org.jacop.constraints.geost

Class InArea

java.lang.Object

org.jacop.constraints.geost.InArea

All Implemented Interfaces:

ExternalConstraint

public class InArea
extends Object
implements ExternalConstraint

Version:

4.9

InArea constraint allows on to define an area within which objects should be contained, as well as a collection of "holes" within the area

TODO implement the use of a subset of objects only. In some applications, classes of objects may need to be placed in different portions of the space. Possibly, create class InAreaSetOfObjects extending from InArea to allow specification of the objects in the focus of the constraint.

Author:

Marc-Olivier Fleury and Radoslaw Szymanek

Field Summary

Fields

Modifier and Type	Field and Description
DBox	allowedArea It specifies the allowed area in which the objects can reside.
Set<InternalConstraint>	constraints It holds all the constraints which have been generated from this external constraints.
Collection<DBox>	holes It specifies the holes within the allowed area in which the objects can not be placed.

Constructor Summary

Constructors

Constructor and Description
InArea(DBox area, Collection<DBox> holes) It constructs an external constraint to enforce that all objects within Geost constraint are placed within a specified area with holes in that area specfied as well.

Method Summary

Modifier and Type	Method and Description
boolean	addPrunableObjects(GeostObject o, SimpleHashSet<GeostObject> accumulator) It adds to the accumulator collection the objects that are likely to be pruned if the given object changes.
String	checkInvariants() It checks whether the InArea is consistent.
Collection<InternalConstraint>	genInternalConstraints(Geost geost) It generates internal constraints which will be used by Geost's sweeping algorithm.
Collection<? extends InternalConstraint>	getObjectConstraints(GeostObject o) It provides the collection of internal constraints that the given object has to satisfy.
GeostObject[]	getObjectScope() Provides the collection of objects that this constraint applies to
boolean	isInternalConstraintApplicableTo(InternalConstraint ic, GeostObject o) Returns true if the external constraint generated the supplied internal constraint ic, and that ic applies to object o.
void	onObjectUpdate(GeostObject o) Handler method called by the Geost kernel when the domain of the object changes.

Methods inherited from class java.lang.Object

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

Field Detail

allowedArea

public DBox allowedArea

It specifies the allowed area in which the objects can reside.

holes

public Collection<DBox> holes

It specifies the holes within the allowed area in which the objects can not be placed.

constraints

public Set<InternalConstraint> constraints

It holds all the constraints which have been generated from this external constraints.

Constructor Detail

InArea

public InArea(DBox area,
              Collection<DBox> holes)

It constructs an external constraint to enforce that all objects within Geost constraint are placed within a specified area with holes in that area specfied as well.

Parameters:

area - the specification of the area within which the objects have to be placed.

holes - the holes in which the objects can not be placed.

Method Detail

checkInvariants

public String checkInvariants()

It checks whether the InArea is consistent.

Returns:

It returns the string description of the problem, or null if no problem with data structure consistency encountered.

genInternalConstraints

public Collection<InternalConstraint> genInternalConstraints(Geost geost)

Description copied from interface: ExternalConstraint

It generates internal constraints which will be used by Geost's sweeping algorithm.

The generation of internal constraints is done only once per search, implying that it is possible to do costly operations in order to generate internal constraints. However, another implication of this one-time use is that the internal constraints generated have to remain valid during the whole search.

Specified by:

genInternalConstraints in interface ExternalConstraint

Parameters:

geost - the geost kernel that will use the generated constraint

Returns:

the collection of internal constraints which correspond to this external constraint

addPrunableObjects

public boolean addPrunableObjects(GeostObject o,
                                  SimpleHashSet<GeostObject> accumulator)

Description copied from interface: ExternalConstraint

It adds to the accumulator collection the objects that are likely to be pruned if the given object changes. For instance, in the case of the non-overlapping constraint, these would be the objects that are close to the given object.

TODO, optimize all the code around this functionality, avoid situation when accumulator has all objects anyway and external constraints are continuously queried to add objects and keep adding objects which are already in the set.

Specified by:

addPrunableObjects in interface ExternalConstraint

Parameters:

o - the object that was pruned

accumulator - the set of objects to add the object to

Returns:

true if a value was added, false otherwise

onObjectUpdate

public void onObjectUpdate(GeostObject o)

Description copied from interface: ExternalConstraint

Handler method called by the Geost kernel when the domain of the object changes. Use this method to make changes to the state of the constraint (and of its relative internal constraints) if needed.

Specified by:

onObjectUpdate in interface ExternalConstraint

Parameters:

o - the object

getObjectConstraints

public Collection<? extends InternalConstraint> getObjectConstraints(GeostObject o)

Description copied from interface: ExternalConstraint

It provides the collection of internal constraints that the given object has to satisfy. For instance, for the non overlapping constraint, the result would contain all the constraints corresponding to the objects in the non overlapping group.

This method is used by the kernel only once per object, at the beginning of the search, to collect the set of constraints to use for each object.

Specified by:

getObjectConstraints in interface ExternalConstraint

Parameters:

o - the geost object that needs to be constrained

Returns:

the collection of internal constraints acting on the given object

isInternalConstraintApplicableTo

public boolean isInternalConstraintApplicableTo(InternalConstraint ic,
                                                GeostObject o)

Description copied from interface: ExternalConstraint

Returns true if the external constraint generated the supplied internal constraint ic, and that ic applies to object o.

Specified by:

isInternalConstraintApplicableTo in interface ExternalConstraint

Parameters:

ic - internal constraint being checked

o - object to which internal constrain should apply to

Returns:

true if the constraint was generated by this external constraint for the object o.

getObjectScope

public GeostObject[] getObjectScope()

Description copied from interface: ExternalConstraint

Provides the collection of objects that this constraint applies to

Specified by:

getObjectScope in interface ExternalConstraint

Returns:

the collection of objects, or null if the constraint applies to all objects