JaCoP.search
Class Shaving<T extends IntVar>

java.lang.Object
  JaCoP.search.Shaving<T>

All Implemented Interfaces:

ConsistencyListener, ExitChildListener<T>

public class Shaving<T extends IntVar>
extends java.lang.Object
implements ExitChildListener<T>, ConsistencyListener

Defines functionality of shaving. Plugin in this object to search to change your depth first search to a search with shaving capabilities. Shaving Each search level stores the variable value pairs which were shaved at a given level. Shaving speculation. The right child is using all the shavable pairs from the subtree rooted at the sibling of the current search node. If shaving fails then it is recorded in non shavable. Not-shavable speculation Every time a variable value pair is being schedule for shavability check then it is checked if that pair was not already checked for shavability before with a negative results. If so, then check is not performed but also entry in not-shavable is removed. If variable value pair proofs to be not shavable then this variable value pair is recorded into Not-shavable speculation. Quick shave - upon exiting any subtree the variable value pair which was choosen at the root of that subtree is recorded as shavable variable value pair.

Version:

3.1

Author:

Radoslaw Szymanek and Krzysztof Kuchcinski

Field Summary

int	failures It stores number of failed shaving attempts.
boolean	onlyFailedConstraint It specifies if only the last failed constraint is allowed to suggest shaving values.
boolean	onlyIntVarsOfFailedConstraint It specifies if only variables in the scope of the last failed constraint are allowed to be used in shaving attempts.
boolean	quickShave It specifies if the quickShave approach should be also used.
int	successes It stores number of successful shaving attempts.
java.util.HashSet<IntVar>	varsOfFailedConstraint It stores the variables of the last failed constraints.

Constructor Summary

Shaving()

Method Summary

void	addShavingConstraint(Constraint c) It adds shaving constraint to the list of constraints guiding shaving.
boolean	executeAfterConsistency(boolean consistent) It is executed right after consistency of the current search node.
boolean	leftChild(IntVar var, int value, boolean status) It is executed after exiting the left child.
boolean	leftChild(PrimitiveConstraint choice, boolean status) It is executed after exiting the left child.
void	rightChild(IntVar var, int value, boolean status) It is executed after exiting the right child.
void	rightChild(PrimitiveConstraint choice, boolean status) It is executed after exiting the right child.
void	setChildrenListeners(ConsistencyListener child) Setting one child listener.
void	setChildrenListeners(ConsistencyListener[] children) Each of the child listeners will be called and the return code from them will be combined (taken into account) by a parent).
void	setChildrenListeners(ExitChildListener child) It adds one child listener.
void	setChildrenListeners(ExitChildListener[] children) It sets the children listeners for the current listener.
void	setStore(Store store) It specifies the constraint store in which context the shaving will take place.

Methods inherited from class java.lang.Object

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

Field Detail

onlyFailedConstraint

public boolean onlyFailedConstraint

It specifies if only the last failed constraint is allowed to suggest shaving values.

onlyIntVarsOfFailedConstraint

public boolean onlyIntVarsOfFailedConstraint

It specifies if only variables in the scope of the last failed constraint are allowed to be used in shaving attempts.

varsOfFailedConstraint

public java.util.HashSet<IntVar> varsOfFailedConstraint

It stores the variables of the last failed constraints.

quickShave

public boolean quickShave

It specifies if the quickShave approach should be also used. Quickshave uses variable-value pairs which lead to wrong decisions as shaving values higher in the search tree (until the first time shaving attempt for this value fails).

successes

public int successes

It stores number of successful shaving attempts.

failures

public int failures

It stores number of failed shaving attempts.

Constructor Detail

Shaving

public Shaving()

Method Detail

leftChild

public boolean leftChild(IntVar var,
                         int value,
                         boolean status)

Description copied from interface: ExitChildListener

It is executed after exiting the left child.

Specified by:

leftChild in interface ExitChildListener<T extends IntVar>

Parameters:

var - variable used in the choice point.

value - value used in the choice point.

status - true if the solution was found in the child subtree, false otherwise.

Returns:

true if the search should continue undisturbed, false if it should exit the current node with false

leftChild

public boolean leftChild(PrimitiveConstraint choice,
                         boolean status)

Description copied from interface: ExitChildListener

It is executed after exiting the left child.

Specified by:

leftChild in interface ExitChildListener<T extends IntVar>

Parameters:

choice - primitive constraint used as the base of the choice point.

status - true if the solution was found in the child subtree, false otherwise.

Returns:

true if the search should continue undisturbed to the right node, false if it should exit the current node with false

rightChild

public void rightChild(IntVar var,
                       int value,
                       boolean status)

Description copied from interface: ExitChildListener

It is executed after exiting the right child.

Specified by:

rightChild in interface ExitChildListener<T extends IntVar>

Parameters:

var - variable used in the choice point.

value - value used in the choice point.

status - true if the solution was found in the child subtree, false otherwise. exit the current node with false

rightChild

public void rightChild(PrimitiveConstraint choice,
                       boolean status)

Description copied from interface: ExitChildListener

It is executed after exiting the right child.

Specified by:

rightChild in interface ExitChildListener<T extends IntVar>

Parameters:

choice - primitive constraint used as the base of the choice point.

status - true if the solution was found in the child subtree, false otherwise. exit the current node with false

setChildrenListeners

public void setChildrenListeners(ConsistencyListener[] children)

Description copied from interface: ConsistencyListener

Each of the child listeners will be called and the return code from them will be combined (taken into account) by a parent).

Specified by:

setChildrenListeners in interface ConsistencyListener

Parameters:

children - the children listeners attached to this listener.

setChildrenListeners

public void setChildrenListeners(ExitChildListener[] children)

Description copied from interface: ExitChildListener

It sets the children listeners for the current listener.

Specified by:

setChildrenListeners in interface ExitChildListener<T extends IntVar>

Parameters:

children - array containing children listeners.

setChildrenListeners

public void setChildrenListeners(ConsistencyListener child)

Description copied from interface: ConsistencyListener

Setting one child listener.

Specified by:

setChildrenListeners in interface ConsistencyListener

Parameters:

child - the only child listener added to this consistency listener.

setChildrenListeners

public void setChildrenListeners(ExitChildListener child)

Description copied from interface: ExitChildListener

It adds one child listener.

Specified by:

setChildrenListeners in interface ExitChildListener<T extends IntVar>

Parameters:

child - added child listener.

executeAfterConsistency

public boolean executeAfterConsistency(boolean consistent)

Description copied from interface: ConsistencyListener

It is executed right after consistency of the current search node. Returning true when the parameter was false is not advised as things like invalid solutions can be found.

Specified by:

executeAfterConsistency in interface ConsistencyListener

Parameters:

consistent - specifies if the consistency call returned true or false.

Returns:

true if the search should continue, false if the search should act as the consistency returned false.

addShavingConstraint

public void addShavingConstraint(Constraint c)

It adds shaving constraint to the list of constraints guiding shaving.

Parameters:

c - constraint which is added to the list of guiding constraints.

setStore

public void setStore(Store store)

It specifies the constraint store in which context the shaving will take place.

Parameters:

store - constraint store.