JaCoP.constraints.geost
Interface ExternalConstraint

All Known Implementing Classes:

InArea, NonOverlapping

public interface ExternalConstraint

Author:

Marc-Olivier Fleury and Radoslaw Szymanek This interface defines the minimal functionality that is required by a constraint in order to be used by Geost as an external constraint. External constraints are loosely coupled with Geost internals, in the sense that they are only required to be able to provide a representation usable by Geost. The generation of internal constraints is done only once per search, implying that it is possible to do costly operations in order to generate these constraints.

Method Summary

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.
java.util.Collection<? extends InternalConstraint>	genInternalConstraints(Geost geost) It generates internal constraints which will be used by Geost's sweeping algorithm.
java.util.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.

Method Detail

genInternalConstraints

java.util.Collection<? extends InternalConstraint> genInternalConstraints(Geost geost)

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.

Parameters:

geost - the geost kernel that will use the generated constraint

Returns:

the collection of internal constraints which correspond to this external constraint

getObjectConstraints

java.util.Collection<? extends InternalConstraint> getObjectConstraints(GeostObject o)

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.

Parameters:

o - the geost object that needs to be constrained

Returns:

the collection of internal constraints acting on the given object

addPrunableObjects

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. 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.

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

void onObjectUpdate(GeostObject o)

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.

Parameters:

o -

isInternalConstraintApplicableTo

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.

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

GeostObject[] getObjectScope()

Provides the collection of objects that this constraint applies to

Returns:

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