Package org.jacop.constraints

Class AmongVar

java.lang.Object
org.jacop.constraints.DecomposedConstraint<Constraint>
org.jacop.constraints.Constraint
org.jacop.constraints.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:
4.10

  • Field Details

    • debugAll

      public static final boolean debugAll
      It turns out printing debugging information.
      See Also:

    • idNumber

      static final AtomicInteger idNumber
      Number of Among constraints created.

    • xIndex

      private Map<IntVar,Integer> xIndex

    • yIndex

      private Map<IntVar,Integer> yIndex

    • lbS

      private MutableVar lbS

    • futureLbS

      private MutableVar futureLbS

    • variableQueueY

      private LinkedHashSet<Integer> variableQueueY

    • lb0TS

      private TimeStamp<Integer> lb0TS

    • ub0TS

      private TimeStamp<Integer> ub0TS

    • yGrounded

      private TimeStamp<Integer> yGrounded

    • xGrounded

      private TimeStamp<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 Details

    • 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(List<? extends IntVar> listOfX, List<? extends 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 Details

    • 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.

    • 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