Package org.jacop.constraints

Class LexOrder

java.lang.Object
org.jacop.constraints.DecomposedConstraint<Constraint>
org.jacop.constraints.Constraint
org.jacop.constraints.LexOrder
All Implemented Interfaces:
RemoveLevelLate, SatisfiedPresent, UsesQueueVariable
public class LexOrder extends Constraint implements UsesQueueVariable, SatisfiedPresent, RemoveLevelLate
It constructs a LexOrder (lexicographical order) constraint.

The algorithm is based on paper

"Propagation algorithms for lexicographic ordering constraints" by Alan M. Frisch, Brahim Hnich, Zeynep Kiziltan, Ian Miguel, and Toby Walsh , Artificial Intelligence 170 (2006) 803-834.

Version:
4.8

  • Field Details

    • idNumber

      static AtomicInteger idNumber

    • debug

      static final boolean debug
      See Also:

    • x

      public IntVar[] x
      Two vectors that have to be lexicographically ordered.

    • y

      public IntVar[] y

    • lexLT

      public boolean lexLT
      Is Lex enforcing "<" relationship?

    • originalLexLT

      public boolean originalLexLT
      Is Lex enforcing "<" relationship?

    • n

      int n
      size of the longest vector

    • satisfied

      boolean satisfied

    • store

      private Store store

    • satisfiedWhenDefined

      private boolean satisfiedWhenDefined

    • alpha

      private int alpha

    • beta

      private int beta

    • indexQueue

      SimpleHashSet<Integer> indexQueue

    • varXToIndex

      Map<IntVar,int[]> varXToIndex

    • varYToIndex

      Map<IntVar,int[]> varYToIndex

  • Constructor Details

    • LexOrder

      public LexOrder(IntVar[] x, IntVar[] y)
      It creates a lexicographical order for vectors x and y,

      vectors x and y does not need to be of the same size. boolean lt defines if we require strict order, Lex_{<} (lt = true) or Lex_{=<} (lt = false)

      Parameters:
      x - first vector constrained by LexOrder constraint.
      y - second vector constrained by LexOrder constraint.

    • LexOrder

      public LexOrder(IntVar[] x, IntVar[] y, boolean lt)

  • Method Details

    • 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.

    • getDefaultConsistencyPruningEvent

      public int getDefaultConsistencyPruningEvent()
      Specified by:
      getDefaultConsistencyPruningEvent in class Constraint

    • 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.

    • 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.

    • 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.

    • removeLevelLate

      public void removeLevelLate(int level)
      Description copied from interface: RemoveLevelLate
      This function is called in case of the backtrack. It is called after all timestamps, variables, mutablevariables have reverted to their values *after* removing the level.
      Specified by:
      removeLevelLate in interface RemoveLevelLate
      Parameters:
      level - the level which is being removed.

    • toString

      public String toString()
      Description copied from class: Constraint
      It produces a string representation of a constraint state.
      Overrides:
      toString in class Constraint

    • establishGACInit

      protected void establishGACInit()

    • reestablishGAC

      void reestablishGAC(int i)

    • updateAlpha

      public void updateAlpha()

    • updateBeta

      public void updateBeta(int i)

    • eqSingletons

      private boolean eqSingletons(IntVar x, IntVar y)

    • forceLT

      private void forceLT(int i)

    • forceLE

      private void forceLE(int i)