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/>.
38 Key Position::zobrist[2][8][64];
39 Key Position::zobEp[8];
40 Key Position::zobCastle[16];
41 Key Position::zobSideToMove;
42 Key Position::zobExclusion;
44 Score Position::pieceSquareTable[16][64];
46 // Material values arrays, indexed by Piece
47 const Value PieceValueMidgame[17] = {
49 PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
50 RookValueMidgame, QueenValueMidgame,
51 VALUE_ZERO, VALUE_ZERO, VALUE_ZERO,
52 PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
53 RookValueMidgame, QueenValueMidgame
56 const Value PieceValueEndgame[17] = {
58 PawnValueEndgame, KnightValueEndgame, BishopValueEndgame,
59 RookValueEndgame, QueenValueEndgame,
60 VALUE_ZERO, VALUE_ZERO, VALUE_ZERO,
61 PawnValueEndgame, KnightValueEndgame, BishopValueEndgame,
62 RookValueEndgame, QueenValueEndgame
65 // To convert a Piece to and from a FEN char
66 static const string PieceToChar(" PNBRQK pnbrqk");
71 CheckInfo::CheckInfo(const Position& pos) {
73 Color them = ~pos.side_to_move();
74 ksq = pos.king_square(them);
76 pinned = pos.pinned_pieces();
77 dcCandidates = pos.discovered_check_candidates();
79 checkSq[PAWN] = pos.attacks_from<PAWN>(ksq, them);
80 checkSq[KNIGHT] = pos.attacks_from<KNIGHT>(ksq);
81 checkSq[BISHOP] = pos.attacks_from<BISHOP>(ksq);
82 checkSq[ROOK] = pos.attacks_from<ROOK>(ksq);
83 checkSq[QUEEN] = checkSq[BISHOP] | checkSq[ROOK];
88 /// Position::operator=() creates a copy of 'pos'. We want the new born Position
89 /// object do not depend on any external data so we detach state pointer from
92 void Position::operator=(const Position& pos) {
94 memcpy(this, &pos, sizeof(Position));
103 /// Position::from_fen() initializes the position object with the given FEN
104 /// string. This function is not very robust - make sure that input FENs are
105 /// correct (this is assumed to be the responsibility of the GUI).
107 void Position::from_fen(const string& fenStr, bool isChess960, Thread* th) {
109 A FEN string defines a particular position using only the ASCII character set.
111 A FEN string contains six fields separated by a space. The fields are:
113 1) Piece placement (from white's perspective). Each rank is described, starting
114 with rank 8 and ending with rank 1; within each rank, the contents of each
115 square are described from file A through file H. Following the Standard
116 Algebraic Notation (SAN), each piece is identified by a single letter taken
117 from the standard English names. White pieces are designated using upper-case
118 letters ("PNBRQK") while Black take lowercase ("pnbrqk"). Blank squares are
119 noted using digits 1 through 8 (the number of blank squares), and "/"
122 2) Active color. "w" means white moves next, "b" means black.
124 3) Castling availability. If neither side can castle, this is "-". Otherwise,
125 this has one or more letters: "K" (White can castle kingside), "Q" (White
126 can castle queenside), "k" (Black can castle kingside), and/or "q" (Black
127 can castle queenside).
129 4) En passant target square (in algebraic notation). If there's no en passant
130 target square, this is "-". If a pawn has just made a 2-square move, this
131 is the position "behind" the pawn. This is recorded regardless of whether
132 there is a pawn in position to make an en passant capture.
134 5) Halfmove clock. This is the number of halfmoves since the last pawn advance
135 or capture. This is used to determine if a draw can be claimed under the
138 6) Fullmove number. The number of the full move. It starts at 1, and is
139 incremented after Black's move.
142 char col, row, token;
145 std::istringstream fen(fenStr);
148 fen >> std::noskipws;
150 // 1. Piece placement
151 while ((fen >> token) && !isspace(token))
154 sq += Square(token - '0'); // Advance the given number of files
156 else if (token == '/')
159 else if ((p = PieceToChar.find(token)) != string::npos)
161 put_piece(Piece(p), sq);
168 sideToMove = (token == 'w' ? WHITE : BLACK);
171 // 3. Castling availability. Compatible with 3 standards: Normal FEN standard,
172 // Shredder-FEN that uses the letters of the columns on which the rooks began
173 // the game instead of KQkq and also X-FEN standard that, in case of Chess960,
174 // if an inner rook is associated with the castling right, the castling tag is
175 // replaced by the file letter of the involved rook, as for the Shredder-FEN.
176 while ((fen >> token) && !isspace(token))
179 Color c = islower(token) ? BLACK : WHITE;
181 token = char(toupper(token));
184 for (rsq = relative_square(c, SQ_H1); type_of(piece_on(rsq)) != ROOK; rsq--) {}
186 else if (token == 'Q')
187 for (rsq = relative_square(c, SQ_A1); type_of(piece_on(rsq)) != ROOK; rsq++) {}
189 else if (token >= 'A' && token <= 'H')
190 rsq = make_square(File(token - 'A'), relative_rank(c, RANK_1));
195 set_castle_right(c, rsq);
198 // 4. En passant square. Ignore if no pawn capture is possible
199 if ( ((fen >> col) && (col >= 'a' && col <= 'h'))
200 && ((fen >> row) && (row == '3' || row == '6')))
202 st->epSquare = make_square(File(col - 'a'), Rank(row - '1'));
204 if (!(attackers_to(st->epSquare) & pieces(sideToMove, PAWN)))
205 st->epSquare = SQ_NONE;
208 // 5-6. Halfmove clock and fullmove number
209 fen >> std::skipws >> st->rule50 >> startPosPly;
211 // Convert from fullmove starting from 1 to ply starting from 0,
212 // handle also common incorrect FEN with fullmove = 0.
213 startPosPly = std::max(2 * (startPosPly - 1), 0) + int(sideToMove == BLACK);
215 st->key = compute_key();
216 st->pawnKey = compute_pawn_key();
217 st->materialKey = compute_material_key();
218 st->psqScore = compute_psq_score();
219 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
220 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
221 st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
222 chess960 = isChess960;
229 /// Position::set_castle_right() is an helper function used to set castling
230 /// rights given the corresponding color and the rook starting square.
232 void Position::set_castle_right(Color c, Square rfrom) {
234 Square kfrom = king_square(c);
235 CastlingSide cs = kfrom < rfrom ? KING_SIDE : QUEEN_SIDE;
236 CastleRight cr = make_castle_right(c, cs);
238 st->castleRights |= cr;
239 castleRightsMask[kfrom] |= cr;
240 castleRightsMask[rfrom] |= cr;
241 castleRookSquare[c][cs] = rfrom;
243 Square kto = relative_square(c, cs == KING_SIDE ? SQ_G1 : SQ_C1);
244 Square rto = relative_square(c, cs == KING_SIDE ? SQ_F1 : SQ_D1);
246 for (Square s = std::min(rfrom, rto); s <= std::max(rfrom, rto); s++)
247 if (s != kfrom && s != rfrom)
248 castlePath[c][cs] |= s;
250 for (Square s = std::min(kfrom, kto); s <= std::max(kfrom, kto); s++)
251 if (s != kfrom && s != rfrom)
252 castlePath[c][cs] |= s;
256 /// Position::to_fen() returns a FEN representation of the position. In case
257 /// of Chess960 the Shredder-FEN notation is used. Mainly a debugging function.
259 const string Position::to_fen() const {
261 std::ostringstream fen;
265 for (Rank rank = RANK_8; rank >= RANK_1; rank--)
269 for (File file = FILE_A; file <= FILE_H; file++)
271 sq = make_square(file, rank);
282 fen << PieceToChar[piece_on(sq)];
293 fen << (sideToMove == WHITE ? " w " : " b ");
295 if (can_castle(WHITE_OO))
296 fen << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE, KING_SIDE))))) : 'K');
298 if (can_castle(WHITE_OOO))
299 fen << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE, QUEEN_SIDE))))) : 'Q');
301 if (can_castle(BLACK_OO))
302 fen << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK, KING_SIDE))) : 'k');
304 if (can_castle(BLACK_OOO))
305 fen << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK, QUEEN_SIDE))) : 'q');
307 if (st->castleRights == CASTLES_NONE)
310 fen << (ep_square() == SQ_NONE ? " - " : " " + square_to_string(ep_square()) + " ")
311 << st->rule50 << " " << 1 + (startPosPly - int(sideToMove == BLACK)) / 2;
317 /// Position::print() prints an ASCII representation of the position to
318 /// the standard output. If a move is given then also the san is printed.
320 void Position::print(Move move) const {
322 const string dottedLine = "\n+---+---+---+---+---+---+---+---+";
323 const string twoRows = dottedLine + "\n| | . | | . | | . | | . |"
324 + dottedLine + "\n| . | | . | | . | | . | |";
326 string brd = twoRows + twoRows + twoRows + twoRows + dottedLine;
331 cout << "\nMove is: " << (sideToMove == BLACK ? ".." : "") << move_to_san(p, move);
334 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
335 if (piece_on(sq) != NO_PIECE)
336 brd[513 - 68*rank_of(sq) + 4*file_of(sq)] = PieceToChar[piece_on(sq)];
338 cout << brd << "\nFen is: " << to_fen() << "\nKey is: " << st->key << endl;
342 /// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
343 /// king) pieces for the given color. Or, when template parameter FindPinned is
344 /// false, the function return the pieces of the given color candidate for a
345 /// discovery check against the enemy king.
346 template<bool FindPinned>
347 Bitboard Position::hidden_checkers() const {
349 // Pinned pieces protect our king, dicovery checks attack the enemy king
350 Bitboard b, result = 0;
351 Bitboard pinners = pieces(FindPinned ? ~sideToMove : sideToMove);
352 Square ksq = king_square(FindPinned ? sideToMove : ~sideToMove);
354 // Pinners are sliders, that give check when candidate pinned is removed
355 pinners &= (pieces(ROOK, QUEEN) & PseudoAttacks[ROOK][ksq])
356 | (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq]);
360 b = between_bb(ksq, pop_1st_bit(&pinners)) & pieces();
362 if (b && !more_than_one(b) && (b & pieces(sideToMove)))
368 // Explicit template instantiations
369 template Bitboard Position::hidden_checkers<true>() const;
370 template Bitboard Position::hidden_checkers<false>() const;
373 /// Position::attackers_to() computes a bitboard of all pieces which attack a
374 /// given square. Slider attacks use occ bitboard as occupancy.
376 Bitboard Position::attackers_to(Square s, Bitboard occ) const {
378 return (attacks_from<PAWN>(s, BLACK) & pieces(WHITE, PAWN))
379 | (attacks_from<PAWN>(s, WHITE) & pieces(BLACK, PAWN))
380 | (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
381 | (attacks_bb<ROOK>(s, occ) & pieces(ROOK, QUEEN))
382 | (attacks_bb<BISHOP>(s, occ) & pieces(BISHOP, QUEEN))
383 | (attacks_from<KING>(s) & pieces(KING));
387 /// Position::attacks_from() computes a bitboard of all attacks of a given piece
388 /// put in a given square. Slider attacks use occ bitboard as occupancy.
390 Bitboard Position::attacks_from(Piece p, Square s, Bitboard occ) {
396 case BISHOP: return attacks_bb<BISHOP>(s, occ);
397 case ROOK : return attacks_bb<ROOK>(s, occ);
398 case QUEEN : return attacks_bb<BISHOP>(s, occ) | attacks_bb<ROOK>(s, occ);
399 default : return StepAttacksBB[p][s];
404 /// Position::move_attacks_square() tests whether a move from the current
405 /// position attacks a given square.
407 bool Position::move_attacks_square(Move m, Square s) const {
413 Square from = from_sq(m);
414 Square to = to_sq(m);
415 Piece piece = piece_moved(m);
417 assert(!is_empty(from));
419 // Update occupancy as if the piece is moving
420 occ = pieces() ^ from ^ to;
422 // The piece moved in 'to' attacks the square 's' ?
423 if (attacks_from(piece, to, occ) & s)
426 // Scan for possible X-ray attackers behind the moved piece
427 xray = (attacks_bb< ROOK>(s, occ) & pieces(color_of(piece), QUEEN, ROOK))
428 | (attacks_bb<BISHOP>(s, occ) & pieces(color_of(piece), QUEEN, BISHOP));
430 // Verify attackers are triggered by our move and not already existing
431 return xray && (xray ^ (xray & attacks_from<QUEEN>(s)));
435 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
437 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
440 assert(pinned == pinned_pieces());
442 Color us = sideToMove;
443 Square from = from_sq(m);
445 assert(color_of(piece_moved(m)) == us);
446 assert(piece_on(king_square(us)) == make_piece(us, KING));
448 // En passant captures are a tricky special case. Because they are rather
449 // uncommon, we do it simply by testing whether the king is attacked after
454 Square to = to_sq(m);
455 Square capsq = to + pawn_push(them);
456 Square ksq = king_square(us);
457 Bitboard b = (pieces() ^ from ^ capsq) | to;
459 assert(to == ep_square());
460 assert(piece_moved(m) == make_piece(us, PAWN));
461 assert(piece_on(capsq) == make_piece(them, PAWN));
462 assert(piece_on(to) == NO_PIECE);
464 return !(attacks_bb< ROOK>(ksq, b) & pieces(them, QUEEN, ROOK))
465 && !(attacks_bb<BISHOP>(ksq, b) & pieces(them, QUEEN, BISHOP));
468 // If the moving piece is a king, check whether the destination
469 // square is attacked by the opponent. Castling moves are checked
470 // for legality during move generation.
471 if (type_of(piece_on(from)) == KING)
472 return is_castle(m) || !(attackers_to(to_sq(m)) & pieces(~us));
474 // A non-king move is legal if and only if it is not pinned or it
475 // is moving along the ray towards or away from the king.
478 || squares_aligned(from, to_sq(m), king_square(us));
482 /// Position::move_is_legal() takes a random move and tests whether the move
483 /// is legal. This version is not very fast and should be used only in non
484 /// time-critical paths.
486 bool Position::move_is_legal(const Move m) const {
488 for (MoveList<MV_LEGAL> ml(*this); !ml.end(); ++ml)
496 /// Position::is_pseudo_legal() takes a random move and tests whether the move
497 /// is pseudo legal. It is used to validate moves from TT that can be corrupted
498 /// due to SMP concurrent access or hash position key aliasing.
500 bool Position::is_pseudo_legal(const Move m) const {
502 Color us = sideToMove;
503 Color them = ~sideToMove;
504 Square from = from_sq(m);
505 Square to = to_sq(m);
506 Piece pc = piece_moved(m);
508 // Use a slower but simpler function for uncommon cases
510 return move_is_legal(m);
512 // Is not a promotion, so promotion piece must be empty
513 if (promotion_type(m) - 2 != NO_PIECE_TYPE)
516 // If the from square is not occupied by a piece belonging to the side to
517 // move, the move is obviously not legal.
518 if (pc == NO_PIECE || color_of(pc) != us)
521 // The destination square cannot be occupied by a friendly piece
522 if (color_of(piece_on(to)) == us)
525 // Handle the special case of a pawn move
526 if (type_of(pc) == PAWN)
528 // Move direction must be compatible with pawn color
529 int direction = to - from;
530 if ((us == WHITE) != (direction > 0))
533 // We have already handled promotion moves, so destination
534 // cannot be on the 8/1th rank.
535 if (rank_of(to) == RANK_8 || rank_of(to) == RANK_1)
538 // Proceed according to the square delta between the origin and
539 // destination squares.
546 // Capture. The destination square must be occupied by an enemy
547 // piece (en passant captures was handled earlier).
548 if (color_of(piece_on(to)) != them)
551 // From and to files must be one file apart, avoids a7h5
552 if (abs(file_of(from) - file_of(to)) != 1)
558 // Pawn push. The destination square must be empty.
564 // Double white pawn push. The destination square must be on the fourth
565 // rank, and both the destination square and the square between the
566 // source and destination squares must be empty.
567 if ( rank_of(to) != RANK_4
569 || !is_empty(from + DELTA_N))
574 // Double black pawn push. The destination square must be on the fifth
575 // rank, and both the destination square and the square between the
576 // source and destination squares must be empty.
577 if ( rank_of(to) != RANK_5
579 || !is_empty(from + DELTA_S))
587 else if (!(attacks_from(pc, from) & to))
590 // Evasions generator already takes care to avoid some kind of illegal moves
591 // and pl_move_is_legal() relies on this. So we have to take care that the
592 // same kind of moves are filtered out here.
595 if (type_of(pc) != KING)
597 Bitboard b = checkers();
598 Square checksq = pop_1st_bit(&b);
600 if (b) // double check ? In this case a king move is required
603 // Our move must be a blocking evasion or a capture of the checking piece
604 if (!((between_bb(checksq, king_square(us)) | checkers()) & to))
607 // In case of king moves under check we have to remove king so to catch
608 // as invalid moves like b1a1 when opposite queen is on c1.
609 else if (attackers_to(to, pieces() ^ from) & pieces(~us))
617 /// Position::move_gives_check() tests whether a pseudo-legal move gives a check
619 bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
622 assert(ci.dcCandidates == discovered_check_candidates());
623 assert(color_of(piece_moved(m)) == sideToMove);
625 Square from = from_sq(m);
626 Square to = to_sq(m);
627 PieceType pt = type_of(piece_on(from));
630 if (ci.checkSq[pt] & to)
634 if (ci.dcCandidates && (ci.dcCandidates & from))
636 // For pawn and king moves we need to verify also direction
637 if ( (pt != PAWN && pt != KING)
638 || !squares_aligned(from, to, king_square(~sideToMove)))
642 // Can we skip the ugly special cases ?
646 Color us = sideToMove;
647 Square ksq = king_square(~us);
649 // Promotion with check ?
651 return attacks_from(Piece(promotion_type(m)), to, pieces() ^ from) & ksq;
653 // En passant capture with check ? We have already handled the case
654 // of direct checks and ordinary discovered check, the only case we
655 // need to handle is the unusual case of a discovered check through
656 // the captured pawn.
659 Square capsq = make_square(file_of(to), rank_of(from));
660 Bitboard b = (pieces() ^ from ^ capsq) | to;
662 return (attacks_bb< ROOK>(ksq, b) & pieces(us, QUEEN, ROOK))
663 | (attacks_bb<BISHOP>(ksq, b) & pieces(us, QUEEN, BISHOP));
666 // Castling with check ?
670 Square rfrom = to; // 'King captures the rook' notation
671 Square kto = relative_square(us, rfrom > kfrom ? SQ_G1 : SQ_C1);
672 Square rto = relative_square(us, rfrom > kfrom ? SQ_F1 : SQ_D1);
673 Bitboard b = (pieces() ^ kfrom ^ rfrom) | rto | kto;
675 return attacks_bb<ROOK>(rto, b) & ksq;
682 /// Position::do_move() makes a move, and saves all information necessary
683 /// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
684 /// moves should be filtered out before this function is called.
686 void Position::do_move(Move m, StateInfo& newSt) {
689 do_move(m, newSt, ci, move_gives_check(m, ci));
692 void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
695 assert(&newSt != st);
700 // Copy some fields of old state to our new StateInfo object except the ones
701 // which are recalculated from scratch anyway, then switch our state pointer
702 // to point to the new, ready to be updated, state.
703 memcpy(&newSt, st, sizeof(ReducedStateInfo));
708 // Update side to move
711 // Increment the 50 moves rule draw counter. Resetting it to zero in the
712 // case of a capture or a pawn move is taken care of later.
719 do_castle_move<true>(m);
723 Color us = sideToMove;
725 Square from = from_sq(m);
726 Square to = to_sq(m);
727 Piece piece = piece_on(from);
728 PieceType pt = type_of(piece);
729 PieceType capture = is_enpassant(m) ? PAWN : type_of(piece_on(to));
731 assert(color_of(piece) == us);
732 assert(color_of(piece_on(to)) != us);
733 assert(capture != KING);
739 // If the captured piece is a pawn, update pawn hash key, otherwise
740 // update non-pawn material.
745 capsq += pawn_push(them);
748 assert(to == st->epSquare);
749 assert(relative_rank(us, to) == RANK_6);
750 assert(piece_on(to) == NO_PIECE);
751 assert(piece_on(capsq) == make_piece(them, PAWN));
753 board[capsq] = NO_PIECE;
756 st->pawnKey ^= zobrist[them][PAWN][capsq];
759 st->npMaterial[them] -= PieceValueMidgame[capture];
761 // Remove the captured piece
762 byTypeBB[ALL_PIECES] ^= capsq;
763 byTypeBB[capture] ^= capsq;
764 byColorBB[them] ^= capsq;
766 // Update piece list, move the last piece at index[capsq] position and
769 // WARNING: This is a not revresible operation. When we will reinsert the
770 // captured piece in undo_move() we will put it at the end of the list and
771 // not in its original place, it means index[] and pieceList[] are not
772 // guaranteed to be invariant to a do_move() + undo_move() sequence.
773 Square lastSquare = pieceList[them][capture][--pieceCount[them][capture]];
774 index[lastSquare] = index[capsq];
775 pieceList[them][capture][index[lastSquare]] = lastSquare;
776 pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
779 k ^= zobrist[them][capture][capsq];
780 st->materialKey ^= zobrist[them][capture][pieceCount[them][capture]];
782 // Update incremental scores
783 st->psqScore -= pieceSquareTable[make_piece(them, capture)][capsq];
785 // Reset rule 50 counter
790 k ^= zobrist[us][pt][from] ^ zobrist[us][pt][to];
792 // Reset en passant square
793 if (st->epSquare != SQ_NONE)
795 k ^= zobEp[file_of(st->epSquare)];
796 st->epSquare = SQ_NONE;
799 // Update castle rights if needed
800 if (st->castleRights && (castleRightsMask[from] | castleRightsMask[to]))
802 int cr = castleRightsMask[from] | castleRightsMask[to];
803 k ^= zobCastle[st->castleRights & cr];
804 st->castleRights &= ~cr;
807 // Prefetch TT access as soon as we know key is updated
808 prefetch((char*)TT.first_entry(k));
811 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
812 byTypeBB[ALL_PIECES] ^= from_to_bb;
813 byTypeBB[pt] ^= from_to_bb;
814 byColorBB[us] ^= from_to_bb;
816 board[to] = board[from];
817 board[from] = NO_PIECE;
819 // Update piece lists, index[from] is not updated and becomes stale. This
820 // works as long as index[] is accessed just by known occupied squares.
821 index[to] = index[from];
822 pieceList[us][pt][index[to]] = to;
824 // If the moving piece is a pawn do some special extra work
827 // Set en-passant square, only if moved pawn can be captured
828 if ( (int(to) ^ int(from)) == 16
829 && (attacks_from<PAWN>(from + pawn_push(us), us) & pieces(them, PAWN)))
831 st->epSquare = Square((from + to) / 2);
832 k ^= zobEp[file_of(st->epSquare)];
837 PieceType promotion = promotion_type(m);
839 assert(relative_rank(us, to) == RANK_8);
840 assert(promotion >= KNIGHT && promotion <= QUEEN);
842 // Replace the pawn with the promoted piece
843 byTypeBB[PAWN] ^= to;
844 byTypeBB[promotion] |= to;
845 board[to] = make_piece(us, promotion);
847 // Update piece lists, move the last pawn at index[to] position
848 // and shrink the list. Add a new promotion piece to the list.
849 Square lastSquare = pieceList[us][PAWN][--pieceCount[us][PAWN]];
850 index[lastSquare] = index[to];
851 pieceList[us][PAWN][index[lastSquare]] = lastSquare;
852 pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
853 index[to] = pieceCount[us][promotion];
854 pieceList[us][promotion][index[to]] = to;
857 k ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to];
858 st->pawnKey ^= zobrist[us][PAWN][to];
859 st->materialKey ^= zobrist[us][promotion][pieceCount[us][promotion]++]
860 ^ zobrist[us][PAWN][pieceCount[us][PAWN]];
862 // Update incremental score
863 st->psqScore += pieceSquareTable[make_piece(us, promotion)][to]
864 - pieceSquareTable[make_piece(us, PAWN)][to];
867 st->npMaterial[us] += PieceValueMidgame[promotion];
870 // Update pawn hash key
871 st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
873 // Reset rule 50 draw counter
877 // Prefetch pawn and material hash tables
878 prefetch((char*)thisThread->pawnTable.entries[st->pawnKey]);
879 prefetch((char*)thisThread->materialTable.entries[st->materialKey]);
881 // Update incremental scores
882 st->psqScore += psq_delta(piece, from, to);
885 st->capturedType = capture;
887 // Update the key with the final value
890 // Update checkers bitboard, piece must be already moved
896 st->checkersBB = attackers_to(king_square(them)) & pieces(us);
900 if (ci.checkSq[pt] & to)
901 st->checkersBB |= to;
904 if (ci.dcCandidates && (ci.dcCandidates & from))
907 st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(us, QUEEN, ROOK);
910 st->checkersBB |= attacks_from<BISHOP>(king_square(them)) & pieces(us, QUEEN, BISHOP);
915 sideToMove = ~sideToMove;
921 /// Position::undo_move() unmakes a move. When it returns, the position should
922 /// be restored to exactly the same state as before the move was made.
924 void Position::undo_move(Move m) {
928 sideToMove = ~sideToMove;
932 do_castle_move<false>(m);
936 Color us = sideToMove;
938 Square from = from_sq(m);
939 Square to = to_sq(m);
940 Piece piece = piece_on(to);
941 PieceType pt = type_of(piece);
942 PieceType capture = st->capturedType;
944 assert(is_empty(from));
945 assert(color_of(piece) == us);
946 assert(capture != KING);
950 PieceType promotion = promotion_type(m);
952 assert(promotion == pt);
953 assert(relative_rank(us, to) == RANK_8);
954 assert(promotion >= KNIGHT && promotion <= QUEEN);
956 // Replace the promoted piece with the pawn
957 byTypeBB[promotion] ^= to;
958 byTypeBB[PAWN] |= to;
959 board[to] = make_piece(us, PAWN);
961 // Update piece lists, move the last promoted piece at index[to] position
962 // and shrink the list. Add a new pawn to the list.
963 Square lastSquare = pieceList[us][promotion][--pieceCount[us][promotion]];
964 index[lastSquare] = index[to];
965 pieceList[us][promotion][index[lastSquare]] = lastSquare;
966 pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
967 index[to] = pieceCount[us][PAWN]++;
968 pieceList[us][PAWN][index[to]] = to;
973 // Put the piece back at the source square
974 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
975 byTypeBB[ALL_PIECES] ^= from_to_bb;
976 byTypeBB[pt] ^= from_to_bb;
977 byColorBB[us] ^= from_to_bb;
979 board[from] = board[to];
980 board[to] = NO_PIECE;
982 // Update piece lists, index[to] is not updated and becomes stale. This
983 // works as long as index[] is accessed just by known occupied squares.
984 index[from] = index[to];
985 pieceList[us][pt][index[from]] = from;
993 capsq -= pawn_push(us);
996 assert(to == st->previous->epSquare);
997 assert(relative_rank(us, to) == RANK_6);
998 assert(piece_on(capsq) == NO_PIECE);
1001 // Restore the captured piece
1002 byTypeBB[ALL_PIECES] |= capsq;
1003 byTypeBB[capture] |= capsq;
1004 byColorBB[them] |= capsq;
1006 board[capsq] = make_piece(them, capture);
1008 // Update piece list, add a new captured piece in capsq square
1009 index[capsq] = pieceCount[them][capture]++;
1010 pieceList[them][capture][index[capsq]] = capsq;
1013 // Finally point our state pointer back to the previous state
1016 assert(pos_is_ok());
1020 /// Position::do_castle_move() is a private method used to do/undo a castling
1021 /// move. Note that castling moves are encoded as "king captures friendly rook"
1022 /// moves, for instance white short castling in a non-Chess960 game is encoded
1025 void Position::do_castle_move(Move m) {
1028 assert(is_castle(m));
1030 Square kto, kfrom, rfrom, rto, kAfter, rAfter;
1032 Color us = sideToMove;
1033 Square kBefore = from_sq(m);
1034 Square rBefore = to_sq(m);
1036 // Find after-castle squares for king and rook
1037 if (rBefore > kBefore) // O-O
1039 kAfter = relative_square(us, SQ_G1);
1040 rAfter = relative_square(us, SQ_F1);
1044 kAfter = relative_square(us, SQ_C1);
1045 rAfter = relative_square(us, SQ_D1);
1048 kfrom = Do ? kBefore : kAfter;
1049 rfrom = Do ? rBefore : rAfter;
1051 kto = Do ? kAfter : kBefore;
1052 rto = Do ? rAfter : rBefore;
1054 assert(piece_on(kfrom) == make_piece(us, KING));
1055 assert(piece_on(rfrom) == make_piece(us, ROOK));
1057 // Move the pieces, with some care; in chess960 could be kto == rfrom
1058 Bitboard k_from_to_bb = SquareBB[kfrom] ^ SquareBB[kto];
1059 Bitboard r_from_to_bb = SquareBB[rfrom] ^ SquareBB[rto];
1060 byTypeBB[KING] ^= k_from_to_bb;
1061 byTypeBB[ROOK] ^= r_from_to_bb;
1062 byTypeBB[ALL_PIECES] ^= k_from_to_bb ^ r_from_to_bb;
1063 byColorBB[us] ^= k_from_to_bb ^ r_from_to_bb;
1066 Piece king = make_piece(us, KING);
1067 Piece rook = make_piece(us, ROOK);
1068 board[kfrom] = board[rfrom] = NO_PIECE;
1072 // Update piece lists
1073 pieceList[us][KING][index[kfrom]] = kto;
1074 pieceList[us][ROOK][index[rfrom]] = rto;
1075 int tmp = index[rfrom]; // In Chess960 could be kto == rfrom
1076 index[kto] = index[kfrom];
1081 // Reset capture field
1082 st->capturedType = NO_PIECE_TYPE;
1084 // Update incremental scores
1085 st->psqScore += psq_delta(king, kfrom, kto);
1086 st->psqScore += psq_delta(rook, rfrom, rto);
1089 st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
1090 st->key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto];
1092 // Clear en passant square
1093 if (st->epSquare != SQ_NONE)
1095 st->key ^= zobEp[file_of(st->epSquare)];
1096 st->epSquare = SQ_NONE;
1099 // Update castling rights
1100 st->key ^= zobCastle[st->castleRights & castleRightsMask[kfrom]];
1101 st->castleRights &= ~castleRightsMask[kfrom];
1103 // Update checkers BB
1104 st->checkersBB = attackers_to(king_square(~us)) & pieces(us);
1106 sideToMove = ~sideToMove;
1109 // Undo: point our state pointer back to the previous state
1112 assert(pos_is_ok());
1116 /// Position::do_null_move() is used to do/undo a "null move": It flips the side
1117 /// to move and updates the hash key without executing any move on the board.
1119 void Position::do_null_move(StateInfo& backupSt) {
1121 assert(!in_check());
1123 // Back up the information necessary to undo the null move to the supplied
1124 // StateInfo object. Note that differently from normal case here backupSt
1125 // is actually used as a backup storage not as the new state. This reduces
1126 // the number of fields to be copied.
1127 StateInfo* src = Do ? st : &backupSt;
1128 StateInfo* dst = Do ? &backupSt : st;
1130 dst->key = src->key;
1131 dst->epSquare = src->epSquare;
1132 dst->psqScore = src->psqScore;
1133 dst->rule50 = src->rule50;
1134 dst->pliesFromNull = src->pliesFromNull;
1136 sideToMove = ~sideToMove;
1140 if (st->epSquare != SQ_NONE)
1141 st->key ^= zobEp[file_of(st->epSquare)];
1143 st->key ^= zobSideToMove;
1144 prefetch((char*)TT.first_entry(st->key));
1146 st->epSquare = SQ_NONE;
1148 st->pliesFromNull = 0;
1151 assert(pos_is_ok());
1154 // Explicit template instantiations
1155 template void Position::do_null_move<false>(StateInfo& backupSt);
1156 template void Position::do_null_move<true>(StateInfo& backupSt);
1159 /// Position::see() is a static exchange evaluator: It tries to estimate the
1160 /// material gain or loss resulting from a move. There are three versions of
1161 /// this function: One which takes a destination square as input, one takes a
1162 /// move, and one which takes a 'from' and a 'to' square. The function does
1163 /// not yet understand promotions captures.
1165 int Position::see_sign(Move m) const {
1169 // Early return if SEE cannot be negative because captured piece value
1170 // is not less then capturing one. Note that king moves always return
1171 // here because king midgame value is set to 0.
1172 if (PieceValueMidgame[piece_on(to_sq(m))] >= PieceValueMidgame[piece_moved(m)])
1178 int Position::see(Move m) const {
1181 Bitboard occ, attackers, stmAttackers, b;
1182 int swapList[32], slIndex = 1;
1183 PieceType capturedType, pt;
1188 // As castle moves are implemented as capturing the rook, they have
1189 // SEE == RookValueMidgame most of the times (unless the rook is under
1196 capturedType = type_of(piece_on(to));
1199 // Handle en passant moves
1200 if (is_enpassant(m))
1202 Square capQq = to - pawn_push(sideToMove);
1204 assert(!capturedType);
1205 assert(type_of(piece_on(capQq)) == PAWN);
1207 // Remove the captured pawn
1209 capturedType = PAWN;
1212 // Find all attackers to the destination square, with the moving piece
1213 // removed, but possibly an X-ray attacker added behind it.
1215 attackers = attackers_to(to, occ);
1217 // If the opponent has no attackers we are finished
1218 stm = ~color_of(piece_on(from));
1219 stmAttackers = attackers & pieces(stm);
1221 return PieceValueMidgame[capturedType];
1223 // The destination square is defended, which makes things rather more
1224 // difficult to compute. We proceed by building up a "swap list" containing
1225 // the material gain or loss at each stop in a sequence of captures to the
1226 // destination square, where the sides alternately capture, and always
1227 // capture with the least valuable piece. After each capture, we look for
1228 // new X-ray attacks from behind the capturing piece.
1229 swapList[0] = PieceValueMidgame[capturedType];
1230 capturedType = type_of(piece_on(from));
1233 // Locate the least valuable attacker for the side to move. The loop
1234 // below looks like it is potentially infinite, but it isn't. We know
1235 // that the side to move still has at least one attacker left.
1236 for (pt = PAWN; !(stmAttackers & pieces(pt)); pt++)
1239 // Remove the attacker we just found from the 'occupied' bitboard,
1240 // and scan for new X-ray attacks behind the attacker.
1241 b = stmAttackers & pieces(pt);
1242 occ ^= (b & (~b + 1));
1243 attackers |= (attacks_bb<ROOK>(to, occ) & pieces(ROOK, QUEEN))
1244 | (attacks_bb<BISHOP>(to, occ) & pieces(BISHOP, QUEEN));
1246 attackers &= occ; // Cut out pieces we've already done
1248 // Add the new entry to the swap list
1249 assert(slIndex < 32);
1250 swapList[slIndex] = -swapList[slIndex - 1] + PieceValueMidgame[capturedType];
1253 // Remember the value of the capturing piece, and change the side to
1254 // move before beginning the next iteration.
1257 stmAttackers = attackers & pieces(stm);
1259 // Stop before processing a king capture
1260 if (capturedType == KING && stmAttackers)
1262 assert(slIndex < 32);
1263 swapList[slIndex++] = QueenValueMidgame*10;
1266 } while (stmAttackers);
1268 // Having built the swap list, we negamax through it to find the best
1269 // achievable score from the point of view of the side to move.
1271 swapList[slIndex-1] = std::min(-swapList[slIndex], swapList[slIndex-1]);
1277 /// Position::clear() erases the position object to a pristine state, with an
1278 /// empty board, white to move, and no castling rights.
1280 void Position::clear() {
1282 memset(this, 0, sizeof(Position));
1283 startState.epSquare = SQ_NONE;
1286 for (int i = 0; i < 8; i++)
1287 for (int j = 0; j < 16; j++)
1288 pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
1290 for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
1291 board[sq] = NO_PIECE;
1295 /// Position::put_piece() puts a piece on the given square of the board,
1296 /// updating the board array, pieces list, bitboards, and piece counts.
1298 void Position::put_piece(Piece p, Square s) {
1300 Color c = color_of(p);
1301 PieceType pt = type_of(p);
1304 index[s] = pieceCount[c][pt]++;
1305 pieceList[c][pt][index[s]] = s;
1307 byTypeBB[ALL_PIECES] |= s;
1313 /// Position::compute_key() computes the hash key of the position. The hash
1314 /// key is usually updated incrementally as moves are made and unmade, the
1315 /// compute_key() function is only used when a new position is set up, and
1316 /// to verify the correctness of the hash key when running in debug mode.
1318 Key Position::compute_key() const {
1320 Key k = zobCastle[st->castleRights];
1322 for (Bitboard b = pieces(); b; )
1324 Square s = pop_1st_bit(&b);
1325 k ^= zobrist[color_of(piece_on(s))][type_of(piece_on(s))][s];
1328 if (ep_square() != SQ_NONE)
1329 k ^= zobEp[file_of(ep_square())];
1331 if (sideToMove == BLACK)
1338 /// Position::compute_pawn_key() computes the hash key of the position. The
1339 /// hash key is usually updated incrementally as moves are made and unmade,
1340 /// the compute_pawn_key() function is only used when a new position is set
1341 /// up, and to verify the correctness of the pawn hash key when running in
1344 Key Position::compute_pawn_key() const {
1348 for (Bitboard b = pieces(PAWN); b; )
1350 Square s = pop_1st_bit(&b);
1351 k ^= zobrist[color_of(piece_on(s))][PAWN][s];
1358 /// Position::compute_material_key() computes the hash key of the position.
1359 /// The hash key is usually updated incrementally as moves are made and unmade,
1360 /// the compute_material_key() function is only used when a new position is set
1361 /// up, and to verify the correctness of the material hash key when running in
1364 Key Position::compute_material_key() const {
1368 for (Color c = WHITE; c <= BLACK; c++)
1369 for (PieceType pt = PAWN; pt <= QUEEN; pt++)
1370 for (int cnt = 0; cnt < piece_count(c, pt); cnt++)
1371 k ^= zobrist[c][pt][cnt];
1377 /// Position::compute_psq_score() computes the incremental scores for the middle
1378 /// game and the endgame. These functions are used to initialize the incremental
1379 /// scores when a new position is set up, and to verify that the scores are correctly
1380 /// updated by do_move and undo_move when the program is running in debug mode.
1381 Score Position::compute_psq_score() const {
1383 Score score = SCORE_ZERO;
1385 for (Bitboard b = pieces(); b; )
1387 Square s = pop_1st_bit(&b);
1388 score += pieceSquareTable[piece_on(s)][s];
1395 /// Position::compute_non_pawn_material() computes the total non-pawn middle
1396 /// game material value for the given side. Material values are updated
1397 /// incrementally during the search, this function is only used while
1398 /// initializing a new Position object.
1400 Value Position::compute_non_pawn_material(Color c) const {
1402 Value value = VALUE_ZERO;
1404 for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
1405 value += piece_count(c, pt) * PieceValueMidgame[pt];
1411 /// Position::is_draw() tests whether the position is drawn by material,
1412 /// repetition, or the 50 moves rule. It does not detect stalemates, this
1413 /// must be done by the search.
1414 template<bool SkipRepetition>
1415 bool Position::is_draw() const {
1417 // Draw by material?
1419 && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMidgame))
1422 // Draw by the 50 moves rule?
1423 if (st->rule50 > 99 && (!in_check() || MoveList<MV_LEGAL>(*this).size()))
1426 // Draw by repetition?
1427 if (!SkipRepetition)
1429 int i = 4, e = std::min(st->rule50, st->pliesFromNull);
1433 StateInfo* stp = st->previous->previous;
1436 stp = stp->previous->previous;
1438 if (stp->key == st->key)
1450 // Explicit template instantiations
1451 template bool Position::is_draw<false>() const;
1452 template bool Position::is_draw<true>() const;
1455 /// Position::init() is a static member function which initializes at startup
1456 /// the various arrays used to compute hash keys and the piece square tables.
1457 /// The latter is a two-step operation: First, the white halves of the tables
1458 /// are copied from PSQT[] tables. Second, the black halves of the tables are
1459 /// initialized by flipping and changing the sign of the white scores.
1461 void Position::init() {
1465 for (Color c = WHITE; c <= BLACK; c++)
1466 for (PieceType pt = PAWN; pt <= KING; pt++)
1467 for (Square s = SQ_A1; s <= SQ_H8; s++)
1468 zobrist[c][pt][s] = rk.rand<Key>();
1470 for (File f = FILE_A; f <= FILE_H; f++)
1471 zobEp[f] = rk.rand<Key>();
1473 for (int cr = CASTLES_NONE; cr <= ALL_CASTLES; cr++)
1478 Key k = zobCastle[1ULL << pop_1st_bit(&b)];
1479 zobCastle[cr] ^= k ? k : rk.rand<Key>();
1483 zobSideToMove = rk.rand<Key>();
1484 zobExclusion = rk.rand<Key>();
1486 for (PieceType pt = PAWN; pt <= KING; pt++)
1488 Score v = make_score(PieceValueMidgame[pt], PieceValueEndgame[pt]);
1490 for (Square s = SQ_A1; s <= SQ_H8; s++)
1492 pieceSquareTable[make_piece(WHITE, pt)][ s] = (v + PSQT[pt][s]);
1493 pieceSquareTable[make_piece(BLACK, pt)][~s] = -(v + PSQT[pt][s]);
1499 /// Position::flip() flips position with the white and black sides reversed. This
1500 /// is only useful for debugging especially for finding evaluation symmetry bugs.
1502 void Position::flip() {
1504 const Position pos(*this);
1508 sideToMove = ~pos.side_to_move();
1509 thisThread = pos.this_thread();
1510 nodes = pos.nodes_searched();
1511 chess960 = pos.is_chess960();
1512 startPosPly = pos.startpos_ply_counter();
1514 for (Square s = SQ_A1; s <= SQ_H8; s++)
1515 if (!pos.is_empty(s))
1516 put_piece(Piece(pos.piece_on(s) ^ 8), ~s);
1518 if (pos.can_castle(WHITE_OO))
1519 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, KING_SIDE));
1520 if (pos.can_castle(WHITE_OOO))
1521 set_castle_right(BLACK, ~pos.castle_rook_square(WHITE, QUEEN_SIDE));
1522 if (pos.can_castle(BLACK_OO))
1523 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, KING_SIDE));
1524 if (pos.can_castle(BLACK_OOO))
1525 set_castle_right(WHITE, ~pos.castle_rook_square(BLACK, QUEEN_SIDE));
1527 if (pos.st->epSquare != SQ_NONE)
1528 st->epSquare = ~pos.st->epSquare;
1530 st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
1532 st->key = compute_key();
1533 st->pawnKey = compute_pawn_key();
1534 st->materialKey = compute_material_key();
1535 st->psqScore = compute_psq_score();
1536 st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
1537 st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
1539 assert(pos_is_ok());
1543 /// Position::pos_is_ok() performs some consitency checks for the position object.
1544 /// This is meant to be helpful when debugging.
1546 bool Position::pos_is_ok(int* failedStep) const {
1548 int dummy, *step = failedStep ? failedStep : &dummy;
1550 // What features of the position should be verified?
1551 const bool all = false;
1553 const bool debugBitboards = all || false;
1554 const bool debugKingCount = all || false;
1555 const bool debugKingCapture = all || false;
1556 const bool debugCheckerCount = all || false;
1557 const bool debugKey = all || false;
1558 const bool debugMaterialKey = all || false;
1559 const bool debugPawnKey = all || false;
1560 const bool debugIncrementalEval = all || false;
1561 const bool debugNonPawnMaterial = all || false;
1562 const bool debugPieceCounts = all || false;
1563 const bool debugPieceList = all || false;
1564 const bool debugCastleSquares = all || false;
1568 if (sideToMove != WHITE && sideToMove != BLACK)
1571 if ((*step)++, piece_on(king_square(WHITE)) != W_KING)
1574 if ((*step)++, piece_on(king_square(BLACK)) != B_KING)
1577 if ((*step)++, debugKingCount)
1579 int kingCount[2] = {};
1581 for (Square s = SQ_A1; s <= SQ_H8; s++)
1582 if (type_of(piece_on(s)) == KING)
1583 kingCount[color_of(piece_on(s))]++;
1585 if (kingCount[0] != 1 || kingCount[1] != 1)
1589 if ((*step)++, debugKingCapture)
1590 if (attackers_to(king_square(~sideToMove)) & pieces(sideToMove))
1593 if ((*step)++, debugCheckerCount && popcount<Full>(st->checkersBB) > 2)
1596 if ((*step)++, debugBitboards)
1598 // The intersection of the white and black pieces must be empty
1599 if (pieces(WHITE) & pieces(BLACK))
1602 // The union of the white and black pieces must be equal to all
1604 if ((pieces(WHITE) | pieces(BLACK)) != pieces())
1607 // Separate piece type bitboards must have empty intersections
1608 for (PieceType p1 = PAWN; p1 <= KING; p1++)
1609 for (PieceType p2 = PAWN; p2 <= KING; p2++)
1610 if (p1 != p2 && (pieces(p1) & pieces(p2)))
1614 if ((*step)++, ep_square() != SQ_NONE && relative_rank(sideToMove, ep_square()) != RANK_6)
1617 if ((*step)++, debugKey && st->key != compute_key())
1620 if ((*step)++, debugPawnKey && st->pawnKey != compute_pawn_key())
1623 if ((*step)++, debugMaterialKey && st->materialKey != compute_material_key())
1626 if ((*step)++, debugIncrementalEval && st->psqScore != compute_psq_score())
1629 if ((*step)++, debugNonPawnMaterial)
1631 if ( st->npMaterial[WHITE] != compute_non_pawn_material(WHITE)
1632 || st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
1636 if ((*step)++, debugPieceCounts)
1637 for (Color c = WHITE; c <= BLACK; c++)
1638 for (PieceType pt = PAWN; pt <= KING; pt++)
1639 if (pieceCount[c][pt] != popcount<Full>(pieces(c, pt)))
1642 if ((*step)++, debugPieceList)
1643 for (Color c = WHITE; c <= BLACK; c++)
1644 for (PieceType pt = PAWN; pt <= KING; pt++)
1645 for (int i = 0; i < pieceCount[c][pt]; i++)
1647 if (piece_on(piece_list(c, pt)[i]) != make_piece(c, pt))
1650 if (index[piece_list(c, pt)[i]] != i)
1654 if ((*step)++, debugCastleSquares)
1655 for (Color c = WHITE; c <= BLACK; c++)
1656 for (CastlingSide s = KING_SIDE; s <= QUEEN_SIDE; s = CastlingSide(s + 1))
1658 CastleRight cr = make_castle_right(c, s);
1660 if (!can_castle(cr))
1663 if ((castleRightsMask[king_square(c)] & cr) != cr)
1666 if ( piece_on(castleRookSquare[c][s]) != make_piece(c, ROOK)
1667 || castleRightsMask[castleRookSquare[c][s]] != cr)