[1104] | 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/smart_graph.h> |
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| 6 | #include <lemon/list_graph.h> |
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| 7 | #include <lemon/dimacs.h> |
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| 8 | #include <lemon/time_measure.h> |
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| 9 | #include <lp_solver_wrapper_3.h> |
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| 10 | |
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| 11 | using std::cout; |
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| 12 | using std::endl; |
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| 13 | using namespace lemon; |
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| 14 | |
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| 15 | template<typename Edge, typename EdgeIndexMap> |
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| 16 | class PrimalMap { |
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| 17 | protected: |
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| 18 | LPGLPK* lp; |
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| 19 | EdgeIndexMap* edge_index_map; |
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| 20 | public: |
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| 21 | PrimalMap(LPGLPK& _lp, EdgeIndexMap& _edge_index_map) : |
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| 22 | lp(&_lp), edge_index_map(&_edge_index_map) { } |
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| 23 | double operator[](Edge e) const { |
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| 24 | return lp->getPrimal((*edge_index_map)[e]); |
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| 25 | } |
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| 26 | }; |
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| 27 | |
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| 28 | // Use a DIMACS max flow file as stdin. |
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| 29 | // max_flow_expresion < dimacs_max_flow_file |
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| 30 | |
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| 31 | int main(int, char **) { |
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| 32 | |
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| 33 | typedef ListGraph Graph; |
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| 34 | typedef Graph::Node Node; |
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| 35 | typedef Graph::Edge Edge; |
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| 36 | typedef Graph::EdgeIt EdgeIt; |
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| 37 | |
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| 38 | Graph g; |
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| 39 | |
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| 40 | Node s, t; |
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| 41 | Graph::EdgeMap<int> cap(g); |
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| 42 | readDimacs(std::cin, g, cap, s, t); |
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| 43 | Timer ts; |
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| 44 | |
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| 45 | typedef LPGLPK LPSolver; |
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| 46 | LPSolver lp; |
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| 47 | lp.setMaximize(); |
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| 48 | typedef LPSolver::ColIt ColIt; |
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| 49 | typedef LPSolver::RowIt RowIt; |
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| 50 | typedef Graph::EdgeMap<ColIt> EdgeIndexMap; |
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| 51 | EdgeIndexMap edge_index_map(g); |
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[1110] | 52 | PrimalMap<Edge, EdgeIndexMap> flow(lp, edge_index_map); |
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[1104] | 53 | |
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| 54 | // capacity function |
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| 55 | for (Graph::EdgeIt e(g); e!=INVALID; ++e) { |
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| 56 | ColIt col_it=lp.addCol(); |
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| 57 | edge_index_map.set(e, col_it); |
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[1110] | 58 | // interesting property in GLPK: |
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| 59 | // if you change the order of the following two lines, the |
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| 60 | // two runs of GLPK are extremely different |
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| 61 | lp.setColUpperBound(col_it, cap[e]); |
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| 62 | lp.setColLowerBound(col_it, 0); |
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[1104] | 63 | } |
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| 64 | |
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| 65 | for (Graph::NodeIt n(g); n!=INVALID; ++n) { |
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| 66 | LPSolver::Expression expr; |
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| 67 | for (Graph::OutEdgeIt e(g, n); e!=INVALID; ++e) |
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| 68 | expr+=edge_index_map[e]; |
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| 69 | for (Graph::InEdgeIt e(g, n); e!=INVALID; ++e) |
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| 70 | expr-=edge_index_map[e]; |
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| 71 | // cost function |
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| 72 | if (n==s) { |
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| 73 | lp.setObjCoeffs(expr); |
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| 74 | } |
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| 75 | // flow conservation |
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| 76 | if ((n!=s) && (n!=t)) { |
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| 77 | RowIt row_it=lp.addRow(); |
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| 78 | lp.setRowCoeffs(row_it, expr); |
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| 79 | lp.setRowBounds(row_it, LPSolver::FIXED, 0.0, 0.0); |
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| 80 | } |
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| 81 | } |
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| 82 | lp.solveSimplex(); |
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[1110] | 83 | cout << "elapsed time: " << ts << endl; |
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[1104] | 84 | } |
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