def min_max_search(self, game: ChessGame, depth: int,
maximize_color: Color, parent_max: int, parent_min: int,
first_move: bool):
"""
Use minmax search with alpha beta prune to calculate the next best move
"""
board = game.board
game_status = game.check_game_status()
if not depth or game_status != 'Continue':
if (game_status == "BlackLoss" and maximize_color
== Color.WHITE) or (game_status == "WhiteLoss"
and maximize_color == Color.BLACK):
return math.inf
ret = self.game_evaluation(maximize_color)
return ret
else:
turn = game.turn
if turn == maximize_color:
max_score = parent_min
for row in range(8):
for col in range(8):
piece = board[row][col]
if piece.color == turn:
moves = piece.get_checked_moves()["moves"]
src = (row, col)
for tar in moves:
game.update(src, tar, 'Queen', is_ai=True)
child_score = self.min_max_search(
game, depth - 1, maximize_color,
parent_max, max_score, False)
game.undo()
if child_score > max_score:
if first_move:
self.best_move = [src, tar]
max_score = child_score
if max_score > parent_max:
return parent_max
return max_score
else:
min_score = parent_max
for row in range(8):
for col in range(8):
piece = board[row][col]
if piece.color == turn:
moves = piece.get_checked_moves()["moves"]
src = (row, col)
for tar in moves:
game.update(src, tar, 'Queen', is_ai=True)
child_score = self.min_max_search(
game, depth - 1, maximize_color, min_score,
parent_min, False)
game.undo()
if child_score < min_score:
if first_move:
self.best_move = [src, tar]
min_score = child_score
if min_score < parent_min:
return parent_min
return min_score
class TestUpDate(unittest.TestCase):
def setUp(self) -> None:
self.game = ChessGame(fen="start")
def test_update_start_move_black(self):
random_num_1 = random.randint(0, 7)
random_num_2 = random.randint(0, 7)
for row in range(6, 8):
for col in range(8):
self.assertFalse(self.game.update((row, col),
(random_num_1, random_num_2), "Queen"))
def test_update_ended_without_continue(self):
self.game.half_move_clock = 49
self.game.full_move_clock = 100
self.game.count = 200
self.game.en_passant_target_notation = "-"
self.game.castling_notation = "-"
self.game.turn = Color.WHITE
empty = Empty(None, Color.EMPTY, -1, -1)
for row in range(8):
for col in range(8):
self.game.board[row][col] = empty
self.game.board[7][3] = King(self.game, Color.BLACK, 7, 3)
self.game.board[0][5] = King(self.game, Color.WHITE, 0, 5)
self.assertTrue(self.game.update((0, 5), (0, 4), "Queen"))
self.assertFalse(self.game.update((7, 3), (7, 2), "Queen"))
def test_update_move_pawn(self):
for col in range(8):
self.assertTrue(self.game.update((1, col), (3, col), "Queen"))
self.assertEqual(self.game.en_passant_target_notation, chr(ord('a') + col) + "3")
self.game.turn = Color.WHITE
for col in range(8):
self.assertTrue(self.game.update((3, col), (4, col), "Queen"))
self.game.turn = Color.WHITE
def test_update_move_white(self):
random_num_1 = random.randint(0, 7)
random_num_2 = random.randint(0, 7)
self.assertFalse(self.game.update((0, 0), (random_num_1, random_num_2), "Queen"))
self.game.turn = Color.WHITE
self.assertTrue(self.game.update((0, 1), (2, 0), "Queen"))
self.game.turn = Color.WHITE
self.assertTrue(self.game.update((2, 0), (0, 1), "Queen"))
self.game.turn = Color.WHITE
self.assertFalse(self.game.update((0, 2), (random_num_1, random_num_2), "Queen"))
self.game.turn = Color.WHITE
self.assertFalse(self.game.update((0, 3), (random_num_1, random_num_2), "Queen"))
self.game.turn = Color.WHITE
self.assertFalse(self.game.update((0, 4), (random_num_1, random_num_2), "Queen"))
self.game.turn = Color.WHITE
self.assertFalse(self.game.update((0, 5), (random_num_1, random_num_2), "Queen"))
self.game.turn = Color.WHITE
self.assertTrue(self.game.update((0, 6), (2, 7), "Queen"))
self.game.turn = Color.WHITE
self.assertTrue(self.game.update((2, 7), (0, 6), "Queen"))
self.game.turn = Color.WHITE
self.assertFalse(self.game.update((0, 7), (random_num_1, random_num_2), "Queen"))
def test_update_kings_coordinate(self):
self.game.update((1, 4), (3, 4), "Queen")
self.game.update((6, 4), (4, 4), "Queen")
self.game.update((0, 4), (1, 4), "Queen")
self.game.update((7, 4), (6, 4), "Queen")
self.assertEqual(self.game.kings_coordinate[0], (1, 4))
self.assertEqual(self.game.kings_coordinate[1], (6, 4))
def test_update_history(self):
self.game.update((1, 0), (3, 0), "Queen")
self.game.update((6, 0), (4, 0), "Queen")
self.game.update((0, 0), (2, 0), "Queen")
self.game.update((7, 0), (5, 0), "Queen")
self.game.update((1, 7), (3, 7), "Queen")
self.game.update((6, 7), (4, 7), "Queen")
self.game.update((0, 7), (2, 7), "Queen")
self.game.update((7, 7), (5, 7), "Queen")
self.assertEqual(self.game.history[0]["fen"], "rnbqkbnr/pppppppp/8/8/P7/8/1PPPPPPP/RNBQKBNR b KQkq a3 0 1")
self.assertEqual(self.game.history[0]["movement"], {"src": "a2", "tar": "a4"})
self.assertEqual(self.game.history[1]["fen"], "rnbqkbnr/1ppppppp/8/p7/P7/8/1PPPPPPP/RNBQKBNR w KQkq a6 0 2")
self.assertEqual(self.game.history[1]["movement"], {"src": "a7", "tar": "a5"})
self.assertEqual(self.game.history[2]["fen"], "rnbqkbnr/1ppppppp/8/p7/P7/R7/1PPPPPPP/1NBQKBNR b Kkq - 1 2")
self.assertEqual(self.game.history[2]["movement"], {"src": "a1", "tar": "a3"})
self.assertEqual(self.game.history[3]["fen"], "1nbqkbnr/1ppppppp/r7/p7/P7/R7/1PPPPPPP/1NBQKBNR w Kk - 2 3")
self.assertEqual(self.game.history[3]["movement"], {"src": "a8", "tar": "a6"})
self.assertEqual(self.game.history[4]["fen"], "1nbqkbnr/1ppppppp/r7/p7/P6P/R7/1PPPPPP1/1NBQKBNR b Kk h3 0 3")
self.assertEqual(self.game.history[4]["movement"], {"src": "h2", "tar": "h4"})
self.assertEqual(self.game.history[5]["fen"], "1nbqkbnr/1pppppp1/r7/p6p/P6P/R7/1PPPPPP1/1NBQKBNR w Kk h6 0 4")
self.assertEqual(self.game.history[5]["movement"], {"src": "h7", "tar": "h5"})
self.assertEqual(self.game.history[6]["fen"], "1nbqkbnr/1pppppp1/r7/p6p/P6P/R6R/1PPPPPP1/1NBQKBN1 b k - 1 4")
self.assertEqual(self.game.history[6]["movement"], {"src": "h1", "tar": "h3"})
self.assertEqual(self.game.history[7]["fen"], "1nbqkbn1/1pppppp1/r6r/p6p/P6P/R6R/1PPPPPP1/1NBQKBN1 w - - 2 5")
self.assertEqual(self.game.history[7]["movement"], {"src": "h8", "tar": "h6"})