org.jacop.search

Class RandomSelect<T extends Var>

java.lang.Object

org.jacop.search.RandomSelect<T>

All Implemented Interfaces:

SelectChoicePoint<T>

public class RandomSelect<T extends Var>
extends Object
implements SelectChoicePoint<T>

It is simple and customizable selector of decisions (constraints) which will be enforced by search.

Version:

4.2

Author:

Krzysztof Kuchcinski and Radoslaw Szymanek

Field Summary

Fields

Modifier and Type	Field and Description
IdentityHashMap<T,Integer>	position It stores the original positions of variables to be used for input order tie-breaking.
T[]	searchVariables

Constructor Summary

Constructors

Constructor and Description
RandomSelect(T[] variables, Indomain<T> indomain) The constructor to create a simple choice select mechanism.

Method Summary

Modifier and Type	Method and Description
PrimitiveConstraint	getChoiceConstraint(int index) It always returns null as choice point is obtained by getChoiceVariable and getChoiceValue.
int	getChoiceValue() It returns a value which is the base of the next choice point.
T	getChoiceVariable(int index) It returns the variable which is the base on the next choice point.
int	getIndex() It returns the current index.
IdentityHashMap<T,Integer>	getVariablesMapping() It returns the variables for which assignment in the solution is given.
T	placeSearchVariable(int searchPosition, int variablePosition) It gets as input the index of the variable which is chosen by search to be instantiated at this stage.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

searchVariables

public T extends Var[] searchVariables

position

public IdentityHashMap<T extends Var,Integer> position

It stores the original positions of variables to be used for input order tie-breaking.

Constructor Detail

RandomSelect

public RandomSelect(T[] variables,
                    Indomain<T> indomain)

The constructor to create a simple choice select mechanism.

Parameters:

variables - variables upon which the choice points are created.

indomain - the value heuristic to choose a value for a given variable.

Method Detail

getChoiceVariable

public T getChoiceVariable(int index)

It returns the variable which is the base on the next choice point. Only if choice is of an X = C type. This function returns null if all variables have a value assigned or a choice point based on other type of constraint is being selected. The parameter index is the last value which have been return by this SelectChoicePoint object which has not been backtracked upon yet.

Specified by:

getChoiceVariable in interface SelectChoicePoint<T extends Var>

Parameters:

index - the position of the last variable in selection choice point heuristic.

Returns:

variable based on which the choice needs to be created.

getChoiceValue

public int getChoiceValue()

It returns a value which is the base of the next choice point. Only if choice is of an X = C type.

Specified by:

getChoiceValue in interface SelectChoicePoint<T extends Var>

Returns:

value used in the choice point (value).

getChoiceConstraint

public PrimitiveConstraint getChoiceConstraint(int index)

It always returns null as choice point is obtained by getChoiceVariable and getChoiceValue.

Specified by:

getChoiceConstraint in interface SelectChoicePoint<T extends Var>

Parameters:

index - the position of the last variable returned by selection choice point heuristic.

Returns:

primitive constraint which is a base of a choice point.

getVariablesMapping

public IdentityHashMap<T,Integer> getVariablesMapping()

It returns the variables for which assignment in the solution is given.

Specified by:

getVariablesMapping in interface SelectChoicePoint<T extends Var>

Returns:

mapping of variables to the positions in the variables array.

getIndex

public int getIndex()

It returns the current index. Supplying this value in the next invocation of select will make search for next variable faster without comprimising efficiency.

Specified by:

getIndex in interface SelectChoicePoint<T extends Var>

Returns:

internal position of the last variable chosen to be the base of the choice point.

placeSearchVariable

public T placeSearchVariable(int searchPosition,
                             int variablePosition)

It gets as input the index of the variable which is chosen by search to be instantiated at this stage. The variable is positioned at search position.

Parameters:

searchPosition - position at which search store currently choosen variable.

variablePosition - current position of the variable choosen by search.

Returns:

variable choosen to be a base of the choice point.

toString

public String toString()

Overrides:

toString in class Object