1 | // -*- c++ -*- |
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2 | #include <iostream> |
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3 | #include <fstream> |
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4 | |
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5 | #include <lemon/graph_utils.h> |
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6 | #include <lemon/smart_graph.h> |
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7 | #include <lemon/list_graph.h> |
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8 | #include <lemon/dimacs.h> |
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9 | #include <lemon/time_measure.h> |
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10 | #include <lp_solver_glpk.h> |
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11 | |
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12 | using std::cout; |
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13 | using std::endl; |
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14 | using namespace lemon; |
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15 | |
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16 | template<typename Edge, typename EdgeIndexMap> |
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17 | class PrimalMap { |
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18 | protected: |
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19 | LpGlpk* lp; |
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20 | EdgeIndexMap* edge_index_map; |
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21 | public: |
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22 | PrimalMap(LpGlpk& _lp, EdgeIndexMap& _edge_index_map) : |
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23 | lp(&_lp), edge_index_map(&_edge_index_map) { } |
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24 | double operator[](Edge e) const { |
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25 | return lp->getPrimal((*edge_index_map)[e]); |
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26 | } |
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27 | }; |
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28 | |
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29 | // Use a DIMACS max flow file as stdin. |
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30 | // max_flow_expresion < dimacs_max_flow_file |
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31 | |
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32 | int main(int, char **) { |
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33 | |
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34 | typedef ListGraph Graph; |
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35 | typedef Graph::Node Node; |
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36 | typedef Graph::Edge Edge; |
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37 | typedef Graph::EdgeIt EdgeIt; |
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38 | |
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39 | Graph g; |
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40 | |
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41 | Node s, t; |
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42 | Graph::EdgeMap<int> cap(g); |
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43 | readDimacs(std::cin, g, cap, s, t); |
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44 | Timer ts; |
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45 | |
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46 | typedef LpGlpk LPSolver; |
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47 | LPSolver lp; |
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48 | lp.setMaximize(); |
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49 | typedef LPSolver::Col Col; |
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50 | typedef LPSolver::Row Row; |
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51 | typedef Graph::EdgeMap<Col> EdgeIndexMap; |
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52 | typedef Graph::NodeMap<Row> NodeIndexMap; |
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53 | EdgeIndexMap edge_index_map(g); |
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54 | NodeIndexMap node_index_map(g); |
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55 | PrimalMap<Edge, EdgeIndexMap> flow(lp, edge_index_map); |
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56 | |
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57 | // nonnegativity of flow and capacity function |
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58 | for (Graph::EdgeIt e(g); e!=INVALID; ++e) { |
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59 | Col col=lp.addCol(); |
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60 | edge_index_map.set(e, col); |
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61 | // interesting property in GLPK: |
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62 | // if you change the order of the following two lines, the |
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63 | // two runs of GLPK are extremely different |
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64 | lp.setColLowerBound(col, 0); |
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65 | lp.setColUpperBound(col, cap[e]); |
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66 | } |
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67 | |
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68 | for (Graph::NodeIt n(g); n!=INVALID; ++n) { |
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69 | LPSolver::Expression expr; |
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70 | for (Graph::OutEdgeIt e(g, n); e!=INVALID; ++e) |
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71 | expr+=edge_index_map[e]; |
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72 | for (Graph::InEdgeIt e(g, n); e!=INVALID; ++e) |
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73 | expr-=edge_index_map[e]; |
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74 | // cost function |
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75 | if (n==s) { |
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76 | lp.setObjCoeffs(expr); |
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77 | } |
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78 | // flow conservation constraints |
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79 | if ((n!=s) && (n!=t)) { |
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80 | node_index_map.set(n, lp.addRow(expr == 0.0)); |
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81 | } |
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82 | } |
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83 | lp.solveSimplex(); |
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84 | cout << "elapsed time: " << ts << endl; |
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85 | // cout << "rows:" << endl; |
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86 | // for ( |
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87 | // LPSolver::Rows::ClassIt i(lp.row_iter_map, 0); |
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88 | // i!=INVALID; |
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89 | // ++i) { |
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90 | // cout << i << " "; |
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91 | // } |
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92 | // cout << endl; |
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93 | // cout << "cols:" << endl; |
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94 | // for ( |
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95 | // LPSolver::Cols::ClassIt i(lp.col_iter_map, 0); |
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96 | // i!=INVALID; |
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97 | // ++i) { |
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98 | // cout << i << " "; |
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99 | // } |
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100 | // cout << endl; |
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101 | lp.setMIP(); |
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102 | cout << "elapsed time: " << ts << endl; |
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103 | for (LPSolver::Cols::ClassIt it(lp.col_iter_map ,1); it!=INVALID; ++it) { |
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104 | lp.setColInt(it); |
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105 | } |
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106 | cout << "elapsed time: " << ts << endl; |
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107 | lp.solveBandB(); |
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108 | cout << "elapsed time: " << ts << endl; |
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109 | } |
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