diff --git a/AlphaGo/game.py b/AlphaGo/game.py
index 82cf254..60e09f0 100644
--- a/AlphaGo/game.py
+++ b/AlphaGo/game.py
@@ -35,6 +35,7 @@ class Game:
             self.komi = 3.75
             self.history_length = 8
             self.history = []
+            self.history_set = set()
             self.game_engine = go.Go(size=self.size, komi=self.komi, role=self.role)
             self.board = [utils.EMPTY] * (self.size ** 2)
         elif self.name == "reversi":
@@ -92,7 +93,10 @@ class Game:
         # this function can be called directly to play the opponent's move
         if vertex == utils.PASS:
             return True
-        res = self.game_engine.executor_do_move(self.history, self.latest_boards, self.board, color, vertex)
+        if self.name == "reversi":
+            res = self.game_engine.executor_do_move(self.history, self.latest_boards, self.board, color, vertex)
+        if self.name == "go":
+            res = self.game_engine.executor_do_move(self.history, self.history_set, self.latest_boards, self.board, color, vertex)
         return res
 
     def think_play_move(self, color):
@@ -124,6 +128,6 @@ class Game:
 
 if __name__ == "__main__":
     game = Game(name="reversi", checkpoint_path=None)
-    game.debug = True
+    game.debug = False
     game.think_play_move(utils.BLACK)
 
diff --git a/AlphaGo/go.py b/AlphaGo/go.py
index 987fe93..cf6b7aa 100644
--- a/AlphaGo/go.py
+++ b/AlphaGo/go.py
@@ -97,12 +97,12 @@ class Go:
                     for b in group:
                         current_board[self._flatten(b)] = utils.EMPTY
 
-    def _check_global_isomorphous(self, history_boards, current_board, color, vertex):
+    def _check_global_isomorphous(self, history_boards_set, current_board, color, vertex):
         repeat = False
         next_board = copy.deepcopy(current_board)
         next_board[self._flatten(vertex)] = color
         self._process_board(next_board, color, vertex)
-        if next_board in history_boards:
+        if hash(tuple(next_board)) in history_boards_set:
             repeat = True
         return repeat
 
@@ -158,7 +158,7 @@ class Go:
             vertex = self._deflatten(action)
         return vertex
 
-    def _rule_check(self, history_boards, current_board, color, vertex):
+    def _rule_check(self, history_boards_set, current_board, color, vertex):
         ### in board
         if not self._in_board(vertex):
             return False
@@ -172,7 +172,7 @@ class Go:
             return False
 
         ### forbid global isomorphous
-        if self._check_global_isomorphous(history_boards, current_board, color, vertex):
+        if self._check_global_isomorphous(history_boards_set, current_board, color, vertex):
             return False
 
         return True
@@ -226,13 +226,14 @@ class Go:
         # since go is MDP, we only need the last board for hashing
         return tuple(state[0][-1])
 
-    def executor_do_move(self, history, latest_boards, current_board, color, vertex):
-        if not self._rule_check(history, current_board, color, vertex):
+    def executor_do_move(self, history, history_set, latest_boards, current_board, color, vertex):
+        if not self._rule_check(history_set, current_board, color, vertex):
             return False
         current_board[self._flatten(vertex)] = color
         self._process_board(current_board, color, vertex)
         history.append(copy.deepcopy(current_board))
         latest_boards.append(copy.deepcopy(current_board))
+        history_set.add(hash(tuple(current_board)))
         return True
 
     def _find_empty(self, current_board):