JaCoP.constraints
Class AmongVar

java.lang.Object
  JaCoP.constraints.DecomposedConstraint
      JaCoP.constraints.Constraint
          JaCoP.constraints.AmongVar

public class AmongVar
extends Constraint

Among constraint in its general form. It establishes the following relation. The given number N of X`s take values from the set specified by Y`s. This constraint significantly extends the algorithms presented in the literature as it does not use the decomposition into simpler constraints. Therefore as a result, it provides stronger pruning methods without noticeable increase in the execution time. The large part of the computation is reused across following executions of the consistency function. The strength of propagation algorithm is incomporable to BC.

Version:

3.1

Author:

Polina Makeeva and Radoslaw Szymanek

Field Summary

static int	counter Number of Among constraints created.
static boolean	debugAll It turns out printing debugging information.
IntVar[]	listOfX List of variables x which values are checked against values of variables y.
IntVar[]	listOfY It specifies what values we are counting in the list of x's.
IntVar	n It specifies the number of x variables equal to at least one value present in the list of y.
static java.lang.String[]	xmlAttributes It specifies the arguments required to be saved by an XML format as well as the constructor being called to recreate an object from an XML format.

Fields inherited from class JaCoP.constraints.Constraint

atomicExecution, consistencyPruningEvents, earlyTerminationOK, id, increaseWeight, numberArgs, numberId

Fields inherited from class JaCoP.constraints.DecomposedConstraint

queueIndex

Constructor Summary

AmongVar(java.util.ArrayList<IntVar> listOfX, java.util.ArrayList<IntVar> listOfY, IntVar n)
It constructs an AmongVar constraint.

AmongVar(IntVar[] listOfX, IntVar[] listOfY, IntVar n)
It constructs an AmongVar constraint.

Method Summary

java.util.ArrayList<Var>	arguments() It returns the variables in a scope of the constraint.
void	consistency(Store store) It is a (most probably incomplete) consistency function which removes the values from variables domains.
void	consistencyForX(Store store) Is called when all y are grounded and amongForSet is equivalent to simple version of Among.
void	consistencyForY(Store store) It is a function which makes Y consistent if all X's are grounded.
void	consistencyWhen_LB0_EQ_UB0(Store store) The number of x in lbsDom is equal to the number of X intersecting ubSDom.
int	getConsistencyPruningEvent(Var var) It retrieves the pruning event which causes reevaluation of the constraint.
java.lang.String	id() It gives the id string of a constraint.
void	impose(Store store) It imposes the constraint in a given store.
void	increaseWeight() It increases the weight of the variables in the constraint scope.
void	queueVariable(int level, Var var) This is a function called to indicate which variable in a scope of constraint has changed.
void	removeConstraint() It removes the constraint by removing this constraint from all variables.
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.
java.lang.String	toString() It produces a string representation of a constraint state.

Methods inherited from class JaCoP.constraints.Constraint

cleanAfterFailure, decompose, getGuideConstraint, getGuideValue, getGuideVariable, impose, imposeDecomposition, numberArgs, removeLevelLate, requiresMonotonicity, setConsistencyPruningEvent, supplyGuideFeedback

Methods inherited from class JaCoP.constraints.DecomposedConstraint

auxiliaryVariables, imposeDecomposition

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

debugAll

public static final boolean debugAll

It turns out printing debugging information.

See Also:

Constant Field Values

counter

public static int counter

Number of Among constraints created.

listOfX

public IntVar[] listOfX

List of variables x which values are checked against values of variables y. Each x is counted only once as equal to one of the elements of list y.

listOfY

public IntVar[] listOfY

It specifies what values we are counting in the list of x's.

n

public IntVar n

It specifies the number of x variables equal to at least one value present in the list of y.

xmlAttributes

public static java.lang.String[] xmlAttributes

It specifies the arguments required to be saved by an XML format as well as the constructor being called to recreate an object from an XML format.

Constructor Detail

AmongVar

public AmongVar(IntVar[] listOfX,
                IntVar[] listOfY,
                IntVar n)

It constructs an AmongVar constraint.

Parameters:

listOfX - the list of variables whose equality to other set of variables we count

listOfY - the list of variable to which equality is counted.

n - how many variables from list x are equal to at least one variable from list y.

AmongVar

public AmongVar(java.util.ArrayList<IntVar> listOfX,
                java.util.ArrayList<IntVar> listOfY,
                IntVar n)

It constructs an AmongVar constraint.

Parameters:

listOfX - the list of variables whose equality to other set of variables we count

listOfY - the list of variable to which equality is counted.

n - how many variables from list x are equal to at least one variable from list y.

Method Detail

arguments

public java.util.ArrayList<Var> arguments()

Description copied from class: Constraint

It returns the variables in a scope of the constraint.

Specified by:

arguments in class Constraint

Returns:

variables in a scope of the constraint.

removeLevel

public void removeLevel(int level)

Description copied from class: Constraint

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.

Overrides:

removeLevel in class Constraint

Parameters:

level - the level which is being removed.

consistencyForX

public void consistencyForX(Store store)

Is called when all y are grounded and amongForSet is equivalent to simple version of Among.

Parameters:

store - constraint store in which context that consistency function is being executed.

consistencyWhen_LB0_EQ_UB0

public void consistencyWhen_LB0_EQ_UB0(Store store)

The number of x in lbsDom is equal to the number of X intersecting ubSDom. 1) If there are not enough of y to cover future domain then fail 2)

Parameters:

store -

consistencyForY

public void consistencyForY(Store store)

It is a function which makes Y consistent if all X's are grounded.

Parameters:

store - a constraint store in which context all prunings are executed.

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.

getConsistencyPruningEvent

public int getConsistencyPruningEvent(Var var)

Description copied from class: Constraint

It retrieves the pruning event which causes reevaluation of the constraint.

Specified by:

getConsistencyPruningEvent in class Constraint

Parameters:

var - variable for which pruning event is retrieved

Returns:

it returns the int code of the pruning event (GROUND, BOUND, ANY, NONE)

id

public java.lang.String id()

Description copied from class: Constraint

It gives the id string of a constraint.

Specified by:

id in class Constraint

Returns:

string id of the constraint.

impose

public void impose(Store store)

Description copied from class: Constraint

It imposes the constraint in a given store.

Specified by:

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.

removeConstraint

public void removeConstraint()

Description copied from class: Constraint

It removes the constraint by removing this constraint from all variables.

Specified by:

removeConstraint in class Constraint

satisfied

public boolean satisfied()

Description copied from class: Constraint

It checks if the constraint is satisfied. If this function is incorrectly implemented a constraint may not be satisfied in a solution.

Specified by:

satisfied in class Constraint

Returns:

true if the constraint is for certain satisfied, false otherwise.

toString

public java.lang.String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Specified by:

toString in class Constraint

increaseWeight

public void increaseWeight()

Description copied from class: Constraint

It increases the weight of the variables in the constraint scope.

Specified by:

increaseWeight in class Constraint