2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
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/>.
30 // Simple macro to wrap a very common while loop, no facny, no flexibility,
31 // hardcoded list name 'mlist' and from square 'from'.
32 #define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
34 // Version used for pawns, where the 'from' square is given as a delta from the 'to' square
35 #define SERIALIZE_MOVES_D(b, d) while (b) { to = pop_1st_bit(&b); (*mlist++).move = make_move(to + (d), to); }
38 //// Local definitions
56 bool castling_is_check(const Position&, CastlingSide);
59 template<CastlingSide Side>
60 MoveStack* generate_castle_moves(const Position&, MoveStack*);
62 template<Color Us, MoveType Type>
63 MoveStack* generate_pawn_moves(const Position&, MoveStack*, Bitboard = EmptyBoardBB,
64 Square = SQ_NONE, Bitboard = EmptyBoardBB);
66 // Template generate_piece_moves (captures and non-captures) with specializations and overloads
68 MoveStack* generate_piece_moves(const Position&, MoveStack*, Color, Bitboard);
71 MoveStack* generate_piece_moves<KING>(const Position&, MoveStack*, Color, Bitboard);
73 template<PieceType Piece, MoveType Type>
74 inline MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us) {
76 assert(Piece == PAWN);
77 assert(Type == CAPTURE || Type == NON_CAPTURE);
79 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m)
80 : generate_pawn_moves<BLACK, Type>(p, m));
83 // Template generate_piece_checks with specializations
85 MoveStack* generate_piece_checks(const Position&, MoveStack*, Color, Bitboard, Square);
88 inline MoveStack* generate_piece_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
90 return (us == WHITE ? generate_pawn_moves<WHITE, CHECK>(p, m, dc, ksq)
91 : generate_pawn_moves<BLACK, CHECK>(p, m, dc, ksq));
94 // Template generate_piece_evasions with specializations
96 MoveStack* generate_piece_evasions(const Position&, MoveStack*, Color, Bitboard, Bitboard);
99 inline MoveStack* generate_piece_evasions<PAWN>(const Position& p, MoveStack* m,
100 Color us, Bitboard t, Bitboard pnd) {
102 return (us == WHITE ? generate_pawn_moves<WHITE, EVASION>(p, m, pnd, SQ_NONE, t)
103 : generate_pawn_moves<BLACK, EVASION>(p, m, pnd, SQ_NONE, t));
113 /// generate_captures() generates all pseudo-legal captures and queen
114 /// promotions. Returns a pointer to the end of the move list.
116 MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
119 assert(!pos.is_check());
121 Color us = pos.side_to_move();
122 Bitboard target = pos.pieces_of_color(opposite_color(us));
124 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
125 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
126 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
127 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
128 mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us);
129 return generate_piece_moves<KING>(pos, mlist, us, target);
133 /// generate_noncaptures() generates all pseudo-legal non-captures and
134 /// underpromotions. Returns a pointer to the end of the move list.
136 MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
139 assert(!pos.is_check());
141 Color us = pos.side_to_move();
142 Bitboard target = pos.empty_squares();
144 mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us);
145 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
146 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
147 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
148 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
149 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
150 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
151 return generate_castle_moves<QUEEN_SIDE>(pos, mlist);
155 /// generate_non_capture_checks() generates all pseudo-legal non-captures and
156 /// underpromotions that give check. Returns a pointer to the end of the move list.
158 MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
161 assert(!pos.is_check());
163 Color us = pos.side_to_move();
164 Square ksq = pos.king_square(opposite_color(us));
166 assert(pos.piece_on(ksq) == piece_of_color_and_type(opposite_color(us), KING));
169 mlist = generate_piece_checks<PAWN>(pos, mlist, us, dc, ksq);
170 mlist = generate_piece_checks<KNIGHT>(pos, mlist, us, dc, ksq);
171 mlist = generate_piece_checks<BISHOP>(pos, mlist, us, dc, ksq);
172 mlist = generate_piece_checks<ROOK>(pos, mlist, us, dc, ksq);
173 mlist = generate_piece_checks<QUEEN>(pos, mlist, us, dc, ksq);
174 mlist = generate_piece_checks<KING>(pos, mlist, us, dc, ksq);
176 // Castling moves that give check. Very rare but nice to have!
177 if ( pos.can_castle_queenside(us)
178 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
179 && castling_is_check(pos, QUEEN_SIDE))
180 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
182 if ( pos.can_castle_kingside(us)
183 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
184 && castling_is_check(pos, KING_SIDE))
185 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
191 /// generate_evasions() generates all check evasions when the side to move is
192 /// in check. Unlike the other move generation functions, this one generates
193 /// only legal moves. Returns a pointer to the end of the move list.
195 MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
198 assert(pos.is_check());
201 Color us = pos.side_to_move();
202 Color them = opposite_color(us);
203 Square ksq = pos.king_square(us);
204 Bitboard sliderAttacks = EmptyBoardBB;
205 Bitboard checkers = pos.checkers();
207 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
209 // The bitboard of occupied pieces without our king
210 Bitboard b_noKing = pos.occupied_squares();
211 clear_bit(&b_noKing, ksq);
213 // Find squares attacked by slider checkers, we will remove
214 // them from the king evasions set so to avoid a couple
215 // of cycles in the slow king evasions legality check loop
216 // and to be able to use attackers_to().
217 Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
220 from = pop_1st_bit(&b);
221 sliderAttacks |= bishop_attacks_bb(from, b_noKing);
224 b = checkers & pos.pieces(ROOK, QUEEN);
227 from = pop_1st_bit(&b);
228 sliderAttacks |= rook_attacks_bb(from, b_noKing);
231 // Generate evasions for king, capture and non capture moves
232 Bitboard enemy = pos.pieces_of_color(them);
233 Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
236 // Note that we can use attackers_to() only because we have already
237 // removed from b1 the squares attacked by slider checkers.
238 to = pop_1st_bit(&b1);
239 if (!(pos.attackers_to(to) & enemy))
240 (*mlist++).move = make_move(ksq, to);
243 // Generate evasions for other pieces only if not double check. We use a
244 // simple bit twiddling hack here rather than calling count_1s in order to
245 // save some time (we know that pos.checkers() has at most two nonzero bits).
246 if (!(checkers & (checkers - 1))) // Only one bit set?
248 Square checksq = first_1(checkers);
250 assert(pos.color_of_piece_on(checksq) == them);
252 // Generate captures of the checking piece
255 b1 = pos.attacks_from<PAWN>(checksq, them) & pos.pieces(PAWN, us) & ~pinned;
258 from = pop_1st_bit(&b1);
259 if (relative_rank(us, checksq) == RANK_8)
261 (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
262 (*mlist++).move = make_promotion_move(from, checksq, ROOK);
263 (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
264 (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
266 (*mlist++).move = make_move(from, checksq);
270 b1 = ( (pos.attacks_from<KNIGHT>(checksq) & pos.pieces(KNIGHT, us))
271 | (pos.attacks_from<BISHOP>(checksq) & pos.pieces(BISHOP, QUEEN, us))
272 | (pos.attacks_from<ROOK>(checksq) & pos.pieces(ROOK, QUEEN, us)) ) & ~pinned;
276 from = pop_1st_bit(&b1);
277 (*mlist++).move = make_move(from, checksq);
280 // Blocking check evasions are possible only if the checking piece is a slider
283 Bitboard blockSquares = squares_between(checksq, ksq);
285 assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
289 mlist = generate_piece_evasions<PAWN>(pos, mlist, us, blockSquares, pinned);
290 mlist = generate_piece_evasions<KNIGHT>(pos, mlist, us, blockSquares, pinned);
291 mlist = generate_piece_evasions<BISHOP>(pos, mlist, us, blockSquares, pinned);
292 mlist = generate_piece_evasions<ROOK>(pos, mlist, us, blockSquares, pinned);
293 mlist = generate_piece_evasions<QUEEN>(pos, mlist, us, blockSquares, pinned);
297 // Finally, the special case of en passant captures. An en passant
298 // capture can only be a check evasion if the check is not a discovered
299 // check. If pos.ep_square() is set, the last move made must have been
300 // a double pawn push. If, furthermore, the checking piece is a pawn,
301 // an en passant check evasion may be possible.
302 if (pos.ep_square() != SQ_NONE && (checkers & pos.pieces(PAWN, them)))
304 to = pos.ep_square();
305 b1 = pos.attacks_from<PAWN>(to, them) & pos.pieces(PAWN, us);
307 // The checking pawn cannot be a discovered (bishop) check candidate
308 // otherwise we were in check also before last double push move.
309 assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
310 assert(count_1s(b1) == 1 || count_1s(b1) == 2);
315 from = pop_1st_bit(&b1);
316 // Move is always legal because checking pawn is not a discovered
317 // check candidate and our capturing pawn has been already tested
318 // against pinned pieces.
319 (*mlist++).move = make_ep_move(from, to);
327 /// generate_moves() computes a complete list of legal or pseudo-legal moves in
328 /// the current position. This function is not very fast, and should be used
329 /// only in non time-critical paths.
331 MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLegal) {
335 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
338 return generate_evasions(pos, mlist, pinned);
340 // Generate pseudo-legal moves
341 MoveStack* last = generate_captures(pos, mlist);
342 last = generate_noncaptures(pos, last);
346 // Remove illegal moves from the list
347 for (MoveStack* cur = mlist; cur != last; cur++)
348 if (!pos.pl_move_is_legal(cur->move, pinned))
350 cur->move = (--last)->move;
357 /// move_is_legal() takes a position and a (not necessarily pseudo-legal)
358 /// move and tests whether the move is legal. This version is not very fast
359 /// and should be used only in non time-critical paths.
361 bool move_is_legal(const Position& pos, const Move m) {
363 MoveStack mlist[256];
364 MoveStack* last = generate_moves(pos, mlist, true);
365 for (MoveStack* cur = mlist; cur != last; cur++)
367 return pos.pl_move_is_legal(m);
373 /// Fast version of move_is_legal() that takes a position a move and a
374 /// bitboard of pinned pieces as input, and tests whether the move is legal.
375 /// This version must only be used when the side to move is not in check.
377 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
380 assert(!pos.is_check());
381 assert(move_is_ok(m));
382 assert(pinned == pos.pinned_pieces(pos.side_to_move()));
384 // Use a slower but simpler function for uncommon cases
385 if (move_is_ep(m) || move_is_castle(m))
386 return move_is_legal(pos, m);
388 Color us = pos.side_to_move();
389 Color them = opposite_color(us);
390 Square from = move_from(m);
391 Square to = move_to(m);
392 Piece pc = pos.piece_on(from);
394 // If the from square is not occupied by a piece belonging to the side to
395 // move, the move is obviously not legal.
396 if (color_of_piece(pc) != us)
399 // The destination square cannot be occupied by a friendly piece
400 if (pos.color_of_piece_on(to) == us)
403 // Handle the special case of a pawn move
404 if (type_of_piece(pc) == PAWN)
406 // Move direction must be compatible with pawn color
407 int direction = to - from;
408 if ((us == WHITE) != (direction > 0))
411 // A pawn move is a promotion iff the destination square is
412 // on the 8/1th rank.
413 if (( (square_rank(to) == RANK_8 && us == WHITE)
414 ||(square_rank(to) == RANK_1 && us != WHITE)) != bool(move_is_promotion(m)))
417 // Proceed according to the square delta between the origin and
418 // destination squares.
425 // Capture. The destination square must be occupied by an enemy
426 // piece (en passant captures was handled earlier).
427 if (pos.color_of_piece_on(to) != them)
433 // Pawn push. The destination square must be empty.
434 if (!pos.square_is_empty(to))
439 // Double white pawn push. The destination square must be on the fourth
440 // rank, and both the destination square and the square between the
441 // source and destination squares must be empty.
442 if ( square_rank(to) != RANK_4
443 || !pos.square_is_empty(to)
444 || !pos.square_is_empty(from + DELTA_N))
449 // Double black pawn push. The destination square must be on the fifth
450 // rank, and both the destination square and the square between the
451 // source and destination squares must be empty.
452 if ( square_rank(to) != RANK_5
453 || !pos.square_is_empty(to)
454 || !pos.square_is_empty(from + DELTA_S))
461 // The move is pseudo-legal, check if it is also legal
462 return pos.pl_move_is_legal(m, pinned);
465 // Luckly we can handle all the other pieces in one go
466 return ( bit_is_set(pos.attacks_from(pc, from), to)
467 && pos.pl_move_is_legal(m, pinned)
468 && !move_is_promotion(m));
474 template<PieceType Piece>
475 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
479 const Square* ptr = pos.piece_list_begin(us, Piece);
481 while ((from = *ptr++) != SQ_NONE)
483 b = pos.attacks_from<Piece>(from) & target;
490 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
493 Square from = pos.king_square(us);
495 b = pos.attacks_from<KING>(from) & target;
500 template<PieceType Piece>
501 MoveStack* generate_piece_evasions(const Position& pos, MoveStack* mlist,
502 Color us, Bitboard target, Bitboard pinned) {
505 const Square* ptr = pos.piece_list_begin(us, Piece);
507 while ((from = *ptr++) != SQ_NONE)
509 if (pinned && bit_is_set(pinned, from))
512 b = pos.attacks_from<Piece>(from) & target;
518 template<Color Us, SquareDelta Direction>
519 inline Bitboard move_pawns(Bitboard p) {
521 if (Direction == DELTA_N)
522 return Us == WHITE ? p << 8 : p >> 8;
523 else if (Direction == DELTA_NE)
524 return Us == WHITE ? p << 9 : p >> 7;
525 else if (Direction == DELTA_NW)
526 return Us == WHITE ? p << 7 : p >> 9;
531 template<Color Us, SquareDelta Diagonal>
532 MoveStack* generate_pawn_diagonal_captures(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion) {
534 // Calculate our parametrized parameters at compile time
535 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
536 const Bitboard TFileABB = (Diagonal == DELTA_NE ? FileABB : FileHBB);
537 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
538 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
539 const SquareDelta TTDELTA_NE = (Diagonal == DELTA_NE ? TDELTA_NE : TDELTA_NW);
543 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
544 Bitboard b1 = move_pawns<Us, Diagonal>(pawns) & ~TFileABB & enemyPieces;
546 // Capturing promotions
549 Bitboard b2 = b1 & TRank8BB;
553 to = pop_1st_bit(&b2);
554 (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, QUEEN);
558 // Capturing non-promotions
559 SERIALIZE_MOVES_D(b1, -TTDELTA_NE);
563 template<Color Us, MoveType Type>
564 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard dcp,
565 Square ksq, Bitboard blockSquares) {
567 // Calculate our parametrized parameters at compile time
568 const Color Them = (Us == WHITE ? BLACK : WHITE);
569 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
570 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
571 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
572 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
573 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
574 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
576 Bitboard b1, b2, dcPawns1, dcPawns2;
578 Bitboard pawns = (Type == EVASION ? pos.pieces(PAWN, Us) & ~dcp : pos.pieces(PAWN, Us));
579 bool possiblePromotion = pawns & TRank7BB;
583 // Standard captures and capturing promotions in both directions
584 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
585 mlist = generate_pawn_diagonal_captures<Us, DELTA_NE>(mlist, pawns, enemyPieces, possiblePromotion);
586 mlist = generate_pawn_diagonal_captures<Us, DELTA_NW>(mlist, pawns, enemyPieces, possiblePromotion);
589 if (possiblePromotion)
591 // When generating checks consider under-promotion moves (both captures
592 // and non captures) only if can give a discovery check. Note that dcp
593 // is dc bitboard or pinned bitboard when Type == EVASION.
594 Bitboard pp = (Type == CHECK ? pawns & dcp : pawns);
596 if (Type != EVASION && Type != CAPTURE)
598 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
600 // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
601 b1 = move_pawns<Us, DELTA_NE>(pp) & ~FileABB & enemyPieces & TRank8BB;
604 to = pop_1st_bit(&b1);
605 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
606 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
607 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
610 // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
611 b1 = move_pawns<Us, DELTA_NW>(pp) & ~FileHBB & enemyPieces & TRank8BB;
614 to = pop_1st_bit(&b1);
615 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
616 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
617 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
621 // Underpromotion pawn pushes. Also queen promotions for evasions and captures.
622 b1 = move_pawns<Us, DELTA_N>(pp) & TRank8BB;
623 b1 &= (Type == EVASION ? blockSquares : pos.empty_squares());
627 to = pop_1st_bit(&b1);
628 if (Type == EVASION || Type == CAPTURE)
629 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
633 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
634 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
635 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
642 Bitboard emptySquares = pos.empty_squares();
643 dcPawns1 = dcPawns2 = EmptyBoardBB;
644 if (Type == CHECK && (pawns & dcp))
646 // Pawn moves which gives discovered check. This is possible only if the
647 // pawn is not on the same file as the enemy king, because we don't
648 // generate captures.
649 dcPawns1 = move_pawns<Us, DELTA_N>(pawns & dcp & ~file_bb(ksq)) & emptySquares & ~TRank8BB;
650 dcPawns2 = move_pawns<Us, DELTA_N>(dcPawns1 & TRank3BB) & emptySquares;
653 // Single pawn pushes
654 b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & ~TRank8BB;
655 b2 = (Type == CHECK ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns1 :
656 (Type == EVASION ? b1 & blockSquares : b1));
657 SERIALIZE_MOVES_D(b2, -TDELTA_N);
659 // Double pawn pushes
660 b1 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
661 b2 = (Type == CHECK ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns2 :
662 (Type == EVASION ? b1 & blockSquares : b1));
663 SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
665 else if (pos.ep_square() != SQ_NONE) // En passant captures
667 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
668 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
670 b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
671 assert(b1 != EmptyBoardBB);
675 to = pop_1st_bit(&b1);
676 (*mlist++).move = make_ep_move(to, pos.ep_square());
682 template<PieceType Piece>
683 MoveStack* generate_piece_checks(const Position& pos, MoveStack* mlist, Color us,
684 Bitboard dc, Square ksq) {
686 Bitboard target = pos.pieces(Piece, us);
688 // Discovered non-capture checks
689 Bitboard b = target & dc;
691 assert(Piece != QUEEN || !b);
695 Square from = pop_1st_bit(&b);
696 Bitboard bb = pos.attacks_from<Piece>(from) & pos.empty_squares();
698 bb &= ~QueenPseudoAttacks[ksq];
703 // Direct non-capture checks
705 Bitboard checkSqs = pos.attacks_from<Piece>(ksq) & pos.empty_squares();
706 if (Piece != KING && checkSqs)
710 Square from = pop_1st_bit(&b);
711 if ( (Piece == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
712 || (Piece == ROOK && !(RookPseudoAttacks[from] & checkSqs))
713 || (Piece == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
716 Bitboard bb = pos.attacks_from<Piece>(from) & checkSqs;
723 template<CastlingSide Side>
724 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
726 Color us = pos.side_to_move();
728 if ( (Side == KING_SIDE && pos.can_castle_kingside(us))
729 ||(Side == QUEEN_SIDE && pos.can_castle_queenside(us)))
731 Color them = opposite_color(us);
732 Square ksq = pos.king_square(us);
734 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
736 Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
737 Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
738 Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
740 bool illegal = false;
742 assert(pos.piece_on(rsq) == piece_of_color_and_type(us, ROOK));
744 // It is a bit complicated to correctly handle Chess960
745 for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
746 if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
747 ||(pos.attackers_to(s) & pos.pieces_of_color(them)))
750 for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
751 if (s != ksq && s != rsq && pos.square_is_occupied(s))
754 if ( Side == QUEEN_SIDE
755 && square_file(rsq) == FILE_B
756 && ( pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, ROOK)
757 || pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, QUEEN)))
761 (*mlist++).move = make_castle_move(ksq, rsq);
766 bool castling_is_check(const Position& pos, CastlingSide side) {
768 // After castling opponent king is attacked by the castled rook?
769 File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
770 Color us = pos.side_to_move();
771 Square ksq = pos.king_square(us);
772 Bitboard occ = pos.occupied_squares();
774 clear_bit(&occ, ksq); // Remove our king from the board
775 Square rsq = make_square(rookFile, square_rank(ksq));
776 return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));