Package ai.timefold.solver.core.impl.heuristic.selector.move.generic.list

Class ListChangeMove<Solution_>

  • Type Parameters:
    Solution_ - the solution type, the class with the PlanningSolution annotation
    All Implemented Interfaces:
    Move<Solution_>
    public class ListChangeMove<Solution_>
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 Detail

      • ListChangeMove

        public ListChangeMove​(ListVariableDescriptor<Solution_> variableDescriptor,
                      Object sourceEntity,
                      int sourceIndex,
                      Object 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:
        variableDescriptor - descriptor of a list variable, for example Employee.taskList
        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 Detail

      • getSourceEntity

        public Object getSourceEntity()

      • getSourceIndex

        public int getSourceIndex()

      • getDestinationEntity

        public Object getDestinationEntity()

      • getDestinationIndex

        public int getDestinationIndex()

      • getMovedValue

        public Object getMovedValue()

      • isMoveDoable

        public boolean isMoveDoable​(ScoreDirector<Solution_> scoreDirector)
        Description copied from interface: Move
        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.

      • rebase

        public ListChangeMove<Solution_> rebase​(ScoreDirector<Solution_> destinationScoreDirector)
        Description copied from interface: Move
        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 planning facts, which is 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

      • getSimpleMoveTypeDescription

        public String getSimpleMoveTypeDescription()
        Description copied from interface: Move
        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

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object