v); e!=INVALID; ++e) {
307          if ( (*capacity)[e] <= (*flow)[e] ) continue;
308          Node u=g->tail(e);
309          if ( level[u] >= n ) {
310            bfs_queue.push(u);
311            level.set(u, l);
312            if ( excess[u] > 0 ) {
313              next.set(u,first[l]);
314              first[l]=u;
315            }
316          }
317        }
318
319        for(OutEdgeIt e(*g,v); e!=INVALID; ++e) {
320          if ( 0 >= (*flow)[e] ) continue;
321          Node u=g->head(e);
322          if ( level[u] >= n ) {
323            bfs_queue.push(u);
324            level.set(u, l);
325            if ( excess[u] > 0 ) {
326              next.set(u,first[l]);
327              first[l]=u;
328            }
329          }
330        }
331      }
332      b=n-2;
333
334      while ( true ) {
335
336        if ( b == 0 ) break;
337        if ( first[b]==INVALID ) --b;
338        else {
339          Node w=first[b];
340          first[b]=next[w];
341          int newlevel=push(w,next, first);
342         
343          //relabel
344          if ( excess[w] > 0 ) {
345            level.set(w,++newlevel);
346            next.set(w,first[newlevel]);
347            first[newlevel]=w;
348            b=newlevel;
349          }
350        }
351      } // while(true)
352      flow_prop=GEN_FLOW;
353      status=AFTER_PREFLOW_PHASE_2;
354    }
355
356    /// Returns the value of the maximum flow.
357
358    /// Returns the value of the maximum flow by returning the excess
359    /// of the target node \c t. This value equals to the value of
360    /// the maximum flow already after running \ref phase1.
361    Num flowValue() const {
362      return excess[t];
363    }
364
365
366    ///Returns a minimum value cut.
367
368    ///Sets \c M to the characteristic vector of a minimum value
369    ///cut. This method can be called both after running \ref
370    ///phase1 and \ref phase2. It is much faster after
371    ///\ref phase1.  \pre M should be a bool-valued node-map. \pre
372    ///If \ref minCut() is called after \ref phase2() then M should
373    ///be initialized to false.
374    template<typename _CutMap>
375    void minCut(_CutMap& M) const {
376      switch ( status ) {
377        case AFTER_PREFLOW_PHASE_1:
378        for(NodeIt v(*g); v!=INVALID; ++v) {
379          if (level[v] < n) {
380            M.set(v, false);
381          } else {
382            M.set(v, true);
383          }
384        }
385        break;
386        case AFTER_PREFLOW_PHASE_2:
387        minMinCut(M);
388        break;
389        case AFTER_NOTHING:
390        break;
391      }
392    }
393
394    ///Returns the inclusionwise minimum of the minimum value cuts.
395
396    ///Sets \c M to the characteristic vector of the minimum value cut
397    ///which is inclusionwise minimum. It is computed by processing a
398    ///bfs from the source node \c s in the residual graph.  \pre M
399    ///should be a node map of bools initialized to false.  \pre \ref
400    ///phase2 should already be run.
401    template<typename _CutMap>
402    void minMinCut(_CutMap& M) const {
403
404      std::queue<Node> queue;
405      M.set(s,true);
406      queue.push(s);
407     
408      while (!queue.empty()) {
409        Node w=queue.front();
410        queue.pop();
411       
412        for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
413          Node v=g->head(e);
414          if (!M[v] && (*flow)[e] < (*capacity)[e] ) {
415            queue.push(v);
416            M.set(v, true);
417          }
418        }
419       
420        for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
421          Node v=g->tail(e);
422          if (!M[v] && (*flow)[e] > 0 ) {
423            queue.push(v);
424            M.set(v, true);
425          }
426        }
427      }
428    }
429   
430    ///Returns the inclusionwise maximum of the minimum value cuts.
431
432    ///Sets \c M to the characteristic vector of the minimum value cut
433    ///which is inclusionwise maximum. It is computed by processing a
434    ///backward bfs from the target node \c t in the residual graph.
435    ///\pre \ref phase2() or run() should already be run.
436    template<typename _CutMap>
437    void maxMinCut(_CutMap& M) const {
438
439      for(NodeIt v(*g) ; v!=INVALID; ++v) M.set(v, true);
440
441      std::queue<Node> queue;
442
443      M.set(t,false);
444      queue.push(t);
445
446      while (!queue.empty()) {
447        Node w=queue.front();
448        queue.pop();
449
450        for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
451          Node v=g->tail(e);
452          if (M[v] && (*flow)[e] < (*capacity)[e] ) {
453            queue.push(v);
454            M.set(v, false);
455          }
456        }
457
458        for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
459          Node v=g->head(e);
460          if (M[v] && (*flow)[e] > 0 ) {
461            queue.push(v);
462            M.set(v, false);
463          }
464        }
465      }
466    }
467
468    ///Sets the source node to \c _s.
469
470    ///Sets the source node to \c _s.
471    ///
472    void setSource(Node _s) {
473      s=_s;
474      if ( flow_prop != ZERO_FLOW ) flow_prop=NO_FLOW;
475      status=AFTER_NOTHING;
476    }
477
478    ///Sets the target node to \c _t.
479
480    ///Sets the target node to \c _t.
481    ///
482    void setTarget(Node _t) {
483      t=_t;
484      if ( flow_prop == GEN_FLOW ) flow_prop=PRE_FLOW;
485      status=AFTER_NOTHING;
486    }
487
488    /// Sets the edge map of the capacities to _cap.
489
490    /// Sets the edge map of the capacities to _cap.
491    ///
492    void setCap(const CapMap& _cap) {
493      capacity=&_cap;
494      status=AFTER_NOTHING;
495    }
496
497    /// Sets the edge map of the flows to _flow.
498
499    /// Sets the edge map of the flows to _flow.
500    ///
501    void setFlow(FlowMap& _flow) {
502      flow=&_flow;
503      flow_prop=NO_FLOW;
504      status=AFTER_NOTHING;
505    }
506
507
508  private:
509
510    int push(Node w, NNMap& next, VecNode& first) {
511
512      int lev=level[w];
513      Num exc=excess[w];
514      int newlevel=n;       //bound on the next level of w
515
516      for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
517        if ( (*flow)[e] >= (*capacity)[e] ) continue;
518        Node v=g->head(e);
519
520        if( lev > level[v] ) { //Push is allowed now
521         
522          if ( excess[v]<=0 && v!=t && v!=s ) {
523            next.set(v,first[level[v]]);
524            first[level[v]]=v;
525          }
526
527          Num cap=(*capacity)[e];
528          Num flo=(*flow)[e];
529          Num remcap=cap-flo;
530         
531          if ( remcap >= exc ) { //A nonsaturating push.
532           
533            flow->set(e, flo+exc);
534            excess.set(v, excess[v]+exc);
535            exc=0;
536            break;
537
538          } else { //A saturating push.
539            flow->set(e, cap);
540            excess.set(v, excess[v]+remcap);
541            exc-=remcap;
542          }
543        } else if ( newlevel > level[v] ) newlevel = level[v];
544      } //for out edges wv
545
546      if ( exc > 0 ) {
547        for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
548         
549          if( (*flow)[e] <= 0 ) continue;
550          Node v=g->tail(e);
551
552          if( lev > level[v] ) { //Push is allowed now
553
554            if ( excess[v]<=0 && v!=t && v!=s ) {
555              next.set(v,first[level[v]]);
556              first[level[v]]=v;
557            }
558
559            Num flo=(*flow)[e];
560
561            if ( flo >= exc ) { //A nonsaturating push.
562
563              flow->set(e, flo-exc);
564              excess.set(v, excess[v]+exc);
565              exc=0;
566              break;
567            } else {  //A saturating push.
568
569              excess.set(v, excess[v]+flo);
570              exc-=flo;
571              flow->set(e,0);
572            }
573          } else if ( newlevel > level[v] ) newlevel = level[v];
574        } //for in edges vw
575
576      } // if w still has excess after the out edge for cycle
577
578      excess.set(w, exc);
579     
580      return newlevel;
581    }
582   
583   
584   
585    void preflowPreproc(VecNode& first, NNMap& next,
586                        VecNode& level_list, NNMap& left, NNMap& right)
587    {
588      for(NodeIt v(*g); v!=INVALID; ++v) level.set(v,n);
589      std::queue<Node> bfs_queue;
590     
591      if ( flow_prop == GEN_FLOW || flow_prop == PRE_FLOW ) {
592        //Reverse_bfs from t in the residual graph,
593        //to find the starting level.
594        level.set(t,0);
595        bfs_queue.push(t);
596       
597        while ( !bfs_queue.empty() ) {
598         
599          Node v=bfs_queue.front();
600          bfs_queue.pop();
601          int l=level[v]+1;
602         
603          for(InEdgeIt e(*g,v) ; e!=INVALID; ++e) {
604            if ( (*capacity)[e] <= (*flow)[e] ) continue;
605            Node w=g->tail(e);
606            if ( level[w] == n && w != s ) {
607              bfs_queue.push(w);
608              Node z=level_list[l];
609              if ( z!=INVALID ) left.set(z,w);
610              right.set(w,z);
611              level_list[l]=w;
612              level.set(w, l);
613            }
614          }
615         
616          for(OutEdgeIt e(*g,v) ; e!=INVALID; ++e) {
617            if ( 0 >= (*flow)[e] ) continue;
618            Node w=g->head(e);
619            if ( level[w] == n && w != s ) {
620              bfs_queue.push(w);
621              Node z=level_list[l];
622              if ( z!=INVALID ) left.set(z,w);
623              right.set(w,z);
624              level_list[l]=w;
625              level.set(w, l);
626            }
627          }
628        } //while
629      } //if
630
631
632      switch (flow_prop) {
633        case NO_FLOW: 
634        for(EdgeIt e(*g); e!=INVALID; ++e) flow->set(e,0);
635        case ZERO_FLOW:
636        for(NodeIt v(*g); v!=INVALID; ++v) excess.set(v,0);
637       
638        //Reverse_bfs from t, to find the starting level.
639        level.set(t,0);
640        bfs_queue.push(t);
641       
642        while ( !bfs_queue.empty() ) {
643         
644          Node v=bfs_queue.front();
645          bfs_queue.pop();
646          int l=level[v]+1;
647         
648          for(InEdgeIt e(*g,v) ; e!=INVALID; ++e) {
649            Node w=g->tail(e);
650            if ( level[w] == n && w != s ) {
651              bfs_queue.push(w);
652              Node z=level_list[l];
653              if ( z!=INVALID ) left.set(z,w);
654              right.set(w,z);
655              level_list[l]=w;
656              level.set(w, l);
657            }
658          }
659        }
660       
661        //the starting flow
662        for(OutEdgeIt e(*g,s) ; e!=INVALID; ++e) {
663          Num c=(*capacity)[e];
664          if ( c <= 0 ) continue;
665          Node w=g->head(e);
666          if ( level[w] < n ) {
667            if ( excess[w] <= 0 && w!=t ) { //putting into the stack
668              next.set(w,first[level[w]]);
669              first[level[w]]=w;
670            }
671            flow->set(e, c);
672            excess.set(w, excess[w]+c);
673          }
674        }
675        break;
676
677        case GEN_FLOW:
678        for(NodeIt v(*g); v!=INVALID; ++v) excess.set(v,0);
679        {
680          Num exc=0;
681          for(InEdgeIt e(*g,t) ; e!=INVALID; ++e) exc+=(*flow)[e];
682          for(OutEdgeIt e(*g,t) ; e!=INVALID; ++e) exc-=(*flow)[e];
683          excess.set(t,exc);
684        }
685
686        //the starting flow
687        for(OutEdgeIt e(*g,s); e!=INVALID; ++e) {
688          Num rem=(*capacity)[e]-(*flow)[e];
689          if ( rem <= 0 ) continue;
690          Node w=g->head(e);
691          if ( level[w] < n ) {
692            if ( excess[w] <= 0 && w!=t ) { //putting into the stack
693              next.set(w,first[level[w]]);
694              first[level[w]]=w;
695            }   
696            flow->set(e, (*capacity)[e]);
697            excess.set(w, excess[w]+rem);
698          }
699        }
700       
701        for(InEdgeIt e(*g,s); e!=INVALID; ++e) {
702          if ( (*flow)[e] <= 0 ) continue;
703          Node w=g->tail(e);
704          if ( level[w] < n ) {
705            if ( excess[w] <= 0 && w!=t ) {
706              next.set(w,first[level[w]]);
707              first[level[w]]=w;
708            } 
709            excess.set(w, excess[w]+(*flow)[e]);
710            flow->set(e, 0);
711          }
712        }
713        break;
714
715        case PRE_FLOW: 
716        //the starting flow
717        for(OutEdgeIt e(*g,s) ; e!=INVALID; ++e) {
718          Num rem=(*capacity)[e]-(*flow)[e];
719          if ( rem <= 0 ) continue;
720          Node w=g->head(e);
721          if ( level[w] < n ) flow->set(e, (*capacity)[e]);
722        }
723       
724        for(InEdgeIt e(*g,s) ; e!=INVALID; ++e) {
725          if ( (*flow)[e] <= 0 ) continue;
726          Node w=g->tail(e);
727          if ( level[w] < n ) flow->set(e, 0);
728        }
729       
730        //computing the excess
731        for(NodeIt w(*g); w!=INVALID; ++w) {
732          Num exc=0;
733          for(InEdgeIt e(*g,w); e!=INVALID; ++e) exc+=(*flow)[e];
734          for(OutEdgeIt e(*g,w); e!=INVALID; ++e) exc-=(*flow)[e];
735          excess.set(w,exc);
736         
737          //putting the active nodes into the stack
738          int lev=level[w];
739            if ( exc > 0 && lev < n && Node(w) != t ) {
740              next.set(w,first[lev]);
741              first[lev]=w;
742            }
743        }
744        break;
745      } //switch
746    } //preflowPreproc
747
748
749    void relabel(Node w, int newlevel, VecNode& first, NNMap& next,
750                 VecNode& level_list, NNMap& left,
751                 NNMap& right, int& b, int& k, bool what_heur )
752    {
753
754      int lev=level[w];
755
756      Node right_n=right[w];
757      Node left_n=left[w];
758
759      //unlacing starts
760      if ( right_n!=INVALID ) {
761        if ( left_n!=INVALID ) {
762          right.set(left_n, right_n);
763          left.set(right_n, left_n);
764        } else {
765          level_list[lev]=right_n;
766          left.set(right_n, INVALID);
767        }
768      } else {
769        if ( left_n!=INVALID ) {
770          right.set(left_n, INVALID);
771        } else {
772          level_list[lev]=INVALID;
773        }
774      }
775      //unlacing ends
776
777      if ( level_list[lev]==INVALID ) {
778
779        //gapping starts
780        for (int i=lev; i!=k ; ) {
781          Node v=level_list[++i];
782          while ( v!=INVALID ) {
783            level.set(v,n);
784            v=right[v];
785          }
786          level_list[i]=INVALID;
787          if ( !what_heur ) first[i]=INVALID;
788        }
789
790        level.set(w,n);
791        b=lev-1;
792        k=b;
793        //gapping ends
794
795      } else {
796
797        if ( newlevel == n ) level.set(w,n);
798        else {
799          level.set(w,++newlevel);
800          next.set(w,first[newlevel]);
801          first[newlevel]=w;
802          if ( what_heur ) b=newlevel;
803          if ( k < newlevel ) ++k;      //now k=newlevel
804          Node z=level_list[newlevel];
805          if ( z!=INVALID ) left.set(z,w);
806          right.set(w,z);
807          left.set(w,INVALID);
808          level_list[newlevel]=w;
809        }
810      }
811    } //relabel
812
813  };
814} //namespace lemon
815
816#endif //LEMON_PREFLOW_H
817
818
819
820
Note: See TracBrowser for help on using the repository browser.