org.jamesframework.ext.search.neigh

Class CompositeNeighbourhood<SolutionType extends Solution>

java.lang.Object

org.jamesframework.ext.search.neigh.CompositeNeighbourhood<SolutionType>

Type Parameters:

SolutionType - solution type for which this neighbourhood can be applied, required to extend Solution

All Implemented Interfaces:

Neighbourhood<SolutionType>

public class CompositeNeighbourhood<SolutionType extends Solution>
extends Object
implements Neighbourhood<SolutionType>

A composite neighbourhood combines a collection of other neighbourhoods which each have a weight that determines the relative frequency with which random moves are sampled from each contained neighbourhood. When requesting a random move to the composite neighbourhood, a random move produced by one of the contained neighbourhoods is returned, picked through roulette selection based on the weights given at construction. When requesting all moves, the union of all moves generated by all contained neighbourhoods is returned, regardless of the assigned weights.

Author:

Herman De Beukelaer

Constructor Summary

Constructors

Constructor and Description
CompositeNeighbourhood(List<? extends Neighbourhood<? super SolutionType>> neighbourhoods, List<Double> neighbourhoodWeights) Creates a composite neighbourhood consisting of the list of given neighbourhoods and specified weights.

Method Summary

Modifier and Type	Method and Description
List<Move<? super SolutionType>>	getAllMoves(SolutionType solution) Creates and returns the union of all moves generated by each of the contained neighbourhoods.
Move<? super SolutionType>	getRandomMove(SolutionType solution, Random rnd) Produces a random move generated by one of the contained neighbourhoods based on the assigned weights.
String	toString() Create string representation that indicates the contained neighbourhoods and respective weights.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.jamesframework.core.search.neigh.Neighbourhood

getRandomMove

Constructor Detail

CompositeNeighbourhood

public CompositeNeighbourhood(List<? extends Neighbourhood<? super SolutionType>> neighbourhoods,
                              List<Double> neighbourhoodWeights)

Creates a composite neighbourhood consisting of the list of given neighbourhoods and specified weights. The list of neighbourhoods and weights can not be null, should be of the same size and can not contain any null elements. At least one neighbourhood should be given and all weights should be strictly positive.

Parameters:

neighbourhoods - list of neighbourhoods

neighbourhoodWeights - list of weights assigned to the neighbourhoods (same order as neighbourhoods)

Throws:

NullPointerException - if neighbourhoods or neighbourhoodWeights are null or contain any null elements

IllegalArgumentException - if neighbourhoods and neighbourhoodWeights are not of the same size or both empty, or if neighbourhoodWeights contains any weight ≤ 0

Method Detail

getRandomMove

public Move<? super SolutionType> getRandomMove(SolutionType solution,
                                                Random rnd)

Produces a random move generated by one of the contained neighbourhoods based on the assigned weights. First, a random move is requested from each neighbourhood as it may happen that one or more neighbourhoods are unable to produce a random move. If no moves are obtained, this method returns null. Else, it selects a move through roulette selection based on the weights assigned at construction.

Specified by:

getRandomMove in interface Neighbourhood<SolutionType extends Solution>

Parameters:

solution - solution for which a move is generated

rnd - source of randomness used to generate random move

Returns:

random move generated by one of the contained neighbourhoods, which is selected by roulette selection based on the assigned weights; null if none of the contained neighbourhoods are able to produce a random move

getAllMoves

public List<Move<? super SolutionType>> getAllMoves(SolutionType solution)

Creates and returns the union of all moves generated by each of the contained neighbourhoods. The returned list may be empty if none of the contained neighbourhoods can generate any move.

Specified by:

getAllMoves in interface Neighbourhood<SolutionType extends Solution>

Parameters:

solution - solution for which all moves are generated

Returns:

union of all possible moves generated by each contained neighbourhood

toString

public String toString()

Create string representation that indicates the contained neighbourhoods and respective weights.

Overrides:

toString in class Object

Returns:

string representation