COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/work/jacint/preflow_push_hl.h @ 84:56e879edcca6

Last change on this file since 84:56e879edcca6 was 84:56e879edcca6, checked in by jacint, 17 years ago

after debugging

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1// -*- C++ -*-
2/*
3preflow_push_hl.h
4by jacint.
5Runs the highest label variant of the preflow push algorithm with
6running time O(n^2\sqrt(m)).
7
8Member functions:
9
10void run() : runs the algorithm
11
12 The following functions should be used after run() was already run.
13
14T maxflow() : returns the value of a maximum flow
15
16T flowonedge(EdgeIt e) : for a fixed maximum flow x it returns x(e)
17
18Graph::EdgeMap<T> allflow() : returns the fixed maximum flow x
19
20Graph::NodeMap<bool> mincut() : returns a
21     characteristic vector of a minimum cut. (An empty level
22     in the algorithm gives a minimum cut.)
23*/
24
25#ifndef PREFLOW_PUSH_HL_H
26#define PREFLOW_PUSH_HL_H
27
28#include <algorithm>
29#include <vector>
30#include <stack>
31
32#include <list_graph.hh>
33#include <reverse_bfs.h>
34
35namespace marci {
36
37  template <typename Graph, typename T>
38  class preflow_push_hl {
39   
40    typedef typename Graph::NodeIt NodeIt;
41    typedef typename Graph::EdgeIt EdgeIt;
42    typedef typename Graph::EachNodeIt EachNodeIt;
43    typedef typename Graph::OutEdgeIt OutEdgeIt;
44    typedef typename Graph::InEdgeIt InEdgeIt;
45   
46    Graph& G;
47    NodeIt s;
48    NodeIt t;
49    typename Graph::EdgeMap<T> flow;
50    typename Graph::EdgeMap<T> capacity;
51    T value;
52    typename Graph::NodeMap<bool> mincutvector;
53
54  public:
55
56    preflow_push_hl(Graph& _G, NodeIt _s, NodeIt _t,
57                    typename Graph::EdgeMap<T>& _capacity) :
58      G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity),
59      mincutvector(_G, true) { }
60
61
62    /*
63      The run() function runs the highest label preflow-push,
64      running time: O(n^2\sqrt(m))
65    */
66    void run() {
67 
68      typename Graph::NodeMap<int> level(G);     
69      typename Graph::NodeMap<T> excess(G);
70      std::cout <<"excess s:"<<excess.get(s);      //delme
71           
72      int n=G.nodeNum();
73      int b=n-2;
74      /*
75        b is a bound on the highest level of an active node.
76        In the beginning it is at most n-2.
77      */
78
79      std::vector<std::stack<NodeIt> > stack(2*n-1);   
80      //Stack of the active nodes in level i.
81
82
83      /*Reverse_bfs from t, to find the starting level.*/
84      reverse_bfs<Graph> bfs(G, t);
85      bfs.run();
86      for(EachNodeIt v=G.template first<EachNodeIt>(); v.valid(); ++v)
87        {
88          level.set(v, bfs.dist(v));
89        }
90
91      level.set(s,n);
92
93
94      /* Starting flow. It is everywhere 0 at the moment. */     
95      for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e)
96        {
97          if ( capacity.get(e) > 0 ) {
98            NodeIt w=G.head(e);
99            if ( excess.get(w) == 0 && w!=t && w!=s ) stack[level.get(w)].push(w);
100            flow.set(e, capacity.get(e));
101            excess.set(w, excess.get(w)+capacity.get(e));
102          }
103        }
104
105      /*
106         End of preprocessing
107      */
108
109
110
111      /*
112        Push/relabel on the highest level active nodes.
113      */
114       
115      /*While there exists active node.*/
116      while (b) {
117
118        /*We decrease the bound if there is no active Node of level b.*/
119        if (stack[b].empty()) {
120          --b;
121        } else {
122
123          NodeIt w=stack[b].top();        //w is a highest label active node.
124          stack[b].pop();           
125       
126          int newlevel=2*n-2;             //In newlevel we bound the next level of w.
127       
128          for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {
129           
130            if ( flow.get(e) < capacity.get(e) ) {             
131              /*e is an edge of the residual graph */
132
133              NodeIt v=G.head(e);               /*e is the edge wv.*/
134
135              if( level.get(w) > level.get(v)+1 ) { std::cout<<"HIBA1!";} //delme     
136
137              if( level.get(w) == level.get(v)+1 ) {     
138                /*Push is allowed now*/
139
140                if (capacity.get(e)-flow.get(e) > excess.get(w)) {       
141                  /*A nonsaturating push.*/
142                 
143                  if (excess.get(v)==0 && v != s && v !=t) stack[level.get(v)].push(v);
144                  /*v becomes active.*/
145
146                  flow.set(e, flow.get(e)+excess.get(w));
147                  excess.set(v, excess.get(v)+excess.get(w));
148                  excess.set(w,0);
149                  //std::cout << w << " " << v <<" elore elen nonsat pump "  << std::endl;
150                  break;
151                } else {
152                  /*A saturating push.*/
153
154                  if (excess.get(v)==0 && v != s&& v !=t) stack[level.get(v)].push(v);
155                  /*v becomes active.*/
156
157                  excess.set(v, excess.get(v)+capacity.get(e)-flow.get(e));
158                  excess.set(w, excess.get(w)-capacity.get(e)+flow.get(e));
159                  flow.set(e, capacity.get(e));
160                  //std::cout << w<<" " <<v<<" elore elen sat pump "   << std::endl;
161                  if (excess.get(w)==0) break;
162                  /*If w is not active any more, then we go on to the next Node.*/
163                 
164                  //std::cout<<++i;
165                 
166                } // if (capacity.get(e)-flow.get(e) > excess.get(w))
167              } // if(level.get(w)==level.get(v)+1)
168           
169              else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);}
170           
171            } //if (flow.get(e)<capacity.get(e))
172         
173          } //for(OutEdgeIt e=G.first_OutEdge(w); e.valid(); ++e)
174         
175
176
177          for(InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
178            NodeIt v=G.tail(e);
179            /*e is the Edge vw.*/
180
181            if (excess.get(w)==0) break;
182            /*It may happen, that w became inactive in the first for cycle.*/           
183            if(flow.get(e)>0) {             
184              /*e is an Edge of the residual graph */
185
186              if(level.get(w)==level.get(v)+1) { 
187                /*Push is allowed now*/
188               
189                if (flow.get(e) > excess.get(w)) {
190                  /*A nonsaturating push.*/
191                 
192                  if (excess.get(v)==0 && v != s&& v !=t) stack[level.get(v)].push(v);
193                  /*v becomes active.*/
194
195                  flow.set(e, flow.get(e)-excess.get(w));
196                  excess.set(v, excess.get(v)+excess.get(w));
197                  excess.set(w,0);
198                  //std::cout << v << " " << w << " vissza elen nonsat pump "     << std::endl;
199                  break;
200                } else {                                               
201                  /*A saturating push.*/
202                 
203                  if (excess.get(v)==0 && v != s&& v !=t) stack[level.get(v)].push(v);
204                  /*v becomes active.*/
205                 
206                  excess.set(v, excess.get(v)+flow.get(e));
207                  excess.set(w, excess.get(w)-flow.get(e));
208                  flow.set(e,0);
209                  //std::cout << v <<" " << w << " vissza elen sat pump "     << std::endl;
210                  if (excess.get(w)==0) { break;}
211                } //if (flow.get(e) > excess.get(v))
212              } //if(level.get(w)==level.get(v)+1)
213             
214              else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);}
215             
216
217            } //if (flow.get(e)>0)
218
219          } //for
220
221
222          if (excess.get(w)>0) {
223            level.set(w,++newlevel);
224            stack[newlevel].push(w);
225            b=newlevel;
226            //std::cout << "The new level of " << w << " is "<< newlevel <<std::endl;
227          }
228
229
230        } //else
231       
232      } //while(b)
233
234      value = excess.get(t);
235      /*Max flow value.*/
236
237
238
239
240    } //void run()
241
242
243
244
245
246    /*
247      Returns the maximum value of a flow.
248     */
249
250    T maxflow() {
251      return value;
252    }
253
254
255
256    /*
257      For the maximum flow x found by the algorithm, it returns the flow value on Edge e, i.e. x(e).
258    */
259
260    T flowonEdge(EdgeIt e) {
261      return flow.get(e);
262    }
263
264
265
266    /*
267      Returns the maximum flow x found by the algorithm.
268    */
269
270    typename Graph::EdgeMap<T> allflow() {
271      return flow;
272    }
273
274
275
276    /*
277      Returns a minimum cut by using a reverse bfs from t in the residual graph.
278    */
279   
280    typename Graph::NodeMap<bool> mincut() {
281   
282      std::queue<NodeIt> queue;
283     
284      mincutvector.set(t,false);     
285      queue.push(t);
286
287      while (!queue.empty()) {
288        NodeIt w=queue.front();
289        queue.pop();
290
291        for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
292          NodeIt v=G.tail(e);
293          if (mincutvector.get(v) && flow.get(e) < capacity.get(e) ) {
294            queue.push(v);
295            mincutvector.set(v, false);
296          }
297        } // for
298
299        for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
300          NodeIt v=G.head(e);
301          if (mincutvector.get(v) && flow.get(e) > 0 ) {
302            queue.push(v);
303            mincutvector.set(v, false);
304          }
305        } // for
306
307      }
308
309      return mincutvector;
310   
311    }
312  };
313}//namespace marci
314#endif
315
316
317
318
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