add neighborhood cache

mesa/space.py

@@ -100,6 +100,9 @@ def __init__(self, width: int, height: int, torus: bool) -> None:
         # Add all cells to the empties list.
         self.empties = set(itertools.product(*(range(self.width), range(self.height))))
 
+        # Neighborhood Cache
+        self._neighborhood_cache = dict()  # type: Dict[Any, List[Coordinate]]
+
     @staticmethod
     def default_val() -> None:
         """ Default value for new cell elements. """
@@ -162,31 +165,7 @@ def iter_neighborhood(
             including the center).
 
         """
-        x, y = pos
-        coordinates: Set[Coordinate] = set()
-        for dy in range(-radius, radius + 1):
-            for dx in range(-radius, radius + 1):
-                if dx == 0 and dy == 0 and not include_center:
-                    continue
-                # Skip coordinates that are outside manhattan distance
-                if not moore and abs(dx) + abs(dy) > radius:
-                    continue
-                # Skip if not a torus and new coords out of bounds.
-                if not self.torus and (
-                    not (0 <= dx + x < self.width) or not (0 <= dy + y < self.height)
-                ):
-                    continue
-
-                px, py = self.torus_adj((x + dx, y + dy))
-
-                # Skip if new coords out of bounds.
-                if self.out_of_bounds((px, py)):
-                    continue
-
-                coords = (px, py)
-                if coords not in coordinates:
-                    coordinates.add(coords)
-                    yield coords
+        yield from self.get_neighborhood(pos, moore, include_center, radius)
 
     def get_neighborhood(
         self,
@@ -214,7 +193,35 @@ def get_neighborhood(
             if not including the center).
 
         """
-        return list(self.iter_neighborhood(pos, moore, include_center, radius))
+        cache_key = (pos, moore, include_center, radius)
+        neighborhood = self._neighborhood_cache.get(cache_key, None)
+
+        if neighborhood is None:
+            coordinates = set()  # type: Set[Coordinate]
+
+            x, y = pos
+            for dy in range(-radius, radius + 1):
+                for dx in range(-radius, radius + 1):
+                    if dx == 0 and dy == 0 and not include_center:
+                        continue
+                    # Skip coordinates that are outside manhattan distance
+                    if not moore and abs(dx) + abs(dy) > radius:
+                        continue
+
+                    coord = (x + dx, y + dy)
+
+                    if self.out_of_bounds(coord):
+                        # Skip if not a torus and new coords out of bounds.
+                        if not self.torus:
+                            continue
+                        coord = self.torus_adj(coord)
+
+                    coordinates.add(coord)
+
+            neighborhood = sorted(coordinates)
+            self._neighborhood_cache[cache_key] = neighborhood
+
+        return neighborhood
 
     def iter_neighbors(
         self,