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 // Templates for non-capture checks generation
85 template<PieceType Piece>
86 MoveStack* generate_discovered_checks(const Position& pos, Square from, MoveStack* mlist);
89 MoveStack* generate_direct_checks(const Position&, MoveStack*, Color, Bitboard, Square);
92 inline MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
94 return (us == WHITE ? generate_pawn_moves<WHITE, CHECK>(p, m, dc, ksq)
95 : generate_pawn_moves<BLACK, CHECK>(p, m, dc, ksq));
98 // Template generate_piece_evasions with specializations
100 MoveStack* generate_piece_evasions(const Position&, MoveStack*, Color, Bitboard, Bitboard);
103 inline MoveStack* generate_piece_evasions<PAWN>(const Position& p, MoveStack* m,
104 Color us, Bitboard t, Bitboard pnd) {
106 return (us == WHITE ? generate_pawn_moves<WHITE, EVASION>(p, m, pnd, SQ_NONE, t)
107 : generate_pawn_moves<BLACK, EVASION>(p, m, pnd, SQ_NONE, t));
117 /// generate_captures() generates all pseudo-legal captures and queen
118 /// promotions. Returns a pointer to the end of the move list.
120 MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
123 assert(!pos.is_check());
125 Color us = pos.side_to_move();
126 Bitboard target = pos.pieces_of_color(opposite_color(us));
128 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
129 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
130 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
131 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
132 mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us);
133 return generate_piece_moves<KING>(pos, mlist, us, target);
137 /// generate_noncaptures() generates all pseudo-legal non-captures and
138 /// underpromotions. Returns a pointer to the end of the move list.
140 MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
143 assert(!pos.is_check());
145 Color us = pos.side_to_move();
146 Bitboard target = pos.empty_squares();
148 mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us);
149 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
150 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
151 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
152 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
153 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
154 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
155 return generate_castle_moves<QUEEN_SIDE>(pos, mlist);
159 /// generate_non_capture_checks() generates all pseudo-legal non-captures and
160 /// underpromotions that give check. Returns a pointer to the end of the move list.
162 MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
165 assert(!pos.is_check());
167 Color us = pos.side_to_move();
168 Square ksq = pos.king_square(opposite_color(us));
170 assert(pos.piece_on(ksq) == piece_of_color_and_type(opposite_color(us), KING));
172 // Discovered non-capture checks
176 Square from = pop_1st_bit(&b);
177 switch (pos.type_of_piece_on(from))
179 case PAWN: /* Will be generated togheter with pawns direct checks */ break;
180 case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, from, mlist); break;
181 case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, from, mlist); break;
182 case ROOK: mlist = generate_discovered_checks<ROOK>(pos, from, mlist); break;
183 case KING: mlist = generate_discovered_checks<KING>(pos, from, mlist); break;
184 default: assert(false); break;
188 // Direct non-capture checks
189 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
190 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
191 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
192 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
193 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
195 // Castling moves that give check. Very rare but nice to have!
196 if ( pos.can_castle_queenside(us)
197 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
198 && castling_is_check(pos, QUEEN_SIDE))
199 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
201 if ( pos.can_castle_kingside(us)
202 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
203 && castling_is_check(pos, KING_SIDE))
204 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
210 /// generate_evasions() generates all check evasions when the side to move is
211 /// in check. Unlike the other move generation functions, this one generates
212 /// only legal moves. Returns a pointer to the end of the move list.
214 MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
217 assert(pos.is_check());
220 Color us = pos.side_to_move();
221 Color them = opposite_color(us);
222 Square ksq = pos.king_square(us);
223 Bitboard sliderAttacks = EmptyBoardBB;
224 Bitboard checkers = pos.checkers();
226 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
228 // The bitboard of occupied pieces without our king
229 Bitboard b_noKing = pos.occupied_squares();
230 clear_bit(&b_noKing, ksq);
232 // Find squares attacked by slider checkers, we will remove
233 // them from the king evasions set so to avoid a couple
234 // of cycles in the slow king evasions legality check loop
235 // and to be able to use attackers_to().
236 Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
239 from = pop_1st_bit(&b);
240 sliderAttacks |= bishop_attacks_bb(from, b_noKing);
243 b = checkers & pos.pieces(ROOK, QUEEN);
246 from = pop_1st_bit(&b);
247 sliderAttacks |= rook_attacks_bb(from, b_noKing);
250 // Generate evasions for king, capture and non capture moves
251 Bitboard enemy = pos.pieces_of_color(them);
252 Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
255 // Note that we can use attackers_to() only because we have already
256 // removed from b1 the squares attacked by slider checkers.
257 to = pop_1st_bit(&b1);
258 if (!(pos.attackers_to(to) & enemy))
259 (*mlist++).move = make_move(ksq, to);
262 // Generate evasions for other pieces only if not double check. We use a
263 // simple bit twiddling hack here rather than calling count_1s in order to
264 // save some time (we know that pos.checkers() has at most two nonzero bits).
265 if (!(checkers & (checkers - 1))) // Only one bit set?
267 Square checksq = first_1(checkers);
269 assert(pos.color_of_piece_on(checksq) == them);
271 // Generate captures of the checking piece
274 b1 = pos.attacks_from<PAWN>(checksq, them) & pos.pieces(PAWN, us) & ~pinned;
277 from = pop_1st_bit(&b1);
278 if (relative_rank(us, checksq) == RANK_8)
280 (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
281 (*mlist++).move = make_promotion_move(from, checksq, ROOK);
282 (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
283 (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
285 (*mlist++).move = make_move(from, checksq);
289 b1 = ( (pos.attacks_from<KNIGHT>(checksq) & pos.pieces(KNIGHT, us))
290 | (pos.attacks_from<BISHOP>(checksq) & pos.pieces(BISHOP, QUEEN, us))
291 | (pos.attacks_from<ROOK>(checksq) & pos.pieces(ROOK, QUEEN, us)) ) & ~pinned;
295 from = pop_1st_bit(&b1);
296 (*mlist++).move = make_move(from, checksq);
299 // Blocking check evasions are possible only if the checking piece is a slider
302 Bitboard blockSquares = squares_between(checksq, ksq);
304 assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
308 mlist = generate_piece_evasions<PAWN>(pos, mlist, us, blockSquares, pinned);
309 mlist = generate_piece_evasions<KNIGHT>(pos, mlist, us, blockSquares, pinned);
310 mlist = generate_piece_evasions<BISHOP>(pos, mlist, us, blockSquares, pinned);
311 mlist = generate_piece_evasions<ROOK>(pos, mlist, us, blockSquares, pinned);
312 mlist = generate_piece_evasions<QUEEN>(pos, mlist, us, blockSquares, pinned);
316 // Finally, the special case of en passant captures. An en passant
317 // capture can only be a check evasion if the check is not a discovered
318 // check. If pos.ep_square() is set, the last move made must have been
319 // a double pawn push. If, furthermore, the checking piece is a pawn,
320 // an en passant check evasion may be possible.
321 if (pos.ep_square() != SQ_NONE && (checkers & pos.pieces(PAWN, them)))
323 to = pos.ep_square();
324 b1 = pos.attacks_from<PAWN>(to, them) & pos.pieces(PAWN, us);
326 // The checking pawn cannot be a discovered (bishop) check candidate
327 // otherwise we were in check also before last double push move.
328 assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
329 assert(count_1s(b1) == 1 || count_1s(b1) == 2);
334 from = pop_1st_bit(&b1);
335 // Move is always legal because checking pawn is not a discovered
336 // check candidate and our capturing pawn has been already tested
337 // against pinned pieces.
338 (*mlist++).move = make_ep_move(from, to);
346 /// generate_moves() computes a complete list of legal or pseudo-legal moves in
347 /// the current position. This function is not very fast, and should be used
348 /// only in non time-critical paths.
350 MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLegal) {
354 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
357 return generate_evasions(pos, mlist, pinned);
359 // Generate pseudo-legal moves
360 MoveStack* last = generate_captures(pos, mlist);
361 last = generate_noncaptures(pos, last);
365 // Remove illegal moves from the list
366 for (MoveStack* cur = mlist; cur != last; cur++)
367 if (!pos.pl_move_is_legal(cur->move, pinned))
369 cur->move = (--last)->move;
376 /// move_is_legal() takes a position and a (not necessarily pseudo-legal)
377 /// move and tests whether the move is legal. This version is not very fast
378 /// and should be used only in non time-critical paths.
380 bool move_is_legal(const Position& pos, const Move m) {
382 MoveStack mlist[256];
383 MoveStack* last = generate_moves(pos, mlist, true);
384 for (MoveStack* cur = mlist; cur != last; cur++)
386 return pos.pl_move_is_legal(m);
392 /// Fast version of move_is_legal() that takes a position a move and a
393 /// bitboard of pinned pieces as input, and tests whether the move is legal.
394 /// This version must only be used when the side to move is not in check.
396 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
399 assert(!pos.is_check());
400 assert(move_is_ok(m));
401 assert(pinned == pos.pinned_pieces(pos.side_to_move()));
403 // Use a slower but simpler function for uncommon cases
404 if (move_is_ep(m) || move_is_castle(m))
405 return move_is_legal(pos, m);
407 Color us = pos.side_to_move();
408 Color them = opposite_color(us);
409 Square from = move_from(m);
410 Square to = move_to(m);
411 Piece pc = pos.piece_on(from);
413 // If the from square is not occupied by a piece belonging to the side to
414 // move, the move is obviously not legal.
415 if (color_of_piece(pc) != us)
418 // The destination square cannot be occupied by a friendly piece
419 if (pos.color_of_piece_on(to) == us)
422 // Handle the special case of a pawn move
423 if (type_of_piece(pc) == PAWN)
425 // Move direction must be compatible with pawn color
426 int direction = to - from;
427 if ((us == WHITE) != (direction > 0))
430 // A pawn move is a promotion iff the destination square is
431 // on the 8/1th rank.
432 if (( (square_rank(to) == RANK_8 && us == WHITE)
433 ||(square_rank(to) == RANK_1 && us != WHITE)) != bool(move_is_promotion(m)))
436 // Proceed according to the square delta between the origin and
437 // destination squares.
444 // Capture. The destination square must be occupied by an enemy
445 // piece (en passant captures was handled earlier).
446 if (pos.color_of_piece_on(to) != them)
452 // Pawn push. The destination square must be empty.
453 if (!pos.square_is_empty(to))
458 // Double white pawn push. The destination square must be on the fourth
459 // rank, and both the destination square and the square between the
460 // source and destination squares must be empty.
461 if ( square_rank(to) != RANK_4
462 || !pos.square_is_empty(to)
463 || !pos.square_is_empty(from + DELTA_N))
468 // Double black pawn push. The destination square must be on the fifth
469 // rank, and both the destination square and the square between the
470 // source and destination squares must be empty.
471 if ( square_rank(to) != RANK_5
472 || !pos.square_is_empty(to)
473 || !pos.square_is_empty(from + DELTA_S))
480 // The move is pseudo-legal, check if it is also legal
481 return pos.pl_move_is_legal(m, pinned);
484 // Luckly we can handle all the other pieces in one go
485 return ( bit_is_set(pos.attacks_from(pc, from), to)
486 && pos.pl_move_is_legal(m, pinned)
487 && !move_is_promotion(m));
493 template<PieceType Piece>
494 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
498 const Square* ptr = pos.piece_list_begin(us, Piece);
500 while ((from = *ptr++) != SQ_NONE)
502 b = pos.attacks_from<Piece>(from) & target;
509 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
512 Square from = pos.king_square(us);
514 b = pos.attacks_from<KING>(from) & target;
519 template<PieceType Piece>
520 MoveStack* generate_piece_evasions(const Position& pos, MoveStack* mlist,
521 Color us, Bitboard target, Bitboard pinned) {
524 const Square* ptr = pos.piece_list_begin(us, Piece);
526 while ((from = *ptr++) != SQ_NONE)
528 if (pinned && bit_is_set(pinned, from))
531 b = pos.attacks_from<Piece>(from) & target;
537 template<Color Us, SquareDelta Direction>
538 inline Bitboard move_pawns(Bitboard p) {
540 if (Direction == DELTA_N)
541 return Us == WHITE ? p << 8 : p >> 8;
542 else if (Direction == DELTA_NE)
543 return Us == WHITE ? p << 9 : p >> 7;
544 else if (Direction == DELTA_NW)
545 return Us == WHITE ? p << 7 : p >> 9;
550 template<Color Us, SquareDelta Diagonal>
551 MoveStack* generate_pawn_diagonal_captures(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion) {
553 // Calculate our parametrized parameters at compile time
554 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
555 const Bitboard TFileABB = (Diagonal == DELTA_NE ? FileABB : FileHBB);
556 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
557 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
558 const SquareDelta TTDELTA_NE = (Diagonal == DELTA_NE ? TDELTA_NE : TDELTA_NW);
562 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
563 Bitboard b1 = move_pawns<Us, Diagonal>(pawns) & ~TFileABB & enemyPieces;
565 // Capturing promotions
568 Bitboard b2 = b1 & TRank8BB;
572 to = pop_1st_bit(&b2);
573 (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, QUEEN);
577 // Capturing non-promotions
578 SERIALIZE_MOVES_D(b1, -TTDELTA_NE);
582 template<Color Us, MoveType Type>
583 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard dcp,
584 Square ksq, Bitboard blockSquares) {
586 // Calculate our parametrized parameters at compile time
587 const Color Them = (Us == WHITE ? BLACK : WHITE);
588 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
589 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
590 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
591 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
592 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
593 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
595 Bitboard b1, b2, dcPawns1, dcPawns2;
597 Bitboard pawns = (Type == EVASION ? pos.pieces(PAWN, Us) & ~dcp : pos.pieces(PAWN, Us));
598 bool possiblePromotion = pawns & TRank7BB;
602 // Standard captures and capturing promotions in both directions
603 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
604 mlist = generate_pawn_diagonal_captures<Us, DELTA_NE>(mlist, pawns, enemyPieces, possiblePromotion);
605 mlist = generate_pawn_diagonal_captures<Us, DELTA_NW>(mlist, pawns, enemyPieces, possiblePromotion);
608 if (possiblePromotion)
610 // When generating checks consider under-promotion moves (both captures
611 // and non captures) only if can give a discovery check. Note that dcp
612 // is dc bitboard or pinned bitboard when Type == EVASION.
613 Bitboard pp = (Type == CHECK ? pawns & dcp : pawns);
615 if (Type != EVASION && Type != CAPTURE)
617 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
619 // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
620 b1 = move_pawns<Us, DELTA_NE>(pp) & ~FileABB & enemyPieces & TRank8BB;
623 to = pop_1st_bit(&b1);
624 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
625 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
626 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
629 // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
630 b1 = move_pawns<Us, DELTA_NW>(pp) & ~FileHBB & enemyPieces & TRank8BB;
633 to = pop_1st_bit(&b1);
634 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
635 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
636 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
640 // Underpromotion pawn pushes. Also queen promotions for evasions and captures.
641 b1 = move_pawns<Us, DELTA_N>(pp) & TRank8BB;
642 b1 &= (Type == EVASION ? blockSquares : pos.empty_squares());
646 to = pop_1st_bit(&b1);
647 if (Type == EVASION || Type == CAPTURE)
648 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
652 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
653 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
654 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
661 Bitboard emptySquares = pos.empty_squares();
662 dcPawns1 = dcPawns2 = EmptyBoardBB;
663 if (Type == CHECK && (pawns & dcp))
665 // Pawn moves which gives discovered check. This is possible only if the
666 // pawn is not on the same file as the enemy king, because we don't
667 // generate captures.
668 dcPawns1 = move_pawns<Us, DELTA_N>(pawns & dcp & ~file_bb(ksq)) & emptySquares & ~TRank8BB;
669 dcPawns2 = move_pawns<Us, DELTA_N>(dcPawns1 & TRank3BB) & emptySquares;
672 // Single pawn pushes
673 b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & ~TRank8BB;
674 b2 = (Type == CHECK ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns1 :
675 (Type == EVASION ? b1 & blockSquares : b1));
676 SERIALIZE_MOVES_D(b2, -TDELTA_N);
678 // Double pawn pushes
679 b1 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
680 b2 = (Type == CHECK ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns2 :
681 (Type == EVASION ? b1 & blockSquares : b1));
682 SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
684 else if (pos.ep_square() != SQ_NONE) // En passant captures
686 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
687 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
689 b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
690 assert(b1 != EmptyBoardBB);
694 to = pop_1st_bit(&b1);
695 (*mlist++).move = make_ep_move(to, pos.ep_square());
701 template<PieceType Piece>
702 MoveStack* generate_discovered_checks(const Position& pos, Square from, MoveStack* mlist) {
704 assert(Piece != QUEEN);
706 Bitboard b = pos.attacks_from<Piece>(from) & pos.empty_squares();
709 Square ksq = pos.king_square(opposite_color(pos.side_to_move()));
710 b &= ~QueenPseudoAttacks[ksq];
716 template<PieceType Piece>
717 MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
718 Bitboard dc, Square ksq) {
719 assert(Piece != KING);
723 const Square* ptr = pos.piece_list_begin(us, Piece);
725 if ((from = *ptr++) == SQ_NONE)
728 checkSqs = pos.attacks_from<Piece>(ksq) & pos.empty_squares();
732 if ( (Piece == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
733 || (Piece == ROOK && !(RookPseudoAttacks[from] & checkSqs))
734 || (Piece == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
737 if (dc && bit_is_set(dc, from))
740 Bitboard bb = pos.attacks_from<Piece>(from) & checkSqs;
743 } while ((from = *ptr++) != SQ_NONE);
748 template<CastlingSide Side>
749 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
751 Color us = pos.side_to_move();
753 if ( (Side == KING_SIDE && pos.can_castle_kingside(us))
754 ||(Side == QUEEN_SIDE && pos.can_castle_queenside(us)))
756 Color them = opposite_color(us);
757 Square ksq = pos.king_square(us);
759 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
761 Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
762 Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
763 Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
765 bool illegal = false;
767 assert(pos.piece_on(rsq) == piece_of_color_and_type(us, ROOK));
769 // It is a bit complicated to correctly handle Chess960
770 for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
771 if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
772 ||(pos.attackers_to(s) & pos.pieces_of_color(them)))
775 for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
776 if (s != ksq && s != rsq && pos.square_is_occupied(s))
779 if ( Side == QUEEN_SIDE
780 && square_file(rsq) == FILE_B
781 && ( pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, ROOK)
782 || pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, QUEEN)))
786 (*mlist++).move = make_castle_move(ksq, rsq);
791 bool castling_is_check(const Position& pos, CastlingSide side) {
793 // After castling opponent king is attacked by the castled rook?
794 File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
795 Color us = pos.side_to_move();
796 Square ksq = pos.king_square(us);
797 Bitboard occ = pos.occupied_squares();
799 clear_bit(&occ, ksq); // Remove our king from the board
800 Square rsq = make_square(rookFile, square_rank(ksq));
801 return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));