org.cpsolver.ifs.algorithms.neighbourhoods

Class RandomSwapMove<V extends Variable<V,T>,T extends Value<V,T>>

java.lang.Object

org.cpsolver.ifs.algorithms.neighbourhoods.RandomSwapMove<V,T>

Type Parameters:

V - Variable

T - Value

All Implemented Interfaces:

HillClimberSelection, NeighbourSelection<V,T>

Direct Known Subclasses:

RoomSwap, SuggestionMove, TimeSwap

public class RandomSwapMove<V extends Variable<V,T>,T extends Value<V,T>>
extends Object
implements NeighbourSelection<V,T>, HillClimberSelection

Try to assign a variable with a new value. A variable is selected randomly, a different value is randomly selected for the variable -- the variable is assigned with the new value. If there is a conflict, it tries to resolve these conflicts by assigning conflicting variables to other values as well.

Version:

IFS 1.3 (Iterative Forward Search)
Copyright (C) 2014 Tomáš Müller
muller@unitime.org
http://muller.unitime.org

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not see http://www.gnu.org/licenses/.

Author:

Tomáš Müller

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	RandomSwapMove.SwapNeighbour

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	iHC
protected int	iMaxAttempts
protected int	iTimeLimit

Constructor Summary

Constructors

Constructor and Description
RandomSwapMove(DataProperties config)

Method Summary

Modifier and Type	Method and Description
void	init(Solver<V,T> solver) Criterion initialization
protected boolean	isTimeLimitReached(long startTime) Return true if the time limit was reached, number of attempts are limited to 1 in such a case.
protected Double	resolve(Solution<V,T> solution, double total, long startTime, Map<V,T> assignments, List<T> conflicts, int index) Try to resolve given conflicts.
Neighbour<V,T>	selectNeighbour(Solution<V,T> solution) select a neighbour of a given solution
void	setHcMode(boolean hcMode) True if employed by a hill climber, e.g., worsening moves may be skipped.

Methods inherited from class java.lang.Object

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

Field Detail

iMaxAttempts

protected int iMaxAttempts

iHC

protected boolean iHC

iTimeLimit

protected int iTimeLimit

Constructor Detail

RandomSwapMove

public RandomSwapMove(DataProperties config)

Method Detail

setHcMode

public void setHcMode(boolean hcMode)

Description copied from interface: HillClimberSelection

True if employed by a hill climber, e.g., worsening moves may be skipped.

Specified by:

setHcMode in interface HillClimberSelection

Parameters:

hcMode - true if used by a hill climber (worsening moves are automatically discarded)

init

public void init(Solver<V,T> solver)

Description copied from interface: NeighbourSelection

Criterion initialization

Specified by:

init in interface NeighbourSelection<V extends Variable<V,T>,T extends Value<V,T>>

Parameters:

solver - current solver

selectNeighbour

public Neighbour<V,T> selectNeighbour(Solution<V,T> solution)

Description copied from interface: NeighbourSelection

select a neighbour of a given solution

Specified by:

selectNeighbour in interface NeighbourSelection<V extends Variable<V,T>,T extends Value<V,T>>

Parameters:

solution - given solution

Returns:

a neighbour assignment

isTimeLimitReached

protected boolean isTimeLimitReached(long startTime)

Return true if the time limit was reached, number of attempts are limited to 1 in such a case.

Parameters:

startTime - start time

Returns:

true if the given time limit was reached

resolve

protected Double resolve(Solution<V,T> solution,
                         double total,
                         long startTime,
                         Map<V,T> assignments,
                         List<T> conflicts,
                         int index)

Try to resolve given conflicts. For each conflicting variable it tries to find a value with no conflict that is compatible with some other assignment of the other conflicting variables.

Parameters:

solution - current solution

total - original value of the current solution

startTime - starting time

assignments - re-assignments to be made

conflicts - list of conflicts to resolve

index - index in the list of conflicts

Returns:

value of the modified solution, null if cannot be resolved