COIN-OR::LEMON - Graph Library

source: lemon-0.x/demo/lp_maxflow_demo.cc @ 1435:8e85e6bbefdf

Last change on this file since 1435:8e85e6bbefdf was 1435:8e85e6bbefdf, checked in by Akos Ladanyi, 16 years ago

trunk/src/* move to trunk/

File size: 1.7 KB
Line 
1#ifdef HAVE_CONFIG_H
2#include <config.h>
3#endif
4
5#include<lemon/graph_reader.h>
6#include<lemon/list_graph.h>
7
8
9#ifdef HAVE_GLPK
10#include <lemon/lp_glpk.h>
11#elif HAVE_CPLEX
12#include <lemon/lp_cplex.h>
13#endif
14
15using namespace lemon;
16
17#ifdef HAVE_GLPK
18typedef LpGlpk LpDefault;
19#elif HAVE_CPLEX
20typedef LpCplex LpDefault;
21#endif
22
23
24template<class G,class C>
25double maxFlow(const G &g,const C &cap,typename G::Node s,typename G::Node t)
26{
27  LpDefault lp;
28 
29  typedef G Graph;
30  typedef typename G::Node Node;
31  typedef typename G::NodeIt NodeIt;
32  typedef typename G::Edge Edge;
33  typedef typename G::EdgeIt EdgeIt;
34  typedef typename G::OutEdgeIt OutEdgeIt;
35  typedef typename G::InEdgeIt InEdgeIt;
36 
37  typename G::template EdgeMap<LpDefault::Col> x(g);
38  lp.addColSet(x);
39 
40  for(EdgeIt e(g);e!=INVALID;++e) {
41    lp.colUpperBound(x[e],cap[e]);
42    lp.colLowerBound(x[e],0);
43  }
44
45  for(NodeIt n(g);n!=INVALID;++n) if(n!=s&&n!=t) {
46    LpDefault::Expr ex;
47    for(InEdgeIt  e(g,n);e!=INVALID;++e) ex+=x[e];
48    for(OutEdgeIt e(g,n);e!=INVALID;++e) ex-=x[e];
49    lp.addRow(ex==0);
50  }
51  {
52    LpDefault::Expr ex;
53    for(InEdgeIt  e(g,t);e!=INVALID;++e) ex+=x[e];
54    for(OutEdgeIt e(g,t);e!=INVALID;++e) ex-=x[e];
55    lp.setObj(ex);
56  }
57  lp.max();
58
59#ifdef HAVE_GLPK
60  lp.presolver(true);
61  lp.messageLevel(3);
62#endif
63
64  lp.solve();
65
66  return lp.primalValue();
67}
68
69int main()
70{
71  ListGraph g;
72  ListGraph::Node s;
73  ListGraph::Node t;
74 
75  ListGraph::EdgeMap<double> cap(g);
76 
77  GraphReader<ListGraph> reader(std::cin,g);
78  reader.readNode("source",s).readNode("target",t)
79    .readEdgeMap("capacity",cap).run();
80 
81  // std::ifstream file("../test/preflow_");
82//   readDimacs(file, g, cap, s, t);
83
84  std::cout << "Max flow value = " << maxFlow(g,cap,s,t) << std::endl;
85
86}
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