在Alpha Beta剪枝算法中,negamax是一种常用的搜索算法,可以解决零和博弈问题。然而,有时候Alpha Beta剪枝可能会导致negamax选择了糟糕的着法。下面是一个包含代码示例的解决方法:
transposition_table = {}
def negamax_alpha_beta(board, alpha, beta, depth):
if depth == 0 or board.is_game_over():
return evaluate(board)
key = board.get_key() # 获取局面的唯一标识
if key in transposition_table:
return transposition_table[key]
best_value = float('-inf')
for move in board.get_legal_moves():
board.make_move(move)
value = -negamax_alpha_beta(board, -beta, -alpha, depth - 1)
board.undo_move(move)
best_value = max(best_value, value)
alpha = max(alpha, value)
if alpha >= beta:
break
transposition_table[key] = best_value
return best_value
history_table = {}
def negamax_alpha_beta(board, alpha, beta, depth):
if depth == 0 or board.is_game_over():
return evaluate(board)
key = board.get_key() # 获取局面的唯一标识
if key in transposition_table:
return transposition_table[key]
best_value = float('-inf')
for move in board.get_legal_moves():
board.make_move(move)
value = -negamax_alpha_beta(board, -beta, -alpha, depth - 1)
board.undo_move(move)
best_value = max(best_value, value)
alpha = max(alpha, value)
if alpha >= beta:
break
transposition_table[key] = best_value
# 更新历史启发表
if move in history_table:
history_table[move] += depth
else:
history_table[move] = depth
return best_value
通过添加置换表和历史启发,可以提高Alpha Beta剪枝算法的效率和搜索质量,减少选择糟糕着法的可能性。值得注意的是,具体实现还需要结合具体的编程语言和游戏规则进行调整和优化。