2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) Copyright (C) 2008 Marco Costalba
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
28 // Simple macro to wrap a very common while loop, no facny, no flexibility,
29 // hardcoded list name 'mlist' and from square 'from'.
30 #define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
33 //// Local definitions
43 const bool CAPTURE = true;
44 const bool NON_CAPTURE = false;
47 bool castling_is_check(const Position&, CastlingSide);
50 template<CastlingSide Side>
51 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist);
53 template<Color Us, Rank, Bitboard, SquareDelta>
54 MoveStack* generate_pawn_blocking_evasions(const Position&, Bitboard, Bitboard, MoveStack*);
56 template<Color, Color, Bitboard, SquareDelta, SquareDelta, SquareDelta>
57 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist);
59 template<Color, Color, Bitboard, Bitboard, SquareDelta, SquareDelta, SquareDelta>
60 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist);
62 template<Color, Color, Bitboard, Bitboard, SquareDelta>
63 MoveStack* generate_pawn_checks(const Position&, Bitboard, Square, MoveStack*);
65 // Template generate_piece_checks() with specializations
67 MoveStack* generate_piece_checks(const Position&, MoveStack*, Color, Bitboard, Square);
70 inline MoveStack* generate_piece_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
73 return generate_pawn_checks<WHITE, BLACK, Rank8BB, Rank3BB, DELTA_N>(p, dc, ksq, m);
75 return generate_pawn_checks<BLACK, WHITE, Rank1BB, Rank6BB, DELTA_S>(p, dc, ksq, m);
79 // Template generate_piece_moves() with specializations
81 MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard);
84 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target);
86 template<PieceType Piece, bool Capture>
87 inline MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us) {
89 assert(Piece == PAWN);
92 return (us == WHITE ? generate_pawn_captures<WHITE, BLACK, Rank8BB, DELTA_NE, DELTA_NW, DELTA_N>(p, m)
93 : generate_pawn_captures<BLACK, WHITE, Rank1BB, DELTA_SE, DELTA_SW, DELTA_S>(p, m));
95 return (us == WHITE ? generate_pawn_noncaptures<WHITE, BLACK, Rank8BB, Rank3BB, DELTA_NE, DELTA_NW, DELTA_N>(p, m)
96 : generate_pawn_noncaptures<BLACK, WHITE, Rank1BB, Rank6BB, DELTA_SE, DELTA_SW, DELTA_S>(p, m));
99 // Template generate_piece_blocking_evasions() with specializations
101 MoveStack* generate_piece_blocking_evasions(const Position&, MoveStack*, Color us, Bitboard, Bitboard);
104 inline MoveStack* generate_piece_blocking_evasions<PAWN>(const Position& p, MoveStack* m, Color us,
105 Bitboard pnd, Bitboard bs) {
107 return generate_pawn_blocking_evasions<WHITE, RANK_8, Rank3BB, DELTA_N>(p, pnd, bs, m);
109 return generate_pawn_blocking_evasions<BLACK, RANK_1, Rank6BB, DELTA_S>(p, pnd, bs, m);
119 /// generate_captures generates() all pseudo-legal captures and queen
120 /// promotions. The return value is the number of moves generated.
122 int generate_captures(const Position& pos, MoveStack* mlist) {
125 assert(!pos.is_check());
127 Color us = pos.side_to_move();
128 Bitboard target = pos.pieces_of_color(opposite_color(us));
129 MoveStack* mlist_start = mlist;
131 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
132 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
133 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
134 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
135 mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us);
136 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
137 return int(mlist - mlist_start);
141 /// generate_noncaptures() generates all pseudo-legal non-captures and
142 /// underpromotions. The return value is the number of moves generated.
144 int generate_noncaptures(const Position& pos, MoveStack* mlist) {
147 assert(!pos.is_check());
149 Color us = pos.side_to_move();
150 Bitboard target = pos.empty_squares();
151 MoveStack* mlist_start = mlist;
153 mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us);
154 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
155 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
156 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
157 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
158 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
159 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
160 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
161 return int(mlist - mlist_start);
165 /// generate_checks() generates all pseudo-legal non-capturing, non-promoting
166 /// checks. It returns the number of generated moves.
168 int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
171 assert(!pos.is_check());
173 Color us = pos.side_to_move();
174 Square ksq = pos.king_square(opposite_color(us));
175 MoveStack* mlist_start = mlist;
177 assert(pos.piece_on(ksq) == king_of_color(opposite_color(us)));
180 mlist = generate_piece_checks<PAWN>(pos, mlist, us, dc, ksq);
181 mlist = generate_piece_checks<KNIGHT>(pos, mlist, us, dc, ksq);
182 mlist = generate_piece_checks<BISHOP>(pos, mlist, us, dc, ksq);
183 mlist = generate_piece_checks<ROOK>(pos, mlist, us, dc, ksq);
184 mlist = generate_piece_checks<QUEEN>(pos, mlist, us, dc, ksq);
185 mlist = generate_piece_checks<KING>(pos, mlist, us, dc, ksq);
187 // Castling moves that give check. Very rare but nice to have!
188 if ( pos.can_castle_queenside(us)
189 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
190 && castling_is_check(pos, QUEEN_SIDE))
191 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
193 if ( pos.can_castle_kingside(us)
194 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
195 && castling_is_check(pos, KING_SIDE))
196 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
198 return int(mlist - mlist_start);
202 /// generate_evasions() generates all check evasions when the side to move is
203 /// in check. Unlike the other move generation functions, this one generates
204 /// only legal moves. It returns the number of generated moves.
206 int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
209 assert(pos.is_check());
212 Color us = pos.side_to_move();
213 Color them = opposite_color(us);
214 Square ksq = pos.king_square(us);
215 MoveStack* mlist_start = mlist;
217 assert(pos.piece_on(ksq) == king_of_color(us));
219 // The bitboard of occupied pieces without our king
220 Bitboard b_noKing = pos.occupied_squares();
221 clear_bit(&b_noKing, ksq);
223 // Find squares attacked by slider checkers, we will
224 // remove them from king evasions set so to avoid a couple
225 // of cycles in the slow king evasions legality check loop
226 // and to be able to use square_is_attacked().
227 Bitboard checkers = pos.checkers();
228 Bitboard checkersAttacks = EmptyBoardBB;
229 Bitboard b = checkers & (pos.queens() | pos.bishops());
232 from = pop_1st_bit(&b);
233 checkersAttacks |= bishop_attacks_bb(from, b_noKing);
236 b = checkers & (pos.queens() | pos.rooks());
239 from = pop_1st_bit(&b);
240 checkersAttacks |= rook_attacks_bb(from, b_noKing);
243 // Generate evasions for king
244 Bitboard b1 = pos.piece_attacks<KING>(ksq) & ~pos.pieces_of_color(us) & ~checkersAttacks;
247 to = pop_1st_bit(&b1);
248 // Note that we can use square_is_attacked() only because we
249 // have already removed slider checkers.
250 if (!pos.square_is_attacked(to, them))
251 (*mlist++).move = make_move(ksq, to);
254 // Generate evasions for other pieces only if not double check. We use a
255 // simple bit twiddling hack here rather than calling count_1s in order to
256 // save some time (we know that pos.checkers() has at most two nonzero bits).
257 if (!(checkers & (checkers - 1))) // Only one bit set?
259 Square checksq = first_1(checkers);
261 assert(pos.color_of_piece_on(checksq) == them);
263 // Generate captures of the checking piece
266 b1 = pos.pawn_attacks(them, checksq) & pos.pawns(us) & ~pinned;
269 from = pop_1st_bit(&b1);
270 if (relative_rank(us, checksq) == RANK_8)
272 (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
273 (*mlist++).move = make_promotion_move(from, checksq, ROOK);
274 (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
275 (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
277 (*mlist++).move = make_move(from, checksq);
281 b1 = ( (pos.piece_attacks<KNIGHT>(checksq) & pos.knights(us))
282 | (pos.piece_attacks<BISHOP>(checksq) & pos.bishops_and_queens(us))
283 | (pos.piece_attacks<ROOK>(checksq) & pos.rooks_and_queens(us)) ) & ~pinned;
287 from = pop_1st_bit(&b1);
288 (*mlist++).move = make_move(from, checksq);
291 // Blocking check evasions are possible only if the checking piece is
293 if (checkers & pos.sliders())
295 Bitboard blockSquares = squares_between(checksq, ksq);
297 assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
299 if (blockSquares != EmptyBoardBB)
302 mlist = generate_piece_blocking_evasions<PAWN>(pos, mlist, us, pinned, blockSquares);
303 mlist = generate_piece_blocking_evasions<KNIGHT>(pos, mlist, us, pinned, blockSquares);
304 mlist = generate_piece_blocking_evasions<BISHOP>(pos, mlist, us, pinned, blockSquares);
305 mlist = generate_piece_blocking_evasions<ROOK>(pos, mlist, us, pinned, blockSquares);
306 mlist = generate_piece_blocking_evasions<QUEEN>(pos, mlist, us, pinned, blockSquares);
310 // Finally, the special case of en passant captures. An en passant
311 // capture can only be a check evasion if the check is not a discovered
312 // check. If pos.ep_square() is set, the last move made must have been
313 // a double pawn push. If, furthermore, the checking piece is a pawn,
314 // an en passant check evasion may be possible.
315 if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them)))
317 to = pos.ep_square();
318 b1 = pos.pawn_attacks(them, to) & pos.pawns(us);
320 // The checking pawn cannot be a discovered (bishop) check candidate
321 // otherwise we were in check also before last double push move.
322 assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
323 assert(count_1s(b1) == 1 || count_1s(b1) == 2);
328 from = pop_1st_bit(&b1);
329 // Move is always legal because checking pawn is not a discovered
330 // check candidate and our capturing pawn has been already tested
331 // against pinned pieces.
332 (*mlist++).move = make_ep_move(from, to);
336 return int(mlist - mlist_start);
340 /// generate_legal_moves() computes a complete list of legal moves in the
341 /// current position. This function is not very fast, and should be used
342 /// only in situations where performance is unimportant. It wouldn't be
343 /// very hard to write an efficient legal move generator, but for the moment
344 /// we don't need it.
346 int generate_legal_moves(const Position& pos, MoveStack* mlist) {
350 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
353 return generate_evasions(pos, mlist, pinned);
355 // Generate pseudo-legal moves
356 int n = generate_captures(pos, mlist);
357 n += generate_noncaptures(pos, mlist + n);
359 // Remove illegal moves from the list
360 for (int i = 0; i < n; i++)
361 if (!pos.pl_move_is_legal(mlist[i].move, pinned))
362 mlist[i--].move = mlist[--n].move;
368 /// move_is_legal() takes a position and a (not necessarily pseudo-legal)
369 /// move and a pinned pieces bitboard as input, and tests whether
370 /// the move is legal. If the move is legal, the move itself is
371 /// returned. If not, the function returns false. This function must
372 /// only be used when the side to move is not in check.
374 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
377 assert(!pos.is_check());
378 assert(move_is_ok(m));
379 assert(pinned == pos.pinned_pieces(pos.side_to_move()));
381 Color us = pos.side_to_move();
382 Color them = opposite_color(us);
383 Square from = move_from(m);
384 Piece pc = pos.piece_on(from);
386 // If the from square is not occupied by a piece belonging to the side to
387 // move, the move is obviously not legal.
388 if (color_of_piece(pc) != us)
391 Square to = move_to(m);
396 // The piece must be a pawn and destination square must be the
397 // en passant square.
398 if ( type_of_piece(pc) != PAWN
399 || to != pos.ep_square())
402 assert(pos.square_is_empty(to));
403 assert(pos.piece_on(to - pawn_push(us)) == pawn_of_color(them));
405 // The move is pseudo-legal, check if it is also legal
406 return pos.pl_move_is_legal(m, pinned);
410 if (move_is_short_castle(m))
412 // The piece must be a king and side to move must still have
413 // the right to castle kingside.
414 if ( type_of_piece(pc) != KING
415 ||!pos.can_castle_kingside(us))
418 assert(from == pos.king_square(us));
419 assert(to == pos.initial_kr_square(us));
420 assert(pos.piece_on(to) == rook_of_color(us));
422 Square g1 = relative_square(us, SQ_G1);
423 Square f1 = relative_square(us, SQ_F1);
425 bool illegal = false;
427 // Check if any of the squares between king and rook
428 // is occupied or under attack.
429 for (s = Min(from, g1); s <= Max(from, g1); s++)
430 if ( (s != from && s != to && !pos.square_is_empty(s))
431 || pos.square_is_attacked(s, them))
434 // Check if any of the squares between king and rook
436 for (s = Min(to, f1); s <= Max(to, f1); s++)
437 if (s != from && s != to && !pos.square_is_empty(s))
443 if (move_is_long_castle(m))
445 // The piece must be a king and side to move must still have
446 // the right to castle kingside.
447 if ( type_of_piece(pc) != KING
448 ||!pos.can_castle_queenside(us))
451 assert(from == pos.king_square(us));
452 assert(to == pos.initial_qr_square(us));
453 assert(pos.piece_on(to) == rook_of_color(us));
455 Square c1 = relative_square(us, SQ_C1);
456 Square d1 = relative_square(us, SQ_D1);
458 bool illegal = false;
460 for (s = Min(from, c1); s <= Max(from, c1); s++)
461 if( (s != from && s != to && !pos.square_is_empty(s))
462 || pos.square_is_attacked(s, them))
465 for (s = Min(to, d1); s <= Max(to, d1); s++)
466 if(s != from && s != to && !pos.square_is_empty(s))
469 if ( square_file(to) == FILE_B
470 && ( pos.piece_on(to + DELTA_W) == rook_of_color(them)
471 || pos.piece_on(to + DELTA_W) == queen_of_color(them)))
479 // The destination square cannot be occupied by a friendly piece
480 if (pos.color_of_piece_on(to) == us)
483 // Proceed according to the type of the moving piece.
484 if (type_of_piece(pc) == PAWN)
486 // If the destination square is on the 8/1th rank, the move must
488 if ( ( (square_rank(to) == RANK_8 && us == WHITE)
489 ||(square_rank(to) == RANK_1 && us != WHITE))
490 && !move_promotion(m))
493 // Proceed according to the square delta between the source and
494 // destionation squares.
501 // Capture. The destination square must be occupied by an enemy
502 // piece (en passant captures was handled earlier).
503 if (pos.color_of_piece_on(to) != them)
509 // Pawn push. The destination square must be empty.
510 if (!pos.square_is_empty(to))
515 // Double white pawn push. The destination square must be on the fourth
516 // rank, and both the destination square and the square between the
517 // source and destination squares must be empty.
518 if ( square_rank(to) != RANK_4
519 || !pos.square_is_empty(to)
520 || !pos.square_is_empty(from + DELTA_N))
525 // Double black pawn push. The destination square must be on the fifth
526 // rank, and both the destination square and the square between the
527 // source and destination squares must be empty.
528 if ( square_rank(to) != RANK_5
529 || !pos.square_is_empty(to)
530 || !pos.square_is_empty(from + DELTA_S))
537 // The move is pseudo-legal, check if it is also legal
538 return pos.pl_move_is_legal(m, pinned);
541 // Luckly we can handle all the other pieces in one go
542 return ( pos.piece_attacks_square(from, to)
543 && pos.pl_move_is_legal(m, pinned)
544 && !move_promotion(m));
550 template<PieceType Piece>
551 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
556 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
558 from = pos.piece_list(us, Piece, i);
559 b = pos.piece_attacks<Piece>(from) & target;
566 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
569 Square from = pos.king_square(us);
571 b = pos.piece_attacks<KING>(from) & target;
576 template<PieceType Piece>
577 MoveStack* generate_piece_blocking_evasions(const Position& pos, MoveStack* mlist, Color us,
578 Bitboard pinned, Bitboard blockSquares) {
582 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
584 from = pos.piece_list(us, Piece, i);
585 if (pinned && bit_is_set(pinned, from))
588 b = pos.piece_attacks<Piece>(from) & blockSquares;
594 template<Color Us, Color Them, Bitboard TRank8BB, SquareDelta TDELTA_NE,
595 SquareDelta TDELTA_NW, SquareDelta TDELTA_N
597 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist) {
600 Bitboard pawns = pos.pawns(Us);
601 Bitboard enemyPieces = pos.pieces_of_color(Them);
603 // Captures in the a1-h8 (a8-h1 for black) direction
604 Bitboard b1 = (Us == WHITE ? pawns << 9 : pawns >> 7) & ~FileABB & enemyPieces;
606 // Capturing promotions
607 Bitboard b2 = b1 & TRank8BB;
610 to = pop_1st_bit(&b2);
611 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, QUEEN);
614 // Capturing non-promotions
618 to = pop_1st_bit(&b2);
619 (*mlist++).move = make_move(to - TDELTA_NE, to);
622 // Captures in the h1-a8 (h8-a1 for black) direction
623 b1 = (Us == WHITE ? pawns << 7 : pawns >> 9) & ~FileHBB & enemyPieces;
625 // Capturing promotions
629 to = pop_1st_bit(&b2);
630 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, QUEEN);
633 // Capturing non-promotions
637 to = pop_1st_bit(&b2);
638 (*mlist++).move = make_move(to - TDELTA_NW, to);
641 // Non-capturing promotions
642 b1 = (Us == WHITE ? pawns << 8 : pawns >> 8) & pos.empty_squares() & TRank8BB;
645 to = pop_1st_bit(&b1);
646 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
649 // En passant captures
650 if (pos.ep_square() != SQ_NONE)
652 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
653 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
655 b1 = pawns & pos.pawn_attacks(Them, pos.ep_square());
656 assert(b1 != EmptyBoardBB);
660 to = pop_1st_bit(&b1);
661 (*mlist++).move = make_ep_move(to, pos.ep_square());
667 template<Color Us, Color Them, Bitboard TRank8BB, Bitboard TRank3BB,
668 SquareDelta TDELTA_NE, SquareDelta TDELTA_NW, SquareDelta TDELTA_N
670 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist) {
672 Bitboard pawns = pos.pawns(Us);
673 Bitboard enemyPieces = pos.pieces_of_color(Them);
674 Bitboard emptySquares = pos.empty_squares();
678 // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
679 b1 = (Us == WHITE ? pawns << 9 : pawns >> 7) & ~FileABB & enemyPieces & TRank8BB;
682 to = pop_1st_bit(&b1);
683 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
684 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
685 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
688 // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
689 b1 = (Us == WHITE ? pawns << 7 : pawns >> 9) & ~FileHBB & enemyPieces & TRank8BB;
692 to = pop_1st_bit(&b1);
693 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
694 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
695 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
698 // Single pawn pushes
699 b1 = (Us == WHITE ? pawns << 8 : pawns >> 8) & emptySquares;
703 to = pop_1st_bit(&b2);
704 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
705 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
706 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
711 to = pop_1st_bit(&b2);
712 (*mlist++).move = make_move(to - TDELTA_N, to);
715 // Double pawn pushes
716 b2 = (Us == WHITE ? (b1 & TRank3BB) << 8 : (b1 & TRank3BB) >> 8) & emptySquares;
719 to = pop_1st_bit(&b2);
720 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
726 template<Color Us, Color Them, Bitboard TRank8BB, Bitboard TRank3BB, SquareDelta TDELTA_N>
727 MoveStack* generate_pawn_checks(const Position& pos, Bitboard dc, Square ksq, MoveStack* mlist)
729 // Find all friendly pawns not on the enemy king's file
731 Bitboard empty = pos.empty_squares();
733 if (dc != EmptyBoardBB)
735 // Pawn moves which gives discovered check. This is possible only if the
736 // pawn is not on the same file as the enemy king, because we don't
737 // generate captures.
738 b1 = pos.pawns(Us) & ~file_bb(ksq);
740 // Discovered checks, single pawn pushes, no promotions
741 b2 = b3 = (Us == WHITE ? (b1 & dc) << 8 : (b1 & dc) >> 8) & empty & ~TRank8BB;
744 Square to = pop_1st_bit(&b3);
745 (*mlist++).move = make_move(to - TDELTA_N, to);
748 // Discovered checks, double pawn pushes
749 b3 = (Us == WHITE ? (b2 & TRank3BB) << 8 : (b2 & TRank3BB) >> 8) & empty;
752 Square to = pop_1st_bit(&b3);
753 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
757 // Direct checks. These are possible only for pawns on neighboring files
758 // of the enemy king.
759 b1 = pos.pawns(Us) & neighboring_files_bb(ksq) & ~dc;
761 // Direct checks, single pawn pushes
762 b2 = (Us == WHITE ? b1 << 8 : b1 >> 8) & empty;
763 b3 = b2 & pos.pawn_attacks(Them, ksq);
766 Square to = pop_1st_bit(&b3);
767 (*mlist++).move = make_move(to - TDELTA_N, to);
770 // Direct checks, double pawn pushes
771 b3 = (Us == WHITE ? (b2 & TRank3BB) << 8 : (b2 & TRank3BB) >> 8)
773 & pos.pawn_attacks(Them, ksq);
776 Square to = pop_1st_bit(&b3);
777 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
782 template<PieceType Piece>
783 MoveStack* generate_piece_checks(const Position& pos, MoveStack* mlist, Color us,
784 Bitboard dc, Square ksq) {
786 Bitboard target = pos.pieces_of_color_and_type(us, Piece);
789 Bitboard b = target & dc;
792 Square from = pop_1st_bit(&b);
793 Bitboard bb = pos.piece_attacks<Piece>(from) & pos.empty_squares();
795 bb &= ~QueenPseudoAttacks[ksq];
802 if (Piece == KING || !b)
805 Bitboard checkSqs = pos.piece_attacks<Piece>(ksq) & pos.empty_squares();
808 Square from = pop_1st_bit(&b);
809 Bitboard bb = pos.piece_attacks<Piece>(from) & checkSqs;
815 template<Color Us, Rank TRANK_8, Bitboard TRank3BB, SquareDelta TDELTA_N>
816 MoveStack* generate_pawn_blocking_evasions(const Position& pos, Bitboard pinned,
817 Bitboard blockSquares, MoveStack* mlist) {
820 // Find non-pinned pawns
821 Bitboard b1 = pos.pawns(Us) & ~pinned;
823 // Single pawn pushes. We don't have to AND with empty squares here,
824 // because the blocking squares will always be empty.
825 Bitboard b2 = (Us == WHITE ? b1 << 8 : b1 >> 8) & blockSquares;
828 to = pop_1st_bit(&b2);
830 assert(pos.piece_on(to) == EMPTY);
832 if (square_rank(to) == TRANK_8)
834 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
835 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
836 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
837 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
839 (*mlist++).move = make_move(to - TDELTA_N, to);
842 // Double pawn pushes
843 b2 = (Us == WHITE ? b1 << 8 : b1 >> 8) & pos.empty_squares() & TRank3BB;
844 b2 = (Us == WHITE ? b2 << 8 : b2 >> 8) & blockSquares;
847 to = pop_1st_bit(&b2);
849 assert(pos.piece_on(to) == EMPTY);
850 assert(Us != WHITE || square_rank(to) == RANK_4);
851 assert(Us != BLACK || square_rank(to) == RANK_5);
853 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
858 template<CastlingSide Side>
859 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
861 Color us = pos.side_to_move();
863 if ( (Side == KING_SIDE && pos.can_castle_kingside(us))
864 ||(Side == QUEEN_SIDE && pos.can_castle_queenside(us)))
866 Color them = opposite_color(us);
867 Square ksq = pos.king_square(us);
869 assert(pos.piece_on(ksq) == king_of_color(us));
871 Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
872 Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
873 Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
875 bool illegal = false;
877 assert(pos.piece_on(rsq) == rook_of_color(us));
879 // It is a bit complicated to correctly handle Chess960
880 for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
881 if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
882 || pos.square_is_attacked(s, them))
885 for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
886 if (s != ksq && s != rsq && pos.square_is_occupied(s))
889 if ( Side == QUEEN_SIDE
890 && square_file(rsq) == FILE_B
891 && ( pos.piece_on(relative_square(us, SQ_A1)) == rook_of_color(them)
892 || pos.piece_on(relative_square(us, SQ_A1)) == queen_of_color(them)))
896 (*mlist++).move = make_castle_move(ksq, rsq);
901 bool castling_is_check(const Position& pos, CastlingSide side) {
903 // After castling opponent king is attacked by the castled rook?
904 File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
905 Color us = pos.side_to_move();
906 Square ksq = pos.king_square(us);
907 Bitboard occ = pos.occupied_squares();
909 clear_bit(&occ, ksq); // Remove our king from the board
910 Square rsq = make_square(rookFile, square_rank(ksq));
911 return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));