[Hex] Extract logic functions (#1288)

pgx/_src/dwg/hex.py

@@ -3,7 +3,11 @@
 import jax.numpy as jnp
 
 from pgx.hex import State as HexState
-from pgx.hex import _get_abs_board
+
+
+def _get_abs_board(state):
+    return state._x.board if state._x.color == 0 else state._x.board * -1
+
 
 r3 = jnp.sqrt(3)
 

pgx/hex.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 from functools import partial
-from typing import NamedTuple
+from typing import NamedTuple, Optional
 
 import jax
 import jax.numpy as jnp
@@ -29,7 +29,7 @@
 class GameState(NamedTuple):
     size: Array = jnp.int32(11)
     # 0(black), 1(white)
-    turn: Array = jnp.int32(0)
+    step_count: Array = jnp.int32(0)
     # 11x11 board
     # [[  0,  1,  2,  ...,  8,  9, 10],
     #  [ 11,  12, 13, ..., 19, 20, 21],
@@ -39,6 +39,10 @@ class GameState(NamedTuple):
     #  [110, 111, 112, ...,  119, 120]]
     board: Array = jnp.zeros(11 * 11, jnp.int32)  # <0(oppo), 0(empty), 0<(self)
 
+    @property
+    def color(self) -> Array:
+        return self.step_count % 2
+
 
 @dataclass
 class State(core.State):
@@ -63,20 +67,37 @@ def __init__(self, *, size: int = 11):
         self.size = size
 
     def _init(self, key: PRNGKey) -> State:
-        return partial(_init, size=self.size)(rng=key)
+        current_player = jnp.int32(jax.random.bernoulli(key))
+        return State(_x=_init(self.size), current_player=current_player)  # type:ignore
 
     def _step(self, state: core.State, action: Array, key) -> State:
         del key
         assert isinstance(state, State)
-        return jax.lax.cond(
+        x = jax.lax.cond(
             action != self.size * self.size,
-            lambda: partial(_step, size=self.size)(state, action),
-            lambda: partial(_swap, size=self.size)(state),
+            lambda: partial(_step, size=self.size)(state._x, action),
+            lambda: partial(_swap, size=self.size)(state._x),
+        )
+
+        terminated = _is_terminal(x, self.size)
+        reward = jax.lax.cond(
+            terminated,
+            lambda: jnp.float32([-1, -1]).at[state.current_player].set(1),
+            lambda: jnp.zeros(2, jnp.float32),
+        )
+
+        return state.replace(  # type:ignore
+            current_player=1 - state.current_player,
+            legal_action_mask=state.legal_action_mask.at[:-1].set(state._x.board == 0).at[-1].set(state._step_count == 1),
+            rewards=reward,
+            terminated=terminated,
+            _x=x,
         )
 
     def _observe(self, state: core.State, player_id: Array) -> Array:
         assert isinstance(state, State)
-        return partial(_observe, size=self.size)(state, player_id)
+        color = jax.lax.select(player_id == state.current_player, state._x.color, 1 - state._x.color)
+        return _observe(state._x, color, self.size)
 
     @property
     def id(self) -> core.EnvId:
@@ -91,14 +112,13 @@ def num_players(self) -> int:
         return 2
 
 
-def _init(rng: PRNGKey, size: int) -> State:
-    current_player = jnp.int32(jax.random.bernoulli(rng))
-    return State(_x=GameState(size=size), current_player=current_player)  # type:ignore
+def _init(size: int) -> GameState:
+    return GameState(size=size)
 
 
-def _step(state: State, action: Array, size: int) -> State:
+def _step(state: GameState, action: Array, size: int) -> GameState:
     set_place_id = action + 1
-    board = state._x.board.at[action].set(set_place_id)
+    board = state.board.at[action].set(set_place_id)
     neighbour = _neighbour(action, size)
 
     def merge(i, b):
@@ -110,57 +130,37 @@ def merge(i, b):
         )
 
     board = jax.lax.fori_loop(0, 6, merge, board)
-    won = _is_game_end(board, size, state._x.turn)
-    reward = jax.lax.cond(
-        won,
-        lambda: jnp.float32([-1, -1]).at[state.current_player].set(1),
-        lambda: jnp.zeros(2, jnp.float32),
+    return state._replace(
+        step_count=state.step_count + 1,
+        board=board * -1,
     )
 
-    state = state.replace(  # type:ignore
-        current_player=1 - state.current_player,
-        _x=GameState(
-            turn=1 - state._x.turn,
-            board=board * -1,
-        ),
-        rewards=reward,
-        terminated=won,
-        legal_action_mask=state.legal_action_mask.at[:-1].set(board == 0).at[-1].set(state._step_count == 1),
-    )
-
-    return state
 
-
-def _swap(state: State, size: int) -> State:
-    ix = jnp.nonzero(state._x.board, size=1)[0]
+def _swap(state: GameState, size: int) -> GameState:
+    ix = jnp.nonzero(state.board, size=1)[0]
     row = ix // size
     col = ix % size
     swapped_ix = col * size + row
     set_place_id = swapped_ix + 1
-    board = state._x.board.at[ix].set(0).at[swapped_ix].set(set_place_id)
-    return state.replace(  # type: ignore
-        current_player=1 - state.current_player,
-        _x=GameState(
-            turn=1 - state._x.turn,
-            board=board * -1,
-        ),
-        legal_action_mask=state.legal_action_mask.at[:-1].set(board == 0).at[-1].set(FALSE),
+    board = state.board.at[ix].set(0).at[swapped_ix].set(set_place_id)
+    return state._replace(
+        step_count=state.step_count + 1,
+        board=board * -1,
     )
 
 
-def _observe(state: State, player_id: Array, size) -> Array:
-    board = jax.lax.select(
-        player_id == state.current_player,
-        state._x.board.reshape((size, size)),
-        -state._x.board.reshape((size, size)),
-    )
+def _observe(state: GameState, color: Optional[Array] = None, size: int = 11) -> Array:
+    if color is None:
+        color = state.color
+
+    board = jax.lax.select(color == state.color, state.board, -state.board)
+    board = board.reshape((size, size))
 
     my_board = board * 1 > 0
     opp_board = board * -1 > 0
     ones = jnp.ones_like(my_board)
-    color = jax.lax.select(player_id == state.current_player, state._x.turn, 1 - state._x.turn)
     color = color * ones
-    can_swap = state.legal_action_mask[-1] * ones
+    can_swap = (state.step_count == 1) * ones
 
     return jnp.stack([my_board, opp_board, color, can_swap], 2, dtype=jnp.bool_)
 
@@ -179,18 +179,14 @@ def _neighbour(xy, size):
     return jnp.where(on_board, xs * size + ys, -1)
 
 
-def _is_game_end(board, size, turn):
+def _is_terminal(x: GameState, size):
     top, bottom = jax.lax.cond(
-        turn == 0,
-        lambda: (board[:size], board[-size:]),
-        lambda: (board[::size], board[size - 1 :: size]),
+        x.color == 0,
+        lambda: (x.board[::size], x.board[size - 1 :: size]),
+        lambda: (x.board[:size], x.board[-size:]),
     )
 
     def check_same_id_exist(_id):
-        return (_id > 0) & (_id == bottom).any()
+        return (_id < 0) & (_id == bottom).any()
 
     return jax.vmap(check_same_id_exist)(top).any()
-
-
-def _get_abs_board(state):
-    return jax.lax.cond(state._x.turn == 0, lambda: state._x.board, lambda: state._x.board * -1)