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. This
205 /// function is very ugly, and needs cleaning up some time later. FIXME
207 int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
210 assert(pos.is_check());
213 Color us = pos.side_to_move();
214 Color them = opposite_color(us);
215 Square ksq = pos.king_square(us);
216 MoveStack* mlist_start = mlist;
218 assert(pos.piece_on(ksq) == king_of_color(us));
220 // The bitboard of occupied pieces without our king
221 Bitboard b2 = pos.occupied_squares();
224 // Find squares attacked by slider checkers, we will
225 // remove them from king evasions set so to avoid a couple
226 // of cycles in the slow king evasions legality check loop
227 // and to be able to use square_is_attacked().
228 Bitboard checkers = pos.checkers();
229 Bitboard checkersAttacks = EmptyBoardBB;
230 Bitboard b = checkers & (pos.queens() | pos.bishops());
233 from = pop_1st_bit(&b);
234 checkersAttacks |= bishop_attacks_bb(from, b2);
237 b = checkers & (pos.queens() | pos.rooks());
240 from = pop_1st_bit(&b);
241 checkersAttacks |= rook_attacks_bb(from, b2);
244 // Generate evasions for king
245 Bitboard b1 = pos.piece_attacks<KING>(ksq) & ~pos.pieces_of_color(us) & ~checkersAttacks;
248 to = pop_1st_bit(&b1);
249 // Note that we can use square_is_attacked() only because we
250 // have already removed sliders checkers.
251 if (!pos.square_is_attacked(to, them))
252 (*mlist++).move = make_move(ksq, to);
255 // Generate evasions for other pieces only if not double check. We use a
256 // simple bit twiddling hack here rather than calling count_1s in order to
257 // save some time (we know that pos.checkers() has at most two nonzero bits).
258 if (!(checkers & (checkers - 1))) // Only one bit set?
260 Square checksq = first_1(checkers);
262 assert(pos.color_of_piece_on(checksq) == them);
264 // Generate captures of the checking piece
267 b1 = pos.pawn_attacks(them, checksq) & pos.pawns(us) & ~pinned;
270 from = pop_1st_bit(&b1);
271 if (relative_rank(us, checksq) == RANK_8)
273 (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
274 (*mlist++).move = make_promotion_move(from, checksq, ROOK);
275 (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
276 (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
278 (*mlist++).move = make_move(from, checksq);
282 b1 = ( (pos.piece_attacks<KNIGHT>(checksq) & pos.knights(us))
283 | (pos.piece_attacks<BISHOP>(checksq) & pos.bishops_and_queens(us))
284 | (pos.piece_attacks<ROOK>(checksq) & pos.rooks_and_queens(us)) ) & ~pinned;
288 from = pop_1st_bit(&b1);
289 (*mlist++).move = make_move(from, checksq);
292 // Blocking check evasions are possible only if the checking piece is
294 if (checkers & pos.sliders())
296 Bitboard blockSquares = squares_between(checksq, ksq);
298 assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
301 mlist = generate_piece_blocking_evasions<PAWN>(pos, mlist, us, pinned, blockSquares);
302 mlist = generate_piece_blocking_evasions<KNIGHT>(pos, mlist, us, pinned, blockSquares);
303 mlist = generate_piece_blocking_evasions<BISHOP>(pos, mlist, us, pinned, blockSquares);
304 mlist = generate_piece_blocking_evasions<ROOK>(pos, mlist, us, pinned, blockSquares);
305 mlist = generate_piece_blocking_evasions<QUEEN>(pos, mlist, us, pinned, blockSquares);
308 // Finally, the ugly special case of en passant captures. An en passant
309 // capture can only be a check evasion if the check is not a discovered
310 // check. If pos.ep_square() is set, the last move made must have been
311 // a double pawn push. If, furthermore, the checking piece is a pawn,
312 // an en passant check evasion may be possible.
313 if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them)))
315 to = pos.ep_square();
316 b1 = pos.pawn_attacks(them, to) & pos.pawns(us);
318 // The checking pawn cannot be a discovered (bishop) check candidate
319 // otherwise we were in check also before last double push move.
320 assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
321 assert(count_1s(b1) == 1 || count_1s(b1) == 2);
326 from = pop_1st_bit(&b1);
327 // Move is always legal because checking pawn is not a discovered
328 // check candidate and our capturing pawn has been already tested
329 // against pinned pieces.
330 (*mlist++).move = make_ep_move(from, to);
334 return int(mlist - mlist_start);
338 /// generate_legal_moves() computes a complete list of legal moves in the
339 /// current position. This function is not very fast, and should be used
340 /// only in situations where performance is unimportant. It wouldn't be
341 /// very hard to write an efficient legal move generator, but for the moment
342 /// we don't need it.
344 int generate_legal_moves(const Position& pos, MoveStack* mlist) {
348 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
351 return generate_evasions(pos, mlist, pinned);
353 // Generate pseudo-legal moves
354 int n = generate_captures(pos, mlist);
355 n += generate_noncaptures(pos, mlist + n);
357 // Remove illegal moves from the list
358 for (int i = 0; i < n; i++)
359 if (!pos.pl_move_is_legal(mlist[i].move, pinned))
360 mlist[i--].move = mlist[--n].move;
366 /// move_is_legal() takes a position and a (not necessarily pseudo-legal)
367 /// move and a pinned pieces bitboard as input, and tests whether
368 /// the move is legal. If the move is legal, the move itself is
369 /// returned. If not, the function returns false. This function must
370 /// only be used when the side to move is not in check.
372 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
375 assert(!pos.is_check());
376 assert(move_is_ok(m));
377 assert(pinned == pos.pinned_pieces(pos.side_to_move()));
379 Color us = pos.side_to_move();
380 Color them = opposite_color(us);
381 Square from = move_from(m);
382 Piece pc = pos.piece_on(from);
384 // If the from square is not occupied by a piece belonging to the side to
385 // move, the move is obviously not legal.
386 if (color_of_piece(pc) != us)
389 Square to = move_to(m);
394 // The piece must be a pawn and destination square must be the
395 // en passant square.
396 if ( type_of_piece(pc) != PAWN
397 || to != pos.ep_square())
400 assert(pos.square_is_empty(to));
401 assert(pos.piece_on(to - pawn_push(us)) == pawn_of_color(them));
403 // The move is pseudo-legal, check if it is also legal
404 return pos.pl_move_is_legal(m, pinned);
408 if (move_is_short_castle(m))
410 // The piece must be a king and side to move must still have
411 // the right to castle kingside.
412 if ( type_of_piece(pc) != KING
413 ||!pos.can_castle_kingside(us))
416 assert(from == pos.king_square(us));
417 assert(to == pos.initial_kr_square(us));
418 assert(pos.piece_on(to) == rook_of_color(us));
420 Square g1 = relative_square(us, SQ_G1);
421 Square f1 = relative_square(us, SQ_F1);
423 bool illegal = false;
425 // Check if any of the squares between king and rook
426 // is occupied or under attack.
427 for (s = Min(from, g1); s <= Max(from, g1); s++)
428 if ( (s != from && s != to && !pos.square_is_empty(s))
429 || pos.square_is_attacked(s, them))
432 // Check if any of the squares between king and rook
434 for (s = Min(to, f1); s <= Max(to, f1); s++)
435 if (s != from && s != to && !pos.square_is_empty(s))
441 if (move_is_long_castle(m))
443 // The piece must be a king and side to move must still have
444 // the right to castle kingside.
445 if ( type_of_piece(pc) != KING
446 ||!pos.can_castle_queenside(us))
449 assert(from == pos.king_square(us));
450 assert(to == pos.initial_qr_square(us));
451 assert(pos.piece_on(to) == rook_of_color(us));
453 Square c1 = relative_square(us, SQ_C1);
454 Square d1 = relative_square(us, SQ_D1);
456 bool illegal = false;
458 for (s = Min(from, c1); s <= Max(from, c1); s++)
459 if( (s != from && s != to && !pos.square_is_empty(s))
460 || pos.square_is_attacked(s, them))
463 for (s = Min(to, d1); s <= Max(to, d1); s++)
464 if(s != from && s != to && !pos.square_is_empty(s))
467 if ( square_file(to) == FILE_B
468 && ( pos.piece_on(to + DELTA_W) == rook_of_color(them)
469 || pos.piece_on(to + DELTA_W) == queen_of_color(them)))
477 // The destination square cannot be occupied by a friendly piece
478 if (pos.color_of_piece_on(to) == us)
481 // Proceed according to the type of the moving piece.
482 if (type_of_piece(pc) == PAWN)
484 // If the destination square is on the 8/1th rank, the move must
486 if ( ( (square_rank(to) == RANK_8 && us == WHITE)
487 ||(square_rank(to) == RANK_1 && us != WHITE))
488 && !move_promotion(m))
491 // Proceed according to the square delta between the source and
492 // destionation squares.
499 // Capture. The destination square must be occupied by an enemy
500 // piece (en passant captures was handled earlier).
501 if (pos.color_of_piece_on(to) != them)
507 // Pawn push. The destination square must be empty.
508 if (!pos.square_is_empty(to))
513 // Double white pawn push. The destination square must be on the fourth
514 // rank, and both the destination square and the square between the
515 // source and destination squares must be empty.
516 if ( square_rank(to) != RANK_4
517 || !pos.square_is_empty(to)
518 || !pos.square_is_empty(from + DELTA_N))
523 // Double black pawn push. The destination square must be on the fifth
524 // rank, and both the destination square and the square between the
525 // source and destination squares must be empty.
526 if ( square_rank(to) != RANK_5
527 || !pos.square_is_empty(to)
528 || !pos.square_is_empty(from + DELTA_S))
535 // The move is pseudo-legal, check if it is also legal
536 return pos.pl_move_is_legal(m, pinned);
539 // Luckly we can handle all the other pieces in one go
540 return ( pos.piece_attacks_square(from, to)
541 && pos.pl_move_is_legal(m, pinned)
542 && !move_promotion(m));
548 template<PieceType Piece>
549 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
554 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
556 from = pos.piece_list(us, Piece, i);
557 b = pos.piece_attacks<Piece>(from) & target;
564 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
567 Square from = pos.king_square(us);
569 b = pos.piece_attacks<KING>(from) & target;
574 template<PieceType Piece>
575 MoveStack* generate_piece_blocking_evasions(const Position& pos, MoveStack* mlist, Color us,
576 Bitboard pinned, Bitboard blockSquares) {
580 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
582 from = pos.piece_list(us, Piece, i);
583 if (pinned && bit_is_set(pinned, from))
586 b = pos.piece_attacks<Piece>(from) & blockSquares;
592 template<Color Us, Color Them, Bitboard TRank8BB, SquareDelta TDELTA_NE,
593 SquareDelta TDELTA_NW, SquareDelta TDELTA_N
595 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist) {
598 Bitboard pawns = pos.pawns(Us);
599 Bitboard enemyPieces = pos.pieces_of_color(Them);
601 // Captures in the a1-h8 (a8-h1 for black) direction
602 Bitboard b1 = (Us == WHITE ? pawns << 9 : pawns >> 7) & ~FileABB & enemyPieces;
604 // Capturing promotions
605 Bitboard b2 = b1 & TRank8BB;
608 to = pop_1st_bit(&b2);
609 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, QUEEN);
612 // Capturing non-promotions
616 to = pop_1st_bit(&b2);
617 (*mlist++).move = make_move(to - TDELTA_NE, to);
620 // Captures in the h1-a8 (h8-a1 for black) direction
621 b1 = (Us == WHITE ? pawns << 7 : pawns >> 9) & ~FileHBB & enemyPieces;
623 // Capturing promotions
627 to = pop_1st_bit(&b2);
628 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, QUEEN);
631 // Capturing non-promotions
635 to = pop_1st_bit(&b2);
636 (*mlist++).move = make_move(to - TDELTA_NW, to);
639 // Non-capturing promotions
640 b1 = (Us == WHITE ? pawns << 8 : pawns >> 8) & pos.empty_squares() & TRank8BB;
643 to = pop_1st_bit(&b1);
644 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
647 // En passant captures
648 if (pos.ep_square() != SQ_NONE)
650 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
651 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
653 b1 = pawns & pos.pawn_attacks(Them, pos.ep_square());
654 assert(b1 != EmptyBoardBB);
658 to = pop_1st_bit(&b1);
659 (*mlist++).move = make_ep_move(to, pos.ep_square());
665 template<Color Us, Color Them, Bitboard TRank8BB, Bitboard TRank3BB,
666 SquareDelta TDELTA_NE, SquareDelta TDELTA_NW, SquareDelta TDELTA_N
668 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist) {
670 Bitboard pawns = pos.pawns(Us);
671 Bitboard enemyPieces = pos.pieces_of_color(Them);
672 Bitboard emptySquares = pos.empty_squares();
676 // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
677 b1 = (Us == WHITE ? pawns << 9 : pawns >> 7) & ~FileABB & enemyPieces & TRank8BB;
680 to = pop_1st_bit(&b1);
681 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
682 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
683 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
686 // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
687 b1 = (Us == WHITE ? pawns << 7 : pawns >> 9) & ~FileHBB & enemyPieces & TRank8BB;
690 to = pop_1st_bit(&b1);
691 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
692 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
693 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
696 // Single pawn pushes
697 b1 = (Us == WHITE ? pawns << 8 : pawns >> 8) & emptySquares;
701 to = pop_1st_bit(&b2);
702 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
703 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
704 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
709 to = pop_1st_bit(&b2);
710 (*mlist++).move = make_move(to - TDELTA_N, to);
713 // Double pawn pushes
714 b2 = (Us == WHITE ? (b1 & TRank3BB) << 8 : (b1 & TRank3BB) >> 8) & emptySquares;
717 to = pop_1st_bit(&b2);
718 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
724 template<Color Us, Color Them, Bitboard TRank8BB, Bitboard TRank3BB, SquareDelta TDELTA_N>
725 MoveStack* generate_pawn_checks(const Position& pos, Bitboard dc, Square ksq, MoveStack* mlist)
727 // Find all friendly pawns not on the enemy king's file
729 Bitboard empty = pos.empty_squares();
731 if (dc != EmptyBoardBB)
733 // Pawn moves which gives discovered check. This is possible only if the
734 // pawn is not on the same file as the enemy king, because we don't
735 // generate captures.
736 b1 = pos.pawns(Us) & ~file_bb(ksq);
738 // Discovered checks, single pawn pushes, no promotions
739 b2 = b3 = (Us == WHITE ? (b1 & dc) << 8 : (b1 & dc) >> 8) & empty & ~TRank8BB;
742 Square to = pop_1st_bit(&b3);
743 (*mlist++).move = make_move(to - TDELTA_N, to);
746 // Discovered checks, double pawn pushes
747 b3 = (Us == WHITE ? (b2 & TRank3BB) << 8 : (b2 & TRank3BB) >> 8) & empty;
750 Square to = pop_1st_bit(&b3);
751 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
755 // Direct checks. These are possible only for pawns on neighboring files
756 // of the enemy king.
757 b1 = pos.pawns(Us) & neighboring_files_bb(ksq) & ~dc;
759 // Direct checks, single pawn pushes
760 b2 = (Us == WHITE ? b1 << 8 : b1 >> 8) & empty;
761 b3 = b2 & pos.pawn_attacks(Them, ksq);
764 Square to = pop_1st_bit(&b3);
765 (*mlist++).move = make_move(to - TDELTA_N, to);
768 // Direct checks, double pawn pushes
769 b3 = (Us == WHITE ? (b2 & TRank3BB) << 8 : (b2 & TRank3BB) >> 8)
771 & pos.pawn_attacks(Them, ksq);
774 Square to = pop_1st_bit(&b3);
775 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
780 template<PieceType Piece>
781 MoveStack* generate_piece_checks(const Position& pos, MoveStack* mlist, Color us,
782 Bitboard dc, Square ksq) {
784 Bitboard target = pos.pieces_of_color_and_type(us, Piece);
787 Bitboard b = target & dc;
790 Square from = pop_1st_bit(&b);
791 Bitboard bb = pos.piece_attacks<Piece>(from) & pos.empty_squares();
793 bb &= ~QueenPseudoAttacks[ksq];
800 if (Piece == KING || !b)
803 Bitboard checkSqs = pos.piece_attacks<Piece>(ksq) & pos.empty_squares();
806 Square from = pop_1st_bit(&b);
807 Bitboard bb = pos.piece_attacks<Piece>(from) & checkSqs;
813 template<Color Us, Rank TRANK_8, Bitboard TRank3BB, SquareDelta TDELTA_N>
814 MoveStack* generate_pawn_blocking_evasions(const Position& pos, Bitboard pinned,
815 Bitboard blockSquares, MoveStack* mlist) {
818 // Find non-pinned pawns
819 Bitboard b1 = pos.pawns(Us) & ~pinned;
821 // Single pawn pushes. We don't have to AND with empty squares here,
822 // because the blocking squares will always be empty.
823 Bitboard b2 = (Us == WHITE ? b1 << 8 : b1 >> 8) & blockSquares;
826 to = pop_1st_bit(&b2);
828 assert(pos.piece_on(to) == EMPTY);
830 if (square_rank(to) == TRANK_8)
832 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
833 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
834 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
835 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
837 (*mlist++).move = make_move(to - TDELTA_N, to);
840 // Double pawn pushes
841 b2 = (Us == WHITE ? b1 << 8 : b1 >> 8) & pos.empty_squares() & TRank3BB;
842 b2 = (Us == WHITE ? b2 << 8 : b2 >> 8) & blockSquares;
845 to = pop_1st_bit(&b2);
847 assert(pos.piece_on(to) == EMPTY);
848 assert(Us != WHITE || square_rank(to) == RANK_4);
849 assert(Us != BLACK || square_rank(to) == RANK_5);
851 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
856 template<CastlingSide Side>
857 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
859 Color us = pos.side_to_move();
861 if ( (Side == KING_SIDE && pos.can_castle_kingside(us))
862 ||(Side == QUEEN_SIDE && pos.can_castle_queenside(us)))
864 Color them = opposite_color(us);
865 Square ksq = pos.king_square(us);
867 assert(pos.piece_on(ksq) == king_of_color(us));
869 Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
870 Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
871 Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
873 bool illegal = false;
875 assert(pos.piece_on(rsq) == rook_of_color(us));
877 // It is a bit complicated to correctly handle Chess960
878 for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
879 if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
880 || pos.square_is_attacked(s, them))
883 for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
884 if (s != ksq && s != rsq && pos.square_is_occupied(s))
887 if ( Side == QUEEN_SIDE
888 && square_file(rsq) == FILE_B
889 && ( pos.piece_on(relative_square(us, SQ_A1)) == rook_of_color(them)
890 || pos.piece_on(relative_square(us, SQ_A1)) == queen_of_color(them)))
894 (*mlist++).move = make_castle_move(ksq, rsq);
899 bool castling_is_check(const Position& pos, CastlingSide side) {
901 // After castling opponent king is attacked by the castled rook?
902 File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
903 Color us = pos.side_to_move();
904 Square ksq = pos.king_square(us);
905 Bitboard occ = pos.occupied_squares();
907 clear_bit(&occ, ksq); // Remove our king from the board
908 Square rsq = make_square(rookFile, square_rank(ksq));
909 return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));