org.jacop.constraints.geost

Class ForbiddenArea

java.lang.Object

org.jacop.constraints.geost.InternalConstraint

org.jacop.constraints.geost.ForbiddenArea

public class ForbiddenArea
extends InternalConstraint

Author:

Marc-Olivier Fleury and Radoslaw Szymanek The simplest possible internal constraint: DBox defining a set of points with which no object can overlap.

Constructor Summary

Constructors

Constructor and Description
ForbiddenArea(Geost geost, int[] origin, int[] length) It constructs an internal constraint forbidding an object to be placed within this aread.

Method Summary

Modifier and Type	Method and Description
int[]	AbsInfeasible(Geost.SweepDirection minlex) It provides the largest or smallest point contained in the forbidden area represented by this constraint.
int	cardInfeasible() It provides an approximation of the number of infeasible points enforced by this constraint only.
String	checkInvariants() It checks whether the ForbiddenArea is consistent.
Collection<Var>	definingVariables() It provides a collection, possibly empty, of variables which define this constraint.
DBox	isFeasible(Geost.SweepDirection min, LexicographicalOrder order, GeostObject o, int currentShape, int[] c) It determines whether the given point is a feasible origin of object o, considering this constraint only.
boolean	isSingleUse() In some cases, a constraint is used only once per sweep direction on a path from root to leaf in the search tree.
boolean	isStatic() It provides information about the constraint future.

Methods inherited from class java.lang.Object

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

Constructor Detail

ForbiddenArea

public ForbiddenArea(Geost geost,
                     int[] origin,
                     int[] length)

It constructs an internal constraint forbidding an object to be placed within this aread.

Parameters:

geost - the geost constraint in which this internal constraint exists.

origin - the origin of the forbidden area.

length - the length of the forbidden area.

Method Detail

checkInvariants

public String checkInvariants()

It checks whether the ForbiddenArea is consistent.

Returns:

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

isFeasible

public DBox isFeasible(Geost.SweepDirection min,
                       LexicographicalOrder order,
                       GeostObject o,
                       int currentShape,
                       int[] c)

Description copied from class: InternalConstraint

It determines whether the given point is a feasible origin of object o, considering this constraint only. If it is not, returns a DBox corresponding to the largest infeasible domain, considering a sweep which uses the given ordering. The boundaries of the forbidden area must have the following properties: the lower extremum has to be infeasible, but the upper extremum has to be feasible (with respect to this constraint only). The dimension of the DBox returned is k+1, where k is the object dimension. The last dimension is time.

Specified by:

isFeasible in class InternalConstraint

Parameters:

min - the direction of the sweep

order - the order to be used

o - the object the constraint is applied to

currentShape - the shape id that is currently considered for o

c - the current position of the sweep.

Returns:

a DBox representing the forbidden region

AbsInfeasible

public int[] AbsInfeasible(Geost.SweepDirection minlex)

Description copied from class: InternalConstraint

It provides the largest or smallest point contained in the forbidden area represented by this constraint. This point must be larger or equal (resp. smaller or equal) to the lexicographically largest (resp. smallest) point included in the forbidden area, whatever the lexical order is. TODO, is this function potentially still useful? If not remove, if yes then adapt the description about event point series. What is it used now for? I will keep it as it may be used later on, but for sure the code implementing those functions is not tested much or requires some cleaning. This allows to build an event point series that stays consistent whatever the lexical order is, and whatever the object to place is (some shifting is applied to take the object's shape into account) The dimension of the point returned is k+1, where k is the object dimension. The last dimension is time.

Specified by:

AbsInfeasible in class InternalConstraint

Parameters:

minlex - defines whether the maximal or minimal point should be returned

Returns:

the infeasible point's coordinates. If constraint cannot generate outbox then it returns null.

cardInfeasible

public final int cardInfeasible()

Description copied from class: InternalConstraint

It provides an approximation of the number of infeasible points enforced by this constraint only. The information provided by this function cannot be accurate, since no object is passed as an argument, but some consistent approximation should exist. For instance, in the case of a forbidden area, the returned value can be the number of points included in the area. This information is used as a heuristic in the sweeping algorithm to decide which constraint to use, so that the constraints that cover the largest space are used first.

Specified by:

cardInfeasible in class InternalConstraint

Returns:

an approximation of the number of infeasible points enforced by this constraint only.

definingVariables

public Collection<Var> definingVariables()

Description copied from class: InternalConstraint

It provides a collection, possibly empty, of variables which define this constraint. This information is used to build a reverse index that allows to update the absolute infeasible points of a constraint when a variable changes.

Specified by:

definingVariables in class InternalConstraint

Returns:

the collection containing variables that define that constraint.

isStatic

public boolean isStatic()

Description copied from class: InternalConstraint

It provides information about the constraint future. If a constraint will always generate the same outboxes deeper in the tree, it should return false, so that jumps in the event point series can be done. TODO the description above suggests that it should be called isDynamic as it returns false if the constraint outboxes stay the same. (not taking placed object into account; i.e. absInfeasible will always return the same points)

Specified by:

isStatic in class InternalConstraint

Returns:

TODO, proper description after fixing the above todo.

isSingleUse

public boolean isSingleUse()

Description copied from class: InternalConstraint

In some cases, a constraint is used only once per sweep direction on a path from root to leaf in the search tree. In that case, the constraint can be ignored if it was seen at some point. TODO, what is the example of such constraint? Use this function to provide the information to Geost.

Specified by:

isSingleUse in class InternalConstraint

Returns:

TODO. Is this function used at all? It seems that all implementations return false and nowhere in geost it is used.