Package ai.timefold.solver.core.impl.heuristic.move

Interface Move<Solution_>

Type Parameters:

Solution_ - the solution type, the class with the PlanningSolution annotation

All Superinterfaces:

Move<Solution_>

All Known Implementing Classes:

AbstractMove, AbstractSimplifiedMove, AbstractUndoMove, ChainedChangeMove, ChainedSwapMove, ChangeMove, CompositeMove, KOptListMove, KOptMove, ListAssignMove, ListChangeMove, ListRuinRecreateMove, ListSwapMove, ListUnassignMove, NoChangeMove, PillarChangeMove, PillarSwapMove, RuinRecreateMove, SubChainChangeMove, SubChainReversingChangeMove, SubChainReversingSwapMove, SubChainSwapMove, SubListChangeMove, SubListSwapMove, SubListUnassignMove, SwapMove, TailChainSwapMove, TwoOptListMove

public interface Move<Solution_>
extends Move<Solution_>

A Move represents a change of 1 or more PlanningVariables of 1 or more PlanningEntitys in the working PlanningSolution.

Usually the move holds a direct reference to each PlanningEntity of the PlanningSolution which it will change when doMoveOnly(ScoreDirector) is called. On that change it should also notify the ScoreDirector accordingly.

A Move should implement Object.equals(Object) and Object.hashCode() for MoveTabuAcceptor.

An implementation must extend AbstractMove to ensure backwards compatibility in future versions. It is highly recommended to override Move.getPlanningEntities() and Move.getPlanningValues(), otherwise the resulting move will throw an exception when used with Tabu search.

To ease interoperability with Neighborhoods API, this interface extends Move, giving the user an option to override certain methods which they should not. Specifically, the following methods must not be overridden by the user, as suitable default implementations are provided:

• execute(MutableSolutionView)
• rebase(Rebaser)
• describe()

The following methods should also not be overridden, on account of being deprecated:

• doMove(ScoreDirector)

This entire interface exists to provide interoperability with move selectors and will eventually be phased out in favor of the Neighborhoods API. It will be marked as deprecated for removal in a future release.

To avoid having to implement this interface and instead use the new Move API directly, you can use MoveAdapters.toLegacyMoveIterator(Iterator) in your move selectors.

See Also:

• AbstractMove

Method Summary

Modifier and Type	Method	Description
default String	describe()	Do not override this default implementation.
default Move<Solution_>	doMove(ScoreDirector<Solution_> scoreDirector)	Deprecated, for removal: This API element is subject to removal in a future version. Prefer doMoveOnly(ScoreDirector) instead, undo moves no longer have any effect.
default void	doMoveOnly(ScoreDirector<Solution_> scoreDirector)	Does the move (which indirectly affects the ScoreDirector.getWorkingSolution()).
default void	execute(MutableSolutionView<Solution_> solutionView)	Do not override this default implementation.
default String	getSimpleMoveTypeDescription()	Describes the move type for statistical purposes.
boolean	isMoveDoable(ScoreDirector<Solution_> scoreDirector)	Called before a move is evaluated to decide whether the move can be done and evaluated.
default Move<Solution_>	rebase(ScoreDirector<Solution_> destinationScoreDirector)	Rebases a move from an origin ScoreDirector to another destination ScoreDirector which is usually on another Thread or JVM.
default Move<Solution_>	rebase(Rebaser rebaser)	Do not override this default implementation.

Methods inherited from interface ai.timefold.solver.core.preview.api.move.Move

getPlanningEntities, getPlanningValues

Method Details

isMoveDoable

boolean isMoveDoable(ScoreDirector<Solution_> scoreDirector)

Called before a move is evaluated to decide whether the move can be done and evaluated. A Move is not doable if:

• Either doing it would change nothing in the PlanningSolution.
• Either it's simply not possible to do (for example due to built-in hard constraints).

It is recommended to keep this method implementation simple: do not use it in an attempt to satisfy normal hard and soft constraints.

Although you could also filter out non-doable moves in for example the MoveSelector or MoveListFactory, this is not needed as the Solver will do it for you.

Parameters:

scoreDirector - the ScoreDirector not yet modified by the move.

Returns:

true if the move achieves a change in the solution and the move is possible to do on the solution.

doMove

@Deprecated(forRemoval=true,
            since="1.16.0")
default Move<Solution_> doMove(ScoreDirector<Solution_> scoreDirector)

Deprecated, for removal: This API element is subject to removal in a future version.

Prefer doMoveOnly(ScoreDirector) instead, undo moves no longer have any effect.

Does the move (which indirectly affects the ScoreDirector.getWorkingSolution()). When the working solution is modified, the ScoreDirector must be correctly notified (through ScoreDirector.beforeVariableChanged(Object, String) and ScoreDirector.afterVariableChanged(Object, String)), otherwise later calculated Scores will be corrupted.

This method must end with calling ScoreDirector.triggerVariableListeners() to ensure all shadow variables are updated.

This method must return an undo move, so the move can be evaluated and then be undone without resulting into a permanent change in the solution.

Parameters:

scoreDirector - never null, the ScoreDirector that needs to get notified of the changes

Returns:

an undoMove which does the exact opposite of this move

doMoveOnly

default void doMoveOnly(ScoreDirector<Solution_> scoreDirector)

Does the move (which indirectly affects the ScoreDirector.getWorkingSolution()). When the working solution is modified, the ScoreDirector must be correctly notified (through ScoreDirector.beforeVariableChanged(Object, String) and ScoreDirector.afterVariableChanged(Object, String)), otherwise later calculated Scores will be corrupted, or the move may not be correctly undone.

This method must end with calling ScoreDirector.triggerVariableListeners() to ensure all shadow variables are updated.

Parameters:

scoreDirector - never null, the ScoreDirector that needs to get notified of the changes

execute

default void execute(MutableSolutionView<Solution_> solutionView)

Do not override this default implementation.

Specified by:

execute in interface Move<Solution_>

Parameters:

solutionView - Exposes all possible mutative operations on the variables. Remembers those mutative operations and can replay them in reverse order when the solver needs to undo the move. Do not store this parameter in a field.

rebase

default Move<Solution_> rebase(ScoreDirector<Solution_> destinationScoreDirector)

Rebases a move from an origin ScoreDirector to another destination ScoreDirector which is usually on another Thread or JVM. The new move returned by this method translates the entities and problem facts to the destination PlanningSolution of the destination ScoreDirector, That destination PlanningSolution is a deep planning clone (or an even deeper clone) of the origin PlanningSolution that this move has been generated from.

That new move does the exact same change as this move, resulting in the same PlanningSolution state, presuming that destination PlanningSolution was in the same state as the original PlanningSolution to begin with.

Generally speaking, an implementation of this method iterates through every entity and fact instance in this move, translates each one to the destination ScoreDirector with ScoreDirector.lookUpWorkingObject(Object) and creates a new move instance of the same move type, using those translated instances.

The destination PlanningSolution can be in a different state than the original PlanningSolution. So, rebasing can only depend on the identity of planning entities and problem facts, which are usually declared by a PlanningId on those classes. It must not depend on the state of the planning variables. One thread might rebase a move before, amid or after another thread does that same move instance.

This method is thread-safe.

Parameters:

destinationScoreDirector - never null, the ScoreDirector.getWorkingSolution() that the new move should change the planning entity instances of.

Returns:

never null, a new move that does the same change as this move on another solution instance

rebase

default Move<Solution_> rebase(Rebaser rebaser)

Do not override this default implementation.

Specified by:

rebase in interface Move<Solution_>

Parameters:

rebaser - Do not store this parameter in a field

Returns:

New move that does the same change as this move on another solution instance

getSimpleMoveTypeDescription

default String getSimpleMoveTypeDescription()

Describes the move type for statistical purposes. For example "ChangeMove(Process.computer)".

The format is not formalized. Never parse the String returned by this method.

Returns:

never null

describe

default String describe()

Do not override this default implementation.

Specified by:

describe in interface Move<Solution_>

Returns:

Non-empty String that describes the move type.