Class ExtensionalSupportVA

  • All Implemented Interfaces:
    Stateful, UsesQueueVariable

    public class ExtensionalSupportVA
    extends Constraint
    implements UsesQueueVariable, Stateful
    Extensional constraint assures that one of the tuples is enforced in the relation.

    This implementation tries to balance the usage of memory versus time efficiency.

    Version:
    4.8
    • Field Detail

      • idNumber

        static java.util.concurrent.atomic.AtomicInteger idNumber
        It specifies the id of the constraint.
      • firstConsistencyCheck

        boolean firstConsistencyCheck
      • levelOfFirstConsistencyCheck

        int levelOfFirstConsistencyCheck
      • tuples

        int[][][][] tuples
        It represents tuples which are supports for each of the variables. The first index denotes variable index. The second index denotes value index. The third index denotes tuple.
      • tuplesFromConstructor

        private int[][] tuplesFromConstructor
      • values

        int[][] values
        It represents values which are supported for a variable.
      • variableQueue

        java.util.LinkedHashSet<IntVar> variableQueue
      • list

        public IntVar[] list
        It stores variables within this extensional constraint, order does matter.
    • Constructor Detail

      • ExtensionalSupportVA

        public ExtensionalSupportVA​(IntVar[] list)
        Partial constructor which stores variables involved in a constraint but does not get information about tuples yet. The tuples must set separately.
        Parameters:
        list - list of variables for the constraint
      • ExtensionalSupportVA

        public ExtensionalSupportVA​(java.util.List<? extends IntVar> variables,
                                    int[][] tuples)
        The constructor does not create local copy of tuples array. Any changes to this array will reflect on constraint behavior. Most probably incorrect as other data structures will not change accordingly.
        Parameters:
        variables - the constraint scope.
        tuples - the tuples which are supports for the constraint.
      • ExtensionalSupportVA

        public ExtensionalSupportVA​(IntVar[] list,
                                    int[][] tuples)
        Constructor stores reference to tuples until imposition, any changes to tuples parameter will be reflected in the constraint behavior. Changes to tuples should not performed under any circumstances. The tuples array is not copied to save memory and time.
        Parameters:
        list - the constraint scope.
        tuples - the tuples which are supports for the constraint.
    • Method Detail

      • removeLevel

        public void removeLevel​(int level)
        It puts back tuples which have lost their support status at the level which is being removed.
        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.
      • findPosition

        protected int findPosition​(int value,
                                   int[] values)
      • 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.
      • smaller

        boolean smaller​(int[] tuple1,
                        int[] tuple2)
      • equal

        boolean equal​(int[] tuple1,
                      int[] tuple2)
      • 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
      • seekSupportVA

        public int[] seekSupportVA​(int varPosition,
                                   int value)
        It seeks support for a given variable-value pair.
        Parameters:
        varPosition - position of the variable for which the support is seek.
        value - value for which the support is seek.
        Returns:
        support tuple.
      • setFirstValid

        public int[] setFirstValid​(int varPosition,
                                   int value)
        It computes the first valid tuple for a given variable-value pair.
        Parameters:
        varPosition - position of the variable.
        value - value for which the fist valid tuple is seek.
        Returns:
        first valid tuple.
      • findFirstAllowed

        public int[] findFirstAllowed​(int varPosition,
                                      int value,
                                      int[] t)
        It finds the first allowed tuple from the given tuple.
        Parameters:
        varPosition - position of the variable.
        value - value for which first allowed tuple is seek.
        t - tuple from which the search commences.
        Returns:
        first allowed tuple for a given variable-value pair.
      • seekInvalidPosition

        public int seekInvalidPosition​(int[] t)
        It gives the position of the variable for which current domain of this variable does not hold the used value. It is variable because of which allowed tuple does not become a support tuple.
        Parameters:
        t - tuple being checked.
        Returns:
        -1 if tuple is both valid and allowed (support), otherwise the position.