COIN-OR::LEMON - Graph Library

source: lemon-0.x/test/arborescence_test.cc @ 2025:93fcadf94ab0

Last change on this file since 2025:93fcadf94ab0 was 2025:93fcadf94ab0, checked in by Balazs Dezso, 15 years ago

Bugfix in the minimum cost arborescence algorithm
Dual solution computation and interface for algorithm
Optimality test on random graph

File size: 2.7 KB
Line 
1#include <iostream>
2#include <set>
3#include <vector>
4#include <iterator>
5
6#include <cmath>
7#include <cstdlib>
8
9#include <lemon/smart_graph.h>
10#include <lemon/min_cost_arborescence.h>
11
12#include <lemon/graph_utils.h>
13#include <lemon/time_measure.h>
14
15#include <lemon/tolerance.h>
16
17using namespace lemon;
18using namespace std;
19
20int main(int argc, const char *argv[]) {
21  srand(time(0));
22  typedef SmartGraph Graph;
23  GRAPH_TYPEDEFS(Graph);
24
25  typedef Graph::EdgeMap<double> CostMap;
26
27  const int n = argc > 1 ? atoi(argv[1]) : 100;
28  const int e = argc > 2 ? atoi(argv[2]) : (int)(n * log(n));
29
30  Graph graph;
31  CostMap cost(graph);
32  vector<Node> nodes;
33 
34  for (int i = 0; i < n; ++i) {
35    nodes.push_back(graph.addNode());
36  }
37
38  for (int i = 0; i < e; ++i) {
39    int s = (int)(n * (double)rand() / (RAND_MAX + 1.0));
40    int t = (int)(n * (double)rand() / (RAND_MAX + 1.0));
41    double c = rand() / (1.0 + RAND_MAX) * 100.0 + 20.0;
42    Edge edge = graph.addEdge(nodes[s], nodes[t]);
43    cost[edge] = c;
44  }
45
46  Node source = nodes[(int)(n * (double)rand() / (RAND_MAX + 1.0))];
47
48  MinCostArborescence<Graph, CostMap> mca(graph, cost);
49  mca.run(source);
50
51  vector<pair<double, set<Node> > > dualSolution(mca.dualSize());
52
53  for (int i = 0; i < mca.dualSize(); ++i) {
54    dualSolution[i].first = mca.dualValue(i);
55    for (MinCostArborescence<Graph, CostMap>::DualIt it(mca, i);
56         it != INVALID; ++it) {
57      dualSolution[i].second.insert(it);
58    }
59  }
60
61  Tolerance<double> tolerance;
62
63  for (EdgeIt it(graph); it != INVALID; ++it) {
64    if (mca.reached(graph.source(it))) {
65      double sum = 0.0;
66      for (int i = 0; i < (int)dualSolution.size(); ++i) {
67        if (dualSolution[i].second.find(graph.target(it))
68            != dualSolution[i].second.end() &&
69            dualSolution[i].second.find(graph.source(it))
70            == dualSolution[i].second.end()) {
71          sum += dualSolution[i].first;
72        }
73      }
74      if (mca.arborescence(it)) {
75        LEMON_ASSERT(!tolerance.less(sum, cost[it]), "INVALID DUAL");
76      }
77      LEMON_ASSERT(!tolerance.less(cost[it], sum), "INVALID DUAL");
78    }
79  }
80
81
82  LEMON_ASSERT(!tolerance.different(mca.dualValue(), mca.arborescenceValue()),
83               "INVALID DUAL");
84
85
86  LEMON_ASSERT(mca.reached(source), "INVALID ARBORESCENCE");
87  for (EdgeIt it(graph); it != INVALID; ++it) {
88    LEMON_ASSERT(!mca.reached(graph.source(it)) ||
89                 mca.reached(graph.target(it)), "INVALID ARBORESCENCE");
90  }
91
92  for (NodeIt it(graph); it != INVALID; ++it) {
93    if (!mca.reached(it)) continue;
94    int cnt = 0;
95    for (InEdgeIt jt(graph, it); jt != INVALID; ++jt) {
96      if (mca.arborescence(jt)) {
97        ++cnt;
98      }
99    }
100    LEMON_ASSERT((it == source ? cnt == 0 : cnt == 1), "INVALID ARBORESCENCE");
101  }
102 
103  return 0;
104}
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