Package org.jacop.core

Class SimpleBacktrackableManager

java.lang.Object

org.jacop.core.SimpleBacktrackableManager

All Implemented Interfaces:

BacktrackableManager

Direct Known Subclasses:

IntervalBasedBacktrackableManager

public class SimpleBacktrackableManager
extends java.lang.Object
implements BacktrackableManager

It is responsible of remembering what variables have changed at given store level.

Version:

4.8

Field Summary

Fields

Modifier and Type	Field	Description
int	currentLevel	It specifies the current level which is active in the manager.
boolean	currentLevelMax	It specifies if for the current level we have reached the cutoff value.
(package private) SparseSet	currentlyChanged	It contains indexes of objects changed at active level.
(package private) int	cutOffValue	It specifies the cutoff value after which a trail is no longer stored and recovery of the old state is done by informing all the variables about the backtracking.
(package private) boolean	debug	It specifies if the debugging information should be displayed.
(package private) int[]	emptyLevel	It is a fake variable to distinguish between empty levels and full levels.
(package private) int[]	fullLevel	It is a fake variable to disinguish between full levels and empty ones.
(package private) java.util.List<java.lang.Integer>	levelInfo	It specifies the levels of the store for which trails are stored.
(package private) int	noOfObjects	It specifies the actual number of objects in the objects array.
Backtrackable[]	objects	It stores objects which change has to be restored upon backtracking.
(package private) java.util.List<int[]>	trail	It specifies a trail.
boolean	trailContainsAllChanges	It specifies if for the current level the all changes are already stored in the trail.

Constructor Summary

Constructors

Constructor	Description
SimpleBacktrackableManager(Backtrackable[] vars, int noOfObjects)	It constructs a trail manager.

Method Summary

Modifier and Type	Method	Description
void	addChanged(int index)	It allows to inform the manager that a given item with id (index) has changed at given level.
int	getLevel()	It returns the current level at which the changes are being registered.
boolean	isRecognizedAsChanged(int index)	It allows for easy testing if a given object is considered by the manager as the object which has changed and needs being informed about backtracking.
void	removeLevel(int removedLevel)	It allows to inform all objects which have changed at removedLevel that the backtracking from that level has occurred.
void	setLevel(int level)	It specifies the level which should become the active one in the manager.
void	setSize(int size)	It specifies how many objects within objects array are being actually managed.
java.lang.String	toString()
void	update(Backtrackable[] objects, int noOfObjects)	It updates the manager with new array of objects to manage and new number of them.

Methods inherited from class java.lang.Object

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

Field Detail

currentLevel

public int currentLevel

It specifies the current level which is active in the manager.

noOfObjects

int noOfObjects

It specifies the actual number of objects in the objects array.

currentlyChanged

SparseSet currentlyChanged

It contains indexes of objects changed at active level. It may be empty if trailContainsAllChanges is set to true.

trail

java.util.List<int[]> trail

It specifies a trail. A recorded changes which will be used upon backtracking to inform the objects about backtracking.

levelInfo

java.util.List<java.lang.Integer> levelInfo

It specifies the levels of the store for which trails are stored.

cutOffValue

int cutOffValue

It specifies the cutoff value after which a trail is no longer stored and recovery of the old state is done by informing all the variables about the backtracking.

objects

public Backtrackable[] objects

It stores objects which change has to be restored upon backtracking. The positions of objects will be stored by the manager and all changed objects will have their function removeLevel() be called.

trailContainsAllChanges

public boolean trailContainsAllChanges

It specifies if for the current level the all changes are already stored in the trail. This situation occurs after each backtrack. If new changes are added then this flag indicates that trail has to be used.

currentLevelMax

public boolean currentLevelMax

It specifies if for the current level we have reached the cutoff value.

emptyLevel

final int[] emptyLevel

It is a fake variable to distinguish between empty levels and full levels.

fullLevel

final int[] fullLevel

It is a fake variable to disinguish between full levels and empty ones.

debug

final boolean debug

It specifies if the debugging information should be displayed.

See Also:

Constant Field Values

Constructor Detail

SimpleBacktrackableManager

public SimpleBacktrackableManager(Backtrackable[] vars,
                                  int noOfObjects)

It constructs a trail manager.

Parameters:

noOfObjects - it specifies number of objects being managed.

vars - it specifies the list of objects being managed.

Method Detail

addChanged

public void addChanged(int index)

It allows to inform the manager that a given item with id (index) has changed at given level.

Specified by:

addChanged in interface BacktrackableManager

Parameters:

index - it specifies the index of the object which has changed.

setLevel

public void setLevel(int level)

It specifies the level which should become the active one in the manager.

Specified by:

setLevel in interface BacktrackableManager

Parameters:

level - the active level at which the changes will be recorded.

removeLevel

public void removeLevel(int removedLevel)

It allows to inform all objects which have changed at removedLevel that the backtracking from that level has occurred.

Specified by:

removeLevel in interface BacktrackableManager

Parameters:

removedLevel - it specifies the level which is being removed.

setSize

public void setSize(int size)

It specifies how many objects within objects array are being actually managed. It allows to specify partially empty array.

Specified by:

setSize in interface BacktrackableManager

Parameters:

size - the number of objects in the array.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

isRecognizedAsChanged

public boolean isRecognizedAsChanged(int index)

It allows for easy testing if a given object is considered by the manager as the object which has changed and needs being informed about backtracking.

Specified by:

isRecognizedAsChanged in interface BacktrackableManager

Parameters:

index - the position of the object which status is in question.

Returns:

it returns true if the manager recognizes object at position index as changed one.

getLevel

public int getLevel()

Description copied from interface: BacktrackableManager

It returns the current level at which the changes are being registered.

Specified by:

getLevel in interface BacktrackableManager

Returns:

the active level for which the changes are being registered.

update

public void update(Backtrackable[] objects,
                   int noOfObjects)

Description copied from interface: BacktrackableManager

It updates the manager with new array of objects to manage and new number of them. This function works properly only during model creation phase, so manager can learn about freshly created objects. If used during search then the old array must be part of the new array to allow manager work properly.

Specified by:

update in interface BacktrackableManager

Parameters:

objects - a new array of objects

noOfObjects - number of objects in the new array to be taken care of.