org.cpsolver.ifs.model

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

java.lang.Object

org.cpsolver.ifs.model.LazyNeighbour<V,T>

Type Parameters:

V - Variable

T - Value

All Implemented Interfaces:

Neighbour<V,T>

Direct Known Subclasses:

LazySwap

public abstract class LazyNeighbour<V extends Variable<V,T>,T extends Value<V,T>>
extends Object
implements Neighbour<V,T>

Lazy neigbour (a change of the overall solution value is unknown before the neighbour is assigned, it is possible to undo the neighbour instead). This neighbour is useful when it is two expensive to compute change of overall solution value before the variable is reassigned. It is possible to undo the neighbour instead. Search strategy has to implement LazyNeighbour.LazyNeighbourAcceptanceCriterion.

Version:

IFS 1.3 (Iterative Forward Search)
Copyright (C) 2013 - 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/.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	LazyNeighbour.LazyNeighbourAcceptanceCriterion<V extends Variable<V,T>,T extends Value<V,T>> Neighbour acceptance criterion interface (to be implemented by search strategies that are using LazyNeighbour.

Constructor Summary

Constructors

Constructor and Description
LazyNeighbour()

Method Summary

Modifier and Type	Method and Description
void	assign(Assignment<V,T> assignment, long iteration) Assign neighbour, check given acceptance criterion, and undo assignment if the change is not accepted.
protected abstract void	doAssign(Assignment<V,T> assignment, long iteration) Perform assignment
LazyNeighbour.LazyNeighbourAcceptanceCriterion<V,T>	getAcceptanceCriterion() Return acceptance criterion (to be used by a search strategy before the neighbour is accepted, so that it can be undone if desired)
abstract Model<V,T>	getModel() Return problem model (it is needed in order to be able to get overall solution value before and after the assignment of this neighbour)
void	setAcceptanceCriterion(LazyNeighbour.LazyNeighbourAcceptanceCriterion<V,T> criterion) Set acceptance criterion (to be used by a search strategy before the neighbour is accepted, so that it can be undone if desired)
protected abstract void	undoAssign(Assignment<V,T> assignment, long iteration) Undo assignment
double	value(Assignment<V,T> assignment) Return -1 (neighbour is always accepted).

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.cpsolver.ifs.model.Neighbour

assignments

Constructor Detail

LazyNeighbour

public LazyNeighbour()

Method Detail

setAcceptanceCriterion

public void setAcceptanceCriterion(LazyNeighbour.LazyNeighbourAcceptanceCriterion<V,T> criterion)

Set acceptance criterion (to be used by a search strategy before the neighbour is accepted, so that it can be undone if desired)

Parameters:

criterion - acceptance criterion

getAcceptanceCriterion

public LazyNeighbour.LazyNeighbourAcceptanceCriterion<V,T> getAcceptanceCriterion()

Return acceptance criterion (to be used by a search strategy before the neighbour is accepted, so that it can be undone if desired)

Returns:

acceptance criterion

assign

public void assign(Assignment<V,T> assignment,
                   long iteration)

Assign neighbour, check given acceptance criterion, and undo assignment if the change is not accepted.

Specified by:

assign in interface Neighbour<V extends Variable<V,T>,T extends Value<V,T>>

Parameters:

assignment - current assignment

iteration - current iteration

value

public double value(Assignment<V,T> assignment)

Return -1 (neighbour is always accepted). The search strategy that is using this neighbour must implement LazyNeighbour.LazyNeighbourAcceptanceCriterion.

Specified by:

value in interface Neighbour<V extends Variable<V,T>,T extends Value<V,T>>

Parameters:

assignment - current assignment

Returns:

difference in the solution value when assigned

doAssign

protected abstract void doAssign(Assignment<V,T> assignment,
                                 long iteration)

Perform assignment

Parameters:

assignment - current assignment

iteration - current iteration

undoAssign

protected abstract void undoAssign(Assignment<V,T> assignment,
                                   long iteration)

Undo assignment

Parameters:

assignment - current assignment

iteration - current iteration

getModel

public abstract Model<V,T> getModel()

Return problem model (it is needed in order to be able to get overall solution value before and after the assignment of this neighbour)

Returns:

problem model