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# Copyright 2018 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
'''
A board is a NxN numpy array.
A Coordinate is a tuple index into the board.
A Move is a (Coordinate c | None).
A PlayerMove is a (Color, Move) tuple
(0, 0) is considered to be the upper left corner of the board, and (18, 0) is the lower left.
'''
from collections import namedtuple
import copy
import itertools
import numpy as np
import os
import coords
N = int(os.environ.get('BOARD_SIZE', 9))
# Represent a board as a numpy array, with 0 empty, 1 is black, -1 is white.
# This means that swapping colors is as simple as multiplying array by -1.
WHITE, EMPTY, BLACK, FILL, KO, UNKNOWN = range(-1, 5)
# Represents "group not found" in the LibertyTracker object
MISSING_GROUP_ID = -1
ALL_COORDS = [(i, j) for i in range(N) for j in range(N)]
EMPTY_BOARD = np.zeros([N, N], dtype=np.int8)
def _check_bounds(c):
return 0 <= c[0] < N and 0 <= c[1] < N
NEIGHBORS = {(x, y): list(filter(_check_bounds, [
(x+1, y), (x-1, y), (x, y+1), (x, y-1)])) for x, y in ALL_COORDS}
DIAGONALS = {(x, y): list(filter(_check_bounds, [
(x+1, y+1), (x+1, y-1), (x-1, y+1), (x-1, y-1)])) for x, y in ALL_COORDS}
class IllegalMove(Exception):
pass
class PlayerMove(namedtuple('PlayerMove', ['color', 'move'])):
pass
class PositionWithContext(namedtuple('SgfPosition', ['position', 'next_move', 'result'])):
pass
def place_stones(board, color, stones):
for s in stones:
board[s] = color
def replay_position(position, result):
'''
Wrapper for a go.Position which replays its history.
Assumes an empty start position! (i.e. no handicap, and history must be exhaustive.)
Result must be passed in, since a resign cannot be inferred from position
history alone.
for position_w_context in replay_position(position):
print(position_w_context.position)
'''
assert position.n == len(position.recent), "Position history is incomplete"
pos = Position(komi=position.komi)
for player_move in position.recent:
color, next_move = player_move
yield PositionWithContext(pos, next_move, result)
pos = pos.play_move(next_move, color=color)
def find_reached(board, c):
color = board[c]
chain = set([c])
reached = set()
frontier = [c]
while frontier:
current = frontier.pop()
chain.add(current)
for n in NEIGHBORS[current]:
if board[n] == color and not n in chain:
frontier.append(n)
elif board[n] != color:
reached.add(n)
return chain, reached
def is_koish(board, c):
'Check if c is surrounded on all sides by 1 color, and return that color'
if board[c] != EMPTY:
return None
neighbors = {board[n] for n in NEIGHBORS[c]}
if len(neighbors) == 1 and not EMPTY in neighbors:
return list(neighbors)[0]
else:
return None
def is_eyeish(board, c):
'Check if c is an eye, for the purpose of restricting MC rollouts.'
# pass is fine.
if c is None:
return
color = is_koish(board, c)
if color is None:
return None
diagonal_faults = 0
diagonals = DIAGONALS[c]
if len(diagonals) < 4:
diagonal_faults += 1
for d in diagonals:
if not board[d] in (color, EMPTY):
diagonal_faults += 1
if diagonal_faults > 1:
return None
else:
return color
class Group(namedtuple('Group', ['id', 'stones', 'liberties', 'color'])):
'''
stones: a frozenset of Coordinates belonging to this group
liberties: a frozenset of Coordinates that are empty and adjacent to this group.
color: color of this group
'''
def __eq__(self, other):
return self.stones == other.stones and self.liberties == other.liberties and self.color == other.color
class LibertyTracker():
@staticmethod
def from_board(board):
board = np.copy(board)
curr_group_id = 0
lib_tracker = LibertyTracker()
for color in (WHITE, BLACK):
while color in board:
curr_group_id += 1
found_color = np.where(board == color)
coord = found_color[0][0], found_color[1][0]
chain, reached = find_reached(board, coord)
liberties = frozenset(r for r in reached if board[r] == EMPTY)
new_group = Group(curr_group_id, frozenset(
chain), liberties, color)
lib_tracker.groups[curr_group_id] = new_group
for s in chain:
lib_tracker.group_index[s] = curr_group_id
place_stones(board, FILL, chain)
lib_tracker.max_group_id = curr_group_id
liberty_counts = np.zeros([N, N], dtype=np.uint8)
for group in lib_tracker.groups.values():
num_libs = len(group.liberties)
for s in group.stones:
liberty_counts[s] = num_libs
lib_tracker.liberty_cache = liberty_counts
return lib_tracker
def __init__(self, group_index=None, groups=None, liberty_cache=None, max_group_id=1):
# group_index: a NxN numpy array of group_ids. -1 means no group
# groups: a dict of group_id to groups
# liberty_cache: a NxN numpy array of liberty counts
self.group_index = group_index if group_index is not None else - \
np.ones([N, N], dtype=np.int32)
self.groups = groups or {}
self.liberty_cache = liberty_cache if liberty_cache is not None else np.zeros([
N, N], dtype=np.uint8)
self.max_group_id = max_group_id
def __deepcopy__(self, memodict={}):
new_group_index = np.copy(self.group_index)
new_lib_cache = np.copy(self.liberty_cache)
# shallow copy
new_groups = copy.copy(self.groups)
return LibertyTracker(new_group_index, new_groups, liberty_cache=new_lib_cache, max_group_id=self.max_group_id)
def add_stone(self, color, c):
assert self.group_index[c] == MISSING_GROUP_ID
captured_stones = set()
opponent_neighboring_group_ids = set()
friendly_neighboring_group_ids = set()
empty_neighbors = set()
for n in NEIGHBORS[c]:
neighbor_group_id = self.group_index[n]
if neighbor_group_id != MISSING_GROUP_ID:
neighbor_group = self.groups[neighbor_group_id]
if neighbor_group.color == color:
friendly_neighboring_group_ids.add(neighbor_group_id)
else:
opponent_neighboring_group_ids.add(neighbor_group_id)
else:
empty_neighbors.add(n)
new_group = self._merge_from_played(
color, c, empty_neighbors, friendly_neighboring_group_ids)
# new_group becomes stale as _update_liberties and
# _handle_captures are called; must refetch with self.groups[new_group.id]
for group_id in opponent_neighboring_group_ids:
neighbor_group = self.groups[group_id]
if len(neighbor_group.liberties) == 1:
captured = self._capture_group(group_id)
captured_stones.update(captured)
else:
self._update_liberties(group_id, remove={c})
self._handle_captures(captured_stones)
# suicide is illegal
if len(self.groups[new_group.id].liberties) == 0:
raise IllegalMove("Move at {} would commit suicide!\n".format(c))
return captured_stones
def _merge_from_played(self, color, played, libs, other_group_ids):
stones = {played}
liberties = set(libs)
for group_id in other_group_ids:
other = self.groups.pop(group_id)
stones.update(other.stones)
liberties.update(other.liberties)
if other_group_ids:
liberties.remove(played)
assert stones.isdisjoint(liberties)
self.max_group_id += 1
result = Group(
self.max_group_id,
frozenset(stones),
frozenset(liberties),
color)
self.groups[result.id] = result
for s in result.stones:
self.group_index[s] = result.id
self.liberty_cache[s] = len(result.liberties)
return result
def _capture_group(self, group_id):
dead_group = self.groups.pop(group_id)
for s in dead_group.stones:
self.group_index[s] = MISSING_GROUP_ID
self.liberty_cache[s] = 0
return dead_group.stones
def _update_liberties(self, group_id, add=set(), remove=set()):
group = self.groups[group_id]
new_libs = (group.liberties | add) - remove
self.groups[group_id] = Group(
group_id, group.stones, new_libs, group.color)
new_lib_count = len(new_libs)
for s in self.groups[group_id].stones:
self.liberty_cache[s] = new_lib_count
def _handle_captures(self, captured_stones):
for s in captured_stones:
for n in NEIGHBORS[s]:
group_id = self.group_index[n]
if group_id != MISSING_GROUP_ID:
self._update_liberties(group_id, add={s})
class Position():
def __init__(self, board=None, n=0, komi=7.5, caps=(0, 0),
lib_tracker=None, ko=None, recent=tuple(),
board_deltas=None, to_play=BLACK):
'''
board: a numpy array
n: an int representing moves played so far
komi: a float, representing points given to the second player.
caps: a (int, int) tuple of captures for B, W.
lib_tracker: a LibertyTracker object
ko: a Move
recent: a tuple of PlayerMoves, such that recent[-1] is the last move.
board_deltas: a np.array of shape (n, go.N, go.N) representing changes
made to the board at each move (played move and captures).
Should satisfy next_pos.board - next_pos.board_deltas[0] == pos.board
to_play: BLACK or WHITE
'''
assert type(recent) is tuple
self.board = board if board is not None else np.copy(EMPTY_BOARD)
self.n = n # With a full history, self.n == len(self.recent) == num moves played
self.komi = komi
self.caps = caps
self.lib_tracker = lib_tracker or LibertyTracker.from_board(self.board)
self.ko = ko
self.recent = recent
self.board_deltas = board_deltas if board_deltas is not None else np.zeros([
0, N, N], dtype=np.int8)
self.to_play = to_play
def __deepcopy__(self, memodict={}):
new_board = np.copy(self.board)
new_lib_tracker = copy.deepcopy(self.lib_tracker)
return Position(new_board, self.n, self.komi, self.caps, new_lib_tracker, self.ko, self.recent, self.board_deltas, self.to_play)
def __str__(self, colors=True):
if colors:
pretty_print_map = {
WHITE: '\x1b[0;31;47mO',
EMPTY: '\x1b[0;31;43m.',
BLACK: '\x1b[0;31;40mX',
FILL: '#',
KO: '*',
}
else:
pretty_print_map = {
WHITE: 'O',
EMPTY: '.',
BLACK: 'X',
FILL: '#',
KO: '*',
}
board = np.copy(self.board)
captures = self.caps
if self.ko is not None:
place_stones(board, KO, [self.ko])
raw_board_contents = []
for i in range(N):
row = []
for j in range(N):
appended = '<' if (self.recent and (i, j) ==
self.recent[-1].move) else ' '
row.append(pretty_print_map[board[i, j]] + appended)
if colors:
row.append('\x1b[0m')
raw_board_contents.append(''.join(row))
row_labels = ['%2d ' % i for i in range(N, 0, -1)]
annotated_board_contents = [''.join(r) for r in zip(
row_labels, raw_board_contents, row_labels)]
header_footer_rows = [
' ' + ' '.join('ABCDEFGHJKLMNOPQRST'[:N]) + ' ']
annotated_board = '\n'.join(itertools.chain(
header_footer_rows, annotated_board_contents, header_footer_rows))
details = "\nMove: {}. Captures X: {} O: {}\n".format(
self.n, *captures)
return annotated_board + details
def is_move_suicidal(self, move):
potential_libs = set()
for n in NEIGHBORS[move]:
neighbor_group_id = self.lib_tracker.group_index[n]
if neighbor_group_id == MISSING_GROUP_ID:
# at least one liberty after playing here, so not a suicide
return False
neighbor_group = self.lib_tracker.groups[neighbor_group_id]
if neighbor_group.color == self.to_play:
potential_libs |= neighbor_group.liberties
elif len(neighbor_group.liberties) == 1:
# would capture an opponent group if they only had one lib.
return False
# it's possible to suicide by connecting several friendly groups
# each of which had one liberty.
potential_libs -= set([move])
return not potential_libs
def is_move_legal(self, move):
'Checks that a move is on an empty space, not on ko, and not suicide'
if move is None:
return True
if self.board[move] != EMPTY:
return False
if move == self.ko:
return False
if self.is_move_suicidal(move):
return False
return True
def all_legal_moves(self):
'Returns a np.array of size go.N**2 + 1, with 1 = legal, 0 = illegal'
# by default, every move is legal
legal_moves = np.ones([N, N], dtype=np.int8)
# ...unless there is already a stone there
legal_moves[self.board != EMPTY] = 0
# calculate which spots have 4 stones next to them
# padding is because the edge always counts as a lost liberty.
adjacent = np.ones([N+2, N+2], dtype=np.int8)
adjacent[1:-1, 1:-1] = np.abs(self.board)
num_adjacent_stones = (adjacent[:-2, 1:-1] + adjacent[1:-1, :-2] +
adjacent[2:, 1:-1] + adjacent[1:-1, 2:])
# Surrounded spots are those that are empty and have 4 adjacent stones.
surrounded_spots = np.multiply(
(self.board == EMPTY),
(num_adjacent_stones == 4))
# Such spots are possibly illegal, unless they are capturing something.
# Iterate over and manually check each spot.
for coord in np.transpose(np.nonzero(surrounded_spots)):
if self.is_move_suicidal(tuple(coord)):
legal_moves[tuple(coord)] = 0
# ...and retaking ko is always illegal
if self.ko is not None:
legal_moves[self.ko] = 0
# and pass is always legal
return np.concatenate([legal_moves.ravel(), [1]])
def pass_move(self, mutate=False):
pos = self if mutate else copy.deepcopy(self)
pos.n += 1
pos.recent += (PlayerMove(pos.to_play, None),)
pos.board_deltas = np.concatenate((
np.zeros([1, N, N], dtype=np.int8),
pos.board_deltas[:6]))
pos.to_play *= -1
pos.ko = None
return pos
def flip_playerturn(self, mutate=False):
pos = self if mutate else copy.deepcopy(self)
pos.ko = None
pos.to_play *= -1
return pos
def get_liberties(self):
return self.lib_tracker.liberty_cache
def play_move(self, c, color=None, mutate=False):
# Obeys CGOS Rules of Play. In short:
# No suicides
# Chinese/area scoring
# Positional superko (this is very crudely approximate at the moment.)
if color is None:
color = self.to_play
pos = self if mutate else copy.deepcopy(self)
if c is None:
pos = pos.pass_move(mutate=mutate)
return pos
if not self.is_move_legal(c):
raise IllegalMove("{} move at {} is illegal: \n{}".format(
"Black" if self.to_play == BLACK else "White",
coords.to_kgs(c), self))
potential_ko = is_koish(self.board, c)
place_stones(pos.board, color, [c])
captured_stones = pos.lib_tracker.add_stone(color, c)
place_stones(pos.board, EMPTY, captured_stones)
opp_color = color * -1
new_board_delta = np.zeros([N, N], dtype=np.int8)
new_board_delta[c] = color
place_stones(new_board_delta, color, captured_stones)
if len(captured_stones) == 1 and potential_ko == opp_color:
new_ko = list(captured_stones)[0]
else:
new_ko = None
if pos.to_play == BLACK:
new_caps = (pos.caps[0] + len(captured_stones), pos.caps[1])
else:
new_caps = (pos.caps[0], pos.caps[1] + len(captured_stones))
pos.n += 1
pos.caps = new_caps
pos.ko = new_ko
pos.recent += (PlayerMove(color, c),)
# keep a rolling history of last 7 deltas - that's all we'll need to
# extract the last 8 board states.
pos.board_deltas = np.concatenate((
new_board_delta.reshape(1, N, N),
pos.board_deltas[:6]))
pos.to_play *= -1
return pos
def is_game_over(self):
return (len(self.recent) >= 2
and self.recent[-1].move is None
and self.recent[-2].move is None)
def score(self):
'Return score from B perspective. If W is winning, score is negative.'
working_board = np.copy(self.board)
while EMPTY in working_board:
unassigned_spaces = np.where(working_board == EMPTY)
c = unassigned_spaces[0][0], unassigned_spaces[1][0]
territory, borders = find_reached(working_board, c)
border_colors = set(working_board[b] for b in borders)
X_border = BLACK in border_colors
O_border = WHITE in border_colors
if X_border and not O_border:
territory_color = BLACK
elif O_border and not X_border:
territory_color = WHITE
else:
territory_color = UNKNOWN # dame, or seki
place_stones(working_board, territory_color, territory)
return np.count_nonzero(working_board == BLACK) - np.count_nonzero(working_board == WHITE) - self.komi
def result(self):
score = self.score()
if score > 0:
return 1
elif score < 0:
return -1
else:
return 0
def result_string(self):
score = self.score()
if score > 0:
return 'B+' + '%.1f' % score
elif score < 0:
return 'W+' + '%.1f' % abs(score)
else:
return 'DRAW'