Package ai.timefold.solver.core.impl.move.streams.generic.move

Class ListChangeMove<Solution_,Entity_,Value_>

java.lang.Object
ai.timefold.solver.core.impl.move.streams.generic.move.AbstractMove<Solution_>
ai.timefold.solver.core.impl.move.streams.generic.move.ListChangeMove<Solution_,Entity_,Value_>
Type Parameters:
Solution_ - the solution type, the class with the PlanningSolution annotation
All Implemented Interfaces:
Move<Solution_>
public final class ListChangeMove<Solution_,Entity_,Value_> extends AbstractMove<Solution_>
Moves an element of a list variable. The moved element is identified by an entity instance and a position in that entity's list variable. The element is inserted at the given index in the given destination entity's list variable.

An undo move is simply created by flipping the source and destination entity+index.

  • Constructor Details

    • ListChangeMove

      public ListChangeMove(PlanningListVariableMetaModel<Solution_,Entity_,Value_> variableMetaModel, Entity_ sourceEntity, int sourceIndex, Entity_ destinationEntity, int destinationIndex)
      The move removes a planning value element from sourceEntity.listVariable[sourceIndex] and inserts the planning value at destinationEntity.listVariable[destinationIndex].

      ListChangeMove anatomy

       
                             / destinationEntity
                             |   / destinationIndex
                             |   |
                A {Ann[0]}->{Bob[2]}
                |  |   |
 planning value /  |   \ sourceIndex
                   \ sourceEntity

      Example 1 - source and destination entities are different

       
 GIVEN
 Ann.tasks = [A, B, C]
 Bob.tasks = [X, Y]

 WHEN
 ListChangeMove: A {Ann[0]->Bob[2]}

 THEN
 Ann.tasks = [B, C]
 Bob.tasks = [X, Y, A]

      Example 2 - source and destination is the same entity

       
 GIVEN
 Ann.tasks = [A, B, C]

 WHEN
 ListChangeMove: A {Ann[0]->Ann[2]}

 THEN
 Ann.tasks = [B, C, A]
      Parameters:
      variableMetaModel - never null
      sourceEntity - planning entity instance from which a planning value will be removed, for example "Ann"
      sourceIndex - index in sourceEntity's list variable from which a planning value will be removed
      destinationEntity - planning entity instance to which a planning value will be moved, for example "Bob"
      destinationIndex - index in destinationEntity's list variable where the moved planning value will be inserted

  • Method Details

    • execute

      public void execute(@NonNull MutableSolutionView<Solution_> solutionView)
      Description copied from interface: Move
      Runs the move and optionally records the changes done, so that they can be undone later.
      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

      public @NonNull ListChangeMove<Solution_,Entity_,Value_> rebase(@NonNull Rebaser rebaser)
      Description copied from interface: Move
      Rebases a move from an origin ScoreDirector to another destination ScoreDirector which is usually on another Thread. It is necessary for multithreaded solving to function.

      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.

      An implementation of this method typically iterates through every entity and fact instance in this move, translates each one to the destination ScoreDirector with Rebaser.rebase(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:
      rebaser - Do not store this parameter in a field
      Returns:
      New move that does the same change as this move on another solution instance

    • extractPlanningEntities

      public @NonNull Collection<Object> extractPlanningEntities()
      Description copied from interface: Move
      Returns all planning entities that this move is changing. Required for entity tabu.

      This method is only called after Move.execute(MutableSolutionView), which might affect the return values.

      Duplicate entries in the returned Collection are best avoided. The returned Collection is recommended to be in a stable order. For example, use List or LinkedHashSet, but not HashSet.

      Returns:
      Each entity only once.

    • extractPlanningValues

      public @NonNull Collection<Object> extractPlanningValues()
      Description copied from interface: Move
      Returns all planning values that this move is assigning to entity variables. Required for value tabu.

      This method is only called after Move.execute(MutableSolutionView), which might affect the return values.

      Duplicate entries in the returned Collection are best avoided. The returned Collection is recommended to be in a stable order. For example, use List or LinkedHashSet, but not HashSet.

      Returns:
      Each value only once.

    • getVariableMetaModels

      protected List<VariableMetaModel<Solution_,?,?>> getVariableMetaModels()
      Overrides:
      getVariableMetaModels in class AbstractMove<Solution_>

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public @NonNull String toString()
      Description copied from interface: Move
      The solver will make sure to only call this when the move is actually printed out during debug logging.
      Specified by:
      toString in interface Move<Solution_>
      Specified by:
      toString in class AbstractMove<Solution_>
      Returns:
      A description of the move, ideally including the state of the planning entities being changed.