org.jacop.constraints

Class NoGood

java.lang.Object

org.jacop.constraints.DecomposedConstraint<Constraint>

org.jacop.constraints.Constraint

org.jacop.constraints.NoGood

public class NoGood
extends Constraint

NoGood constraints implements a constraint which disallows given combination of values for given variables. NoGoods are special constraints as they can be only triggered only when all variables except one are grounded and equal to disallow values. This allows efficient implementation based on watched literals idea from SAT community.

Do not be fooled by watched literals, if you add thousands of no-goods then traversing even 1/10 of them if they are watched by variable which has been grounded can slow down search considerably.

NoGoods constraints are imposed at all levels once added. Do not use in subsearches, as it will not take into account the assignments performed in master search.

Version:

4.9

Author:

Radoslaw Szymanek and Krzysztof Kuchcinski

Field Summary

Fields

Modifier and Type	Field and Description
protected int[]	listOfValues It specifies a list of values in no-good constraint.
protected IntVar[]	listOfVars It specifies a list of variables in no-good constraint.

Fields inherited from class org.jacop.constraints.Constraint

atomicExecution, consistencyPruningEvents, constraintScope, earlyTerminationOK, increaseWeight, numberId, scope, trace

Fields inherited from class org.jacop.constraints.DecomposedConstraint

queueIndex

Constructor Summary

Constructors

Constructor and Description
NoGood(IntVar[] listOfVars, int[] listOfValues) It creates a no-good constraint.
NoGood(List<? extends IntVar> listOfVars, List<Integer> listOfValues) It creates a no-good constraint.

Method Summary

Modifier and Type	Method and Description
void	consistency(Store store) It is a (most probably incomplete) consistency function which removes the values from variables domains.
int	getDefaultConsistencyPruningEvent()
void	impose(Store store) It imposes the constraint in a given store.
void	removeConstraint() This function does nothing as constraints can not be removed for a given level.
String	toString() It produces a string representation of a constraint state.

Methods inherited from class org.jacop.constraints.Constraint

afc, arguments, cleanAfterFailure, decompose, getConsistencyPruningEvent, getGuideConstraint, getGuideValue, getGuideVariable, grounded, grounded, id, impose, imposeDecomposition, increaseWeight, intArrayToString, long2int, numberArgs, queueVariable, requiresMonotonicity, setConsistencyPruningEvent, setConstraintScope, setScope, setScope, setScope, setScope, setScope, setWatchedVariableGrounded, supplyGuideFeedback, updateAFC, watchedVariableGrounded

Methods inherited from class org.jacop.constraints.DecomposedConstraint

auxiliaryVariables, checkInput, checkInput, checkInputForDuplication, checkInputForDuplicationSkipSingletons, checkInputForNullness, checkInputForNullness, checkInputForNullness, derivative, getDubletonsSkipSingletons, imposeDecomposition

Methods inherited from class java.lang.Object

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

Field Detail

listOfVars

protected IntVar[] listOfVars

It specifies a list of variables in no-good constraint.

listOfValues

protected int[] listOfValues

It specifies a list of values in no-good constraint.

Constructor Detail

NoGood

public NoGood(IntVar[] listOfVars,
              int[] listOfValues)

It creates a no-good constraint.

Parameters:

listOfVars - the scope of the constraint.

listOfValues - no-good values which all-together assignment to variables within constraint scope is a no-good.

NoGood

public NoGood(List<? extends IntVar> listOfVars,
              List<Integer> listOfValues)

It creates a no-good constraint.

Parameters:

listOfVars - the scope of the constraint.

listOfValues - no-good values which all-together assignment to variables within constraint scope is a no-good.

Method Detail

consistency

public void consistency(Store store)

Description copied from class: Constraint

It is a (most probably incomplete) consistency function which removes the values from variables domains. Only values which do not have any support in a solution space are removed.

Specified by:

consistency in class Constraint

Parameters:

store - constraint store within which the constraint consistency is being checked.

getDefaultConsistencyPruningEvent

public int getDefaultConsistencyPruningEvent()

Specified by:

getDefaultConsistencyPruningEvent in class Constraint

impose

public void impose(Store store)

Description copied from class: Constraint

It imposes the constraint in a given store.

Overrides:

impose in class Constraint

Parameters:

store - the constraint store to which the constraint is imposed to.

removeConstraint

public void removeConstraint()

This function does nothing as constraints can not be removed for a given level. In addition, watched literals mechanism makes sure that constraint is not put in the queue when it can not propagate.

Overrides:

removeConstraint in class Constraint

toString

public String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Overrides:

toString in class Constraint