add better enemy constrictor projection

snakes/BestBattleSnake.py

@@ -583,6 +583,12 @@ class BestBattleSnake(TemplateSnake):
         width=width,
         height=height,
       )
+      enemy_best_space, enemy_total_options = self._enemy_constrictor_projection(
+        other_snakes=other_snakes,
+        blocked=blocked,
+        width=width,
+        height=height,
+      )
 
       enemy_len = enemy_attack_map.get(point)
       is_losing_head_to_head = enemy_len is not None and enemy_len >= my_len
@@ -596,6 +602,13 @@ class BestBattleSnake(TemplateSnake):
       score += liberties * 24.0
       score += next_options * 16.0
       score += territory * 0.65
+      score += (reachable_space - enemy_best_space) * 3.2
+      score += (max(0, 8 - enemy_total_options)) * 18.0
+
+      if enemy_total_options <= 2:
+        score += 110.0
+      if enemy_best_space > int(reachable_space * 1.2):
+        score -= 320.0
 
       if is_dead_end:
         score -= 2600.0
@@ -992,6 +1005,33 @@ class BestBattleSnake(TemplateSnake):
     )
     return enemy_space, enemy_options
 
+  def _enemy_constrictor_projection(self, other_snakes:list[SnakeState], blocked:set[Point], width:int, height: int) -> tuple[int, int]:
+    """Estimate enemy best-space and total options after our candidate move."""
+    best_enemy_space = 0
+    total_enemy_options = 0
+
+    for enemy in other_snakes:
+      enemy_head = (enemy["head"]["x"], enemy["head"]["y"])
+      enemy_best_for_snake = 0
+
+      for neighbor in self._neighbors(enemy_head):
+        if not self._in_bounds(neighbor, width, height):
+          continue
+        if neighbor in blocked:
+          continue
+
+        total_enemy_options += 1
+        enemy_blocked = set(blocked)
+        enemy_blocked.add(neighbor)
+        enemy_space = self._flood_fill_count(
+          neighbor, enemy_blocked, width, height
+        )
+        enemy_best_for_snake = max(enemy_best_for_snake, enemy_space)
+
+      best_enemy_space = max(best_enemy_space, enemy_best_for_snake)
+
+    return best_enemy_space, total_enemy_options
+
   def _neighbors(self, point:Point) -> Iterator[Point]:
     """Yield orthogonal neighbor coordinates for a point."""
     for dx, dy in self.DIRECTIONS.values():

tests/test_BestBattleSnake.py

@@ -681,5 +681,75 @@ class TestBestBattleSnake(unittest.TestCase):
     move = make_board(game_state).snake_neat_make_a_move()
     self.assertEqual(move, "right")
 
+  def test_constrictor_prefers_choke_when_safe(self):
+    game_state = {
+      "game": {
+        "id": "test-constrictor-choke",
+        "ruleset": {"name": "constrictor", "version": "v1.0.0"},
+        "source": "custom",
+        "map": "standard",
+      },
+      "turn": 25,
+      "board": {
+        "height": 7,
+        "width": 7,
+        "food": [],
+        "hazards": [],
+        "snakes": [
+          {
+            "id": "me",
+            "name": "me",
+            "health": 100,
+            "length": 7,
+            "head": {"x": 2, "y": 3},
+            "body": [
+              {"x": 2, "y": 3},
+              {"x": 2, "y": 2},
+              {"x": 1, "y": 2},
+              {"x": 1, "y": 3},
+              {"x": 1, "y": 4},
+              {"x": 2, "y": 4},
+              {"x": 2, "y": 5},
+            ],
+          },
+          {
+            "id": "enemy",
+            "name": "enemy",
+            "health": 100,
+            "length": 7,
+            "head": {"x": 4, "y": 3},
+            "body": [
+              {"x": 4, "y": 3},
+              {"x": 5, "y": 3},
+              {"x": 5, "y": 2},
+              {"x": 4, "y": 2},
+              {"x": 4, "y": 1},
+              {"x": 5, "y": 1},
+              {"x": 6, "y": 1},
+            ],
+          },
+        ],
+      },
+      "you": {
+        "id": "me",
+        "name": "me",
+        "health": 100,
+        "length": 7,
+        "head": {"x": 2, "y": 3},
+        "body": [
+          {"x": 2, "y": 3},
+          {"x": 2, "y": 2},
+          {"x": 1, "y": 2},
+          {"x": 1, "y": 3},
+          {"x": 1, "y": 4},
+          {"x": 2, "y": 4},
+          {"x": 2, "y": 5},
+        ],
+      },
+    }
+
+    move = make_board(game_state).snake_neat_make_a_move()
+    self.assertEqual(move, "right")
+
 if __name__ == "__main__":
   unittest.main()