diff -r b5dee93d7abd -r 3a98a1aa5a8f src/hugo/mincostflows.h --- a/src/hugo/mincostflows.h Wed Sep 22 07:22:34 2004 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,241 +0,0 @@ -// -*- c++ -*- -#ifndef HUGO_MINCOSTFLOWS_H -#define HUGO_MINCOSTFLOWS_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 hugo { - -/// \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 hugo::MinCostFlows "MinCostFlows" 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-weitghs 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 use 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 MinCostFlows { - - typedef typename LengthMap::ValueType Length; - - //Warning: this should be integer type - typedef typename CapacityMap::ValueType 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 ResGraphWrapper ResGraphType; - typedef typename ResGraphType::Edge ResGraphEdge; - - class ModLengthMap { - typedef typename Graph::template NodeMap NodeMap; - const ResGraphType& G; - const LengthMap &ol; - const NodeMap &pot; - public : - typedef typename LengthMap::KeyType KeyType; - typedef typename LengthMap::ValueType ValueType; - - ValueType operator[](typename ResGraphType::Edge e) const { - if (G.forward(e)) - return ol[e]-(pot[G.head(e)]-pot[G.tail(e)]); - else - return -ol[e]-(pot[G.head(e)]-pot[G.tail(e)]); - } - - ModLengthMap(const ResGraphType& _G, - const LengthMap &o, const NodeMap &p) : - G(_G), /*rev(_rev),*/ ol(o), pot(p){}; - };//ModLengthMap - - - protected: - - //Input - const Graph& G; - const LengthMap& length; - const CapacityMap& capacity; - - - //auxiliary variables - - //To store the flow - EdgeIntMap flow; - //To store the potential (dual variables) - typedef typename Graph::template NodeMap PotentialMap; - PotentialMap potential; - - - Length total_length; - - - public : - - /// 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. - MinCostFlows(Graph& _G, LengthMap& _length, CapacityMap& _cap) : G(_G), - length(_length), capacity(_cap), flow(_G), potential(_G){ } - - - ///Runs the algorithm. - - ///Runs the algorithm. - ///Returns k if there is a flow of value at least k edge-disjoint - ///from s to t. - ///Otherwise it returns the maximum value of a flow from s to t. - /// - ///\param s The source node. - ///\param t The target node. - ///\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. - int run(Node s, Node t, int k) { - - //Resetting variables from previous runs - total_length = 0; - - for (typename Graph::EdgeIt e(G); e!=INVALID; ++e) flow.set(e, 0); - - //Initialize the potential to zero - for (typename Graph::NodeIt n(G); n!=INVALID; ++n) potential.set(n, 0); - - - //We need a residual graph - ResGraphType res_graph(G, capacity, flow); - - - ModLengthMap mod_length(res_graph, length, potential); - - Dijkstra dijkstra(res_graph, mod_length); - - int i; - for (i=0; i 0 && fl_e != 0) - return false; - if (mod_pot < 0 && fl_e != capacity[e]) - return false; - } - } - return true; - } - - - }; //class MinCostFlows - - ///@} - -} //namespace hugo - -#endif //HUGO_MINCOSTFLOWS_H