Class 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:
    4.8
    • Field Detail

      • idNumber

        static final java.util.concurrent.atomic.AtomicInteger idNumber
      • 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.
      • lowerBorder

        private TimeStamp<java.lang.Integer> lowerBorder
      • upperBorder

        private TimeStamp<java.lang.Integer> upperBorder
      • variableQueue

        java.util.LinkedHashSet<IntVar> variableQueue
      • position

        private java.util.Map<IntVar,​java.lang.Integer> position
    • 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​(java.util.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.
      • 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