JaCoP.constraints
Class Alldistinct

java.lang.Object
  JaCoP.constraints.DecomposedConstraint
      JaCoP.constraints.Constraint
          JaCoP.constraints.Alldistinct

public class Alldistinct
extends Constraint

Alldistinct constraint assures that all FDVs have different values. This implementation is based on Regin paper. It uses slightly modified Hopcroft-Karp algorithm to compute maximum matching. The value graph is analysed and Tarjan algorithm for finding strongly connected components is used. Maximum matching and Value Graph is stored as TimeStamp Mutable variables to minimize recomputation. Value graph is expensive in terms of memory usage. Use this constraint with care. One variable with domain 0..1000000 will make it use few MB already and kill the efficiency.

Version:

3.1

Author:

Radoslaw Szymanek and Krzysztof Kuchcinski

Field Summary

int	consistencyChecks It counts the number of executions of the consistency function.
int	fullConsistencyPassesWithNarrowingEvent It computes how many times did consistency execution has been re-executed due to narrowing event at the end of the consistency function.
IntVar[]	list It specifies all variables which have to have different values.
static java.lang.String[]	xmlAttributes It specifies the arguments required to be saved by an XML format as well as the constructor being called to recreate an object from an XML format.

Fields inherited from class JaCoP.constraints.Constraint

atomicExecution, consistencyPruningEvents, earlyTerminationOK, id, increaseWeight, numberArgs, numberId

Fields inherited from class JaCoP.constraints.DecomposedConstraint

queueIndex

Constructor Summary

Alldistinct(java.util.ArrayList<? extends IntVar> list)
It constructs an alldistinct constraint.

Alldistinct(IntVar[] list)
It constructs an alldistinct constraint.

Method Summary

java.util.ArrayList<Var>	arguments() It returns the variables in a scope of the constraint.
void	consistency(Store store) It is a (most probably incomplete) consistency function which removes the values from variables domains.
int	getConsistencyPruningEvent(Var var) It retrieves the pruning event which causes reevaluation of the constraint.
Constraint	getGuideConstraint() It specifies a constraint which if imposed by search will enhance propagation of this constraint.
int	getGuideValue() This function provides a value which if assigned to a variable returned by getGuideVariable() will enhance propagation of this constraint.
Var	getGuideVariable() This function provides a variable which assigned a value returned by will enhance propagation of this constraint.
java.lang.String	id() It gives the id string of a constraint.
void	impose(Store store) It imposes the constraint in a given store.
void	increaseWeight() It increases the weight of the variables in the constraint scope.
void	queueVariable(int level, Var var) This is a function called to indicate which variable in a scope of constraint has changed.
void	removeConstraint() It removes the constraint by removing this constraint from all variables.
void	removeLevel(int level) This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid.
boolean	satisfied() It checks if the constraint is satisfied.
java.lang.String	toString() It produces a string representation of a constraint state.

Methods inherited from class JaCoP.constraints.Constraint

cleanAfterFailure, decompose, impose, imposeDecomposition, numberArgs, removeLevelLate, requiresMonotonicity, setConsistencyPruningEvent, supplyGuideFeedback

Methods inherited from class JaCoP.constraints.DecomposedConstraint

auxiliaryVariables, imposeDecomposition

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

consistencyChecks

public int consistencyChecks

It counts the number of executions of the consistency function.

fullConsistencyPassesWithNarrowingEvent

public int fullConsistencyPassesWithNarrowingEvent

It computes how many times did consistency execution has been re-executed due to narrowing event at the end of the consistency function.

list

public IntVar[] list

It specifies all variables which have to have different values.

xmlAttributes

public static java.lang.String[] xmlAttributes

It specifies the arguments required to be saved by an XML format as well as the constructor being called to recreate an object from an XML format.

Constructor Detail

Alldistinct

public Alldistinct(IntVar[] list)

It constructs an alldistinct constraint.

Parameters:

list - an array of variables.

Alldistinct

public Alldistinct(java.util.ArrayList<? extends IntVar> list)

It constructs an alldistinct constraint.

Parameters:

list - arraylist of variables.

Method Detail

arguments

public java.util.ArrayList<Var> arguments()

Description copied from class: Constraint

It returns the variables in a scope of the constraint.

Specified by:

arguments in class Constraint

Returns:

variables in a scope of the constraint.

removeLevel

public void removeLevel(int level)

Description copied from class: Constraint

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.

Overrides:

removeLevel in class Constraint

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.

getConsistencyPruningEvent

public int getConsistencyPruningEvent(Var var)

Description copied from class: Constraint

It retrieves the pruning event which causes reevaluation of the constraint.

Specified by:

getConsistencyPruningEvent in class Constraint

Parameters:

var - variable for which pruning event is retrieved

Returns:

it returns the int code of the pruning event (GROUND, BOUND, ANY, NONE)

id

public java.lang.String id()

Description copied from class: Constraint

It gives the id string of a constraint.

Specified by:

id in class Constraint

Returns:

string id of the constraint.

impose

public void impose(Store store)

Description copied from class: Constraint

It imposes the constraint in a given store.

Specified by:

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.

removeConstraint

public void removeConstraint()

Description copied from class: Constraint

It removes the constraint by removing this constraint from all variables.

Specified by:

removeConstraint in class Constraint

satisfied

public boolean satisfied()

Description copied from class: Constraint

It checks if the constraint is satisfied. If this function is incorrectly implemented a constraint may not be satisfied in a solution.

Specified by:

satisfied in class Constraint

Returns:

true if the constraint is for certain satisfied, false otherwise.

toString

public java.lang.String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Specified by:

toString in class Constraint

getGuideConstraint

public Constraint getGuideConstraint()

Description copied from class: Constraint

It specifies a constraint which if imposed by search will enhance propagation of this constraint.

Overrides:

getGuideConstraint in class Constraint

Returns:

Constraint enhancing propagation of this constraint.

getGuideValue

public int getGuideValue()

Description copied from class: Constraint

This function provides a value which if assigned to a variable returned by getGuideVariable() will enhance propagation of this constraint.

Overrides:

getGuideValue in class Constraint

Returns:

Value which is a base of enhancing constraint.

getGuideVariable

public Var getGuideVariable()

Description copied from class: Constraint

This function provides a variable which assigned a value returned by will enhance propagation of this constraint.

Overrides:

getGuideVariable in class Constraint

Returns:

Variable which is a base of enhancing constraint.

increaseWeight

public void increaseWeight()

Description copied from class: Constraint

It increases the weight of the variables in the constraint scope.

Specified by:

increaseWeight in class Constraint