1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/src/work/marci/lp/max_flow_expression.cc	Fri Jan 28 14:33:32 2005 +0000
     1.3 @@ -0,0 +1,87 @@
     1.4 +// -*- c++ -*-
     1.5 +#include <iostream>
     1.6 +#include <fstream>
     1.7 +
     1.8 +#include <lemon/smart_graph.h>
     1.9 +#include <lemon/list_graph.h>
    1.10 +#include <lemon/dimacs.h>
    1.11 +#include <lemon/time_measure.h>
    1.12 +#include <lp_solver_wrapper_3.h>
    1.13 +
    1.14 +using std::cout;
    1.15 +using std::endl;
    1.16 +using namespace lemon;
    1.17 +
    1.18 +template<typename Edge, typename EdgeIndexMap> 
    1.19 +class PrimalMap {
    1.20 +protected:
    1.21 +  LPGLPK* lp;
    1.22 +  EdgeIndexMap* edge_index_map;
    1.23 +public:
    1.24 +  PrimalMap(LPGLPK& _lp, EdgeIndexMap& _edge_index_map) : 
    1.25 +    lp(&_lp), edge_index_map(&_edge_index_map) { }
    1.26 +  double operator[](Edge e) const { 
    1.27 +    return lp->getPrimal((*edge_index_map)[e]);
    1.28 +  }
    1.29 +};
    1.30 +
    1.31 +// Use a DIMACS max flow file as stdin.
    1.32 +// max_flow_expresion < dimacs_max_flow_file
    1.33 +
    1.34 +int main(int, char **) {
    1.35 +
    1.36 +  typedef ListGraph Graph;
    1.37 +  typedef Graph::Node Node;
    1.38 +  typedef Graph::Edge Edge;
    1.39 +  typedef Graph::EdgeIt EdgeIt;
    1.40 +
    1.41 +  Graph g;
    1.42 +  
    1.43 +  Node s, t;
    1.44 +  Graph::EdgeMap<int> cap(g);
    1.45 +  readDimacs(std::cin, g, cap, s, t);
    1.46 +  Timer ts;
    1.47 +  
    1.48 +  typedef LPGLPK LPSolver;
    1.49 +  LPSolver lp;
    1.50 +  lp.setMaximize();
    1.51 +  typedef LPSolver::ColIt ColIt;
    1.52 +  typedef LPSolver::RowIt RowIt;
    1.53 +  typedef Graph::EdgeMap<ColIt> EdgeIndexMap;
    1.54 +  EdgeIndexMap edge_index_map(g);
    1.55 +  PrimalMap<Edge, EdgeIndexMap> lp_flow(lp, edge_index_map);
    1.56 +
    1.57 +  // capacity function
    1.58 +  for (Graph::EdgeIt e(g); e!=INVALID; ++e) {
    1.59 +    ColIt col_it=lp.addCol();
    1.60 +    edge_index_map.set(e, col_it);
    1.61 +    if (cap[e]==0)
    1.62 +      lp.setColBounds(col_it, LPSolver::FIXED, 0, cap[e]);
    1.63 +    else 
    1.64 +      lp.setColBounds(col_it, LPSolver::DOUBLE, 0, cap[e]);
    1.65 +  }
    1.66 +  
    1.67 +  for (Graph::NodeIt n(g); n!=INVALID; ++n) {
    1.68 +    LPSolver::Expression expr;
    1.69 +    for (Graph::OutEdgeIt e(g, n); e!=INVALID; ++e)
    1.70 +      expr+=edge_index_map[e];
    1.71 +    for (Graph::InEdgeIt e(g, n); e!=INVALID; ++e)
    1.72 +      expr-=edge_index_map[e];
    1.73 +    // cost function
    1.74 +    if (n==s) {
    1.75 +      lp.setObjCoeffs(expr);      
    1.76 +    }
    1.77 +    // flow conservation
    1.78 +    if ((n!=s) && (n!=t)) {
    1.79 +      RowIt row_it=lp.addRow();
    1.80 +      lp.setRowCoeffs(row_it, expr);
    1.81 +      lp.setRowBounds(row_it, LPSolver::FIXED, 0.0, 0.0);
    1.82 +    }
    1.83 +  }
    1.84 +  lp.solveSimplex();
    1.85 +  //std::cout << lp.colNum() << std::endl;
    1.86 +  //std::cout << lp.rowNum() << std::endl;
    1.87 +  //std::cout << "flow value: "<< lp.getObjVal() << std::endl;
    1.88 +  for (Graph::EdgeIt e(g); e!=INVALID; ++e) 
    1.89 +    flow.set(e, lp_flow[e]);
    1.90 +}