def __init__(self, node_type, board_state, parent):
self.id = str(uuid.uuid4()) # to make it unique
self.name = self.id[
-3:] # to make it simple during visualizations (for the test purposes)
self.type = node_type # for visualization
self.board = board_state # for MCTS
untriedMoves = HexBoard.getFreeMoves(board_state)
self.untriedMoves = untriedMoves # for MCTS
self.children = [] # for MCTS
if parent is not None:
self.parents = [parent]
self.parent_type = parent.type # for visualization
else:
self.parents = [] # for MCTS
self.parent_type = None # for visualization
self.searched = False
self.value = None
self.visit = 0 # for MCTS UCT-Selection and finding the best move
self.wins = np.inf # for MCTS UCT-Selection
self.loss = np.inf
def search(self, root, itermax, delta, isMaximizer):
"""Return the best moves based on MCTS"""
end_time = datetime.now() + timedelta(seconds=delta)
# now = time.time()
while datetime.now() < end_time and itermax > 0:
# We don't want to change the game, we will turn to it in each iteration
game_state = deepcopy(self.game)
# we will change the root (will be Expanded)
node = root
path = [root.board.tobytes()]
# Select
# node is fully expanded and non-terminal
while (node.untriedMoves == []) and (node.children != []) and (
not game_state.isTerminal()):
node = self.UCTSelectChild(node, isMaximizer)
m = HexBoard.getMove(game_state.board, node.board)
game_state = HexBoard.makeMove(m, game_state)
path.append(node.board.tobytes())
# Expand
if (node.untriedMoves != []) and (not game_state.isTerminal()):
# node is expanded and updated with child
node = self.Expand(node, game_state)
path.append(node.board.tobytes())
# Playouts
for p in range(self.N):
# for each playout we want to return to same game_state
_game = deepcopy(game_state)
while not _game.isTerminal():
move = choice(HexBoard.getFreeMoves(_game.board))
_game = HexBoard.makeMove(move, _game)
# This works just once for a particular node
if node.wins == np.inf:
node.wins = 0
if node.loss == np.inf:
node.loss = 0
if _game.checkWin(_game.maximizer):
node.wins += 1
else:
node.loss += 1
# print(f'Playout {p} is done!')
# Backpropagate
# We are removing current node from path
path.pop()
while node is not None:
# backpropagate works from the current node to the root node
if len(path) > 0:
parent = node.getParent(path.pop())
if parent.wins == np.inf:
parent.wins = 0
parent.loss = 0
parent.wins += node.wins
parent.loss += node.loss
else:
parent = None
node.visit += 1
node = parent
itermax -= 1
# print(f"Iteration completed!: It took {time.time() - now}s")
sortedList = sorted(root.children, key=lambda c: c.visit)
# return the move that was most visited
return HexBoard.getMove(root.board, sortedList[-1].board), root