Optimize: Cache player occupied squares for faster corner validation

src/blokus_gym/core/board.py

@@ -16,11 +16,15 @@ class Board:
     def __init__(self, size: int):
         self.size = size
         self.grid = np.zeros((size, size), dtype=np.int8)
+        self._occupied_cache: dict[int, set[tuple[int, int]]] = {}  # player_idx -> occupied squares
 
     def place(self, player_idx: int, squares: list[tuple[int, int]]) -> None:
         """Place a player's piece on the board."""
         for x, y in squares:
             self.grid[y, x] = player_idx
+        # Update occupied cache incrementally instead of clearing
+        if player_idx in self._occupied_cache:
+            self._occupied_cache[player_idx].update(squares)
 
     def clear(self) -> None:
         """Reset the board to empty."""
@@ -50,6 +54,12 @@ class Board:
         ys, xs = np.where(self.grid == player_idx)
         return [(int(x), int(y)) for x, y in zip(xs, ys, strict=True)]
 
+    def get_player_occupied(self, player_idx: int) -> set[tuple[int, int]]:
+        """Get all squares occupied by a player as a set for fast lookup."""
+        if player_idx not in self._occupied_cache:
+            self._occupied_cache[player_idx] = set(self.get_player_squares(player_idx))
+        return self._occupied_cache[player_idx]
+
     def get_player_corners(self, player_idx: int) -> set[tuple[int, int]]:
         """Get all corner cells adjacent to a player's pieces.
 

src/blokus_gym/core/game.py

@@ -206,12 +206,12 @@ class BlokusGame:
         # Rule 4: Corner rule (must touch same-color at a corner)
         if player.has_started:
             placed_corners = self._get_placed_corners(move)
-            touches_corner = False
-            for cx, cy in placed_corners:
-                if self.board.in_bounds(cx, cy):
-                    if self.board.get_cell(cx, cy) == player_board_idx:
-                        touches_corner = True
-                        break
+            # Use cached occupied squares from board for fast lookup
+            player_occupied = self.board.get_player_occupied(player_idx)
+            touches_corner = any(
+                self.board.in_bounds(cx, cy) and (cx, cy) in player_occupied
+                for cx, cy in placed_corners
+            )
             if not touches_corner:
                 return False
 
@@ -238,49 +238,46 @@ class BlokusGame:
             return mask
 
         player_board_idx = player_idx + self.PLAYER_OFFSET
+        
+        # Pre-compute player's occupied squares ONCE (cached)
+        player_occupied = self.board.get_player_occupied(player_idx)
 
         for piece_id in available_piece_ids:
             for action_idx in self._actions_by_piece[piece_id]:
                 move = self._action_moves[action_idx]
                 placed_corners = self._get_placed_corners(move)
 
-                touches_corner = False
-                for cx, cy in placed_corners:
-                    if self.board.in_bounds(cx, cy):
-                        if self.board.get_cell(cx, cy) == player_board_idx:
-                            touches_corner = True
-                            break
+                # Early exit: check corner touch using cached occupied squares
+                touches_corner = any(
+                    self.board.in_bounds(cx, cy) and (cx, cy) in player_occupied
+                    for cx, cy in placed_corners
+                )
                 if not touches_corner:
-                    continue
+                    continue  # Skip expensive overlap/edge checks
 
                 placed_squares = self._get_placed_squares(move)
 
-                valid = True
-                for x, y in placed_squares:
-                    if not self.board.in_bounds(x, y):
-                        valid = False
-                        break
-                if not valid:
+                # Check bounds
+                if not all(self.board.in_bounds(x, y) for x, y in placed_squares):
                     continue
 
+                # Check overlap
                 if self.board.has_overlap(placed_squares):
                     continue
 
+                # Check edge adjacency (no same-color edges)
+                edge_invalid = False
                 for x, y in placed_squares:
-                    edge_invalid = False
                     for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
                         nx, ny = x + dx, y + dy
-                        if self.board.in_bounds(nx, ny):
-                            if self.board.get_cell(nx, ny) == player_board_idx:
-                                edge_invalid = True
-                                break
+                        if self.board.in_bounds(nx, ny) and self.board.get_cell(nx, ny) == player_board_idx:
+                            edge_invalid = True
+                            break
                     if edge_invalid:
-                        valid = False
                         break
-                if not valid:
-                    continue
 
-                mask[action_idx] = True
+                if not edge_invalid:
+                    mask[action_idx] = True
 
         return mask