2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
39 static const string PieceToChar(" PNBRQK pnbrqk");
43 Score pieceSquareTable[PIECE_NB][SQUARE_NB];
44 Value PieceValue[PHASE_NB][PIECE_NB] = {
45 { VALUE_ZERO, PawnValueMg, KnightValueMg, BishopValueMg, RookValueMg, QueenValueMg },
46 { VALUE_ZERO, PawnValueEg, KnightValueEg, BishopValueEg, RookValueEg, QueenValueEg } };
50 Key psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB];
51 Key enpassant[FILE_NB];
52 Key castle[CASTLE_RIGHT_NB];
56 /// init() initializes at startup the various arrays used to compute hash keys
57 /// and the piece square tables. The latter is a two-step operation: First, the
58 /// white halves of the tables are copied from PSQT[] tables. Second, the black
59 /// halves of the tables are initialized by flipping and changing the sign of
66 for (Color c = WHITE; c <= BLACK; c++)
67 for (PieceType pt = PAWN; pt <= KING; pt++)
68 for (Square s = SQ_A1; s <= SQ_H8; s++)
69 psq[c][pt][s] = rk.rand<Key>();
71 for (File f = FILE_A; f <= FILE_H; f++)
72 enpassant[f] = rk.rand<Key>();
74 for (int cr = CASTLES_NONE; cr <= ALL_CASTLES; cr++)
79 Key k = castle[1ULL << pop_lsb(&b)];
80 castle[cr] ^= k ? k : rk.rand<Key>();
84 side = rk.rand<Key>();
85 exclusion = rk.rand<Key>();
87 for (PieceType pt = PAWN; pt <= KING; pt++)
89 PieceValue[MG][make_piece(BLACK, pt)] = PieceValue[MG][pt];
90 PieceValue[EG][make_piece(BLACK, pt)] = PieceValue[EG][pt];
92 Score v = make_score(PieceValue[MG][pt], PieceValue[EG][pt]);
94 for (Square s = SQ_A1; s <= SQ_H8; s++)
96 pieceSquareTable[make_piece(WHITE, pt)][ s] = (v + PSQT[pt][s]);
97 pieceSquareTable[make_piece(BLACK, pt)][~s] = -(v + PSQT[pt][s]);
102 } // namespace Zobrist
107 /// next_attacker() is an helper function used by see() to locate the least
108 /// valuable attacker for the side to move, remove the attacker we just found
109 /// from the 'occupied' bitboard and scan for new X-ray attacks behind it.
111 template<int Pt> FORCE_INLINE
112 PieceType next_attacker(const Bitboard* bb, const Square& to, const Bitboard& stmAttackers,
113 Bitboard& occupied, Bitboard& attackers) {
115 if (stmAttackers & bb[Pt])
117 Bitboard b = stmAttackers & bb[Pt];
118 occupied ^= b & ~(b - 1);
120 if (Pt == PAWN || Pt == BISHOP || Pt == QUEEN)
121 attackers |= attacks_bb<BISHOP>(to, occupied) & (bb[BISHOP] | bb[QUEEN]);
123 if (Pt == ROOK || Pt == QUEEN)
124 attackers |= attacks_bb<ROOK>(to, occupied) & (bb[ROOK] | bb[QUEEN]);
126 return (PieceType)Pt;
128 return next_attacker<Pt+1>(bb, to, stmAttackers, occupied, attackers);
131 template<> FORCE_INLINE
132 PieceType next_attacker<KING>(const Bitboard*, const Square&, const Bitboard&, Bitboard&, Bitboard&) {
133 return KING; // No need to update bitboards, it is the last cycle
141 CheckInfo::CheckInfo(const Position& pos) {
143 Color them = ~pos.side_to_move();
144 ksq = pos.king_square(them);
146 pinned = pos.pinned_pieces();
147 dcCandidates = pos.discovered_check_candidates();
149 checkSq[PAWN] = pos.attacks_from<PAWN>(ksq, them);
150 checkSq[KNIGHT] = pos.attacks_from<KNIGHT>(ksq);
151 checkSq[BISHOP] = pos.attacks_from<BISHOP>(ksq);
152 checkSq[ROOK] = pos.attacks_from<ROOK>(ksq);
153 checkSq[QUEEN] = checkSq[BISHOP] | checkSq[ROOK];
158 /// Position::operator=() creates a copy of 'pos'. We want the new born Position
159 /// object do not depend on any external data so we detach state pointer from
162 Position& Position::operator=(const Position& pos) {
164 memcpy(this, &pos, sizeof(Position));
175 /// Position::set() initializes the position object with the given FEN string.
176 /// This function is not very robust - make sure that input FENs are correct,
177 /// this is assumed to be the responsibility of the GUI.
179 void Position::set(const string& fenStr, bool isChess960, Thread* th) {
181 A FEN string defines a particular position using only the ASCII character set.
183 A FEN string contains six fields separated by a space. The fields are:
185 1) Piece placement (from white's perspective). Each rank is described, starting
186 with rank 8 and ending with rank 1; within each rank, the contents of each
187 square are described from file A through file H. Following the Standard
188 Algebraic Notation (SAN), each piece is identified by a single letter taken
189 from the standard English names. White pieces are designated using upper-case
190 letters ("PNBRQK") while Black take lowercase ("pnbrqk"). Blank squares are
191 noted using digits 1 through 8 (the number of blank squares), and "/"
194 2) Active color. "w" means white moves next, "b" means black.
196 3) Castling availability. If neither side can castle, this is "-". Otherwise,
197 this has one or more letters: "K" (White can castle kingside), "Q" (White
198 can castle queenside), "k" (Black can castle kingside), and/or "q" (Black
199 can castle queenside).
201 4) En passant target square (in algebraic notation). If there's no en passant
202 target square, this is "-". If a pawn has just made a 2-square move, this
203 is the position "behind" the pawn. This is recorded regardless of whether
204 there is a pawn in position to make an en passant capture.
206 5) Halfmove clock. This is the number of halfmoves since the last pawn advance
207 or capture. This is used to determine if a draw can be claimed under the
210 6) Fullmove number. The number of the full move. It starts at 1, and is
211 incremented after Black's move.
214 char col, row, token;
217 std::istringstream ss(fenStr);
222 // 1. Piece placement
223 while ((ss >> token) && !isspace(token))
226 sq += Square(token - '0'); // Advance the given number of files
228 else if (token == '/')
231 else if ((p = PieceToChar.find(token)) != string::npos)
233 put_piece(Piece(p), sq);
240 sideToMove = (token == 'w' ? WHITE : BLACK);
243 // 3. Castling availability. Compatible with 3 standards: Normal FEN standard,
244 // Shredder-FEN that uses the letters of the columns on which the rooks began
245 // the game instead of KQkq and also X-FEN standard that, in case of Chess960,
246 // if an inner rook is associated with the castling right, the castling tag is
247 // replaced by the file letter of the involved rook, as for the Shredder-FEN.
248 while ((ss >> token) && !isspace(token))
251 Color c = islower(token) ? BLACK : WHITE;
253 token = char(toupper(token));
256 for (rsq = relative_square(c, SQ_H1); type_of(piece_on(rsq)) != ROOK; rsq--) {}
258 else if (token == 'Q')
259 for (rsq = relative_square(c, SQ_A1); type_of(piece_on(rsq)) != ROOK; rsq++) {}
261 else if (token >= 'A' && token <= 'H')
262 rsq = File(token - 'A') | relative_rank(c, RANK_1);
267 set_castle_right(c, rsq);
270 // 4. En passant square. Ignore if no pawn capture is possible
271 if ( ((ss >> col) && (col >= 'a' && col <= 'h'))
272 && ((ss >> row) && (row == '3' || row == '6')))
274 st->epSquare = File(col - 'a') | Rank(row - '1');
276 if (!(attackers_to(st->epSquare) & pieces(sideToMove, PAWN)))
277 st->epSquare = SQ_NONE;
280 // 5-6. Halfmove clock and fullmove number
281 ss >> std::skipws >> st->rule50 >> startPosPly;
283 // Convert from fullmove starting from 1 to ply starting from 0,
284 // handle also common incorrect FEN with fullmove = 0.
285 startPosPly = std::max(2 * (startPosPly - 1), 0) + int(sideToMove == BLACK);
287 st->key = compute_key();
288 st->pawnKey = compute_pawn_key();
289 st->materialKey = compute_material_key();
290 st->psqScore = compute_psq_score();
291 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
292 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
293 st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
294 chess960 = isChess960;
301 /// Position::set_castle_right() is an helper function used to set castling
302 /// rights given the corresponding color and the rook starting square.
304 void Position::set_castle_right(Color c, Square rfrom) {
306 Square kfrom = king_square(c);
307 CastlingSide cs = kfrom < rfrom ? KING_SIDE : QUEEN_SIDE;
308 CastleRight cr = make_castle_right(c, cs);
310 st->castleRights |= cr;
311 castleRightsMask[kfrom] |= cr;
312 castleRightsMask[rfrom] |= cr;
313 castleRookSquare[c][cs] = rfrom;
315 Square kto = relative_square(c, cs == KING_SIDE ? SQ_G1 : SQ_C1);
316 Square rto = relative_square(c, cs == KING_SIDE ? SQ_F1 : SQ_D1);
318 for (Square s = std::min(rfrom, rto); s <= std::max(rfrom, rto); s++)
319 if (s != kfrom && s != rfrom)
320 castlePath[c][cs] |= s;
322 for (Square s = std::min(kfrom, kto); s <= std::max(kfrom, kto); s++)
323 if (s != kfrom && s != rfrom)
324 castlePath[c][cs] |= s;
328 /// Position::fen() returns a FEN representation of the position. In case
329 /// of Chess960 the Shredder-FEN notation is used. Mainly a debugging function.
331 const string Position::fen() const {
333 std::ostringstream ss;
337 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
341 for (File file = FILE_A; file <= FILE_H; file++)
354 ss << PieceToChar[piece_on(sq)];
365 ss << (sideToMove == WHITE ? " w " : " b ");
367 if (can_castle(WHITE_OO))
368 ss << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE, KING_SIDE))))) : 'K');
370 if (can_castle(WHITE_OOO))
371 ss << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE, QUEEN_SIDE))))) : 'Q');
373 if (can_castle(BLACK_OO))
374 ss << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK, KING_SIDE))) : 'k');
376 if (can_castle(BLACK_OOO))
377 ss << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK, QUEEN_SIDE))) : 'q');
379 if (st->castleRights == CASTLES_NONE)
382 ss << (ep_square() == SQ_NONE ? " - " : " " + square_to_string(ep_square()) + " ")
383 << st->rule50 << " " << 1 + (startPosPly - int(sideToMove == BLACK)) / 2;
389 /// Position::pretty() returns an ASCII representation of the position to be
390 /// printed to the standard output together with the move's san notation.
392 const string Position::pretty(Move move) const {
394 const string dottedLine = "\n+---+---+---+---+---+---+---+---+";
395 const string twoRows = dottedLine + "\n| | . | | . | | . | | . |"
396 + dottedLine + "\n| . | | . | | . | | . | |";
398 string brd = twoRows + twoRows + twoRows + twoRows + dottedLine;
400 std::ostringstream ss;
403 ss << "\nMove is: " << (sideToMove == BLACK ? ".." : "")
404 << move_to_san(*const_cast<Position*>(this), move);
406 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
407 if (piece_on(sq) != NO_PIECE)
408 brd[513 - 68*rank_of(sq) + 4*file_of(sq)] = PieceToChar[piece_on(sq)];
410 ss << brd << "\nFen is: " << fen() << "\nKey is: " << st->key;
415 /// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
416 /// king) pieces for the given color. Or, when template parameter FindPinned is
417 /// false, the function return the pieces of the given color candidate for a
418 /// discovery check against the enemy king.
419 template<bool FindPinned>
420 Bitboard Position::hidden_checkers() const {
422 // Pinned pieces protect our king, dicovery checks attack the enemy king
423 Bitboard b, result = 0;
424 Bitboard pinners = pieces(FindPinned ? ~sideToMove : sideToMove);
425 Square ksq = king_square(FindPinned ? sideToMove : ~sideToMove);
427 // Pinners are sliders, that give check when candidate pinned is removed
428 pinners &= (pieces(ROOK, QUEEN) & PseudoAttacks[ROOK][ksq])
429 | (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq]);
433 b = between_bb(ksq, pop_lsb(&pinners)) & pieces();
435 if (b && !more_than_one(b) && (b & pieces(sideToMove)))
441 // Explicit template instantiations
442 template Bitboard Position::hidden_checkers<true>() const;
443 template Bitboard Position::hidden_checkers<false>() const;
446 /// Position::attackers_to() computes a bitboard of all pieces which attack a
447 /// given square. Slider attacks use occ bitboard as occupancy.
449 Bitboard Position::attackers_to(Square s, Bitboard occ) const {
451 return (attacks_from<PAWN>(s, BLACK) & pieces(WHITE, PAWN))
452 | (attacks_from<PAWN>(s, WHITE) & pieces(BLACK, PAWN))
453 | (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
454 | (attacks_bb<ROOK>(s, occ) & pieces(ROOK, QUEEN))
455 | (attacks_bb<BISHOP>(s, occ) & pieces(BISHOP, QUEEN))
456 | (attacks_from<KING>(s) & pieces(KING));
460 /// Position::attacks_from() computes a bitboard of all attacks of a given piece
461 /// put in a given square. Slider attacks use occ bitboard as occupancy.
463 Bitboard Position::attacks_from(Piece p, Square s, Bitboard occ) {
469 case BISHOP: return attacks_bb<BISHOP>(s, occ);
470 case ROOK : return attacks_bb<ROOK>(s, occ);
471 case QUEEN : return attacks_bb<BISHOP>(s, occ) | attacks_bb<ROOK>(s, occ);
472 default : return StepAttacksBB[p][s];
477 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
479 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
482 assert(pinned == pinned_pieces());
484 Color us = sideToMove;
485 Square from = from_sq(m);
487 assert(color_of(piece_moved(m)) == us);
488 assert(piece_on(king_square(us)) == make_piece(us, KING));
490 // En passant captures are a tricky special case. Because they are rather
491 // uncommon, we do it simply by testing whether the king is attacked after
493 if (type_of(m) == ENPASSANT)
496 Square to = to_sq(m);
497 Square capsq = to + pawn_push(them);
498 Square ksq = king_square(us);
499 Bitboard b = (pieces() ^ from ^ capsq) | to;
501 assert(to == ep_square());
502 assert(piece_moved(m) == make_piece(us, PAWN));
503 assert(piece_on(capsq) == make_piece(them, PAWN));
504 assert(piece_on(to) == NO_PIECE);
506 return !(attacks_bb< ROOK>(ksq, b) & pieces(them, QUEEN, ROOK))
507 && !(attacks_bb<BISHOP>(ksq, b) & pieces(them, QUEEN, BISHOP));
510 // If the moving piece is a king, check whether the destination
511 // square is attacked by the opponent. Castling moves are checked
512 // for legality during move generation.
513 if (type_of(piece_on(from)) == KING)
514 return type_of(m) == CASTLE || !(attackers_to(to_sq(m)) & pieces(~us));
516 // A non-king move is legal if and only if it is not pinned or it
517 // is moving along the ray towards or away from the king.
520 || squares_aligned(from, to_sq(m), king_square(us));
524 /// Position::move_is_legal() takes a random move and tests whether the move
525 /// is legal. This version is not very fast and should be used only in non
526 /// time-critical paths.
528 bool Position::move_is_legal(const Move m) const {
530 for (MoveList<LEGAL> ml(*this); !ml.end(); ++ml)
538 /// Position::is_pseudo_legal() takes a random move and tests whether the move
539 /// is pseudo legal. It is used to validate moves from TT that can be corrupted
540 /// due to SMP concurrent access or hash position key aliasing.
542 bool Position::is_pseudo_legal(const Move m) const {
544 Color us = sideToMove;
545 Color them = ~sideToMove;
546 Square from = from_sq(m);
547 Square to = to_sq(m);
548 Piece pc = piece_moved(m);
550 // Use a slower but simpler function for uncommon cases
551 if (type_of(m) != NORMAL)
552 return move_is_legal(m);
554 // Is not a promotion, so promotion piece must be empty
555 if (promotion_type(m) - 2 != NO_PIECE_TYPE)
558 // If the from square is not occupied by a piece belonging to the side to
559 // move, the move is obviously not legal.
560 if (pc == NO_PIECE || color_of(pc) != us)
563 // The destination square cannot be occupied by a friendly piece
564 if (color_of(piece_on(to)) == us)
567 // Handle the special case of a pawn move
568 if (type_of(pc) == PAWN)
570 // Move direction must be compatible with pawn color
571 int direction = to - from;
572 if ((us == WHITE) != (direction > 0))
575 // We have already handled promotion moves, so destination
576 // cannot be on the 8/1th rank.
577 if (rank_of(to) == RANK_8 || rank_of(to) == RANK_1)
580 // Proceed according to the square delta between the origin and
581 // destination squares.
588 // Capture. The destination square must be occupied by an enemy
589 // piece (en passant captures was handled earlier).
590 if (color_of(piece_on(to)) != them)
593 // From and to files must be one file apart, avoids a7h5
594 if (abs(file_of(from) - file_of(to)) != 1)
600 // Pawn push. The destination square must be empty.
606 // Double white pawn push. The destination square must be on the fourth
607 // rank, and both the destination square and the square between the
608 // source and destination squares must be empty.
609 if ( rank_of(to) != RANK_4
611 || !is_empty(from + DELTA_N))
616 // Double black pawn push. The destination square must be on the fifth
617 // rank, and both the destination square and the square between the
618 // source and destination squares must be empty.
619 if ( rank_of(to) != RANK_5
621 || !is_empty(from + DELTA_S))
629 else if (!(attacks_from(pc, from) & to))
632 // Evasions generator already takes care to avoid some kind of illegal moves
633 // and pl_move_is_legal() relies on this. So we have to take care that the
634 // same kind of moves are filtered out here.
637 if (type_of(pc) != KING)
639 Bitboard b = checkers();
640 Square checksq = pop_lsb(&b);
642 if (b) // double check ? In this case a king move is required
645 // Our move must be a blocking evasion or a capture of the checking piece
646 if (!((between_bb(checksq, king_square(us)) | checkers()) & to))
649 // In case of king moves under check we have to remove king so to catch
650 // as invalid moves like b1a1 when opposite queen is on c1.
651 else if (attackers_to(to, pieces() ^ from) & pieces(~us))
659 /// Position::move_gives_check() tests whether a pseudo-legal move gives a check
661 bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
664 assert(ci.dcCandidates == discovered_check_candidates());
665 assert(color_of(piece_moved(m)) == sideToMove);
667 Square from = from_sq(m);
668 Square to = to_sq(m);
669 PieceType pt = type_of(piece_on(from));
672 if (ci.checkSq[pt] & to)
676 if (ci.dcCandidates && (ci.dcCandidates & from))
678 // For pawn and king moves we need to verify also direction
679 if ( (pt != PAWN && pt != KING)
680 || !squares_aligned(from, to, king_square(~sideToMove)))
684 // Can we skip the ugly special cases ?
685 if (type_of(m) == NORMAL)
688 Color us = sideToMove;
689 Square ksq = king_square(~us);
694 return attacks_from(Piece(promotion_type(m)), to, pieces() ^ from) & ksq;
696 // En passant capture with check ? We have already handled the case
697 // of direct checks and ordinary discovered check, the only case we
698 // need to handle is the unusual case of a discovered check through
699 // the captured pawn.
702 Square capsq = file_of(to) | rank_of(from);
703 Bitboard b = (pieces() ^ from ^ capsq) | to;
705 return (attacks_bb< ROOK>(ksq, b) & pieces(us, QUEEN, ROOK))
706 | (attacks_bb<BISHOP>(ksq, b) & pieces(us, QUEEN, BISHOP));
711 Square rfrom = to; // 'King captures the rook' notation
712 Square kto = relative_square(us, rfrom > kfrom ? SQ_G1 : SQ_C1);
713 Square rto = relative_square(us, rfrom > kfrom ? SQ_F1 : SQ_D1);
714 Bitboard b = (pieces() ^ kfrom ^ rfrom) | rto | kto;
716 return attacks_bb<ROOK>(rto, b) & ksq;
725 /// Position::do_move() makes a move, and saves all information necessary
726 /// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
727 /// moves should be filtered out before this function is called.
729 void Position::do_move(Move m, StateInfo& newSt) {
732 do_move(m, newSt, ci, move_gives_check(m, ci));
735 void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
738 assert(&newSt != st);
743 // Copy some fields of old state to our new StateInfo object except the ones
744 // which are going to be recalculated from scratch anyway, then switch our state
745 // pointer to point to the new, ready to be updated, state.
746 memcpy(&newSt, st, StateCopySize64 * sizeof(uint64_t));
751 // Update side to move
754 // Increment the 50 moves rule draw counter. Resetting it to zero in the
755 // case of a capture or a pawn move is taken care of later.
759 if (type_of(m) == CASTLE)
762 do_castle_move<true>(m);
766 Color us = sideToMove;
768 Square from = from_sq(m);
769 Square to = to_sq(m);
770 Piece piece = piece_on(from);
771 PieceType pt = type_of(piece);
772 PieceType capture = type_of(m) == ENPASSANT ? PAWN : type_of(piece_on(to));
774 assert(color_of(piece) == us);
775 assert(color_of(piece_on(to)) != us);
776 assert(capture != KING);
782 // If the captured piece is a pawn, update pawn hash key, otherwise
783 // update non-pawn material.
786 if (type_of(m) == ENPASSANT)
788 capsq += pawn_push(them);
791 assert(to == st->epSquare);
792 assert(relative_rank(us, to) == RANK_6);
793 assert(piece_on(to) == NO_PIECE);
794 assert(piece_on(capsq) == make_piece(them, PAWN));
796 board[capsq] = NO_PIECE;
799 st->pawnKey ^= Zobrist::psq[them][PAWN][capsq];
802 st->npMaterial[them] -= PieceValue[MG][capture];
804 // Remove the captured piece
805 byTypeBB[ALL_PIECES] ^= capsq;
806 byTypeBB[capture] ^= capsq;
807 byColorBB[them] ^= capsq;
809 // Update piece list, move the last piece at index[capsq] position and
812 // WARNING: This is a not revresible operation. When we will reinsert the
813 // captured piece in undo_move() we will put it at the end of the list and
814 // not in its original place, it means index[] and pieceList[] are not
815 // guaranteed to be invariant to a do_move() + undo_move() sequence.
816 Square lastSquare = pieceList[them][capture][--pieceCount[them][capture]];
817 index[lastSquare] = index[capsq];
818 pieceList[them][capture][index[lastSquare]] = lastSquare;
819 pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
822 k ^= Zobrist::psq[them][capture][capsq];
823 st->materialKey ^= Zobrist::psq[them][capture][pieceCount[them][capture]];
825 // Update incremental scores
826 st->psqScore -= pieceSquareTable[make_piece(them, capture)][capsq];
828 // Reset rule 50 counter
833 k ^= Zobrist::psq[us][pt][from] ^ Zobrist::psq[us][pt][to];
835 // Reset en passant square
836 if (st->epSquare != SQ_NONE)
838 k ^= Zobrist::enpassant[file_of(st->epSquare)];
839 st->epSquare = SQ_NONE;
842 // Update castle rights if needed
843 if (st->castleRights && (castleRightsMask[from] | castleRightsMask[to]))
845 int cr = castleRightsMask[from] | castleRightsMask[to];
846 k ^= Zobrist::castle[st->castleRights & cr];
847 st->castleRights &= ~cr;
850 // Prefetch TT access as soon as we know key is updated
851 prefetch((char*)TT.first_entry(k));
854 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
855 byTypeBB[ALL_PIECES] ^= from_to_bb;
856 byTypeBB[pt] ^= from_to_bb;
857 byColorBB[us] ^= from_to_bb;
859 board[to] = board[from];
860 board[from] = NO_PIECE;
862 // Update piece lists, index[from] is not updated and becomes stale. This
863 // works as long as index[] is accessed just by known occupied squares.
864 index[to] = index[from];
865 pieceList[us][pt][index[to]] = to;
867 // If the moving piece is a pawn do some special extra work
870 // Set en-passant square, only if moved pawn can be captured
871 if ( (int(to) ^ int(from)) == 16
872 && (attacks_from<PAWN>(from + pawn_push(us), us) & pieces(them, PAWN)))
874 st->epSquare = Square((from + to) / 2);
875 k ^= Zobrist::enpassant[file_of(st->epSquare)];
878 if (type_of(m) == PROMOTION)
880 PieceType promotion = promotion_type(m);
882 assert(relative_rank(us, to) == RANK_8);
883 assert(promotion >= KNIGHT && promotion <= QUEEN);
885 // Replace the pawn with the promoted piece
886 byTypeBB[PAWN] ^= to;
887 byTypeBB[promotion] |= to;
888 board[to] = make_piece(us, promotion);
890 // Update piece lists, move the last pawn at index[to] position
891 // and shrink the list. Add a new promotion piece to the list.
892 Square lastSquare = pieceList[us][PAWN][--pieceCount[us][PAWN]];
893 index[lastSquare] = index[to];
894 pieceList[us][PAWN][index[lastSquare]] = lastSquare;
895 pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
896 index[to] = pieceCount[us][promotion];
897 pieceList[us][promotion][index[to]] = to;
900 k ^= Zobrist::psq[us][PAWN][to] ^ Zobrist::psq[us][promotion][to];
901 st->pawnKey ^= Zobrist::psq[us][PAWN][to];
902 st->materialKey ^= Zobrist::psq[us][promotion][pieceCount[us][promotion]++]
903 ^ Zobrist::psq[us][PAWN][pieceCount[us][PAWN]];
905 // Update incremental score
906 st->psqScore += pieceSquareTable[make_piece(us, promotion)][to]
907 - pieceSquareTable[make_piece(us, PAWN)][to];
910 st->npMaterial[us] += PieceValue[MG][promotion];
913 // Update pawn hash key
914 st->pawnKey ^= Zobrist::psq[us][PAWN][from] ^ Zobrist::psq[us][PAWN][to];
916 // Reset rule 50 draw counter
920 // Prefetch pawn and material hash tables
921 prefetch((char*)thisThread->pawnTable.entries[st->pawnKey]);
922 prefetch((char*)thisThread->materialTable.entries[st->materialKey]);
924 // Update incremental scores
925 st->psqScore += psq_delta(piece, from, to);
928 st->capturedType = capture;
930 // Update the key with the final value
933 // Update checkers bitboard, piece must be already moved
938 if (type_of(m) != NORMAL)
939 st->checkersBB = attackers_to(king_square(them)) & pieces(us);
943 if (ci.checkSq[pt] & to)
944 st->checkersBB |= to;
947 if (ci.dcCandidates && (ci.dcCandidates & from))
950 st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(us, QUEEN, ROOK);
953 st->checkersBB |= attacks_from<BISHOP>(king_square(them)) & pieces(us, QUEEN, BISHOP);
958 sideToMove = ~sideToMove;
964 /// Position::undo_move() unmakes a move. When it returns, the position should
965 /// be restored to exactly the same state as before the move was made.
967 void Position::undo_move(Move m) {
971 sideToMove = ~sideToMove;
973 if (type_of(m) == CASTLE)
975 do_castle_move<false>(m);
979 Color us = sideToMove;
981 Square from = from_sq(m);
982 Square to = to_sq(m);
983 Piece piece = piece_on(to);
984 PieceType pt = type_of(piece);
985 PieceType capture = st->capturedType;
987 assert(is_empty(from));
988 assert(color_of(piece) == us);
989 assert(capture != KING);
991 if (type_of(m) == PROMOTION)
993 PieceType promotion = promotion_type(m);
995 assert(promotion == pt);
996 assert(relative_rank(us, to) == RANK_8);
997 assert(promotion >= KNIGHT && promotion <= QUEEN);
999 // Replace the promoted piece with the pawn
1000 byTypeBB[promotion] ^= to;
1001 byTypeBB[PAWN] |= to;
1002 board[to] = make_piece(us, PAWN);
1004 // Update piece lists, move the last promoted piece at index[to] position
1005 // and shrink the list. Add a new pawn to the list.
1006 Square lastSquare = pieceList[us][promotion][--pieceCount[us][promotion]];
1007 index[lastSquare] = index[to];
1008 pieceList[us][promotion][index[lastSquare]] = lastSquare;
1009 pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
1010 index[to] = pieceCount[us][PAWN]++;
1011 pieceList[us][PAWN][index[to]] = to;
1016 // Put the piece back at the source square
1017 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
1018 byTypeBB[ALL_PIECES] ^= from_to_bb;
1019 byTypeBB[pt] ^= from_to_bb;
1020 byColorBB[us] ^= from_to_bb;
1022 board[from] = board[to];
1023 board[to] = NO_PIECE;
1025 // Update piece lists, index[to] is not updated and becomes stale. This
1026 // works as long as index[] is accessed just by known occupied squares.
1027 index[from] = index[to];
1028 pieceList[us][pt][index[from]] = from;
1034 if (type_of(m) == ENPASSANT)
1036 capsq -= pawn_push(us);
1039 assert(to == st->previous->epSquare);
1040 assert(relative_rank(us, to) == RANK_6);
1041 assert(piece_on(capsq) == NO_PIECE);
1044 // Restore the captured piece
1045 byTypeBB[ALL_PIECES] |= capsq;
1046 byTypeBB[capture] |= capsq;
1047 byColorBB[them] |= capsq;
1049 board[capsq] = make_piece(them, capture);
1051 // Update piece list, add a new captured piece in capsq square
1052 index[capsq] = pieceCount[them][capture]++;
1053 pieceList[them][capture][index[capsq]] = capsq;
1056 // Finally point our state pointer back to the previous state
1059 assert(pos_is_ok());
1063 /// Position::do_castle_move() is a private method used to do/undo a castling
1064 /// move. Note that castling moves are encoded as "king captures friendly rook"
1065 /// moves, for instance white short castling in a non-Chess960 game is encoded
1068 void Position::do_castle_move(Move m) {
1071 assert(type_of(m) == CASTLE);
1073 Square kto, kfrom, rfrom, rto, kAfter, rAfter;
1075 Color us = sideToMove;
1076 Square kBefore = from_sq(m);
1077 Square rBefore = to_sq(m);
1079 // Find after-castle squares for king and rook
1080 if (rBefore > kBefore) // O-O
1082 kAfter = relative_square(us, SQ_G1);
1083 rAfter = relative_square(us, SQ_F1);
1087 kAfter = relative_square(us, SQ_C1);
1088 rAfter = relative_square(us, SQ_D1);
1091 kfrom = Do ? kBefore : kAfter;
1092 rfrom = Do ? rBefore : rAfter;
1094 kto = Do ? kAfter : kBefore;
1095 rto = Do ? rAfter : rBefore;
1097 assert(piece_on(kfrom) == make_piece(us, KING));
1098 assert(piece_on(rfrom) == make_piece(us, ROOK));
1100 // Move the pieces, with some care; in chess960 could be kto == rfrom
1101 Bitboard k_from_to_bb = SquareBB[kfrom] ^ SquareBB[kto];
1102 Bitboard r_from_to_bb = SquareBB[rfrom] ^ SquareBB[rto];
1103 byTypeBB[KING] ^= k_from_to_bb;
1104 byTypeBB[ROOK] ^= r_from_to_bb;
1105 byTypeBB[ALL_PIECES] ^= k_from_to_bb ^ r_from_to_bb;
1106 byColorBB[us] ^= k_from_to_bb ^ r_from_to_bb;
1109 Piece king = make_piece(us, KING);
1110 Piece rook = make_piece(us, ROOK);
1111 board[kfrom] = board[rfrom] = NO_PIECE;
1115 // Update piece lists
1116 pieceList[us][KING][index[kfrom]] = kto;
1117 pieceList[us][ROOK][index[rfrom]] = rto;
1118 int tmp = index[rfrom]; // In Chess960 could be kto == rfrom
1119 index[kto] = index[kfrom];
1124 // Reset capture field
1125 st->capturedType = NO_PIECE_TYPE;
1127 // Update incremental scores
1128 st->psqScore += psq_delta(king, kfrom, kto);
1129 st->psqScore += psq_delta(rook, rfrom, rto);
1132 st->key ^= Zobrist::psq[us][KING][kfrom] ^ Zobrist::psq[us][KING][kto];
1133 st->key ^= Zobrist::psq[us][ROOK][rfrom] ^ Zobrist::psq[us][ROOK][rto];
1135 // Clear en passant square
1136 if (st->epSquare != SQ_NONE)
1138 st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
1139 st->epSquare = SQ_NONE;
1142 // Update castling rights
1143 st->key ^= Zobrist::castle[st->castleRights & castleRightsMask[kfrom]];
1144 st->castleRights &= ~castleRightsMask[kfrom];
1146 // Update checkers BB
1147 st->checkersBB = attackers_to(king_square(~us)) & pieces(us);
1149 sideToMove = ~sideToMove;
1152 // Undo: point our state pointer back to the previous state
1155 assert(pos_is_ok());
1159 /// Position::do_null_move() is used to do/undo a "null move": It flips the side
1160 /// to move and updates the hash key without executing any move on the board.
1162 void Position::do_null_move(StateInfo& backupSt) {
1164 assert(!in_check());
1166 // Back up the information necessary to undo the null move to the supplied
1167 // StateInfo object. Note that differently from normal case here backupSt
1168 // is actually used as a backup storage not as the new state. This reduces
1169 // the number of fields to be copied.
1170 StateInfo* src = Do ? st : &backupSt;
1171 StateInfo* dst = Do ? &backupSt : st;
1173 dst->key = src->key;
1174 dst->epSquare = src->epSquare;
1175 dst->psqScore = src->psqScore;
1176 dst->rule50 = src->rule50;
1177 dst->pliesFromNull = src->pliesFromNull;
1179 sideToMove = ~sideToMove;
1183 if (st->epSquare != SQ_NONE)
1184 st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
1186 st->key ^= Zobrist::side;
1187 prefetch((char*)TT.first_entry(st->key));
1189 st->epSquare = SQ_NONE;
1191 st->pliesFromNull = 0;
1194 assert(pos_is_ok());
1197 // Explicit template instantiations
1198 template void Position::do_null_move<false>(StateInfo& backupSt);
1199 template void Position::do_null_move<true>(StateInfo& backupSt);
1202 /// Position::see() is a static exchange evaluator: It tries to estimate the
1203 /// material gain or loss resulting from a move. There are three versions of
1204 /// this function: One which takes a destination square as input, one takes a
1205 /// move, and one which takes a 'from' and a 'to' square. The function does
1206 /// not yet understand promotions captures.
1208 int Position::see_sign(Move m) const {
1212 // Early return if SEE cannot be negative because captured piece value
1213 // is not less then capturing one. Note that king moves always return
1214 // here because king midgame value is set to 0.
1215 if (PieceValue[MG][piece_on(to_sq(m))] >= PieceValue[MG][piece_moved(m)])
1221 int Position::see(Move m) const {
1224 Bitboard occupied, attackers, stmAttackers;
1225 int swapList[32], slIndex = 1;
1233 captured = type_of(piece_on(to));
1234 occupied = pieces() ^ from;
1236 // Handle en passant moves
1237 if (type_of(m) == ENPASSANT)
1239 Square capQq = to - pawn_push(sideToMove);
1242 assert(type_of(piece_on(capQq)) == PAWN);
1244 // Remove the captured pawn
1248 else if (type_of(m) == CASTLE)
1249 // Castle moves are implemented as king capturing the rook so cannot be
1250 // handled correctly. Simply return 0 that is always the correct value
1251 // unless the rook is ends up under attack.
1254 // Find all attackers to the destination square, with the moving piece
1255 // removed, but possibly an X-ray attacker added behind it.
1256 attackers = attackers_to(to, occupied);
1258 // If the opponent has no attackers we are finished
1259 stm = ~color_of(piece_on(from));
1260 stmAttackers = attackers & pieces(stm);
1262 return PieceValue[MG][captured];
1264 // The destination square is defended, which makes things rather more
1265 // difficult to compute. We proceed by building up a "swap list" containing
1266 // the material gain or loss at each stop in a sequence of captures to the
1267 // destination square, where the sides alternately capture, and always
1268 // capture with the least valuable piece. After each capture, we look for
1269 // new X-ray attacks from behind the capturing piece.
1270 swapList[0] = PieceValue[MG][captured];
1271 captured = type_of(piece_on(from));
1274 assert(slIndex < 32);
1276 // Add the new entry to the swap list
1277 swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured];
1280 // Locate and remove from 'occupied' the next least valuable attacker
1281 captured = next_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
1283 attackers &= occupied; // Remove the just found attacker
1285 stmAttackers = attackers & pieces(stm);
1287 if (captured == KING)
1289 // Stop before processing a king capture
1291 swapList[slIndex++] = QueenValueMg * 16;
1296 } while (stmAttackers);
1298 // Having built the swap list, we negamax through it to find the best
1299 // achievable score from the point of view of the side to move.
1301 swapList[slIndex-1] = std::min(-swapList[slIndex], swapList[slIndex-1]);
1307 /// Position::clear() erases the position object to a pristine state, with an
1308 /// empty board, white to move, and no castling rights.
1310 void Position::clear() {
1312 memset(this, 0, sizeof(Position));
1313 startState.epSquare = SQ_NONE;
1316 for (int i = 0; i < 8; i++)
1317 for (int j = 0; j < 16; j++)
1318 pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
1322 /// Position::put_piece() puts a piece on the given square of the board,
1323 /// updating the board array, pieces list, bitboards, and piece counts.
1325 void Position::put_piece(Piece p, Square s) {
1327 Color c = color_of(p);
1328 PieceType pt = type_of(p);
1331 index[s] = pieceCount[c][pt]++;
1332 pieceList[c][pt][index[s]] = s;
1334 byTypeBB[ALL_PIECES] |= s;
1340 /// Position::compute_key() computes the hash key of the position. The hash
1341 /// key is usually updated incrementally as moves are made and unmade, the
1342 /// compute_key() function is only used when a new position is set up, and
1343 /// to verify the correctness of the hash key when running in debug mode.
1345 Key Position::compute_key() const {
1347 Key k = Zobrist::castle[st->castleRights];
1349 for (Bitboard b = pieces(); b; )
1351 Square s = pop_lsb(&b);
1352 k ^= Zobrist::psq[color_of(piece_on(s))][type_of(piece_on(s))][s];
1355 if (ep_square() != SQ_NONE)
1356 k ^= Zobrist::enpassant[file_of(ep_square())];
1358 if (sideToMove == BLACK)
1365 /// Position::compute_pawn_key() computes the hash key of the position. The
1366 /// hash key is usually updated incrementally as moves are made and unmade,
1367 /// the compute_pawn_key() function is only used when a new position is set
1368 /// up, and to verify the correctness of the pawn hash key when running in
1371 Key Position::compute_pawn_key() const {
1375 for (Bitboard b = pieces(PAWN); b; )
1377 Square s = pop_lsb(&b);
1378 k ^= Zobrist::psq[color_of(piece_on(s))][PAWN][s];
1385 /// Position::compute_material_key() computes the hash key of the position.
1386 /// The hash key is usually updated incrementally as moves are made and unmade,
1387 /// the compute_material_key() function is only used when a new position is set
1388 /// up, and to verify the correctness of the material hash key when running in
1391 Key Position::compute_material_key() const {
1395 for (Color c = WHITE; c <= BLACK; c++)
1396 for (PieceType pt = PAWN; pt <= QUEEN; pt++)
1397 for (int cnt = 0; cnt < piece_count(c, pt); cnt++)
1398 k ^= Zobrist::psq[c][pt][cnt];
1404 /// Position::compute_psq_score() computes the incremental scores for the middle
1405 /// game and the endgame. These functions are used to initialize the incremental
1406 /// scores when a new position is set up, and to verify that the scores are correctly
1407 /// updated by do_move and undo_move when the program is running in debug mode.
1408 Score Position::compute_psq_score() const {
1410 Score score = SCORE_ZERO;
1412 for (Bitboard b = pieces(); b; )
1414 Square s = pop_lsb(&b);
1415 score += pieceSquareTable[piece_on(s)][s];
1422 /// Position::compute_non_pawn_material() computes the total non-pawn middle
1423 /// game material value for the given side. Material values are updated
1424 /// incrementally during the search, this function is only used while
1425 /// initializing a new Position object.
1427 Value Position::compute_non_pawn_material(Color c) const {
1429 Value value = VALUE_ZERO;
1431 for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
1432 value += piece_count(c, pt) * PieceValue[MG][pt];
1438 /// Position::is_draw() tests whether the position is drawn by material,
1439 /// repetition, or the 50 moves rule. It does not detect stalemates, this
1440 /// must be done by the search.
1441 template<bool CheckRepetition, bool CheckThreeFold>
1442 bool Position::is_draw() const {
1445 && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg))
1448 if (st->rule50 > 99 && (!in_check() || MoveList<LEGAL>(*this).size()))
1451 if (CheckRepetition)
1453 int i = 4, e = std::min(st->rule50, st->pliesFromNull), cnt;
1457 StateInfo* stp = st->previous->previous;
1459 for (cnt = 0; i <= e; i += 2)
1461 stp = stp->previous->previous;
1463 if (stp->key == st->key && (!CheckThreeFold || ++cnt >= 2))
1472 // Explicit template instantiations
1473 template bool Position::is_draw<true, true>() const;
1474 template bool Position::is_draw<true, false>() const;
1475 template bool Position::is_draw<false,false>() const;
1478 /// Position::flip() flips position with the white and black sides reversed. This
1479 /// is only useful for debugging especially for finding evaluation symmetry bugs.
1481 void Position::flip() {
1483 const Position pos(*this);
1487 sideToMove = ~pos.side_to_move();
1488 thisThread = pos.this_thread();
1489 nodes = pos.nodes_searched();
1490 chess960 = pos.is_chess960();
1491 startPosPly = pos.startpos_ply_counter();
1493 for (Square s = SQ_A1; s <= SQ_H8; s++)
1494 if (!pos.is_empty(s))
1495 put_piece(Piece(pos.piece_on(s) ^ 8), ~s);
1497 if (pos.can_castle(WHITE_OO))
1498 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, KING_SIDE));
1499 if (pos.can_castle(WHITE_OOO))
1500 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, QUEEN_SIDE));
1501 if (pos.can_castle(BLACK_OO))
1502 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, KING_SIDE));
1503 if (pos.can_castle(BLACK_OOO))
1504 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, QUEEN_SIDE));
1506 if (pos.st->epSquare != SQ_NONE)
1507 st->epSquare = ~pos.st->epSquare;
1509 st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
1511 st->key = compute_key();
1512 st->pawnKey = compute_pawn_key();
1513 st->materialKey = compute_material_key();
1514 st->psqScore = compute_psq_score();
1515 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
1516 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
1518 assert(pos_is_ok());
1522 /// Position::pos_is_ok() performs some consitency checks for the position object.
1523 /// This is meant to be helpful when debugging.
1525 bool Position::pos_is_ok(int* failedStep) const {
1527 int dummy, *step = failedStep ? failedStep : &dummy;
1529 // What features of the position should be verified?
1530 const bool all = false;
1532 const bool debugBitboards = all || false;
1533 const bool debugKingCount = all || false;
1534 const bool debugKingCapture = all || false;
1535 const bool debugCheckerCount = all || false;
1536 const bool debugKey = all || false;
1537 const bool debugMaterialKey = all || false;
1538 const bool debugPawnKey = all || false;
1539 const bool debugIncrementalEval = all || false;
1540 const bool debugNonPawnMaterial = all || false;
1541 const bool debugPieceCounts = all || false;
1542 const bool debugPieceList = all || false;
1543 const bool debugCastleSquares = all || false;
1547 if (sideToMove != WHITE && sideToMove != BLACK)
1550 if ((*step)++, piece_on(king_square(WHITE)) != W_KING)
1553 if ((*step)++, piece_on(king_square(BLACK)) != B_KING)
1556 if ((*step)++, debugKingCount)
1558 int kingCount[COLOR_NB] = {};
1560 for (Square s = SQ_A1; s <= SQ_H8; s++)
1561 if (type_of(piece_on(s)) == KING)
1562 kingCount[color_of(piece_on(s))]++;
1564 if (kingCount[0] != 1 || kingCount[1] != 1)
1568 if ((*step)++, debugKingCapture)
1569 if (attackers_to(king_square(~sideToMove)) & pieces(sideToMove))
1572 if ((*step)++, debugCheckerCount && popcount<Full>(st->checkersBB) > 2)
1575 if ((*step)++, debugBitboards)
1577 // The intersection of the white and black pieces must be empty
1578 if (pieces(WHITE) & pieces(BLACK))
1581 // The union of the white and black pieces must be equal to all
1583 if ((pieces(WHITE) | pieces(BLACK)) != pieces())
1586 // Separate piece type bitboards must have empty intersections
1587 for (PieceType p1 = PAWN; p1 <= KING; p1++)
1588 for (PieceType p2 = PAWN; p2 <= KING; p2++)
1589 if (p1 != p2 && (pieces(p1) & pieces(p2)))
1593 if ((*step)++, ep_square() != SQ_NONE && relative_rank(sideToMove, ep_square()) != RANK_6)
1596 if ((*step)++, debugKey && st->key != compute_key())
1599 if ((*step)++, debugPawnKey && st->pawnKey != compute_pawn_key())
1602 if ((*step)++, debugMaterialKey && st->materialKey != compute_material_key())
1605 if ((*step)++, debugIncrementalEval && st->psqScore != compute_psq_score())
1608 if ((*step)++, debugNonPawnMaterial)
1610 if ( st->npMaterial[WHITE] != compute_non_pawn_material(WHITE)
1611 || st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
1615 if ((*step)++, debugPieceCounts)
1616 for (Color c = WHITE; c <= BLACK; c++)
1617 for (PieceType pt = PAWN; pt <= KING; pt++)
1618 if (pieceCount[c][pt] != popcount<Full>(pieces(c, pt)))
1621 if ((*step)++, debugPieceList)
1622 for (Color c = WHITE; c <= BLACK; c++)
1623 for (PieceType pt = PAWN; pt <= KING; pt++)
1624 for (int i = 0; i < pieceCount[c][pt]; i++)
1626 if (piece_on(piece_list(c, pt)[i]) != make_piece(c, pt))
1629 if (index[piece_list(c, pt)[i]] != i)
1633 if ((*step)++, debugCastleSquares)
1634 for (Color c = WHITE; c <= BLACK; c++)
1635 for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1))
1637 CastleRight cr = make_castle_right(c, s);
1639 if (!can_castle(cr))
1642 if ((castleRightsMask[king_square(c)] & cr) != cr)
1645 if ( piece_on(castleRookSquare[c][s]) != make_piece(c, ROOK)
1646 || castleRightsMask[castleRookSquare[c][s]] != cr)