def rook_position_bonus(self, rook, side):
position = self.position
pawns_us = position.pieces[Pt.piece(Pt.P, side)]
pawns_them = position.pieces[Pt.piece(Pt.P, side ^ 1)]
bonus = 0
fill = south_attack(rook, FULL_BOARD) | north_attack(rook, FULL_BOARD)
if pawns_us & fill and not pawns_them & fill:
# rook supporting passed pawn bonus
bonus += 5
if not pawns_us & fill:
if pawns_them & fill:
# semi-open file
bonus += 20
else:
# open file
bonus += 45
rank_fill = east_attack(rook, FULL_BOARD) | west_attack(
rook, FULL_BOARD)
bonus += count_bits(rank_fill & pawns_them) * 8
# connected rooks, gets bonused once for each rook so halving it
if self.piece_attacks[Pt.piece(Pt.R, side)] & rook:
bonus += 15
return bonus
def set_position(self, position):
self.position = position
self.piece_attacks = [0] * 13
self.all_attacks = [0] * 2
self.double_attacks = [0] * 2
occ = self.position.occupied[Side.WHITE] | self.position.occupied[
Side.BLACK]
for side in [Side.WHITE, Side.BLACK]:
pinned = self.position.pinned[Pt.piece(Pt.K, side)]
king_us = self.position.pieces[Pt.piece(Pt.K, side)]
for sq in range(64):
pt = self.position.squares[sq]
if pt == Pt.NULL: continue
pt_side = Pt.get_side(pt)
bt = Pt.base_type(pt)
if pt_side == side:
sq_bb = 1 << sq
if bt == Pt.P:
attacks = pawn_attack(sq_bb, pt_side)
else:
attacks = piece_attack(bt, sq_bb, occ)
if pinned & sq_bb:
attacks &= line_sqs(bit_position(king_us), sq)
self.piece_attacks[pt] |= attacks
self.double_attacks[
side] |= self.all_attacks[side] & attacks
self.all_attacks[side] |= attacks
return self
def unprotected_penalty(self, side, pins):
position = self.position
us = position.occupied[side]
them = position.occupied[side ^ 1]
free = (us | them) ^ FULL_BOARD
us_attacked = attacked_pieces(position, side)
penalty = 0
for pt in Pt.piece_types(side=side):
num = count_bits(position.pieces[pt] & us_attacked)
penalty += num * 10
defended = us_attacked & position.pieces[pt] & self.all_attacks[
side]
for defended_piece in iterate_pieces(defended):
if defended_piece & self.piece_attacks[Pt.piece(Pt.P,
side=side)]:
# defended by pawn
penalty -= MG_PIECES[Pt.P] * .25
else:
penalty -= MG_PIECES[Pt.P] * .125
if Pt.base_type(pt) == Pt.P:
continue
# possible to get attack from pawn. Penalty regardless if defended
for p in iterate_pieces(position.pieces[pt]):
if side == Side.WHITE:
pawn_attack_sqs = (north_east(p) | north_west(p)) & free
else:
pawn_attack_sqs = (south_east(p) | south_west(p)) & free
for pawn_attack_sq in iterate_pieces(pawn_attack_sqs):
if side == Side.WHITE:
pawn_from_sqs = (pawn_attack_sq << 8)
if pawn_attack_sq & RANKS[4]:
pawn_from_sqs |= (pawn_attack_sq << 16)
pawn_from_sqs &= free << 8
else:
pawn_from_sqs = (pawn_attack_sq >> 8)
if pawn_attack_sq & RANKS[3]:
pawn_from_sqs |= (pawn_attack_sq >> 16)
pawn_from_sqs &= free >> 8
pawn_from_sqs &= position.pieces[Pt.piece(Pt.P,
side=side ^ 1)]
if pawn_from_sqs:
# penalty += (MG_PIECES[Pt.base_type(pt)] / 8) - 20
# more penalty if the piece is pinned
if p in pins:
penalty += (MG_PIECES[Pt.base_type(pt)] / 3) - 20
# more penalty if the pawn is supported on the attack square
if self.all_attacks[side ^ 1] & pawn_attack_sq or \
self.all_attacks[side] & pawn_attack_sq == 0:
penalty += (MG_PIECES[Pt.base_type(pt)] /
3) - 20
return int(penalty * 1 / 4)
def safe_attacks(self, bt, stm):
# if attacked by lower weight piece, it doesn't count
lower_wts = (pt for pt in [Pt.P, Pt.N, Pt.B, Pt.R, Pt.Q] if pt < bt)
opp_attacks = 0
for piece_type in lower_wts:
opp_pt = Pt.piece(piece_type, stm ^ 1)
opp_attacks |= self.piece_attacks[opp_pt]
attacks = self.piece_attacks[Pt.piece(bt, stm)]
attacks &= invert(opp_attacks)
# attacks &= invert(self.position.occupied[stm])
return attacks
def mobility(self, bt, stm):
# attacks count, safe attacks count
pos = self.pos
pt = Pt.piece(bt, stm)
attacks = self.base_evaluator.piece_attacks[pt]
safe_attacks = self.base_evaluator.safe_attacks(bt, stm)
return [count_bits(attacks) / 16, count_bits(safe_attacks) / 16]
def bad_bishop_penalty(self, minor, side):
position = self.position
color = minor & DARK_SQUARES
pawns_us = position.pieces[Pt.piece(Pt.P, side)]
if color == 0: pawns = pawns_us & WHITE_SQUARES
else: pawns = pawns_us & DARK_SQUARES
return count_bits(pawns) * 8
def get_pairs(self, bt, side):
# exist 1, exist 2, 1 coords, 2 coords
pos = self.pos
pt = Pt.piece(bt, side)
features = []
b = pos.pieces[pt]
count = count_bits(b)
if count == 1:
if b & LEFT_SIDE:
features.extend([1, 0])
features.extend(self.sq(b, side))
features.extend(self.sq(0, side))
else:
features.extend([0, 1])
features.extend(self.sq(0, side))
features.extend(self.sq(b, side))
elif count >= 2:
features.extend([1, 1])
features.extend(self.sq(ls1b(b), side))
b = reset_ls1b(b)
features.extend(self.sq(ls1b(b), side))
else:
features.extend([0, 0])
features.extend(self.sq(0, side))
features.extend(self.sq(0, side))
return features
def queens(self, side):
# coords, count
queen_t = Pt.piece(Pt.Q, side)
queens = self.pos.pieces[queen_t]
f = self.sq(ls1b(queens), side)
f.extend([count_bits(queens)])
return f
def BRN_pairs(self, bt, side):
# B R and N pairs
# ordered exist flags, coords, count
pt = Pt.piece(bt, side)
b = self.pos.pieces[pt]
features = self.get_pairs(bt, side)
features.extend([count_bits(b)])
return features
def all_pawn_attack_potentials(self, side):
"""Return attack potentials of pawns of side `side`"""
position = self.position
pawns = position.pieces[Pt.piece(Pt.P, side)]
potential = 0
for pawn in iterate_pieces(pawns):
potential |= self.pawn_attack_potential(pawn, side)
return potential
def lowest_attacker(pos, square, side=None, highest_attacker=Pt.NULL):
"""Finds lowest piece of `side` attacking a square. `highest_attacker` means
skip attacks of higher or equal value of given pt"""
position = pos
side = position.side_to_move() if side is None else side
highest_attacker = Pt.K + 1 if highest_attacker == Pt.NULL else highest_attacker
# pawn
if Pt.P < highest_attacker:
possible_from_squares = shift_sw(square, side) | shift_se(square, side)
piece_type = Pt.piece(Pt.P, side)
attackers = position.pieces[piece_type] & possible_from_squares
if attackers:
return piece_type, ls1b(attackers)
# knight
if Pt.N < highest_attacker:
piece_type = Pt.piece(Pt.N, side)
possible_from_squares = knight_attack(square)
attackers = position.pieces[piece_type] & possible_from_squares
if attackers:
return piece_type, ls1b(attackers)
# sliders
for piece_type in [Pt.B, Pt.R]:
if piece_type < highest_attacker:
pt = Pt.piece(piece_type, side)
occ = position.occupied[side] | position.occupied[side ^ 1]
attacks = piece_attack(piece_type, square, occ)
b = attacks & position.pieces[pt]
if b: return pt, ls1b(b)
if Pt.Q < highest_attacker:
qn = Pt.piece(Pt.Q, side)
b = attacks & position.pieces[qn]
if b: return qn, ls1b(b)
# king
if Pt.K < highest_attacker:
piece_type = Pt.piece(Pt.K, side)
possible_from_squares = king_attack(square)
attackers = position.pieces[piece_type] & possible_from_squares
if attackers:
return piece_type, attackers
def pawns_evaluation(self, side):
position = self.position
us, them = side, side ^ 1
pawns_us = position.pieces[Pt.piece(Pt.P, us)]
pawns_them = position.pieces[Pt.piece(Pt.P, them)]
score = 0
files = set(get_file(p) for p in iterate_pieces(pawns_us))
protected = (shift_ne(pawns_us, us)
| shift_nw(pawns_us, us)) & pawns_us
phalanx = (shift_east(pawns_us, us)
| shift_west(pawns_us, us)) & pawns_us
connected = protected | phalanx
isolated = 0
opposed = 0
for f in files:
fl = 1 if f == 0 else f - 1
fr = 6 if f == 7 else f + 1
if not (FILES[fl] & pawns_us) | (FILES[fr] & pawns_us):
isolated |= FILES[f] & pawns_us
if FILES[f] & pawns_them:
opposed |= FILES[f] & pawns_us
doubled = 0
for f in files:
doubled |= reset_ls1b(pawns_us & FILES[f])
score -= count_bits(isolated & opposed) * 30
score -= count_bits(isolated ^ opposed) * 40
for c in iterate_pieces(connected):
val = 2**get_rank(c, us)
if c & phalanx:
val += val - (2**(get_rank(c, us) - 1))
if c & opposed:
val >> 1
score += val
score -= count_bits(doubled) * 25
# TODO: add backward pawns
# don't recount these if backward
score -= count_bits(pawns_us ^ protected) * 15
return score
def king_safety_squares(self, side):
"""squares surrounding king plus one rank further"""
position = self.position
king_sq = position.pieces[Pt.piece(Pt.K, side)]
attacks = king_attack(king_sq)
if side == Side.WHITE:
attacks |= attacks << 8
else:
attacks |= attacks >> 8
return attacks
def pawn_exists(self, side):
# Double pawns disappear but hopefully the counts make up for it
# I'd think this is better than filling in empty slots
pos = self.pos
pt = Pt.piece(Pt.P, side)
features = [0] * 8
pawns = pos.pieces[pt]
for p in iterate_pieces(pawns):
features[get_file(p)] = 1
return features
def mobility(self, side, PINNED):
"""Bonus for legal moves not attacked by lower weight piece. Pinned pieces
have restricted mobility"""
position = self.position
mobility = 0
piece_types = [Pt.P, Pt.N, Pt.B, Pt.R, Pt.Q]
pinned_piece_types = []
if PINNED[Pt.piece(Pt.K, side)]:
pinned_piece_types = [
position.squares[bit_position(p)]
for p in iterate_pieces(PINNED[Pt.piece(Pt.K, side)])
]
for base_pt in piece_types:
pt = Pt.piece(base_pt, side)
safe_attacks = self.safe_attacks(base_pt, side)
mobility_factor = base_pt if base_pt < Pt.K else 1
mobility += count_bits(safe_attacks) * mobility_factor
return mobility
def lowest_attacker(self, side):
f = []
for sqind in range(64):
sq = 1 << sqind
lowest = Pt.NULL
pieces = [Pt.P, Pt.N, Pt.B, Pt.R, Pt.Q, Pt.K]
if self.base_evaluator.all_attacks[side]:
lowest = pieces[-1] + 1
for bt in pieces:
pt = Pt.piece(bt, side)
if self.base_evaluator.piece_attacks[pt] & sq:
lowest = bt
break
f.append((7 - lowest) / 6) # lower pt gives higher "score"
return f
def minor_outpost_bonus(self, minor, side, potentials):
position = self.position
if minor == 0: return 0
us = side
them = side ^ 1
potential_them = potentials[them]
potential_us = potentials[us]
base_type = Pt.base_type(minor)
pawns_us = position.pieces[Pt.piece(Pt.P, side)]
outpost_ranks = [
RANKS[3] | RANKS[4] | RANKS[5], RANKS[2] | RANKS[3] | RANKS[4]
]
outpost_squares = outpost_ranks[side] & invert(
potential_them) & potential_us
if outpost_squares:
# reachable squares
if base_type == Pt.N: bonus = 12
else: bonus = 7
# successfully outposted
if minor & outpost_squares: bonus += 35
return bonus
return 0
def get_feats(pos):
krights = 0
if preserved_kingside_castle_rights(pos.position_flags, Side.W):
krights |= G1 | F1
if preserved_queenside_castle_rights(pos.position_flags, Side.W):
krights |= C1 | D1
if preserved_kingside_castle_rights(pos.position_flags, Side.B):
krights |= G8 | F8
if preserved_kingside_castle_rights(pos.position_flags, Side.B):
krights |= C8 | D8
krights_plane = bitfield(krights)
stm_plane = np.zeros(64).reshape(
(8, 8)) if pos.side_to_move() == S.W else np.ones(64).reshape((8, 8))
wp_plane = bitfield(pos.pieces[Pt.piece(Pt.P, S.W)])
bp_plane = bitfield(pos.pieces[Pt.piece(Pt.P, S.B)])
wn_plane = bitfield(pos.pieces[Pt.piece(Pt.N, S.W)])
bn_plane = bitfield(pos.pieces[Pt.piece(Pt.N, S.B)])
wb_plane = bitfield(pos.pieces[Pt.piece(Pt.B, S.W)])
bb_plane = bitfield(pos.pieces[Pt.piece(Pt.B, S.B)])
wr_plane = bitfield(pos.pieces[Pt.piece(Pt.R, S.W)])
br_plane = bitfield(pos.pieces[Pt.piece(Pt.R, S.B)])
wq_plane = bitfield(pos.pieces[Pt.piece(Pt.Q, S.W)])
bq_plane = bitfield(pos.pieces[Pt.piece(Pt.Q, S.B)])
wk_plane = bitfield(pos.pieces[Pt.piece(Pt.K, S.W)])
bk_plane = bitfield(pos.pieces[Pt.piece(Pt.K, S.B)])
return np.stack([
krights_plane, stm_plane, wp_plane, bp_plane, wn_plane, bn_plane,
wb_plane, bb_plane, wr_plane, br_plane, wq_plane, bq_plane, wk_plane,
bk_plane
],
axis=-1) # 8x8x14
def king_zone_attack_bonus(self, king_zones, side):
"""Attackers of enemy king zone, each weighted by piece weight, including
xray attacks."""
position = self.position
us = side
them = side ^ 1
their_king = position.pieces[Pt.piece(Pt.K, them)]
bonus = 0
if them == Side.WHITE:
camp = (RANKS[0] | RANKS[1] | RANKS[2] | RANKS[3] | RANKS[4])
else:
camp = (RANKS[3] | RANKS[4] | RANKS[5] | RANKS[6] | RANKS[7])
king_file = get_file(their_king)
if 0 <= king_file <= 2: files = range(0, 4)
elif 3 <= king_file <= 4: files = range(2, 6)
else: files = range(4, 8)
flank = 0
for f in files:
flank |= FILES[f]
flank &= camp
# defended by their king only
king_defended = self.piece_attacks[Pt.piece(Pt.K, them)] & invert(
self.double_attacks[them])
bonus += count_bits(king_defended) * 8
# attacks directly around their king
bonus += count_bits(self.all_attacks[us] & king_attack(their_king)) * 4
# bonus for the more coordinated attacks in the king zone
bonus += count_bits(self.double_attacks[us] & king_zones[them]) * 4
# king flank huddling bonus
bonus += count_bits(self.all_attacks[us] & flank) * 4
# extra bonus for double attacks in flank, not defended by pawn
bonus += count_bits(
self.all_attacks[us] & flank & self.double_attacks[us]
& invert(self.piece_attacks[Pt.piece(Pt.P, them)])) * 7
# safe positions to check from
safe = invert(self.all_attacks[them] | position.occupied[us])
# safe positions to check from b/c protected by their queen only
safe2 = safe | self.piece_attacks[Pt.piece(Pt.Q, them)] & invert(
self.double_attacks[them]) & self.double_attacks[us]
bishop_rays = pseudo_attacks(Pt.B, bit_position(their_king))
rook_rays = pseudo_attacks(Pt.R, bit_position(their_king))
# potential safe knight check squares
safe_n_checks = knight_attack(their_king) & safe2 & self.piece_attacks[
Pt.piece(Pt.N, us)]
if safe_n_checks: bonus += 25
# potential safe bishop check squares
safe_b_checks = bishop_rays & safe2 & self.piece_attacks[Pt.piece(
Pt.B, them)]
if safe_b_checks: bonus += 15
# potential safe rook check squares
safe_r_checks = rook_rays & safe2 & self.piece_attacks[Pt.piece(
Pt.R, them)]
if safe_b_checks: bonus += 20
# potential safe queen check squares
safe_q_checks = (bishop_rays
| rook_rays) & safe & self.piece_attacks[Pt.piece(
Pt.Q, them)]
if safe_b_checks: bonus += 20
# safe queen contact checks
safe_q_contact_checks = king_defended & self.double_attacks[
us] & self.piece_attacks[Pt.piece(Pt.Q, us)]
if safe_q_contact_checks: bonus += 35
# attack more difficult without the queen
if position.pieces[Pt.piece(Pt.Q, us)] == 0:
bonus /= 2
return int(bonus)
def evaluate(self, position=None, debug=False):
# if ' '.join(map(str, position.moves)) == "e2-e4 e7-e6 Qd1-f3":
# debug = True
if position:
self.set_position(position)
position = self.position
evals = defaultdict(lambda: [0, 0])
# Check for mate
# if position.is_mate():
# return -1000000
# TODO: implement stalemate
evaluations = [0, 0]
counts = piece_counts(position)
POTENTIALS_BB = [
self.all_pawn_attack_potentials(Side.WHITE),
self.all_pawn_attack_potentials(Side.BLACK)
]
KING_ZONE_BB = [
self.king_safety_squares(Side.WHITE),
self.king_safety_squares(Side.BLACK)
]
q_discoverers, q_pinned, q_sliding_checkers = self.position.get_discoveries_and_pins(
Pt.Q)
PINNED = self.position.pinned
PINNED[Pt.piece(Pt.Q,
Side.WHITE)] = q_pinned[Pt.piece(Pt.Q, Side.WHITE)]
PINNED[Pt.piece(Pt.Q,
Side.BLACK)] = q_pinned[Pt.piece(Pt.Q, Side.BLACK)]
DISCOVERERS = self.position.discoverers
phase = get_phase(self.position)
for side in [Side.WHITE, Side.BLACK]:
side_str = "WHITE" if side == Side.WHITE else "BLACK"
# count material
for base_type in [Pt.P, Pt.N, Pt.B, Pt.R, Pt.Q, Pt.K]:
piece_type = Pt.piece(base_type, side)
if base_type is not Pt.K:
value = counts[piece_type] * material_eval(
phase, counts, base_type, side)
if debug:
evals["Material %s" %
(HUMAN_PIECE[piece_type])][side] += value
evaluations[side] += value
# Positional bonuses and penalties:
# ..rook considerations
if base_type == Pt.R:
for rook in iterate_pieces(position.pieces[piece_type]):
value = self.rook_position_bonus(rook, side)
if debug:
evals["Rook Position %s" %
(HUMAN_PIECE[piece_type])][side] += value
evaluations[side] += value
# ..minor outpost, minor behind pawn
if base_type in [Pt.B, Pt.N]:
for minor in iterate_pieces(position.pieces[piece_type]):
value = self.minor_outpost_bonus(
base_type, side, POTENTIALS_BB)
if debug:
evals["Minor Outpost %s" %
(HUMAN_PIECE[piece_type])][side] += value
evaluations[side] += value
if base_type == Pt.B:
value = self.bad_bishop_penalty(minor, side)
if debug:
evals["Bad Bishop Penalty %s" %
(HUMAN_PIECE[piece_type])][side] += value
evaluations[side] -= value
value = self.minor_behind_pawn(piece_type, side)
if debug:
evals["Minor Behind Pawn %s" %
(HUMAN_PIECE[piece_type])][side] += value
evaluations[side] += value
# ..pawn structure
if base_type == Pt.P:
value = self.pawns_evaluation(side)
if debug: evals["Pawn Structure"][side] += value
evaluations[side] += value
value = self.pawn_potential_penalty(side, POTENTIALS_BB)
if debug: evals["Pawn Potential Penalty"][side] += value
evaluations[side] -= value
# ..piece-square table adjustments
if base_type in [Pt.P, Pt.N, Pt.B, Pt.K]:
value = psqt_value(piece_type, position, side)
if debug: evals["PSQT adjustments"][side] += value
evaluations[side] += value
# center attacks bonus
value = self.center_attacks_bonus(side)
if debug: evals["Center Attack Bonus"][side] += value
evaluations[side] += value
# weak/hanging pieces penalties
# for ep in next_en_prise(side):
# pt, *rest = ep
# bt = Pt.base_type(pt)
# value = (MG_PIECES[bt] / MG_PIECES[Pt.P]) * 30
# if debug: evals["En-prise penalties %s" % (HUMAN_PIECE[bt])][side] += value
# evaluations[side] -= value
# unprotected
# value = unprotected_penalty(side, pinned + q_pinned)
# if debug: evals["Weak/Hanging penalties"][side] += value
# evaluations[side] -= value
# threats
value = self.threats(side, PINNED)
if debug: evals["Threats bonus"][side] += value
evaluations[side] += value
value = count_bits(PINNED[Pt.piece(Pt.K, side)]) * 15
if debug: evals["Pins to King penalty"][side] += value
evaluations[side] -= value
value = count_bits(DISCOVERERS[Pt.piece(Pt.K, side ^ 1)]) * 150
if debug: evals["Discovery threats to King bonus"][side] += value
evaluations[side] += value
value = count_bits(q_pinned[Pt.piece(Pt.Q, side)]) * 10
if debug: evals["Pins to Queen penalty"][side] += value
evaluations[side] -= value
value = count_bits(q_discoverers[Pt.piece(Pt.Q, side ^ 1)]) * 100
if debug: evals["Discovery threats to Queen bonus"][side] += value
evaluations[side] += value
# mobility, taking pins to king into account
value = self.mobility(side, PINNED)
if debug: evals["Mobility"][side] += value
evaluations[side] += value
# king safety, castle readiness
value = 0
if side == Side.WHITE:
if white_can_castle_kingside(position.position_flags,
self.all_attacks[Side.BLACK],
position.occupied[Side.WHITE]):
value += (2 - count_bits(position.occupied[Side.WHITE] &
(F1 | G1))) * 4
elif white_can_castle_queenside(position.position_flags,
self.all_attacks[Side.BLACK],
position.occupied[Side.WHITE]):
value += (3 - count_bits(position.occupied[Side.WHITE] &
(D1 | C1 | B1))) * 4
else:
if black_can_castle_kingside(
position.position_flags, self.all_attacks[Side.WHITE],
position.occupied[Side.BLACK] ^ FULL_BOARD):
value += (2 - count_bits(position.occupied[Side.BLACK] &
(F8 | G8))) * 4
elif black_can_castle_queenside(
position.position_flags, self.all_attacks[Side.WHITE],
position.occupied[Side.BLACK] ^ FULL_BOARD):
value += (3 - count_bits(position.occupied[Side.BLACK] &
(D8 | C8 | B8))) * 4
if debug: evals["Castling readiness"][side] += value
evaluations[side] += value
# .. pawn cover of own king
value = self.pawn_cover_bonus(KING_ZONE_BB, side)
if debug: evals["Pawn cover"][side] += value
evaluations[side] += value
# .. king attack bonuses
value = self.king_zone_attack_bonus(KING_ZONE_BB, side)
if debug: evals["King Attack"][side] += value
evaluations[side] += value
if debug: pprint.pprint(dict(evals))
# pprint.pprint(evals.items())
res_value = int(evaluations[Side.WHITE] - evaluations[Side.BLACK])
if debug: print("EVAL", res_value)
if position.white_to_move():
return res_value
else:
return -res_value
def king(self, side):
# coords
king_t = Pt.piece(Pt.K, side)
k = self.pos.pieces[king_t]
return self.sq(k, side)
def threats(self, side, PINNED):
position = self.position
occupied = position.occupied[Side.WHITE] | position.occupied[
Side.BLACK]
free = occupied ^ FULL_BOARD
rank2 = RANKS[1] if side == Side.WHITE else RANKS[6]
us = side
them = side ^ 1
bonus = 0
penalty = 0
# them_no_qk = position.occupied[side ^ 1] \
# ^ position.pieces[Pt.piece(Pt.Q, side ^ 1)] \
# ^ position.pieces[Pt.piece(Pt.K, side ^ 1)]
# loose_pieces = them_no_qk & ((self.all_attacks[side] | self.all_attacks[side]) ^ FULL_BOARD)
# if loose_pieces:
# bonus += 25
# The following is copied as in stockfish:
# non-pawn enemies attacked by pawn
weak = (position.occupied[them] ^ position.pieces[Pt.piece(Pt.P, them)]) \
& (self.piece_attacks[Pt.piece(Pt.P, us)])
if weak:
# our pawns protected by us or not attacked by them
b = position.pieces[Pt.piece(Pt.P, us)] & (
self.all_attacks[us] | invert(self.all_attacks[side]))
safe_threats = (shift_ne(b, us) | shift_nw(b, us)) & weak
if weak ^ safe_threats:
bonus += 70
for threatened_piece in iterate_pieces(safe_threats):
bonus += 150
if Pt.base_type(
position.squares[bit_position(threatened_piece)]) in [
Pt.R, Pt.Q
]:
bonus += 50
# non-pawn enemies defended by pawn
defended = (position.occupied[them] ^ position.pieces[Pt.piece(Pt.P, them)]) \
& (self.piece_attacks[Pt.piece(Pt.P, them)])
# enemies not defended by a pawn and under our attack
weak = position.occupied[them] \
& invert(self.piece_attacks[Pt.piece(Pt.P, them)]) \
& self.all_attacks[us]
if defended | weak:
# minor attacks
minor_attack = self.piece_attacks[Pt.piece(
Pt.N, us)] | self.piece_attacks[Pt.piece(Pt.B, us)]
b = (defended | weak) & minor_attack
for attacked in iterate_pieces(b):
attacked_type = Pt.base_type(
position.squares[bit_position(attacked)])
if attacked_type == Pt.N:
bonus += 10
if attacked_type > Pt.N:
bonus += 56
if attacked_type == Pt.Q:
bonus += 40
# rook attacks
b = (position.pieces[Pt.piece(Pt.Q, them)]
| weak) & self.piece_attacks[Pt.piece(Pt.R, us)]
for attacked in iterate_pieces(b):
attacked_type = Pt.base_type(
position.squares[bit_position(attacked)])
if attacked_type > Pt.P and attacked_type != Pt.R:
bonus += 40
# hanging
bonus += 44 * count_bits(weak & invert(self.all_attacks[them]))
# king attacks
b = weak & self.piece_attacks[Pt.piece(Pt.K, us)]
more_than_one = reset_ls1b(b) > 0
if more_than_one: bonus += 18 # 120 for endgame
elif b: bonus += 6 # 60 for endgame
# bonus for pawn push that attacks pieces
# pawns already attacking were considered earlier above
b = position.pieces[Pt.piece(Pt.P, us)]
b = shift_north(b | (shift_north(b & rank2, us) & free), us)
b &= free & (self.all_attacks[us] | invert(self.all_attacks[them]))
b = (shift_ne(b, us) | shift_nw(b, us)) & invert(
self.piece_attacks[Pt.piece(Pt.P, us)])
b2 = PINNED[Pt.piece(Pt.K, side ^ 1)] | PINNED[Pt.piece(
Pt.Q, side ^ 1)]
bonus += count_bits(b & b2
& position.occupied[them]) * 70 + count_bits(
b & invert(b2) & position.occupied[them]) * 20
return bonus
def pawn_count(self, side):
pt = Pt.piece(Pt.P, side)
return [count_bits(self.pos.pieces[pt]) / 8]
def minor_behind_pawn(self, minors, side):
position = self.position
pawns_in_front = position.pieces[Pt.piece(Pt.P, side)] & shift_north(
minors, side)
pawns_in_front &= (RANKS[2] | RANKS[3] | RANKS[4] | RANKS[5])
return count_bits(pawns_in_front) * 8
def pawn_cover_bonus(self, king_zones, side):
position = self.position
pawn_type = Pt.piece(Pt.P, side)
pawn_cover = king_zones[side] & position.pieces[pawn_type]
# increase this too much, king will move to get close to e4,d4 pawns! or only do this when king is castled?
return count_bits(pawn_cover) * 6