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 Square from = from_sq(m);
546 Square to = to_sq(m);
547 Piece pc = piece_moved(m);
549 // Use a slower but simpler function for uncommon cases
550 if (type_of(m) != NORMAL)
551 return move_is_legal(m);
553 // Is not a promotion, so promotion piece must be empty
554 if (promotion_type(m) - 2 != NO_PIECE_TYPE)
557 // If the from square is not occupied by a piece belonging to the side to
558 // move, the move is obviously not legal.
559 if (pc == NO_PIECE || color_of(pc) != us)
562 // The destination square cannot be occupied by a friendly piece
563 if (piece_on(to) != NO_PIECE && color_of(piece_on(to)) == us)
566 // Handle the special case of a pawn move
567 if (type_of(pc) == PAWN)
569 // Move direction must be compatible with pawn color
570 int direction = to - from;
571 if ((us == WHITE) != (direction > 0))
574 // We have already handled promotion moves, so destination
575 // cannot be on the 8/1th rank.
576 if (rank_of(to) == RANK_8 || rank_of(to) == RANK_1)
579 // Proceed according to the square delta between the origin and
580 // destination squares.
587 // Capture. The destination square must be occupied by an enemy
588 // piece (en passant captures was handled earlier).
589 if (piece_on(to) == NO_PIECE || color_of(piece_on(to)) != ~us)
592 // From and to files must be one file apart, avoids a7h5
593 if (abs(file_of(from) - file_of(to)) != 1)
599 // Pawn push. The destination square must be empty.
605 // Double white pawn push. The destination square must be on the fourth
606 // rank, and both the destination square and the square between the
607 // source and destination squares must be empty.
608 if ( rank_of(to) != RANK_4
610 || !is_empty(from + DELTA_N))
615 // Double black pawn push. The destination square must be on the fifth
616 // rank, and both the destination square and the square between the
617 // source and destination squares must be empty.
618 if ( rank_of(to) != RANK_5
620 || !is_empty(from + DELTA_S))
628 else if (!(attacks_from(pc, from) & to))
631 // Evasions generator already takes care to avoid some kind of illegal moves
632 // and pl_move_is_legal() relies on this. So we have to take care that the
633 // same kind of moves are filtered out here.
636 if (type_of(pc) != KING)
638 // Double check? In this case a king move is required
639 if (more_than_one(checkers()))
642 // Our move must be a blocking evasion or a capture of the checking piece
643 if (!((between_bb(lsb(checkers()), king_square(us)) | checkers()) & to))
646 // In case of king moves under check we have to remove king so to catch
647 // as invalid moves like b1a1 when opposite queen is on c1.
648 else if (attackers_to(to, pieces() ^ from) & pieces(~us))
656 /// Position::move_gives_check() tests whether a pseudo-legal move gives a check
658 bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
661 assert(ci.dcCandidates == discovered_check_candidates());
662 assert(color_of(piece_moved(m)) == sideToMove);
664 Square from = from_sq(m);
665 Square to = to_sq(m);
666 PieceType pt = type_of(piece_on(from));
669 if (ci.checkSq[pt] & to)
673 if (ci.dcCandidates && (ci.dcCandidates & from))
675 // For pawn and king moves we need to verify also direction
676 if ( (pt != PAWN && pt != KING)
677 || !squares_aligned(from, to, king_square(~sideToMove)))
681 // Can we skip the ugly special cases ?
682 if (type_of(m) == NORMAL)
685 Color us = sideToMove;
686 Square ksq = king_square(~us);
691 return attacks_from(Piece(promotion_type(m)), to, pieces() ^ from) & ksq;
693 // En passant capture with check ? We have already handled the case
694 // of direct checks and ordinary discovered check, the only case we
695 // need to handle is the unusual case of a discovered check through
696 // the captured pawn.
699 Square capsq = file_of(to) | rank_of(from);
700 Bitboard b = (pieces() ^ from ^ capsq) | to;
702 return (attacks_bb< ROOK>(ksq, b) & pieces(us, QUEEN, ROOK))
703 | (attacks_bb<BISHOP>(ksq, b) & pieces(us, QUEEN, BISHOP));
708 Square rfrom = to; // 'King captures the rook' notation
709 Square kto = relative_square(us, rfrom > kfrom ? SQ_G1 : SQ_C1);
710 Square rto = relative_square(us, rfrom > kfrom ? SQ_F1 : SQ_D1);
711 Bitboard b = (pieces() ^ kfrom ^ rfrom) | rto | kto;
713 return attacks_bb<ROOK>(rto, b) & ksq;
722 /// Position::do_move() makes a move, and saves all information necessary
723 /// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
724 /// moves should be filtered out before this function is called.
726 void Position::do_move(Move m, StateInfo& newSt) {
729 do_move(m, newSt, ci, move_gives_check(m, ci));
732 void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
735 assert(&newSt != st);
740 // Copy some fields of old state to our new StateInfo object except the ones
741 // which are going to be recalculated from scratch anyway, then switch our state
742 // pointer to point to the new, ready to be updated, state.
743 memcpy(&newSt, st, StateCopySize64 * sizeof(uint64_t));
748 // Update side to move
751 // Increment the 50 moves rule draw counter. Resetting it to zero in the
752 // case of a capture or a pawn move is taken care of later.
756 if (type_of(m) == CASTLE)
759 do_castle_move<true>(m);
763 Color us = sideToMove;
765 Square from = from_sq(m);
766 Square to = to_sq(m);
767 Piece piece = piece_on(from);
768 PieceType pt = type_of(piece);
769 PieceType capture = type_of(m) == ENPASSANT ? PAWN : type_of(piece_on(to));
771 assert(color_of(piece) == us);
772 assert(piece_on(to) == NO_PIECE || color_of(piece_on(to)) == them);
773 assert(capture != KING);
779 // If the captured piece is a pawn, update pawn hash key, otherwise
780 // update non-pawn material.
783 if (type_of(m) == ENPASSANT)
785 capsq += pawn_push(them);
788 assert(to == st->epSquare);
789 assert(relative_rank(us, to) == RANK_6);
790 assert(piece_on(to) == NO_PIECE);
791 assert(piece_on(capsq) == make_piece(them, PAWN));
793 board[capsq] = NO_PIECE;
796 st->pawnKey ^= Zobrist::psq[them][PAWN][capsq];
799 st->npMaterial[them] -= PieceValue[MG][capture];
801 // Remove the captured piece
802 byTypeBB[ALL_PIECES] ^= capsq;
803 byTypeBB[capture] ^= capsq;
804 byColorBB[them] ^= capsq;
806 // Update piece list, move the last piece at index[capsq] position and
809 // WARNING: This is a not revresible operation. When we will reinsert the
810 // captured piece in undo_move() we will put it at the end of the list and
811 // not in its original place, it means index[] and pieceList[] are not
812 // guaranteed to be invariant to a do_move() + undo_move() sequence.
813 Square lastSquare = pieceList[them][capture][--pieceCount[them][capture]];
814 index[lastSquare] = index[capsq];
815 pieceList[them][capture][index[lastSquare]] = lastSquare;
816 pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
819 k ^= Zobrist::psq[them][capture][capsq];
820 st->materialKey ^= Zobrist::psq[them][capture][pieceCount[them][capture]];
822 // Update incremental scores
823 st->psqScore -= pieceSquareTable[make_piece(them, capture)][capsq];
825 // Reset rule 50 counter
830 k ^= Zobrist::psq[us][pt][from] ^ Zobrist::psq[us][pt][to];
832 // Reset en passant square
833 if (st->epSquare != SQ_NONE)
835 k ^= Zobrist::enpassant[file_of(st->epSquare)];
836 st->epSquare = SQ_NONE;
839 // Update castle rights if needed
840 if (st->castleRights && (castleRightsMask[from] | castleRightsMask[to]))
842 int cr = castleRightsMask[from] | castleRightsMask[to];
843 k ^= Zobrist::castle[st->castleRights & cr];
844 st->castleRights &= ~cr;
847 // Prefetch TT access as soon as we know key is updated
848 prefetch((char*)TT.first_entry(k));
851 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
852 byTypeBB[ALL_PIECES] ^= from_to_bb;
853 byTypeBB[pt] ^= from_to_bb;
854 byColorBB[us] ^= from_to_bb;
856 board[to] = board[from];
857 board[from] = NO_PIECE;
859 // Update piece lists, index[from] is not updated and becomes stale. This
860 // works as long as index[] is accessed just by known occupied squares.
861 index[to] = index[from];
862 pieceList[us][pt][index[to]] = to;
864 // If the moving piece is a pawn do some special extra work
867 // Set en-passant square, only if moved pawn can be captured
868 if ( (int(to) ^ int(from)) == 16
869 && (attacks_from<PAWN>(from + pawn_push(us), us) & pieces(them, PAWN)))
871 st->epSquare = Square((from + to) / 2);
872 k ^= Zobrist::enpassant[file_of(st->epSquare)];
875 if (type_of(m) == PROMOTION)
877 PieceType promotion = promotion_type(m);
879 assert(relative_rank(us, to) == RANK_8);
880 assert(promotion >= KNIGHT && promotion <= QUEEN);
882 // Replace the pawn with the promoted piece
883 byTypeBB[PAWN] ^= to;
884 byTypeBB[promotion] |= to;
885 board[to] = make_piece(us, promotion);
887 // Update piece lists, move the last pawn at index[to] position
888 // and shrink the list. Add a new promotion piece to the list.
889 Square lastSquare = pieceList[us][PAWN][--pieceCount[us][PAWN]];
890 index[lastSquare] = index[to];
891 pieceList[us][PAWN][index[lastSquare]] = lastSquare;
892 pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
893 index[to] = pieceCount[us][promotion];
894 pieceList[us][promotion][index[to]] = to;
897 k ^= Zobrist::psq[us][PAWN][to] ^ Zobrist::psq[us][promotion][to];
898 st->pawnKey ^= Zobrist::psq[us][PAWN][to];
899 st->materialKey ^= Zobrist::psq[us][promotion][pieceCount[us][promotion]++]
900 ^ Zobrist::psq[us][PAWN][pieceCount[us][PAWN]];
902 // Update incremental score
903 st->psqScore += pieceSquareTable[make_piece(us, promotion)][to]
904 - pieceSquareTable[make_piece(us, PAWN)][to];
907 st->npMaterial[us] += PieceValue[MG][promotion];
910 // Update pawn hash key
911 st->pawnKey ^= Zobrist::psq[us][PAWN][from] ^ Zobrist::psq[us][PAWN][to];
913 // Reset rule 50 draw counter
917 // Prefetch pawn and material hash tables
918 prefetch((char*)thisThread->pawnsTable[st->pawnKey]);
919 prefetch((char*)thisThread->materialTable[st->materialKey]);
921 // Update incremental scores
922 st->psqScore += psq_delta(piece, from, to);
925 st->capturedType = capture;
927 // Update the key with the final value
930 // Update checkers bitboard, piece must be already moved
935 if (type_of(m) != NORMAL)
936 st->checkersBB = attackers_to(king_square(them)) & pieces(us);
940 if (ci.checkSq[pt] & to)
941 st->checkersBB |= to;
944 if (ci.dcCandidates && (ci.dcCandidates & from))
947 st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(us, QUEEN, ROOK);
950 st->checkersBB |= attacks_from<BISHOP>(king_square(them)) & pieces(us, QUEEN, BISHOP);
955 sideToMove = ~sideToMove;
961 /// Position::undo_move() unmakes a move. When it returns, the position should
962 /// be restored to exactly the same state as before the move was made.
964 void Position::undo_move(Move m) {
968 sideToMove = ~sideToMove;
970 if (type_of(m) == CASTLE)
972 do_castle_move<false>(m);
976 Color us = sideToMove;
978 Square from = from_sq(m);
979 Square to = to_sq(m);
980 Piece piece = piece_on(to);
981 PieceType pt = type_of(piece);
982 PieceType capture = st->capturedType;
984 assert(is_empty(from));
985 assert(color_of(piece) == us);
986 assert(capture != KING);
988 if (type_of(m) == PROMOTION)
990 PieceType promotion = promotion_type(m);
992 assert(promotion == pt);
993 assert(relative_rank(us, to) == RANK_8);
994 assert(promotion >= KNIGHT && promotion <= QUEEN);
996 // Replace the promoted piece with the pawn
997 byTypeBB[promotion] ^= to;
998 byTypeBB[PAWN] |= to;
999 board[to] = make_piece(us, PAWN);
1001 // Update piece lists, move the last promoted piece at index[to] position
1002 // and shrink the list. Add a new pawn to the list.
1003 Square lastSquare = pieceList[us][promotion][--pieceCount[us][promotion]];
1004 index[lastSquare] = index[to];
1005 pieceList[us][promotion][index[lastSquare]] = lastSquare;
1006 pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
1007 index[to] = pieceCount[us][PAWN]++;
1008 pieceList[us][PAWN][index[to]] = to;
1013 // Put the piece back at the source square
1014 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
1015 byTypeBB[ALL_PIECES] ^= from_to_bb;
1016 byTypeBB[pt] ^= from_to_bb;
1017 byColorBB[us] ^= from_to_bb;
1019 board[from] = board[to];
1020 board[to] = NO_PIECE;
1022 // Update piece lists, index[to] is not updated and becomes stale. This
1023 // works as long as index[] is accessed just by known occupied squares.
1024 index[from] = index[to];
1025 pieceList[us][pt][index[from]] = from;
1031 if (type_of(m) == ENPASSANT)
1033 capsq -= pawn_push(us);
1036 assert(to == st->previous->epSquare);
1037 assert(relative_rank(us, to) == RANK_6);
1038 assert(piece_on(capsq) == NO_PIECE);
1041 // Restore the captured piece
1042 byTypeBB[ALL_PIECES] |= capsq;
1043 byTypeBB[capture] |= capsq;
1044 byColorBB[them] |= capsq;
1046 board[capsq] = make_piece(them, capture);
1048 // Update piece list, add a new captured piece in capsq square
1049 index[capsq] = pieceCount[them][capture]++;
1050 pieceList[them][capture][index[capsq]] = capsq;
1053 // Finally point our state pointer back to the previous state
1056 assert(pos_is_ok());
1060 /// Position::do_castle_move() is a private method used to do/undo a castling
1061 /// move. Note that castling moves are encoded as "king captures friendly rook"
1062 /// moves, for instance white short castling in a non-Chess960 game is encoded
1065 void Position::do_castle_move(Move m) {
1068 assert(type_of(m) == CASTLE);
1070 Square kto, kfrom, rfrom, rto, kAfter, rAfter;
1072 Color us = sideToMove;
1073 Square kBefore = from_sq(m);
1074 Square rBefore = to_sq(m);
1076 // Find after-castle squares for king and rook
1077 if (rBefore > kBefore) // O-O
1079 kAfter = relative_square(us, SQ_G1);
1080 rAfter = relative_square(us, SQ_F1);
1084 kAfter = relative_square(us, SQ_C1);
1085 rAfter = relative_square(us, SQ_D1);
1088 kfrom = Do ? kBefore : kAfter;
1089 rfrom = Do ? rBefore : rAfter;
1091 kto = Do ? kAfter : kBefore;
1092 rto = Do ? rAfter : rBefore;
1094 assert(piece_on(kfrom) == make_piece(us, KING));
1095 assert(piece_on(rfrom) == make_piece(us, ROOK));
1097 // Move the pieces, with some care; in chess960 could be kto == rfrom
1098 Bitboard k_from_to_bb = SquareBB[kfrom] ^ SquareBB[kto];
1099 Bitboard r_from_to_bb = SquareBB[rfrom] ^ SquareBB[rto];
1100 byTypeBB[KING] ^= k_from_to_bb;
1101 byTypeBB[ROOK] ^= r_from_to_bb;
1102 byTypeBB[ALL_PIECES] ^= k_from_to_bb ^ r_from_to_bb;
1103 byColorBB[us] ^= k_from_to_bb ^ r_from_to_bb;
1106 Piece king = make_piece(us, KING);
1107 Piece rook = make_piece(us, ROOK);
1108 board[kfrom] = board[rfrom] = NO_PIECE;
1112 // Update piece lists
1113 pieceList[us][KING][index[kfrom]] = kto;
1114 pieceList[us][ROOK][index[rfrom]] = rto;
1115 int tmp = index[rfrom]; // In Chess960 could be kto == rfrom
1116 index[kto] = index[kfrom];
1121 // Reset capture field
1122 st->capturedType = NO_PIECE_TYPE;
1124 // Update incremental scores
1125 st->psqScore += psq_delta(king, kfrom, kto);
1126 st->psqScore += psq_delta(rook, rfrom, rto);
1129 st->key ^= Zobrist::psq[us][KING][kfrom] ^ Zobrist::psq[us][KING][kto];
1130 st->key ^= Zobrist::psq[us][ROOK][rfrom] ^ Zobrist::psq[us][ROOK][rto];
1132 // Clear en passant square
1133 if (st->epSquare != SQ_NONE)
1135 st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
1136 st->epSquare = SQ_NONE;
1139 // Update castling rights
1140 st->key ^= Zobrist::castle[st->castleRights & castleRightsMask[kfrom]];
1141 st->castleRights &= ~castleRightsMask[kfrom];
1143 // Update checkers BB
1144 st->checkersBB = attackers_to(king_square(~us)) & pieces(us);
1146 sideToMove = ~sideToMove;
1149 // Undo: point our state pointer back to the previous state
1152 assert(pos_is_ok());
1156 /// Position::do_null_move() is used to do/undo a "null move": It flips the side
1157 /// to move and updates the hash key without executing any move on the board.
1159 void Position::do_null_move(StateInfo& backupSt) {
1161 assert(!in_check());
1163 // Back up the information necessary to undo the null move to the supplied
1164 // StateInfo object. Note that differently from normal case here backupSt
1165 // is actually used as a backup storage not as the new state. This reduces
1166 // the number of fields to be copied.
1167 StateInfo* src = Do ? st : &backupSt;
1168 StateInfo* dst = Do ? &backupSt : st;
1170 dst->key = src->key;
1171 dst->epSquare = src->epSquare;
1172 dst->psqScore = src->psqScore;
1173 dst->rule50 = src->rule50;
1174 dst->pliesFromNull = src->pliesFromNull;
1176 sideToMove = ~sideToMove;
1180 if (st->epSquare != SQ_NONE)
1181 st->key ^= Zobrist::enpassant[file_of(st->epSquare)];
1183 st->key ^= Zobrist::side;
1184 prefetch((char*)TT.first_entry(st->key));
1186 st->epSquare = SQ_NONE;
1188 st->pliesFromNull = 0;
1191 assert(pos_is_ok());
1194 // Explicit template instantiations
1195 template void Position::do_null_move<false>(StateInfo& backupSt);
1196 template void Position::do_null_move<true>(StateInfo& backupSt);
1199 /// Position::see() is a static exchange evaluator: It tries to estimate the
1200 /// material gain or loss resulting from a move. There are three versions of
1201 /// this function: One which takes a destination square as input, one takes a
1202 /// move, and one which takes a 'from' and a 'to' square. The function does
1203 /// not yet understand promotions captures.
1205 int Position::see_sign(Move m) const {
1209 // Early return if SEE cannot be negative because captured piece value
1210 // is not less then capturing one. Note that king moves always return
1211 // here because king midgame value is set to 0.
1212 if (PieceValue[MG][piece_on(to_sq(m))] >= PieceValue[MG][piece_moved(m)])
1218 int Position::see(Move m) const {
1221 Bitboard occupied, attackers, stmAttackers;
1222 int swapList[32], slIndex = 1;
1230 captured = type_of(piece_on(to));
1231 occupied = pieces() ^ from;
1233 // Handle en passant moves
1234 if (type_of(m) == ENPASSANT)
1236 Square capQq = to - pawn_push(sideToMove);
1239 assert(type_of(piece_on(capQq)) == PAWN);
1241 // Remove the captured pawn
1245 else if (type_of(m) == CASTLE)
1246 // Castle moves are implemented as king capturing the rook so cannot be
1247 // handled correctly. Simply return 0 that is always the correct value
1248 // unless the rook is ends up under attack.
1251 // Find all attackers to the destination square, with the moving piece
1252 // removed, but possibly an X-ray attacker added behind it.
1253 attackers = attackers_to(to, occupied);
1255 // If the opponent has no attackers we are finished
1256 stm = ~color_of(piece_on(from));
1257 stmAttackers = attackers & pieces(stm);
1259 return PieceValue[MG][captured];
1261 // The destination square is defended, which makes things rather more
1262 // difficult to compute. We proceed by building up a "swap list" containing
1263 // the material gain or loss at each stop in a sequence of captures to the
1264 // destination square, where the sides alternately capture, and always
1265 // capture with the least valuable piece. After each capture, we look for
1266 // new X-ray attacks from behind the capturing piece.
1267 swapList[0] = PieceValue[MG][captured];
1268 captured = type_of(piece_on(from));
1271 assert(slIndex < 32);
1273 // Add the new entry to the swap list
1274 swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured];
1277 // Locate and remove from 'occupied' the next least valuable attacker
1278 captured = next_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
1280 attackers &= occupied; // Remove the just found attacker
1282 stmAttackers = attackers & pieces(stm);
1284 if (captured == KING)
1286 // Stop before processing a king capture
1288 swapList[slIndex++] = QueenValueMg * 16;
1293 } while (stmAttackers);
1295 // Having built the swap list, we negamax through it to find the best
1296 // achievable score from the point of view of the side to move.
1298 swapList[slIndex-1] = std::min(-swapList[slIndex], swapList[slIndex-1]);
1304 /// Position::clear() erases the position object to a pristine state, with an
1305 /// empty board, white to move, and no castling rights.
1307 void Position::clear() {
1309 memset(this, 0, sizeof(Position));
1310 startState.epSquare = SQ_NONE;
1313 for (int i = 0; i < 8; i++)
1314 for (int j = 0; j < 16; j++)
1315 pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
1319 /// Position::put_piece() puts a piece on the given square of the board,
1320 /// updating the board array, pieces list, bitboards, and piece counts.
1322 void Position::put_piece(Piece p, Square s) {
1324 Color c = color_of(p);
1325 PieceType pt = type_of(p);
1328 index[s] = pieceCount[c][pt]++;
1329 pieceList[c][pt][index[s]] = s;
1331 byTypeBB[ALL_PIECES] |= s;
1337 /// Position::compute_key() computes the hash key of the position. The hash
1338 /// key is usually updated incrementally as moves are made and unmade, the
1339 /// compute_key() function is only used when a new position is set up, and
1340 /// to verify the correctness of the hash key when running in debug mode.
1342 Key Position::compute_key() const {
1344 Key k = Zobrist::castle[st->castleRights];
1346 for (Bitboard b = pieces(); b; )
1348 Square s = pop_lsb(&b);
1349 k ^= Zobrist::psq[color_of(piece_on(s))][type_of(piece_on(s))][s];
1352 if (ep_square() != SQ_NONE)
1353 k ^= Zobrist::enpassant[file_of(ep_square())];
1355 if (sideToMove == BLACK)
1362 /// Position::compute_pawn_key() computes the hash key of the position. The
1363 /// hash key is usually updated incrementally as moves are made and unmade,
1364 /// the compute_pawn_key() function is only used when a new position is set
1365 /// up, and to verify the correctness of the pawn hash key when running in
1368 Key Position::compute_pawn_key() const {
1372 for (Bitboard b = pieces(PAWN); b; )
1374 Square s = pop_lsb(&b);
1375 k ^= Zobrist::psq[color_of(piece_on(s))][PAWN][s];
1382 /// Position::compute_material_key() computes the hash key of the position.
1383 /// The hash key is usually updated incrementally as moves are made and unmade,
1384 /// the compute_material_key() function is only used when a new position is set
1385 /// up, and to verify the correctness of the material hash key when running in
1388 Key Position::compute_material_key() const {
1392 for (Color c = WHITE; c <= BLACK; c++)
1393 for (PieceType pt = PAWN; pt <= QUEEN; pt++)
1394 for (int cnt = 0; cnt < piece_count(c, pt); cnt++)
1395 k ^= Zobrist::psq[c][pt][cnt];
1401 /// Position::compute_psq_score() computes the incremental scores for the middle
1402 /// game and the endgame. These functions are used to initialize the incremental
1403 /// scores when a new position is set up, and to verify that the scores are correctly
1404 /// updated by do_move and undo_move when the program is running in debug mode.
1405 Score Position::compute_psq_score() const {
1407 Score score = SCORE_ZERO;
1409 for (Bitboard b = pieces(); b; )
1411 Square s = pop_lsb(&b);
1412 score += pieceSquareTable[piece_on(s)][s];
1419 /// Position::compute_non_pawn_material() computes the total non-pawn middle
1420 /// game material value for the given side. Material values are updated
1421 /// incrementally during the search, this function is only used while
1422 /// initializing a new Position object.
1424 Value Position::compute_non_pawn_material(Color c) const {
1426 Value value = VALUE_ZERO;
1428 for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
1429 value += piece_count(c, pt) * PieceValue[MG][pt];
1435 /// Position::is_draw() tests whether the position is drawn by material,
1436 /// repetition, or the 50 moves rule. It does not detect stalemates, this
1437 /// must be done by the search.
1438 template<bool CheckRepetition, bool CheckThreeFold>
1439 bool Position::is_draw() const {
1442 && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg))
1445 if (st->rule50 > 99 && (!in_check() || MoveList<LEGAL>(*this).size()))
1448 if (CheckRepetition)
1450 int i = 4, e = std::min(st->rule50, st->pliesFromNull), cnt;
1454 StateInfo* stp = st->previous->previous;
1456 for (cnt = 0; i <= e; i += 2)
1458 stp = stp->previous->previous;
1460 if (stp->key == st->key && (!CheckThreeFold || ++cnt >= 2))
1469 // Explicit template instantiations
1470 template bool Position::is_draw<true, true>() const;
1471 template bool Position::is_draw<true, false>() const;
1472 template bool Position::is_draw<false,false>() const;
1475 /// Position::flip() flips position with the white and black sides reversed. This
1476 /// is only useful for debugging especially for finding evaluation symmetry bugs.
1478 void Position::flip() {
1480 const Position pos(*this);
1484 sideToMove = ~pos.side_to_move();
1485 thisThread = pos.this_thread();
1486 nodes = pos.nodes_searched();
1487 chess960 = pos.is_chess960();
1488 startPosPly = pos.startpos_ply_counter();
1490 for (Square s = SQ_A1; s <= SQ_H8; s++)
1491 if (!pos.is_empty(s))
1492 put_piece(Piece(pos.piece_on(s) ^ 8), ~s);
1494 if (pos.can_castle(WHITE_OO))
1495 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, KING_SIDE));
1496 if (pos.can_castle(WHITE_OOO))
1497 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, QUEEN_SIDE));
1498 if (pos.can_castle(BLACK_OO))
1499 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, KING_SIDE));
1500 if (pos.can_castle(BLACK_OOO))
1501 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, QUEEN_SIDE));
1503 if (pos.st->epSquare != SQ_NONE)
1504 st->epSquare = ~pos.st->epSquare;
1506 st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
1508 st->key = compute_key();
1509 st->pawnKey = compute_pawn_key();
1510 st->materialKey = compute_material_key();
1511 st->psqScore = compute_psq_score();
1512 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
1513 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
1515 assert(pos_is_ok());
1519 /// Position::pos_is_ok() performs some consitency checks for the position object.
1520 /// This is meant to be helpful when debugging.
1522 bool Position::pos_is_ok(int* failedStep) const {
1524 int dummy, *step = failedStep ? failedStep : &dummy;
1526 // What features of the position should be verified?
1527 const bool all = false;
1529 const bool debugBitboards = all || false;
1530 const bool debugKingCount = all || false;
1531 const bool debugKingCapture = all || false;
1532 const bool debugCheckerCount = all || false;
1533 const bool debugKey = all || false;
1534 const bool debugMaterialKey = all || false;
1535 const bool debugPawnKey = all || false;
1536 const bool debugIncrementalEval = all || false;
1537 const bool debugNonPawnMaterial = all || false;
1538 const bool debugPieceCounts = all || false;
1539 const bool debugPieceList = all || false;
1540 const bool debugCastleSquares = all || false;
1544 if (sideToMove != WHITE && sideToMove != BLACK)
1547 if ((*step)++, piece_on(king_square(WHITE)) != W_KING)
1550 if ((*step)++, piece_on(king_square(BLACK)) != B_KING)
1553 if ((*step)++, debugKingCount)
1555 int kingCount[COLOR_NB] = {};
1557 for (Square s = SQ_A1; s <= SQ_H8; s++)
1558 if (type_of(piece_on(s)) == KING)
1559 kingCount[color_of(piece_on(s))]++;
1561 if (kingCount[0] != 1 || kingCount[1] != 1)
1565 if ((*step)++, debugKingCapture)
1566 if (attackers_to(king_square(~sideToMove)) & pieces(sideToMove))
1569 if ((*step)++, debugCheckerCount && popcount<Full>(st->checkersBB) > 2)
1572 if ((*step)++, debugBitboards)
1574 // The intersection of the white and black pieces must be empty
1575 if (pieces(WHITE) & pieces(BLACK))
1578 // The union of the white and black pieces must be equal to all
1580 if ((pieces(WHITE) | pieces(BLACK)) != pieces())
1583 // Separate piece type bitboards must have empty intersections
1584 for (PieceType p1 = PAWN; p1 <= KING; p1++)
1585 for (PieceType p2 = PAWN; p2 <= KING; p2++)
1586 if (p1 != p2 && (pieces(p1) & pieces(p2)))
1590 if ((*step)++, ep_square() != SQ_NONE && relative_rank(sideToMove, ep_square()) != RANK_6)
1593 if ((*step)++, debugKey && st->key != compute_key())
1596 if ((*step)++, debugPawnKey && st->pawnKey != compute_pawn_key())
1599 if ((*step)++, debugMaterialKey && st->materialKey != compute_material_key())
1602 if ((*step)++, debugIncrementalEval && st->psqScore != compute_psq_score())
1605 if ((*step)++, debugNonPawnMaterial)
1607 if ( st->npMaterial[WHITE] != compute_non_pawn_material(WHITE)
1608 || st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
1612 if ((*step)++, debugPieceCounts)
1613 for (Color c = WHITE; c <= BLACK; c++)
1614 for (PieceType pt = PAWN; pt <= KING; pt++)
1615 if (pieceCount[c][pt] != popcount<Full>(pieces(c, pt)))
1618 if ((*step)++, debugPieceList)
1619 for (Color c = WHITE; c <= BLACK; c++)
1620 for (PieceType pt = PAWN; pt <= KING; pt++)
1621 for (int i = 0; i < pieceCount[c][pt]; i++)
1623 if (piece_on(piece_list(c, pt)[i]) != make_piece(c, pt))
1626 if (index[piece_list(c, pt)[i]] != i)
1630 if ((*step)++, debugCastleSquares)
1631 for (Color c = WHITE; c <= BLACK; c++)
1632 for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1))
1634 CastleRight cr = make_castle_right(c, s);
1636 if (!can_castle(cr))
1639 if ((castleRightsMask[king_square(c)] & cr) != cr)
1642 if ( piece_on(castleRookSquare[c][s]) != make_piece(c, ROOK)
1643 || castleRightsMask[castleRookSquare[c][s]] != cr)