`prepare()` and `resume()` perform duplicate computation

[NONONOexe]

While developing based on sample_road_detector.py, we noticed that prepare() and resume() perform the same computation. We believe this calculation should be performed by precompute(), not resume().

  def resume(self, precompute_data: PrecomputeData) -> RoadDetector:
    super().resume(precompute_data)
    if self.get_count_resume() >= 2:
      return self

    self._target_areas: set[EntityID] = set()
    entities = self._world_info.get_entities_of_types([Refuge, Building, GasStation])
    for entity in entities:
      if not isinstance(entity, Building):
        continue
      for entity_id in entity.get_neighbors():
        neighbor = self._world_info.get_entity(entity_id)
        if isinstance(neighbor, Road):
          self._target_areas.add(entity_id)

    self._priority_roads = set()
    for entity in self._world_info.get_entities_of_types([Refuge]):
      if not isinstance(entity, Building):
        continue
      for entity_id in entity.get_neighbors():
        neighbor = self._world_info.get_entity(entity_id)
        if isinstance(neighbor, Road):
          self._priority_roads.add(entity_id)

    return self

  def prepare(self) -> RoadDetector:
    super().prepare()
    if self.get_count_prepare() >= 2:
      return self

    self._target_areas = set()
    entities = self._world_info.get_entities_of_types([Refuge, Building, GasStation])
    for entity in entities:
      building: Building = cast(Building, entity)
      for entity_id in building.get_neighbors():
        neighbor = self._world_info.get_entity(entity_id)
        if isinstance(neighbor, Road):
          self._target_areas.add(entity_id)

    self._priority_roads = set()
    for entity in self._world_info.get_entities_of_types([Refuge]):
      refuge: Refuge = cast(Refuge, entity)
      for entity_id in refuge.get_neighbors():
        neighbor = self._world_info.get_entity(entity_id)
        if isinstance(neighbor, Road):
          self._priority_roads.add(entity_id)

    return self

[NONONOexe]

I had mistakenly written precompute() and prepare() in the the explanation, so I have rewrited them.

[NONONOexe]

I think there may be a cleaner way to express this, but here is my attempt at organizing it. This is what I believe that the code should look like when precompute() is used correctly.

...

  def precompute(self, precompute_data: PrecomputeData) -> RoadDetector:
    super().precompute(precompute_data)

    target_areas = self._init_target_areas()
    priority_roads = self._build_priority_roads()

    precompute_data.write_json_data(
      {
        "target_areas": list(target_areas),
        "priority_roads": list(priority_roads)
      },
      "RoadDetector"
    )

    return self

  def resume(self, precompute_data: PrecomputeData) -> RoadDetector:
    super().resume(precompute_data)

    if 1 < self.get_count_resume():
      return self

    data = precompute_data.read_json_data("RoadDetector")
    self._target_areas = data["target_areas"]
    self._priority_roads = frozenset(data["priority_roads"])

    return self

  def prepare(self) -> RoadDetector:
    super().prepare()
    if 1 < self.get_count_prepare():
      return self

    self._target_areas = self._init_target_areas()
    self._priority_roads = self._build_priority_roads()

    return self
  
  def _init_target_areas(self) -> set[EntityID]:
    """Initialize a set of roads adjacent to buildings, refuges, and gas stations."""
    return set(
        entity_id
        for entity in self._world_info.get_entities_of_types([Refuge, Building, GasStation])
        if isinstance(entity, Building)
        for entity_id in entity.get_neighbors()
        if isinstance(self._world_info.get_entity(entity_id), Road)
    )

  def _build_priority_roads(self) -> frozenset[EntityID]:
    """Build an immutable set of roads adjacent to refuges."""
    return frozenset(
        entity_id
        for entity in self._world_info.get_entities_of_types([Refuge])
        if isinstance(entity, Refuge)
        for entity_id in entity.get_neighbors()
        if isinstance(self._world_info.get_entity(entity_id), Road)
    )

...

[ToB213]

I found a similar issue in KMeansClustering. Both precompute() and prepare() call create_cluster(), resulting in the same clustering computation being performed twice.

def precompute(self, precompute_data):
    cluster_entities = self.create_cluster(...)  # computed here
    precompute_data.write_json_data(...)

def prepare(self):
    self.cluster_entities = self.create_cluster(...)  # same computation repeated

As with your proposed fix, I think the solution is to extract create_cluster() as a helper method and call it from both precompute() and prepare().