def min_value(board, player, alpha, beta, depth):
#if terminal state then return utility of leaf node
if is_terminal(board):
u, alp, bet = utility(board, player)
return u, alp, bet, -1
#if reached depth limit then return utility 0
#that is, consider it a draw
if depth == 0:
u = 0
return u, -1, -1, -1
v = math.inf
ret_mov = -1
a, b = alpha, beta
#get list of possible moves and shuffle it
legal_moves = shuffle(board.generate_moves())
#find a move with minimum utility
for mov in legal_moves:
board.make_move(mov)
min_val, a1, b1, m = max_value(board, player, a, b, depth - 1)
if min_val < v:
v, ret_mov = min_val, mov
board.unmake_last_move()
if v <= a:
b = v
return v, a, b, ret_mov
b = min(b, v)
return v, a, b, ret_mov
def min_value(self, board, player, alpha, beta, depth): #check if termial state if self.is_terminal(board): u, alp, bet = self.utility(board, player) return u, alp, bet, -1 #check if depth limit is reached if depth == 0: u = 0 return u, -1, -1, -1 v = math.inf ret_mov = -1 a, b = alpha, beta #Get list of all possible moves legal_moves = self.shuffle(board.generate_moves()) #Search for a move with minimum utility for mov in legal_moves: board.make_move(mov) min_val, a1, b1, m = self.max_value(board, player, a, b, depth - 1) if min_val < v: v, ret_mov = min_val, mov board.unmake_last_move() if v <= a: b = v return v, a, b, ret_mov b = min(b, v) return v, a, b, ret_mov
def perft(board, depth):
#Get all possible moves
legal_moves = board.generate_moves()
#Check if last move caused win
lmv = board.last_move_won()
#if last move won the game or no valid move available
if lmv or len(legal_moves) <= 0:
#Unmake last move made by calling function
board.unmake_last_move()
return 1
#if last move did not win the game and valid moves are available,
#but depth limit is reached
if depth == 1:
board.unmake_last_move()
return len(legal_moves)
#initialize variable to count leaf nodes visited so far
count = 0
#For all legal moves from current state, call perft recursively
for i in legal_moves:
board.make_move(i)
count += perft(board, depth - 1)
#Unmake last move made by calling function before returning count
board.unmake_last_move()
#return number of leaf nodes visited
return count
pass