diff -r d8475431bbbb -r 8e85e6bbefdf src/lemon/min_cost_flow.h --- a/src/lemon/min_cost_flow.h Sat May 21 21:04:57 2005 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,260 +0,0 @@ -/* -*- C++ -*- - * src/lemon/min_cost_flow.h - Part of LEMON, a generic C++ optimization library - * - * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport - * (Egervary Research Group on Combinatorial Optimization, EGRES). - * - * Permission to use, modify and distribute this software is granted - * provided that this copyright notice appears in all copies. For - * precise terms see the accompanying LICENSE file. - * - * This software is provided "AS IS" with no warranty of any kind, - * express or implied, and with no claim as to its suitability for any - * purpose. - * - */ - -#ifndef LEMON_MIN_COST_FLOW_H -#define LEMON_MIN_COST_FLOW_H - -///\ingroup flowalgs -///\file -///\brief An algorithm for finding a flow of value \c k (for small values of \c k) having minimal total cost - - -#include -#include -#include -#include - -namespace lemon { - -/// \addtogroup flowalgs -/// @{ - - ///\brief Implementation of an algorithm for finding a flow of value \c k - ///(for small values of \c k) having minimal total cost between 2 nodes - /// - /// - /// The class \ref lemon::MinCostFlow "MinCostFlow" implements an - /// algorithm for finding a flow of value \c k having minimal total - /// cost from a given source node to a given target node in an - /// edge-weighted directed graph. To this end, the edge-capacities - /// and edge-weights have to be nonnegative. The edge-capacities - /// should be integers, but the edge-weights can be integers, reals - /// or of other comparable numeric type. This algorithm is intended - /// to be used only for small values of \c k, since it is only - /// polynomial in k, not in the length of k (which is log k): in - /// order to find the minimum cost flow of value \c k it finds the - /// minimum cost flow of value \c i for every \c i between 0 and \c - /// k. - /// - ///\param Graph The directed graph type the algorithm runs on. - ///\param LengthMap The type of the length map. - ///\param CapacityMap The capacity map type. - /// - ///\author Attila Bernath - template - class MinCostFlow { - - typedef typename LengthMap::Value Length; - - //Warning: this should be integer type - typedef typename CapacityMap::Value Capacity; - - typedef typename Graph::Node Node; - typedef typename Graph::NodeIt NodeIt; - typedef typename Graph::Edge Edge; - typedef typename Graph::OutEdgeIt OutEdgeIt; - typedef typename Graph::template EdgeMap EdgeIntMap; - - typedef ResGraphAdaptor ResGW; - typedef typename ResGW::Edge ResGraphEdge; - - protected: - - const Graph& g; - const LengthMap& length; - const CapacityMap& capacity; - - EdgeIntMap flow; - typedef typename Graph::template NodeMap PotentialMap; - PotentialMap potential; - - Node s; - Node t; - - Length total_length; - - class ModLengthMap { - typedef typename Graph::template NodeMap NodeMap; - const ResGW& g; - const LengthMap &length; - const NodeMap &pot; - public : - typedef typename LengthMap::Key Key; - typedef typename LengthMap::Value Value; - - ModLengthMap(const ResGW& _g, - const LengthMap &_length, const NodeMap &_pot) : - g(_g), /*rev(_rev),*/ length(_length), pot(_pot) { } - - Value operator[](typename ResGW::Edge e) const { - if (g.forward(e)) - return length[e]-(pot[g.target(e)]-pot[g.source(e)]); - else - return -length[e]-(pot[g.target(e)]-pot[g.source(e)]); - } - - }; //ModLengthMap - - ResGW res_graph; - ModLengthMap mod_length; - Dijkstra dijkstra; - - public : - - /*! \brief The constructor of the class. - - \param _g The directed graph the algorithm runs on. - \param _length The length (weight or cost) of the edges. - \param _cap The capacity of the edges. - \param _s Source node. - \param _t Target node. - */ - MinCostFlow(Graph& _g, LengthMap& _length, CapacityMap& _cap, - Node _s, Node _t) : - g(_g), length(_length), capacity(_cap), flow(_g), potential(_g), - s(_s), t(_t), - res_graph(g, capacity, flow), - mod_length(res_graph, length, potential), - dijkstra(res_graph, mod_length) { - reset(); - } - - /*! Tries to augment the flow between s and t by 1. - The return value shows if the augmentation is successful. - */ - bool augment() { - dijkstra.run(s); - if (!dijkstra.reached(t)) { - - //Unsuccessful augmentation. - return false; - } else { - - //We have to change the potential - for(typename ResGW::NodeIt n(res_graph); n!=INVALID; ++n) - potential.set(n, potential[n]+dijkstra.distMap()[n]); - - //Augmenting on the shortest path - Node n=t; - ResGraphEdge e; - while (n!=s){ - e = dijkstra.pred(n); - n = dijkstra.predNode(n); - res_graph.augment(e,1); - //Let's update the total length - if (res_graph.forward(e)) - total_length += length[e]; - else - total_length -= length[e]; - } - - return true; - } - } - - /*! \brief Runs the algorithm. - - Runs the algorithm. - Returns k if there is a flow of value at least k from s to t. - Otherwise it returns the maximum value of a flow from s to t. - - \param k The value of the flow we are looking for. - - \todo May be it does make sense to be able to start with a nonzero - feasible primal-dual solution pair as well. - - \todo If the actual flow value is bigger than k, then everything is - cleared and the algorithm starts from zero flow. Is it a good approach? - */ - int run(int k) { - if (flowValue()>k) reset(); - while (flowValue() 0 && fl_e != 0) - return false; - if (mod_pot < 0 && fl_e != capacity[e]) - return false; - } - } - return true; - } - - }; //class MinCostFlow - - ///@} - -} //namespace lemon - -#endif //LEMON_MIN_COST_FLOW_H