update UltimateBattleSnake to 4.2.0

snakes/UltimateBattleSnake.py

@@ -10,7 +10,7 @@ from server.dataset.RLBootstrapDataset import RLBootstrapDataset
 
 class UltimateBattleSnake(TemplateSnake):
   """
-  UltimateBattleSnake v4.0.0
+  UltimateBattleSnake v4.2.0
 
   All improvements over BestBattleSnake:
   v3: #1+#9  Simultaneous minimax (both snakes move at once) with hazard/health tracking
@@ -39,9 +39,12 @@ class UltimateBattleSnake(TemplateSnake):
   v4.1 B1   _simulation_blocked now correctly keeps enemy tail blocked when enemy_can_grow=True
   v4.1 B2   _build_enemy_attack_map: can_en_tail=False when enemy is about to eat (won't vacate)
   v4.1 B3   _compute_base_blocked: same enemy_can_grow fix for Voronoi dmap accuracy
+  v4.2 B4   _build_enemy_attack_map: enemy_can_grow now actually passed from choose_move and tree
+  v4.2 B5   _choose_duel_move: removed double food bias (score_move already adds it; duel now only adjusts delta)
+  v4.2 B6   _minimax_sim: occupancy now respects _is_tail_stacked (stacked tail not vacated)
   """
 
-  VERSION = "4.1.0"
+  VERSION = "4.2.0"
   Point = tuple[int, int]
   Coord = dict[str, int]
   SnakeState = dict[str, Any]
@@ -178,6 +181,7 @@ class UltimateBattleSnake(TemplateSnake):
     enemy_attack_map = self._build_enemy_attack_map(
       my_snake=my_snake, other_snakes=other_snakes, food_set=food_set,
       is_constrictor=is_constrictor, width=width, height=height,
+      enemy_can_grow=enemy_can_grow,
     )
 
     safe_moves = self._legal_moves(
@@ -252,7 +256,6 @@ class UltimateBattleSnake(TemplateSnake):
   ) -> tuple[str, dict[str, float]]:
     scores: dict[str, float] = {}
     safety: dict[str, dict] = {}
-    enemy_heads = self._enemy_heads
 
     for move, pos in safe_moves.items():
       if self._time_exceeded(deadline):
@@ -382,11 +385,14 @@ class UltimateBattleSnake(TemplateSnake):
         if dist == 1:
           sc -= 180.0 * dw["distance_safety"]
 
-      # Override food bias with duel style weight
+      # Apply duel-style food multiplier on top of the base food bias already added by _score_move.
+      # _score_move contributes (30+80*hunger)/(nearest_food+1); here we scale that contribution
+      # by (dw["food_bias"] - 1) so the net effect is the full duel-weighted amount.
       nearest_food = info.get("nearest_food")
-      if nearest_food is not None:
+      if nearest_food is not None and dw["food_bias"] != 1.0:
         hunger = max(0.0, (65.0 - my_health) / 65.0)
-        sc += ((25.0 + 90.0 * hunger) * dw["food_bias"]) / (nearest_food + 1)
+        base_food_contribution = (30.0 + 80.0 * hunger) / (nearest_food + 1)
+        sc += base_food_contribution * (dw["food_bias"] - 1.0)
 
       sc += self._territory_fast(point, blocked, width, height, deadline) * 0.55
       scores[move] = round(sc, 5)
@@ -475,7 +481,6 @@ class UltimateBattleSnake(TemplateSnake):
   ) -> tuple[str, dict[str, float]]:
     scores: dict[str, float] = {}
     safety: dict[str, dict] = {}
-    enemy_heads = self._enemy_heads
 
     for move, pos in safe_moves.items():
       if self._time_exceeded(deadline):
@@ -821,9 +826,14 @@ class UltimateBattleSnake(TemplateSnake):
     my_h = my_body[0]
     en_h = enemy_body[0]
 
-    # Occupied: bodies excluding tails (tails vacate this turn)
-    my_occ = {(s["x"], s["y"]) for s in my_body[:-1]}
-    en_occ = {(s["x"], s["y"]) for s in enemy_body[:-1]}
+    # Occupied: bodies excluding tails that will vacate this turn.
+    # A tail only vacates if the snake is NOT stacked (i.e. didn't eat food last turn).
+    my_occ = {(s["x"], s["y"]) for s in my_body}
+    if not self._is_tail_stacked(my_body):
+      my_occ.discard((my_body[-1]["x"], my_body[-1]["y"]))
+    en_occ = {(s["x"], s["y"]) for s in enemy_body}
+    if not self._is_tail_stacked(enemy_body):
+      en_occ.discard((enemy_body[-1]["x"], enemy_body[-1]["y"]))
     all_occ = my_occ | en_occ
 
     my_moves = []
@@ -1019,7 +1029,7 @@ class UltimateBattleSnake(TemplateSnake):
 
     # Build attack map for safe option count
     future_snake = {"head": my_body[0], "body": my_body, "length": len(my_body), "id": "__future__"}
-    atk = self._build_enemy_attack_map(future_snake, other_snakes, food_set, is_constrictor, width, height)
+    atk = self._build_enemy_attack_map(future_snake, other_snakes, food_set, is_constrictor, width, height, enemy_can_grow)
     en_safe = self._safe_next_options(my_body, len(my_body), blocked, atk, food_set, is_constrictor, width, height)
 
     # Zero safe options = will be forced into a losing head-to-head next turn

snakes/__init__.py

@@ -8,7 +8,7 @@ SNAKE_REGISTRY = {
   "BetterMasterSnake": "1.3.0",
   "BestBattleSnake": "2.6.0",
   "TrainedBattleSnake": "0.1.0",
-  "UltimateBattleSnake": "4.1.0",
+  "UltimateBattleSnake": "4.2.0",
 }
 
 def build_snake(selected_snake: str):