diff --git a/src/statebag.py b/src/statebag.py
--- a/src/statebag.py
+++ b/src/statebag.py
@@ -39,9 +39,11 @@ class BoardState:
 		self.moves=[]
 		self.weight=0
 		self.diff2Prev=None
+		self._hash=None
 
 	def hash(self):
-		return hashBoard(self._board)
+		if self._hash is None: self._hash=hashBoard(self._board)
+		return self._hash
 
 	def export(self):
 		return exportBoard(self._board)