org.chocosolver.solver.constraints

Class Constraint

java.lang.Object

org.chocosolver.solver.constraints.Constraint

Direct Known Subclasses:

AllDifferent, Arithmetic, CostRegular, Cumulative, GlobalCardinality, LocalConstructiveDisjunction, Member, NogoodConstraint, NotMember, Opposite, RealConstraint, ReificationConstraint, SatConstraint, SumConstraint

public class Constraint
extends Object

A Constraint is basically a set of Propagator. It can either be posted or reified

Since:

0.01

Version:

major revision 13/01/2014

Author:

Jean-Guillaume Fages, Xavier Lorca, Charles Prud'homme

See Also:

Variable, Propagator, PropagationEngine

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Constraint.Status Status of this constraint wrt the model

Field Summary

Fields

Modifier and Type	Field and Description
protected BoolVar	boolReif BoolVar that reifies this constraint, unique.
protected Propagator[]	propagators Propagators of the constraint (they will filter domains and eventually check solutions)

Constructor Summary

Constructors

Constructor and Description
Constraint(String name, Propagator... propagators) Make a new constraint defined as a set of given propagators

Method Summary

Modifier and Type	Method and Description
void	checkNewStatus(Constraint.Status aStatus) Check if the new status is not in conflict with the current one
PropagatorPriority	computeMaxPriority()
void	declareAs(Constraint.Status aStatus, int idx) For internal usage only, declare the status of this constraint in the model and, if need be, its position in the constraint list.
int	getCidxInModel()
String	getName()
Constraint	getOpposite() Get the opposite constraint of this constraint.
Propagator	getPropagator(int i)
Propagator[]	getPropagators() Return an array which contains the propagators declared in this.
Constraint.Status	getStatus()
boolean	isReified()
ESat	isSatisfied() Test if this Constraint object is satisfied, regarding its Propagators and its Variable current domains.
protected Constraint	makeOpposite() Make the opposite constraint of this.
static Constraint	merge(String name, Constraint... toMerge) Creates a new constraint with all propagators of toMerge
void	post() Posts the constraint to its model so that the constraint must be satisfied.
BoolVar	reify() Get/make the boolean variable indicating whether the constraint is satisfied or not This should not be posted.
void	reifyWith(BoolVar bool) Reifies the constraint with a boolean variable If the reified boolean variable already exists, an additional (equality) constraint is automatically posted.
void	setName(String newName) Changes the name of this constraint
protected void	setOpposite(Constraint opp)
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

propagators

protected final Propagator[] propagators

Propagators of the constraint (they will filter domains and eventually check solutions)

boolReif

protected BoolVar boolReif

BoolVar that reifies this constraint, unique.

Constructor Detail

Constraint

public Constraint(String name,
                  Propagator... propagators)

Make a new constraint defined as a set of given propagators

Parameters:

name - name of the constraint

propagators - set of propagators defining the constraint

Method Detail

getPropagators

public Propagator[] getPropagators()

Return an array which contains the propagators declared in this.

Returns:

an array of Propagator.

getPropagator

public Propagator getPropagator(int i)

isSatisfied

public ESat isSatisfied()

Test if this Constraint object is satisfied, regarding its Propagators and its Variable current domains.

This method is called on each solution as a checker when assertions are enabled (-ea in VM parameters) It is also called for constraint reification (to state whether or not a constraint is satisfied)

The method calls entailment checks of this propagators

Returns:

ESat.FALSE if the constraint cannot be satisfied (from domain consideration), ESat.TRUE if whatever future decisions are, the constraint will be satisfied for sure (without propagating domain modifications) ESat.UNDIFINED otherwise (more decisions/filtering must be made before concluding about constraint satisfaction)

toString

public String toString()

Overrides:

toString in class Object

isReified

public final boolean isReified()

Returns:

true iff this constraint has been reified

reifyWith

public void reifyWith(BoolVar bool)

Reifies the constraint with a boolean variable If the reified boolean variable already exists, an additional (equality) constraint is automatically posted.

Parameters:

bool - the variable to reify with

reify

public final BoolVar reify()

Get/make the boolean variable indicating whether the constraint is satisfied or not This should not be posted.

Returns:

the boolean reifying the constraint

post

public final void post()

Posts the constraint to its model so that the constraint must be satisfied. This should not be reified.

declareAs

public final void declareAs(Constraint.Status aStatus,
                            int idx)
                     throws SolverException

For internal usage only, declare the status of this constraint in the model and, if need be, its position in the constraint list.

Parameters:

aStatus - status of this constraint in the model

idx - position of this constraint in the constraint list.

Throws:

SolverException - if the constraint a incoherent status is declared

checkNewStatus

public final void checkNewStatus(Constraint.Status aStatus)
                          throws SolverException

Check if the new status is not in conflict with the current one

Parameters:

aStatus - new status of the constraint

Throws:

SolverException - if the constraint a incoherent status is declared

getStatus

public final Constraint.Status getStatus()

Returns:

the Constraint.Status of this constraint

getCidxInModel

public int getCidxInModel()

Returns:

the position of this constraint in the model

getOpposite

public Constraint getOpposite()

Get the opposite constraint of this constraint. At first call, it creates the opposite constraint, links them together (the opposite constraint of this opposite constraint is this constraint) and returns the opposite. Next calls will return the previously created opposite constraint. In other words, there can be only one opposite per instance of constraint. The default opposite constraint does not filter domains but fails if this constraint is satisfied.

Returns:

the opposite constraint of this

setOpposite

protected void setOpposite(Constraint opp)

makeOpposite

protected Constraint makeOpposite()

Make the opposite constraint of this. BEWARE: this method should never be called by the user but it can be overridden to provide better constraint negations

setName

public void setName(String newName)

Changes the name of this constraint

Parameters:

newName - the name of the constraint

getName

public String getName()

Returns:

the name of this constraint

computeMaxPriority

public PropagatorPriority computeMaxPriority()

Returns:

the maximum priority of a propagator of this constraint

merge

public static Constraint merge(String name,
                               Constraint... toMerge)

Creates a new constraint with all propagators of toMerge

Parameters:

name - name of the new constraint

toMerge - a set of constraints to merge in this

Returns:

a new constraint with all propagators of toMerge