1 | // -*- c++ -*- |
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2 | |
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3 | // Use a DIMACS max flow file as input. |
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4 | // sub_graph_adaptor_demo < dimacs_max_flow_file |
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5 | // This program computes a maximum number of edge-disjoint shortest paths |
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6 | // between s and t. |
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7 | |
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8 | #include <iostream> |
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9 | #include <fstream> |
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10 | |
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11 | #include <lemon/smart_graph.h> |
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12 | #include <lemon/dijkstra.h> |
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13 | #include <lemon/maps.h> |
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14 | #include <lemon/graph_adaptor.h> |
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15 | #include <lemon/dimacs.h> |
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16 | #include <lemon/preflow.h> |
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17 | #include <tight_edge_filter_map.h> |
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18 | |
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19 | using namespace lemon; |
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20 | |
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21 | using std::cout; |
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22 | using std::endl; |
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23 | |
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24 | int main(int argc, char *argv[]) |
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25 | { |
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26 | if(argc<2) |
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27 | { |
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28 | std::cerr << "USAGE: sub_graph_adaptor_demo <input_file.dim>" << std::endl; |
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29 | std::cerr << "The file 'input_file.dim' has to contain a max flow instance in DIMACS format (e.g. sub_graph_adaptor_demo.dim is such a file)." << std::endl; |
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30 | return 0; |
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31 | } |
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32 | |
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33 | |
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34 | //input stream to read the graph from |
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35 | std::ifstream is(argv[1]); |
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36 | |
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37 | typedef SmartGraph Graph; |
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38 | |
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39 | typedef Graph::Edge Edge; |
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40 | typedef Graph::Node Node; |
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41 | typedef Graph::EdgeIt EdgeIt; |
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42 | typedef Graph::NodeIt NodeIt; |
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43 | typedef Graph::EdgeMap<int> LengthMap; |
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44 | |
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45 | Graph g; |
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46 | Node s, t; |
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47 | LengthMap length(g); |
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48 | |
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49 | readDimacs(is, g, length, s, t); |
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50 | |
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51 | cout << "edges with lengths (of form id, source--length->target): " << endl; |
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52 | for(EdgeIt e(g); e!=INVALID; ++e) |
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53 | cout << " " << g.id(e) << ", " << g.id(g.source(e)) << "--" |
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54 | << length[e] << "->" << g.id(g.target(e)) << endl; |
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55 | |
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56 | cout << "s: " << g.id(s) << " t: " << g.id(t) << endl; |
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57 | |
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58 | typedef Dijkstra<Graph, LengthMap> Dijkstra; |
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59 | Dijkstra dijkstra(g, length); |
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60 | dijkstra.run(s); |
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61 | |
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62 | // This map returns true exactly for those edges which are |
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63 | // tight w.r.t the length funcion and the potential |
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64 | // given by the dijkstra algorithm. |
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65 | typedef TightEdgeFilterMap<Graph, const Dijkstra::DistMap, LengthMap> |
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66 | TightEdgeFilter; |
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67 | TightEdgeFilter tight_edge_filter(g, dijkstra.distMap(), length); |
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68 | |
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69 | // ConstMap<Node, bool> const_true_map(true); |
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70 | // This graph contains exaclty the tight edges. |
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71 | // typedef SubGraphAdaptor<Graph, ConstMap<Node, bool>, TightEdgeFilter> SubGW; |
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72 | typedef EdgeSubGraphAdaptor<Graph, TightEdgeFilter> SubGW; |
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73 | SubGW gw(g, tight_edge_filter); |
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74 | |
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75 | ConstMap<Edge, int> const_1_map(1); |
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76 | Graph::EdgeMap<int> flow(g, 0); |
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77 | // Max flow between s and t in the graph of tight edges. |
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78 | Preflow<SubGW, int, ConstMap<Edge, int>, Graph::EdgeMap<int> > |
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79 | preflow(gw, s, t, const_1_map, flow); |
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80 | preflow.run(); |
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81 | |
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82 | cout << "maximum number of edge-disjoint shortest paths: " |
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83 | << preflow.flowValue() << endl; |
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84 | cout << "edges of the maximum number of edge-disjoint shortest s-t paths: " |
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85 | << endl; |
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86 | for(EdgeIt e(g); e!=INVALID; ++e) |
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87 | if (flow[e]) |
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88 | cout << " " << g.id(e) << ", " |
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89 | << g.id(g.source(e)) << "--" |
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90 | << length[e] << "->" << g.id(g.target(e)) << endl; |
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91 | } |
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