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;
335 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
337 for (File file = FILE_A; file <= FILE_H; file++)
339 Square sq = file | rank;
345 for ( ; file < FILE_H && is_empty(sq++); file++)
351 ss << PieceToChar[piece_on(sq)];
358 ss << (sideToMove == WHITE ? " w " : " b ");
360 if (can_castle(WHITE_OO))
361 ss << (chess960 ? file_to_char(file_of(castle_rook_square(WHITE, KING_SIDE)), false) : 'K');
363 if (can_castle(WHITE_OOO))
364 ss << (chess960 ? file_to_char(file_of(castle_rook_square(WHITE, QUEEN_SIDE)), false) : 'Q');
366 if (can_castle(BLACK_OO))
367 ss << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK, KING_SIDE)), true) : 'k');
369 if (can_castle(BLACK_OOO))
370 ss << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK, QUEEN_SIDE)), true) : 'q');
372 if (st->castleRights == CASTLES_NONE)
375 ss << (ep_square() == SQ_NONE ? " - " : " " + square_to_string(ep_square()) + " ")
376 << st->rule50 << " " << 1 + (startPosPly - int(sideToMove == BLACK)) / 2;
382 /// Position::pretty() returns an ASCII representation of the position to be
383 /// printed to the standard output together with the move's san notation.
385 const string Position::pretty(Move move) const {
387 const string dottedLine = "\n+---+---+---+---+---+---+---+---+";
388 const string twoRows = dottedLine + "\n| | . | | . | | . | | . |"
389 + dottedLine + "\n| . | | . | | . | | . | |";
391 string brd = twoRows + twoRows + twoRows + twoRows + dottedLine;
393 std::ostringstream ss;
396 ss << "\nMove: " << (sideToMove == BLACK ? ".." : "")
397 << move_to_san(*const_cast<Position*>(this), move);
399 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
400 if (piece_on(sq) != NO_PIECE)
401 brd[513 - 68*rank_of(sq) + 4*file_of(sq)] = PieceToChar[piece_on(sq)];
403 ss << brd << "\nFen: " << fen() << "\nKey: " << st->key << "\nCheckers: ";
405 for (Bitboard b = checkers(); b; )
406 ss << square_to_string(pop_lsb(&b)) << " ";
408 ss << "\nLegal moves: ";
409 for (MoveList<LEGAL> ml(*this); !ml.end(); ++ml)
410 ss << move_to_san(*const_cast<Position*>(this), ml.move()) << " ";
416 /// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
417 /// king) pieces for the given color. Or, when template parameter FindPinned is
418 /// false, the function return the pieces of the given color candidate for a
419 /// discovery check against the enemy king.
420 template<bool FindPinned>
421 Bitboard Position::hidden_checkers() const {
423 // Pinned pieces protect our king, dicovery checks attack the enemy king
424 Bitboard b, result = 0;
425 Bitboard pinners = pieces(FindPinned ? ~sideToMove : sideToMove);
426 Square ksq = king_square(FindPinned ? sideToMove : ~sideToMove);
428 // Pinners are sliders, that give check when candidate pinned is removed
429 pinners &= (pieces(ROOK, QUEEN) & PseudoAttacks[ROOK][ksq])
430 | (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq]);
434 b = between_bb(ksq, pop_lsb(&pinners)) & pieces();
436 if (b && !more_than_one(b) && (b & pieces(sideToMove)))
442 // Explicit template instantiations
443 template Bitboard Position::hidden_checkers<true>() const;
444 template Bitboard Position::hidden_checkers<false>() const;
447 /// Position::attackers_to() computes a bitboard of all pieces which attack a
448 /// given square. Slider attacks use occ bitboard as occupancy.
450 Bitboard Position::attackers_to(Square s, Bitboard occ) const {
452 return (attacks_from<PAWN>(s, BLACK) & pieces(WHITE, PAWN))
453 | (attacks_from<PAWN>(s, WHITE) & pieces(BLACK, PAWN))
454 | (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
455 | (attacks_bb<ROOK>(s, occ) & pieces(ROOK, QUEEN))
456 | (attacks_bb<BISHOP>(s, occ) & pieces(BISHOP, QUEEN))
457 | (attacks_from<KING>(s) & pieces(KING));
461 /// Position::attacks_from() computes a bitboard of all attacks of a given piece
462 /// put in a given square. Slider attacks use occ bitboard as occupancy.
464 Bitboard Position::attacks_from(Piece p, Square s, Bitboard occ) {
470 case BISHOP: return attacks_bb<BISHOP>(s, occ);
471 case ROOK : return attacks_bb<ROOK>(s, occ);
472 case QUEEN : return attacks_bb<BISHOP>(s, occ) | attacks_bb<ROOK>(s, occ);
473 default : return StepAttacksBB[p][s];
478 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
480 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
483 assert(pinned == pinned_pieces());
485 Color us = sideToMove;
486 Square from = from_sq(m);
488 assert(color_of(piece_moved(m)) == us);
489 assert(piece_on(king_square(us)) == make_piece(us, KING));
491 // En passant captures are a tricky special case. Because they are rather
492 // uncommon, we do it simply by testing whether the king is attacked after
494 if (type_of(m) == ENPASSANT)
497 Square to = to_sq(m);
498 Square capsq = to + pawn_push(them);
499 Square ksq = king_square(us);
500 Bitboard b = (pieces() ^ from ^ capsq) | to;
502 assert(to == ep_square());
503 assert(piece_moved(m) == make_piece(us, PAWN));
504 assert(piece_on(capsq) == make_piece(them, PAWN));
505 assert(piece_on(to) == NO_PIECE);
507 return !(attacks_bb< ROOK>(ksq, b) & pieces(them, QUEEN, ROOK))
508 && !(attacks_bb<BISHOP>(ksq, b) & pieces(them, QUEEN, BISHOP));
511 // If the moving piece is a king, check whether the destination
512 // square is attacked by the opponent. Castling moves are checked
513 // for legality during move generation.
514 if (type_of(piece_on(from)) == KING)
515 return type_of(m) == CASTLE || !(attackers_to(to_sq(m)) & pieces(~us));
517 // A non-king move is legal if and only if it is not pinned or it
518 // is moving along the ray towards or away from the king.
521 || squares_aligned(from, to_sq(m), king_square(us));
525 /// Position::is_pseudo_legal() takes a random move and tests whether the move
526 /// is pseudo legal. It is used to validate moves from TT that can be corrupted
527 /// due to SMP concurrent access or hash position key aliasing.
529 bool Position::is_pseudo_legal(const Move m) const {
531 Color us = sideToMove;
532 Square from = from_sq(m);
533 Square to = to_sq(m);
534 Piece pc = piece_moved(m);
536 // Use a slower but simpler function for uncommon cases
537 if (type_of(m) != NORMAL)
538 return MoveList<LEGAL>(*this).contains(m);
540 // Is not a promotion, so promotion piece must be empty
541 if (promotion_type(m) - 2 != NO_PIECE_TYPE)
544 // If the from square is not occupied by a piece belonging to the side to
545 // move, the move is obviously not legal.
546 if (pc == NO_PIECE || color_of(pc) != us)
549 // The destination square cannot be occupied by a friendly piece
550 if (piece_on(to) != NO_PIECE && color_of(piece_on(to)) == us)
553 // Handle the special case of a pawn move
554 if (type_of(pc) == PAWN)
556 // Move direction must be compatible with pawn color
557 int direction = to - from;
558 if ((us == WHITE) != (direction > 0))
561 // We have already handled promotion moves, so destination
562 // cannot be on the 8/1th rank.
563 if (rank_of(to) == RANK_8 || rank_of(to) == RANK_1)
566 // Proceed according to the square delta between the origin and
567 // destination squares.
574 // Capture. The destination square must be occupied by an enemy
575 // piece (en passant captures was handled earlier).
576 if (piece_on(to) == NO_PIECE || color_of(piece_on(to)) != ~us)
579 // From and to files must be one file apart, avoids a7h5
580 if (abs(file_of(from) - file_of(to)) != 1)
586 // Pawn push. The destination square must be empty.
592 // Double white pawn push. The destination square must be on the fourth
593 // rank, and both the destination square and the square between the
594 // source and destination squares must be empty.
595 if ( rank_of(to) != RANK_4
597 || !is_empty(from + DELTA_N))
602 // Double black pawn push. The destination square must be on the fifth
603 // rank, and both the destination square and the square between the
604 // source and destination squares must be empty.
605 if ( rank_of(to) != RANK_5
607 || !is_empty(from + DELTA_S))
615 else if (!(attacks_from(pc, from) & to))
618 // Evasions generator already takes care to avoid some kind of illegal moves
619 // and pl_move_is_legal() relies on this. So we have to take care that the
620 // same kind of moves are filtered out here.
623 if (type_of(pc) != KING)
625 // Double check? In this case a king move is required
626 if (more_than_one(checkers()))
629 // Our move must be a blocking evasion or a capture of the checking piece
630 if (!((between_bb(lsb(checkers()), king_square(us)) | checkers()) & to))
633 // In case of king moves under check we have to remove king so to catch
634 // as invalid moves like b1a1 when opposite queen is on c1.
635 else if (attackers_to(to, pieces() ^ from) & pieces(~us))
643 /// Position::move_gives_check() tests whether a pseudo-legal move gives a check
645 bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
648 assert(ci.dcCandidates == discovered_check_candidates());
649 assert(color_of(piece_moved(m)) == sideToMove);
651 Square from = from_sq(m);
652 Square to = to_sq(m);
653 PieceType pt = type_of(piece_on(from));
656 if (ci.checkSq[pt] & to)
660 if (ci.dcCandidates && (ci.dcCandidates & from))
662 // For pawn and king moves we need to verify also direction
663 if ( (pt != PAWN && pt != KING)
664 || !squares_aligned(from, to, king_square(~sideToMove)))
668 // Can we skip the ugly special cases ?
669 if (type_of(m) == NORMAL)
672 Color us = sideToMove;
673 Square ksq = king_square(~us);
678 return attacks_from(Piece(promotion_type(m)), to, pieces() ^ from) & ksq;
680 // En passant capture with check ? We have already handled the case
681 // of direct checks and ordinary discovered check, the only case we
682 // need to handle is the unusual case of a discovered check through
683 // the captured pawn.
686 Square capsq = file_of(to) | rank_of(from);
687 Bitboard b = (pieces() ^ from ^ capsq) | to;
689 return (attacks_bb< ROOK>(ksq, b) & pieces(us, QUEEN, ROOK))
690 | (attacks_bb<BISHOP>(ksq, b) & pieces(us, QUEEN, BISHOP));
695 Square rfrom = to; // 'King captures the rook' notation
696 Square kto = relative_square(us, rfrom > kfrom ? SQ_G1 : SQ_C1);
697 Square rto = relative_square(us, rfrom > kfrom ? SQ_F1 : SQ_D1);
698 Bitboard b = (pieces() ^ kfrom ^ rfrom) | rto | kto;
700 return attacks_bb<ROOK>(rto, b) & ksq;
709 /// Position::do_move() makes a move, and saves all information necessary
710 /// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
711 /// moves should be filtered out before this function is called.
713 void Position::do_move(Move m, StateInfo& newSt) {
716 do_move(m, newSt, ci, move_gives_check(m, ci));
719 void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
722 assert(&newSt != st);
727 // Copy some fields of old state to our new StateInfo object except the ones
728 // which are going to be recalculated from scratch anyway, then switch our state
729 // pointer to point to the new, ready to be updated, state.
730 memcpy(&newSt, st, StateCopySize64 * sizeof(uint64_t));
735 // Update side to move
738 // Increment the 50 moves rule draw counter. Resetting it to zero in the
739 // case of a capture or a pawn move is taken care of later.
743 if (type_of(m) == CASTLE)
746 do_castle_move<true>(m);
750 Color us = sideToMove;
752 Square from = from_sq(m);
753 Square to = to_sq(m);
754 Piece piece = piece_on(from);
755 PieceType pt = type_of(piece);
756 PieceType capture = type_of(m) == ENPASSANT ? PAWN : type_of(piece_on(to));
758 assert(color_of(piece) == us);
759 assert(piece_on(to) == NO_PIECE || color_of(piece_on(to)) == them);
760 assert(capture != KING);
766 // If the captured piece is a pawn, update pawn hash key, otherwise
767 // update non-pawn material.
770 if (type_of(m) == ENPASSANT)
772 capsq += pawn_push(them);
775 assert(to == st->epSquare);
776 assert(relative_rank(us, to) == RANK_6);
777 assert(piece_on(to) == NO_PIECE);
778 assert(piece_on(capsq) == make_piece(them, PAWN));
780 board[capsq] = NO_PIECE;
783 st->pawnKey ^= Zobrist::psq[them][PAWN][capsq];
786 st->npMaterial[them] -= PieceValue[MG][capture];
788 // Remove the captured piece
789 byTypeBB[ALL_PIECES] ^= capsq;
790 byTypeBB[capture] ^= capsq;
791 byColorBB[them] ^= capsq;
793 // Update piece list, move the last piece at index[capsq] position and
796 // WARNING: This is a not revresible operation. When we will reinsert the
797 // captured piece in undo_move() we will put it at the end of the list and
798 // not in its original place, it means index[] and pieceList[] are not
799 // guaranteed to be invariant to a do_move() + undo_move() sequence.
800 Square lastSquare = pieceList[them][capture][--pieceCount[them][capture]];
801 index[lastSquare] = index[capsq];
802 pieceList[them][capture][index[lastSquare]] = lastSquare;
803 pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
806 k ^= Zobrist::psq[them][capture][capsq];
807 st->materialKey ^= Zobrist::psq[them][capture][pieceCount[them][capture]];
809 // Update incremental scores
810 st->psqScore -= pieceSquareTable[make_piece(them, capture)][capsq];
812 // Reset rule 50 counter
817 k ^= Zobrist::psq[us][pt][from] ^ Zobrist::psq[us][pt][to];
819 // Reset en passant square
820 if (st->epSquare != SQ_NONE)
822 k ^= Zobrist::enpassant[file_of(st->epSquare)];
823 st->epSquare = SQ_NONE;
826 // Update castle rights if needed
827 if (st->castleRights && (castleRightsMask[from] | castleRightsMask[to]))
829 int cr = castleRightsMask[from] | castleRightsMask[to];
830 k ^= Zobrist::castle[st->castleRights & cr];
831 st->castleRights &= ~cr;
834 // Prefetch TT access as soon as we know key is updated
835 prefetch((char*)TT.first_entry(k));
838 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
839 byTypeBB[ALL_PIECES] ^= from_to_bb;
840 byTypeBB[pt] ^= from_to_bb;
841 byColorBB[us] ^= from_to_bb;
843 board[to] = board[from];
844 board[from] = NO_PIECE;
846 // Update piece lists, index[from] is not updated and becomes stale. This
847 // works as long as index[] is accessed just by known occupied squares.
848 index[to] = index[from];
849 pieceList[us][pt][index[to]] = to;
851 // If the moving piece is a pawn do some special extra work
854 // Set en-passant square, only if moved pawn can be captured
855 if ( (int(to) ^ int(from)) == 16
856 && (attacks_from<PAWN>(from + pawn_push(us), us) & pieces(them, PAWN)))
858 st->epSquare = Square((from + to) / 2);
859 k ^= Zobrist::enpassant[file_of(st->epSquare)];
862 if (type_of(m) == PROMOTION)
864 PieceType promotion = promotion_type(m);
866 assert(relative_rank(us, to) == RANK_8);
867 assert(promotion >= KNIGHT && promotion <= QUEEN);
869 // Replace the pawn with the promoted piece
870 byTypeBB[PAWN] ^= to;
871 byTypeBB[promotion] |= to;
872 board[to] = make_piece(us, promotion);
874 // Update piece lists, move the last pawn at index[to] position
875 // and shrink the list. Add a new promotion piece to the list.
876 Square lastSquare = pieceList[us][PAWN][--pieceCount[us][PAWN]];
877 index[lastSquare] = index[to];
878 pieceList[us][PAWN][index[lastSquare]] = lastSquare;
879 pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
880 index[to] = pieceCount[us][promotion];
881 pieceList[us][promotion][index[to]] = to;
884 k ^= Zobrist::psq[us][PAWN][to] ^ Zobrist::psq[us][promotion][to];
885 st->pawnKey ^= Zobrist::psq[us][PAWN][to];
886 st->materialKey ^= Zobrist::psq[us][promotion][pieceCount[us][promotion]++]
887 ^ Zobrist::psq[us][PAWN][pieceCount[us][PAWN]];
889 // Update incremental score
890 st->psqScore += pieceSquareTable[make_piece(us, promotion)][to]
891 - pieceSquareTable[make_piece(us, PAWN)][to];
894 st->npMaterial[us] += PieceValue[MG][promotion];
897 // Update pawn hash key
898 st->pawnKey ^= Zobrist::psq[us][PAWN][from] ^ Zobrist::psq[us][PAWN][to];
900 // Reset rule 50 draw counter
904 // Prefetch pawn and material hash tables
905 prefetch((char*)thisThread->pawnsTable[st->pawnKey]);
906 prefetch((char*)thisThread->materialTable[st->materialKey]);
908 // Update incremental scores
909 st->psqScore += psq_delta(piece, from, to);
912 st->capturedType = capture;
914 // Update the key with the final value
917 // Update checkers bitboard, piece must be already moved
922 if (type_of(m) != NORMAL)
923 st->checkersBB = attackers_to(king_square(them)) & pieces(us);
927 if (ci.checkSq[pt] & to)
928 st->checkersBB |= to;
931 if (ci.dcCandidates && (ci.dcCandidates & from))
934 st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(us, QUEEN, ROOK);
937 st->checkersBB |= attacks_from<BISHOP>(king_square(them)) & pieces(us, QUEEN, BISHOP);
942 sideToMove = ~sideToMove;
948 /// Position::undo_move() unmakes a move. When it returns, the position should
949 /// be restored to exactly the same state as before the move was made.
951 void Position::undo_move(Move m) {
955 sideToMove = ~sideToMove;
957 if (type_of(m) == CASTLE)
959 do_castle_move<false>(m);
963 Color us = sideToMove;
965 Square from = from_sq(m);
966 Square to = to_sq(m);
967 Piece piece = piece_on(to);
968 PieceType pt = type_of(piece);
969 PieceType capture = st->capturedType;
971 assert(is_empty(from));
972 assert(color_of(piece) == us);
973 assert(capture != KING);
975 if (type_of(m) == PROMOTION)
977 PieceType promotion = promotion_type(m);
979 assert(promotion == pt);
980 assert(relative_rank(us, to) == RANK_8);
981 assert(promotion >= KNIGHT && promotion <= QUEEN);
983 // Replace the promoted piece with the pawn
984 byTypeBB[promotion] ^= to;
985 byTypeBB[PAWN] |= to;
986 board[to] = make_piece(us, PAWN);
988 // Update piece lists, move the last promoted piece at index[to] position
989 // and shrink the list. Add a new pawn to the list.
990 Square lastSquare = pieceList[us][promotion][--pieceCount[us][promotion]];
991 index[lastSquare] = index[to];
992 pieceList[us][promotion][index[lastSquare]] = lastSquare;
993 pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
994 index[to] = pieceCount[us][PAWN]++;
995 pieceList[us][PAWN][index[to]] = to;
1000 // Put the piece back at the source square
1001 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
1002 byTypeBB[ALL_PIECES] ^= from_to_bb;
1003 byTypeBB[pt] ^= from_to_bb;
1004 byColorBB[us] ^= from_to_bb;
1006 board[from] = board[to];
1007 board[to] = NO_PIECE;
1009 // Update piece lists, index[to] is not updated and becomes stale. This
1010 // works as long as index[] is accessed just by known occupied squares.
1011 index[from] = index[to];
1012 pieceList[us][pt][index[from]] = from;
1018 if (type_of(m) == ENPASSANT)
1020 capsq -= pawn_push(us);
1023 assert(to == st->previous->epSquare);
1024 assert(relative_rank(us, to) == RANK_6);
1025 assert(piece_on(capsq) == NO_PIECE);
1028 // Restore the captured piece
1029 byTypeBB[ALL_PIECES] |= capsq;
1030 byTypeBB[capture] |= capsq;
1031 byColorBB[them] |= capsq;
1033 board[capsq] = make_piece(them, capture);
1035 // Update piece list, add a new captured piece in capsq square
1036 index[capsq] = pieceCount[them][capture]++;
1037 pieceList[them][capture][index[capsq]] = capsq;
1040 // Finally point our state pointer back to the previous state
1043 assert(pos_is_ok());
1047 /// Position::do_castle_move() is a private method used to do/undo a castling
1048 /// move. Note that castling moves are encoded as "king captures friendly rook"
1049 /// moves, for instance white short castling in a non-Chess960 game is encoded
1052 void Position::do_castle_move(Move m) {
1055 assert(type_of(m) == CASTLE);
1057 Square kto, kfrom, rfrom, rto, kAfter, rAfter;
1059 Color us = sideToMove;
1060 Square kBefore = from_sq(m);
1061 Square rBefore = to_sq(m);
1063 // Find after-castle squares for king and rook
1064 if (rBefore > kBefore) // O-O
1066 kAfter = relative_square(us, SQ_G1);
1067 rAfter = relative_square(us, SQ_F1);
1071 kAfter = relative_square(us, SQ_C1);
1072 rAfter = relative_square(us, SQ_D1);
1075 kfrom = Do ? kBefore : kAfter;
1076 rfrom = Do ? rBefore : rAfter;
1078 kto = Do ? kAfter : kBefore;
1079 rto = Do ? rAfter : rBefore;
1081 assert(piece_on(kfrom) == make_piece(us, KING));
1082 assert(piece_on(rfrom) == make_piece(us, ROOK));
1084 // Move the pieces, with some care; in chess960 could be kto == rfrom
1085 Bitboard k_from_to_bb = SquareBB[kfrom] ^ SquareBB[kto];
1086 Bitboard r_from_to_bb = SquareBB[rfrom] ^ SquareBB[rto];
1087 byTypeBB[KING] ^= k_from_to_bb;
1088 byTypeBB[ROOK] ^= r_from_to_bb;
1089 byTypeBB[ALL_PIECES] ^= k_from_to_bb ^ r_from_to_bb;
1090 byColorBB[us] ^= k_from_to_bb ^ r_from_to_bb;
1093 Piece king = make_piece(us, KING);
1094 Piece rook = make_piece(us, ROOK);
1095 board[kfrom] = board[rfrom] = NO_PIECE;
1099 // Update piece lists
1100 pieceList[us][KING][index[kfrom]] = kto;
1101 pieceList[us][ROOK][index[rfrom]] = rto;
1102 int tmp = index[rfrom]; // In Chess960 could be kto == rfrom
1103 index[kto] = index[kfrom];
1108 // Reset capture field
1109 st->capturedType = NO_PIECE_TYPE;
1111 // Update incremental scores
1112 st->psqScore += psq_delta(king, kfrom, kto);
1113 st->psqScore += psq_delta(rook, rfrom, rto);
1116 st->key ^= Zobrist::psq[us][KING][kfrom] ^ Zobrist::psq[us][KING][kto];
1117 st->key ^= Zobrist::psq[us][ROOK][rfrom] ^ Zobrist::psq[us][ROOK][rto];
1119 // Clear en passant square
1120 if (st->epSquare != SQ_NONE)
1122 st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
1123 st->epSquare = SQ_NONE;
1126 // Update castling rights
1127 st->key ^= Zobrist::castle[st->castleRights & castleRightsMask[kfrom]];
1128 st->castleRights &= ~castleRightsMask[kfrom];
1130 // Update checkers BB
1131 st->checkersBB = attackers_to(king_square(~us)) & pieces(us);
1133 sideToMove = ~sideToMove;
1136 // Undo: point our state pointer back to the previous state
1139 assert(pos_is_ok());
1143 /// Position::do_null_move() is used to do/undo a "null move": It flips the side
1144 /// to move and updates the hash key without executing any move on the board.
1146 void Position::do_null_move(StateInfo& backupSt) {
1148 assert(!checkers());
1150 // Back up the information necessary to undo the null move to the supplied
1151 // StateInfo object. Note that differently from normal case here backupSt
1152 // is actually used as a backup storage not as the new state. This reduces
1153 // the number of fields to be copied.
1154 StateInfo* src = Do ? st : &backupSt;
1155 StateInfo* dst = Do ? &backupSt : st;
1157 dst->key = src->key;
1158 dst->epSquare = src->epSquare;
1159 dst->psqScore = src->psqScore;
1160 dst->rule50 = src->rule50;
1161 dst->pliesFromNull = src->pliesFromNull;
1163 sideToMove = ~sideToMove;
1167 if (st->epSquare != SQ_NONE)
1168 st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
1170 st->key ^= Zobrist::side;
1171 prefetch((char*)TT.first_entry(st->key));
1173 st->epSquare = SQ_NONE;
1175 st->pliesFromNull = 0;
1178 assert(pos_is_ok());
1181 // Explicit template instantiations
1182 template void Position::do_null_move<false>(StateInfo& backupSt);
1183 template void Position::do_null_move<true>(StateInfo& backupSt);
1186 /// Position::see() is a static exchange evaluator: It tries to estimate the
1187 /// material gain or loss resulting from a move. There are three versions of
1188 /// this function: One which takes a destination square as input, one takes a
1189 /// move, and one which takes a 'from' and a 'to' square. The function does
1190 /// not yet understand promotions captures.
1192 int Position::see_sign(Move m) const {
1196 // Early return if SEE cannot be negative because captured piece value
1197 // is not less then capturing one. Note that king moves always return
1198 // here because king midgame value is set to 0.
1199 if (PieceValue[MG][piece_on(to_sq(m))] >= PieceValue[MG][piece_moved(m)])
1205 int Position::see(Move m) const {
1208 Bitboard occupied, attackers, stmAttackers;
1209 int swapList[32], slIndex = 1;
1217 captured = type_of(piece_on(to));
1218 occupied = pieces() ^ from;
1220 // Handle en passant moves
1221 if (type_of(m) == ENPASSANT)
1223 Square capQq = to - pawn_push(sideToMove);
1226 assert(type_of(piece_on(capQq)) == PAWN);
1228 // Remove the captured pawn
1232 else if (type_of(m) == CASTLE)
1233 // Castle moves are implemented as king capturing the rook so cannot be
1234 // handled correctly. Simply return 0 that is always the correct value
1235 // unless the rook is ends up under attack.
1238 // Find all attackers to the destination square, with the moving piece
1239 // removed, but possibly an X-ray attacker added behind it.
1240 attackers = attackers_to(to, occupied);
1242 // If the opponent has no attackers we are finished
1243 stm = ~color_of(piece_on(from));
1244 stmAttackers = attackers & pieces(stm);
1246 return PieceValue[MG][captured];
1248 // The destination square is defended, which makes things rather more
1249 // difficult to compute. We proceed by building up a "swap list" containing
1250 // the material gain or loss at each stop in a sequence of captures to the
1251 // destination square, where the sides alternately capture, and always
1252 // capture with the least valuable piece. After each capture, we look for
1253 // new X-ray attacks from behind the capturing piece.
1254 swapList[0] = PieceValue[MG][captured];
1255 captured = type_of(piece_on(from));
1258 assert(slIndex < 32);
1260 // Add the new entry to the swap list
1261 swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured];
1264 // Locate and remove from 'occupied' the next least valuable attacker
1265 captured = next_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
1267 attackers &= occupied; // Remove the just found attacker
1269 stmAttackers = attackers & pieces(stm);
1271 if (captured == KING)
1273 // Stop before processing a king capture
1275 swapList[slIndex++] = QueenValueMg * 16;
1280 } while (stmAttackers);
1282 // Having built the swap list, we negamax through it to find the best
1283 // achievable score from the point of view of the side to move.
1285 swapList[slIndex-1] = std::min(-swapList[slIndex], swapList[slIndex-1]);
1291 /// Position::clear() erases the position object to a pristine state, with an
1292 /// empty board, white to move, and no castling rights.
1294 void Position::clear() {
1296 memset(this, 0, sizeof(Position));
1297 startState.epSquare = SQ_NONE;
1300 for (int i = 0; i < 8; i++)
1301 for (int j = 0; j < 16; j++)
1302 pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
1306 /// Position::put_piece() puts a piece on the given square of the board,
1307 /// updating the board array, pieces list, bitboards, and piece counts.
1309 void Position::put_piece(Piece p, Square s) {
1311 Color c = color_of(p);
1312 PieceType pt = type_of(p);
1315 index[s] = pieceCount[c][pt]++;
1316 pieceList[c][pt][index[s]] = s;
1318 byTypeBB[ALL_PIECES] |= s;
1324 /// Position::compute_key() computes the hash key of the position. The hash
1325 /// key is usually updated incrementally as moves are made and unmade, the
1326 /// compute_key() function is only used when a new position is set up, and
1327 /// to verify the correctness of the hash key when running in debug mode.
1329 Key Position::compute_key() const {
1331 Key k = Zobrist::castle[st->castleRights];
1333 for (Bitboard b = pieces(); b; )
1335 Square s = pop_lsb(&b);
1336 k ^= Zobrist::psq[color_of(piece_on(s))][type_of(piece_on(s))][s];
1339 if (ep_square() != SQ_NONE)
1340 k ^= Zobrist::enpassant[file_of(ep_square())];
1342 if (sideToMove == BLACK)
1349 /// Position::compute_pawn_key() computes the hash key of the position. The
1350 /// hash key is usually updated incrementally as moves are made and unmade,
1351 /// the compute_pawn_key() function is only used when a new position is set
1352 /// up, and to verify the correctness of the pawn hash key when running in
1355 Key Position::compute_pawn_key() const {
1359 for (Bitboard b = pieces(PAWN); b; )
1361 Square s = pop_lsb(&b);
1362 k ^= Zobrist::psq[color_of(piece_on(s))][PAWN][s];
1369 /// Position::compute_material_key() computes the hash key of the position.
1370 /// The hash key is usually updated incrementally as moves are made and unmade,
1371 /// the compute_material_key() function is only used when a new position is set
1372 /// up, and to verify the correctness of the material hash key when running in
1375 Key Position::compute_material_key() const {
1379 for (Color c = WHITE; c <= BLACK; c++)
1380 for (PieceType pt = PAWN; pt <= QUEEN; pt++)
1381 for (int cnt = 0; cnt < piece_count(c, pt); cnt++)
1382 k ^= Zobrist::psq[c][pt][cnt];
1388 /// Position::compute_psq_score() computes the incremental scores for the middle
1389 /// game and the endgame. These functions are used to initialize the incremental
1390 /// scores when a new position is set up, and to verify that the scores are correctly
1391 /// updated by do_move and undo_move when the program is running in debug mode.
1392 Score Position::compute_psq_score() const {
1394 Score score = SCORE_ZERO;
1396 for (Bitboard b = pieces(); b; )
1398 Square s = pop_lsb(&b);
1399 score += pieceSquareTable[piece_on(s)][s];
1406 /// Position::compute_non_pawn_material() computes the total non-pawn middle
1407 /// game material value for the given side. Material values are updated
1408 /// incrementally during the search, this function is only used while
1409 /// initializing a new Position object.
1411 Value Position::compute_non_pawn_material(Color c) const {
1413 Value value = VALUE_ZERO;
1415 for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
1416 value += piece_count(c, pt) * PieceValue[MG][pt];
1422 /// Position::is_draw() tests whether the position is drawn by material,
1423 /// repetition, or the 50 moves rule. It does not detect stalemates, this
1424 /// must be done by the search.
1425 template<bool CheckRepetition, bool CheckThreeFold>
1426 bool Position::is_draw() const {
1429 && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg))
1432 if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))
1435 if (CheckRepetition)
1437 int i = 4, e = std::min(st->rule50, st->pliesFromNull), cnt;
1441 StateInfo* stp = st->previous->previous;
1443 for (cnt = 0; i <= e; i += 2)
1445 stp = stp->previous->previous;
1447 if (stp->key == st->key && (!CheckThreeFold || ++cnt >= 2))
1456 // Explicit template instantiations
1457 template bool Position::is_draw<true, true>() const;
1458 template bool Position::is_draw<true, false>() const;
1459 template bool Position::is_draw<false,false>() const;
1462 /// Position::flip() flips position with the white and black sides reversed. This
1463 /// is only useful for debugging especially for finding evaluation symmetry bugs.
1465 void Position::flip() {
1467 const Position pos(*this);
1471 sideToMove = ~pos.side_to_move();
1472 thisThread = pos.this_thread();
1473 nodes = pos.nodes_searched();
1474 chess960 = pos.is_chess960();
1475 startPosPly = pos.startpos_ply_counter();
1477 for (Square s = SQ_A1; s <= SQ_H8; s++)
1478 if (!pos.is_empty(s))
1479 put_piece(Piece(pos.piece_on(s) ^ 8), ~s);
1481 if (pos.can_castle(WHITE_OO))
1482 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, KING_SIDE));
1483 if (pos.can_castle(WHITE_OOO))
1484 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, QUEEN_SIDE));
1485 if (pos.can_castle(BLACK_OO))
1486 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, KING_SIDE));
1487 if (pos.can_castle(BLACK_OOO))
1488 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, QUEEN_SIDE));
1490 if (pos.st->epSquare != SQ_NONE)
1491 st->epSquare = ~pos.st->epSquare;
1493 st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
1495 st->key = compute_key();
1496 st->pawnKey = compute_pawn_key();
1497 st->materialKey = compute_material_key();
1498 st->psqScore = compute_psq_score();
1499 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
1500 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
1502 assert(pos_is_ok());
1506 /// Position::pos_is_ok() performs some consitency checks for the position object.
1507 /// This is meant to be helpful when debugging.
1509 bool Position::pos_is_ok(int* failedStep) const {
1511 int dummy, *step = failedStep ? failedStep : &dummy;
1513 // What features of the position should be verified?
1514 const bool all = false;
1516 const bool debugBitboards = all || false;
1517 const bool debugKingCount = all || false;
1518 const bool debugKingCapture = all || false;
1519 const bool debugCheckerCount = all || false;
1520 const bool debugKey = all || false;
1521 const bool debugMaterialKey = all || false;
1522 const bool debugPawnKey = all || false;
1523 const bool debugIncrementalEval = all || false;
1524 const bool debugNonPawnMaterial = all || false;
1525 const bool debugPieceCounts = all || false;
1526 const bool debugPieceList = all || false;
1527 const bool debugCastleSquares = all || false;
1531 if (sideToMove != WHITE && sideToMove != BLACK)
1534 if ((*step)++, piece_on(king_square(WHITE)) != W_KING)
1537 if ((*step)++, piece_on(king_square(BLACK)) != B_KING)
1540 if ((*step)++, debugKingCount)
1542 int kingCount[COLOR_NB] = {};
1544 for (Square s = SQ_A1; s <= SQ_H8; s++)
1545 if (type_of(piece_on(s)) == KING)
1546 kingCount[color_of(piece_on(s))]++;
1548 if (kingCount[0] != 1 || kingCount[1] != 1)
1552 if ((*step)++, debugKingCapture)
1553 if (attackers_to(king_square(~sideToMove)) & pieces(sideToMove))
1556 if ((*step)++, debugCheckerCount && popcount<Full>(st->checkersBB) > 2)
1559 if ((*step)++, debugBitboards)
1561 // The intersection of the white and black pieces must be empty
1562 if (pieces(WHITE) & pieces(BLACK))
1565 // The union of the white and black pieces must be equal to all
1567 if ((pieces(WHITE) | pieces(BLACK)) != pieces())
1570 // Separate piece type bitboards must have empty intersections
1571 for (PieceType p1 = PAWN; p1 <= KING; p1++)
1572 for (PieceType p2 = PAWN; p2 <= KING; p2++)
1573 if (p1 != p2 && (pieces(p1) & pieces(p2)))
1577 if ((*step)++, ep_square() != SQ_NONE && relative_rank(sideToMove, ep_square()) != RANK_6)
1580 if ((*step)++, debugKey && st->key != compute_key())
1583 if ((*step)++, debugPawnKey && st->pawnKey != compute_pawn_key())
1586 if ((*step)++, debugMaterialKey && st->materialKey != compute_material_key())
1589 if ((*step)++, debugIncrementalEval && st->psqScore != compute_psq_score())
1592 if ((*step)++, debugNonPawnMaterial)
1594 if ( st->npMaterial[WHITE] != compute_non_pawn_material(WHITE)
1595 || st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
1599 if ((*step)++, debugPieceCounts)
1600 for (Color c = WHITE; c <= BLACK; c++)
1601 for (PieceType pt = PAWN; pt <= KING; pt++)
1602 if (pieceCount[c][pt] != popcount<Full>(pieces(c, pt)))
1605 if ((*step)++, debugPieceList)
1606 for (Color c = WHITE; c <= BLACK; c++)
1607 for (PieceType pt = PAWN; pt <= KING; pt++)
1608 for (int i = 0; i < pieceCount[c][pt]; i++)
1610 if (piece_on(piece_list(c, pt)[i]) != make_piece(c, pt))
1613 if (index[piece_list(c, pt)[i]] != i)
1617 if ((*step)++, debugCastleSquares)
1618 for (Color c = WHITE; c <= BLACK; c++)
1619 for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1))
1621 CastleRight cr = make_castle_right(c, s);
1623 if (!can_castle(cr))
1626 if ((castleRightsMask[king_square(c)] & cr) != cr)
1629 if ( piece_on(castleRookSquare[c][s]) != make_piece(c, ROOK)
1630 || castleRightsMask[castleRookSquare[c][s]] != cr)