Module org.chocosolver.solver
Package org.chocosolver.solver.constraints

Class Constraint

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  Constraint.Status
      Status of this constraint wrt the model

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected BoolVar boolReif
      BoolVar that reifies this constraint, unique.
      protected Propagator<?>[] propagators
      Propagators of the constraint (they will filter domains and eventually check solutions)

    • Constructor Summary

      Constructors 
      Constructor Description
      Constraint​(java.lang.String name, Propagator<?>... propagators)
      Make a new constraint defined as a set of given propagators

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void checkNewStatus​(Constraint.Status aStatus)
      Check if the new status is not in conflict with the current one
      PropagatorPriority computeMaxPriority()  
      void declareAs​(Constraint.Status aStatus, int idx)
      For internal usage only, declare the status of this constraint in the model and, if need be, its position in the constraint list.
      int getCidxInModel()  
      java.lang.String getName()  
      Constraint getOpposite()
      Get the opposite constraint of this constraint.
      Propagator<?> getPropagator​(int i)  
      Propagator[] getPropagators()
      Return an array which contains the propagators declared in this.
      Constraint.Status getStatus()  
      void ignore()
      When a constraint has been declared but neither posted or reified, a call to ignore() ensures this constraint will be ignored when declared constraints are checked.
      void impliedBy​(BoolVar r)
      Encapsulate this constraint in an implication relationship:
      void implies​(BoolVar r)
      Encapsulate this constraint in an implication relationship:
      boolean isEnabled()
      A constraint, when disabled, is prevented from execute propagation during search and from participate in the solution feasibility check.
      boolean isReified()  
      ESat isSatisfied()
      Test if this Constraint object is satisfied, regarding its Propagators and its Variable current domains.
      protected Constraint makeOpposite()
      Make the opposite constraint of this.
      static Constraint merge​(java.lang.String name, Constraint... toMerges)
      Creates a new constraint with all propagators of toMerge0, toMerge1 and toMerges.
      void post()
      Posts the constraint to its model so that the constraint must be satisfied.
      BoolVar reify()
      Get/make the boolean variable indicating whether the constraint is satisfied or not This should not be posted.
      void reifyWith​(BoolVar bool)
      Reifies the constraint with a boolean variable If the reified boolean variable already exists, an additional (equality) constraint is automatically posted.
      void setEnabled​(boolean enabled)
      Disable a constraint from being propagated during search and from feasibility check (Solver.isSatisfied()).
      void setName​(java.lang.String newName)
      Changes the name of this constraint
      protected void setOpposite​(Constraint opp)  
      java.lang.String toString()  

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Field Detail

      • propagators

        protected final Propagator<?>[] propagators
        Propagators of the constraint (they will filter domains and eventually check solutions)

      • boolReif

        protected BoolVar boolReif
        BoolVar that reifies this constraint, unique.

    • Constructor Detail

      • Constraint

        public Constraint​(java.lang.String name,
                  Propagator<?>... propagators)
        Make a new constraint defined as a set of given propagators
        Parameters:
        name - name of the constraint
        propagators - set of propagators defining the constraint

    • Method Detail

      • getPropagators

        public Propagator[] getPropagators()
        Return an array which contains the propagators declared in this.
        Returns:
        an array of Propagator.

      • getPropagator

        public Propagator<?> getPropagator​(int i)

      • isSatisfied

        public ESat isSatisfied()
        Test if this Constraint object is satisfied, regarding its Propagators and its Variable current domains.

        This method is called on each solution as a checker when assertions are enabled (-ea in VM parameters) It is also called for constraint reification (to state whether or not a constraint is satisfied)

        The method calls entailment checks of this propagators

        Returns:
        ESat.FALSE if the constraint cannot be satisfied (from domain consideration), ESat.TRUE if whatever future decisions are, the constraint will be satisfied for sure (without propagating domain modifications) ESat.UNDIFINED otherwise (more decisions/filtering must be made before concluding about constraint satisfaction)

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • isReified

        public final boolean isReified()
        Returns:
        true iff this constraint has been reified

      • reifyWith

        public void reifyWith​(BoolVar bool)
        Reifies the constraint with a boolean variable If the reified boolean variable already exists, an additional (equality) constraint is automatically posted.
        Parameters:
        bool - the variable to reify with

      • reify

        public final BoolVar reify()
        Get/make the boolean variable indicating whether the constraint is satisfied or not This should not be posted.
        Returns:
        the boolean reifying the constraint

      • implies

        public final void implies​(BoolVar r)
        Encapsulate this constraint in an implication relationship:

        c ⇒ r

        where 'c' is this constraint and 'r' is a boolean variable.

        After a call to this method, this constraint 'c' can be posted, but a better option would be to set 'r' to true. 'c' can also be reified, but a better option would be to link the reifying boolean to 'r' directly.

        Parameters:
        r - a boolean variable

      • impliedBy

        public final void impliedBy​(BoolVar r)
        Encapsulate this constraint in an implication relationship:

        r ⇒ c

        where 'r' is a boolean variable and 'c' is this constraint.

        After a call to this method, this constraint 'c' can be posted, but then 'r' can take any value. 'c' can also be reified, but a better option would be to link the reifying boolean to 'r' directly.

        Parameters:
        r - a boolean variable

      • post

        public final void post()
        Posts the constraint to its model so that the constraint must be satisfied. This should not be reified.

      • ignore

        public final void ignore()
        When a constraint has been declared but neither posted or reified, a call to ignore() ensures this constraint will be ignored when declared constraints are checked.

      • declareAs

        public final void declareAs​(Constraint.Status aStatus,
                            int idx)
                     throws SolverException
        For internal usage only, declare the status of this constraint in the model and, if need be, its position in the constraint list.
        Parameters:
        aStatus - status of this constraint in the model
        idx - position of this constraint in the constraint list.
        Throws:
        SolverException - if the constraint a incoherent status is declared

      • checkNewStatus

        public final void checkNewStatus​(Constraint.Status aStatus)
                          throws SolverException
        Check if the new status is not in conflict with the current one
        Parameters:
        aStatus - new status of the constraint
        Throws:
        SolverException - if the constraint a incoherent status is declared

      • getCidxInModel

        public int getCidxInModel()
        Returns:
        the position of this constraint in the model

      • getOpposite

        public Constraint getOpposite()
        Get the opposite constraint of this constraint. At first call, it creates the opposite constraint, links them together (the opposite constraint of this opposite constraint is this constraint) and returns the opposite. Next calls will return the previously created opposite constraint. In other words, there can be only one opposite per instance of constraint. The default opposite constraint does not filter domains but fails if this constraint is satisfied.
        Returns:
        the opposite constraint of this

      • setOpposite

        protected void setOpposite​(Constraint opp)

      • makeOpposite

        protected Constraint makeOpposite()
        Make the opposite constraint of this. BEWARE: this method should never be called by the user but it can be overridden to provide better constraint negations

      • setName

        public void setName​(java.lang.String newName)
        Changes the name of this constraint
        Parameters:
        newName - the name of the constraint

      • getName

        public java.lang.String getName()
        Returns:
        the name of this constraint

      • computeMaxPriority

        public PropagatorPriority computeMaxPriority()
        Returns:
        the maximum priority of a propagator of this constraint

      • merge

        public static Constraint merge​(java.lang.String name,
                               Constraint... toMerges)
        Creates a new constraint with all propagators of toMerge0, toMerge1 and toMerges. Some constraints can be null but at least one propagator must be present.
        Parameters:
        name - name of the new constraint
        toMerges - a set of constraints to merge in this (null are accepted)
        Returns:
        a new constraint with all propagators of toMerge
        Throws:
        java.lang.IllegalArgumentException - when no propagator can be extracted

      • isEnabled

        public boolean isEnabled()
        A constraint, when disabled, is prevented from execute propagation during search and from participate in the solution feasibility check. It's handy to disable constraints for algorithms like (QuickXPlain, that execute massive search to find a minimum conflicting set of constraints, and to do this needs to alternate constraints execution by enabling and disabling it.
        Returns:
        enabled if the constraint is available to the solver

      • setEnabled

        public void setEnabled​(boolean enabled)
        Disable a constraint from being propagated during search and from feasibility check (Solver.isSatisfied()). A constraint shouldn't swap between enabled/disabled during solver execution (branching, filtering, etc...) because there is not control of the side effects it can cause (e.g.: when at node n, if a constraint becomes disabled, it doesn't undo filtering it has done at n-1). It means that, constraint should be disabled only before any interaction with the (Solver) class to prevent side-effects.
        Parameters:
        enabled - a boolean
        Throws:
        SolverException - when setEnabled is called during solving