Opt2Tsp< CM > Class Template Reference

Detailed Description

template<typename CM>
class lemon::Opt2Tsp< CM >

Opt2Tsp implements the 2-opt heuristic for solving symmetric TSP.

This algorithm starts with an initial tour and iteratively improves it. At each step, it removes two edges and the reconnects the created two paths in the other way if the resulting tour is shorter. The algorithm finishes when no such 2-opt move can be applied, and so the tour is 2-optimal.

If no starting tour is given to the run() function, then the algorithm uses the node sequence determined by the node IDs. Oherwise, it starts with the given tour.

This is a rather slow but effective method. Its typical usage is the improvement of the result of a fast tour construction heuristic (e.g. the InsertionTsp algorithm).

Template Parameters

CM	Type of the cost map.

#include <lemon/opt2_tsp.h>

Public Types
typedef CM	CostMap
	Type of the cost map.
typedef CM::Value	Cost
	Type of the edge costs.

Public Member Functions
	Opt2Tsp (const FullGraph &gr, const CostMap &cost)
	Constructor.
Execution Control
Cost	run ()
	Runs the algorithm from scratch.
template<typename Path >
Cost	run (const Path &tour)
	Runs the algorithm starting from the given tour.
Cost	run (const std::vector< Node > &tour)
	Runs the algorithm starting from the given tour.
Query Functions
Cost	tourCost () const
	The total cost of the found tour.
const std::vector< Node > &	tourNodes () const
	Returns a const reference to the node sequence of the found tour.
template<typename Iterator >
void	tourNodes (Iterator out) const
	Gives back the node sequence of the found tour.
template<typename Path >
void	tour (Path &path) const
	Gives back the found tour as a path.

Constructor & Destructor Documentation

Opt2Tsp ( const FullGraph &  gr, const CostMap &  cost  )

inline

Constructor.

Parameters

gr	The full graph the algorithm runs on.
cost	The cost map.

Member Function Documentation

Cost run ( )

inline

This function runs the algorithm starting from the tour that is determined by the node ID sequence.

Returns

The total cost of the found tour.

Cost run ( const Path &  tour )

inline

This function runs the algorithm starting from the given tour.

Parameters

tour	The tour as a path structure. It must be a valid path containing excactly n arcs.

Returns

The total cost of the found tour.

Cost run ( const std::vector< Node > &  tour )

inline

This function runs the algorithm starting from the given tour (node sequence).

Parameters

tour	A vector that stores all Nodes of the graph in the desired order.

Returns

The total cost of the found tour.

Cost tourCost ( ) const

inline

This function returns the total cost of the found tour.

Precondition

run() must be called before using this function.

const std::vector<Node>& tourNodes ( ) const

inline

This function returns a const reference to a vector that stores the node sequence of the found tour.

Precondition

run() must be called before using this function.

void tourNodes ( Iterator  out ) const

inline

This function copies the node sequence of the found tour into an STL container through the given output iterator. The value_type of the container must be FullGraph::Node. For example,

std::vector<FullGraph::Node> nodes(countNodes(graph));
tsp.tourNodes(nodes.begin());

or

std::list<FullGraph::Node> nodes;
tsp.tourNodes(std::back_inserter(nodes));

Precondition

run() must be called before using this function.

void tour ( Path &  path ) const

inline

This function copies the found tour as a list of arcs/edges into the given path structure.

Precondition

run() must be called before using this function.