Class AmongVar

  • All Implemented Interfaces:
    SatisfiedPresent, Stateful, UsesQueueVariable

    public class AmongVar
    extends Constraint
    implements UsesQueueVariable, Stateful, SatisfiedPresent
    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:
    4.7
    • Field Detail

      • debugAll

        public static final boolean debugAll
        It turns out printing debugging information.
        See Also:
        Constant Field Values
      • idNumber

        static final java.util.concurrent.atomic.AtomicInteger idNumber
        Number of Among constraints created.
      • xIndex

        private java.util.Map<IntVar,​java.lang.Integer> xIndex
      • yIndex

        private java.util.Map<IntVar,​java.lang.Integer> yIndex
      • variableQueueY

        private java.util.LinkedHashSet<java.lang.Integer> variableQueueY
      • lb0TS

        private TimeStamp<java.lang.Integer> lb0TS
      • ub0TS

        private TimeStamp<java.lang.Integer> ub0TS
      • yGrounded

        private TimeStamp<java.lang.Integer> yGrounded
      • xGrounded

        private TimeStamp<java.lang.Integer> xGrounded
      • 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.
    • 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.List<IntVar> listOfX,
                        java.util.List<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

      • 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.
      • 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 - a constraint store in which context all prunings are executed.
      • 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.
      • 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 java.lang.String toString()
        Description copied from class: Constraint
        It produces a string representation of a constraint state.
        Overrides:
        toString in class Constraint