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 Details

  • Constructor Details

    • 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(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 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    This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid.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.
    • 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