org.jacop.constraints

Class Among

java.lang.Object

org.jacop.constraints.DecomposedConstraint<Constraint>

org.jacop.constraints.Constraint

org.jacop.constraints.Among

All Implemented Interfaces:

SatisfiedPresent, Stateful, UsesQueueVariable

public class Among
extends Constraint
implements UsesQueueVariable, Stateful, SatisfiedPresent

Among constraint in its simplest form. It establishes the following relation. The given number N of X`s take values from the supplied set of values Kset.

This constraint implements a simple and polynomial algorithm to establish GAC as presented in different research papers. There are number of improvements (iterative execution, optimization of computational load upon backtracking) to improve the constraint further.

Version:

4.9

Author:

Polina Makeeva and Radoslaw Szymanek

Field Summary

Fields

Modifier and Type	Field and Description
IntervalDomain	kSet It specifies a set of values which if assigned to a variable from a list makes variable counted.
IntVar[]	list It specifies the list of variables whose values are checked.
IntVar	n It is a idNumber variable.

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
Among(IntVar[] list, IntervalDomain kSet, IntVar n) It constructs an Among constraint.
Among(List<IntVar> list, IntervalDomain kSet, IntVar n) It constructs an Among 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	queueVariable(int level, Var var) This is a function called to indicate which variable in a scope of constraint has changed.
void	removeLevel(int level) This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid.
boolean	satisfied() It checks if the constraint is satisfied.
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, removeConstraint, 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

Methods inherited from interface org.jacop.api.Stateful

isStateful

Field Detail

list

public final IntVar[] list

It specifies the list of variables whose values are checked.

kSet

public final IntervalDomain kSet

It specifies a set of values which if assigned to a variable from a list makes variable counted.

n

public final IntVar n

It is a idNumber variable.

Constructor Detail

Among

public Among(IntVar[] list,
             IntervalDomain kSet,
             IntVar n)

It constructs an Among constraint.

Parameters:

list - variables which are compared to Kset

kSet - set of integer values against which we check if variables are equal to.

n - number of possible variables equal to a value from Kset.

Among

public Among(List<IntVar> list,
             IntervalDomain kSet,
             IntVar n)

It constructs an Among constraint.

Parameters:

list - variables which are compared to Kset

kSet - set of integer values against which we check if variables are equal to.

n - number of possible variables equal to a value from Kset.

Method Detail

removeLevel

public void removeLevel(int level)

Description copied from interface: Stateful

This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid. This function is called *before* all timestamps, variables, mutablevariables have reverted to their previous value.

Specified by:

removeLevel in interface Stateful

Parameters:

level - the level which is being removed.

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.

queueVariable

public void queueVariable(int level,
                          Var var)

Description copied from class: Constraint

This is a function called to indicate which variable in a scope of constraint has changed. It also indicates a store level at which the change has occurred.

Overrides:

queueVariable in class Constraint

Parameters:

level - the level of the store at which the change has occurred.

var - variable which has changed.

satisfied

public boolean satisfied()

Description copied from interface: SatisfiedPresent

It checks if the constraint is satisfied. It can return false even if constraint is satisfied but not all variables in its scope are grounded. It needs to return true if all variables in its scope are grounded and constraint is satisfied.

Implementations of this interface for constraints that are not PrimitiveConstraint may require constraint imposition and consistency check as a requirement to work correctly.

Specified by:

satisfied in interface SatisfiedPresent

Returns:

true if constraint is possible to verify that it is satisfied.

toString

public String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Overrides:

toString in class Constraint