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
54 bool castling_is_check(const Position&, CastlingSide);
57 template<CastlingSide Side>
58 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist);
61 MoveStack* generate_pawn_blocking_evasions(const Position&, Bitboard, Bitboard, MoveStack*);
64 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist);
66 template<Color Us, SquareDelta Diagonal>
67 MoveStack* generate_pawn_captures_diagonal(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion);
69 template<Color Us, bool Checks>
70 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist, Bitboard dc = EmptyBoardBB, Square ksq = SQ_NONE);
72 template<Color Us, SquareDelta Direction>
73 inline Bitboard move_pawns(Bitboard p) {
75 if (Direction == DELTA_N)
76 return Us == WHITE ? p << 8 : p >> 8;
77 else if (Direction == DELTA_NE)
78 return Us == WHITE ? p << 9 : p >> 7;
79 else if (Direction == DELTA_NW)
80 return Us == WHITE ? p << 7 : p >> 9;
85 // Template generate_piece_checks() with specializations
87 MoveStack* generate_piece_checks(const Position&, MoveStack*, Color, Bitboard, Square);
90 inline MoveStack* generate_piece_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
92 return (us == WHITE ? generate_pawn_noncaptures<WHITE, true>(p, m, dc, ksq)
93 : generate_pawn_noncaptures<BLACK, true>(p, m, dc, ksq));
96 // Template generate_piece_moves() with specializations and overloads
98 MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard);
101 MoveStack* generate_piece_moves<KING>(const Position&, MoveStack*, Color, Bitboard);
103 template<PieceType Piece, MoveType Type>
104 inline MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us) {
106 assert(Piece == PAWN);
109 return (us == WHITE ? generate_pawn_captures<WHITE>(p, m)
110 : generate_pawn_captures<BLACK>(p, m));
112 return (us == WHITE ? generate_pawn_noncaptures<WHITE, false>(p, m)
113 : generate_pawn_noncaptures<BLACK, false>(p, m));
117 MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard, Bitboard);
120 inline MoveStack* generate_piece_moves<PAWN>(const Position& p, MoveStack* m,
121 Color us, Bitboard t, Bitboard pnd) {
123 return (us == WHITE ? generate_pawn_blocking_evasions<WHITE>(p, pnd, t, m)
124 : generate_pawn_blocking_evasions<BLACK>(p, pnd, t, m));
134 /// generate_captures generates() all pseudo-legal captures and queen
135 /// promotions. Returns a pointer to the end of the move list.
137 MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
140 assert(!pos.is_check());
142 Color us = pos.side_to_move();
143 Bitboard target = pos.pieces_of_color(opposite_color(us));
145 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
146 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
147 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
148 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
149 mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us);
150 return generate_piece_moves<KING>(pos, mlist, us, target);
154 /// generate_noncaptures() generates all pseudo-legal non-captures and
155 /// underpromotions. Returns a pointer to the end of the move list.
157 MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
160 assert(!pos.is_check());
162 Color us = pos.side_to_move();
163 Bitboard target = pos.empty_squares();
165 mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us);
166 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
167 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
168 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
169 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
170 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
171 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
172 return generate_castle_moves<QUEEN_SIDE>(pos, mlist);
176 /// generate_non_capture_checks() generates all pseudo-legal non-capturing,
177 /// non-promoting checks. Returns a pointer to the end of the move list.
179 MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
182 assert(!pos.is_check());
184 Color us = pos.side_to_move();
185 Square ksq = pos.king_square(opposite_color(us));
187 assert(pos.piece_on(ksq) == piece_of_color_and_type(opposite_color(us), KING));
190 mlist = generate_piece_checks<PAWN>(pos, mlist, us, dc, ksq);
191 mlist = generate_piece_checks<KNIGHT>(pos, mlist, us, dc, ksq);
192 mlist = generate_piece_checks<BISHOP>(pos, mlist, us, dc, ksq);
193 mlist = generate_piece_checks<ROOK>(pos, mlist, us, dc, ksq);
194 mlist = generate_piece_checks<QUEEN>(pos, mlist, us, dc, ksq);
195 mlist = generate_piece_checks<KING>(pos, mlist, us, dc, ksq);
197 // Castling moves that give check. Very rare but nice to have!
198 if ( pos.can_castle_queenside(us)
199 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
200 && castling_is_check(pos, QUEEN_SIDE))
201 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
203 if ( pos.can_castle_kingside(us)
204 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
205 && castling_is_check(pos, KING_SIDE))
206 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
212 /// generate_evasions() generates all check evasions when the side to move is
213 /// in check. Unlike the other move generation functions, this one generates
214 /// only legal moves. Returns a pointer to the end of the move list.
216 MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
219 assert(pos.is_check());
222 Color us = pos.side_to_move();
223 Color them = opposite_color(us);
224 Square ksq = pos.king_square(us);
225 Bitboard sliderAttacks = EmptyBoardBB;
226 Bitboard checkers = pos.checkers();
228 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
230 // The bitboard of occupied pieces without our king
231 Bitboard b_noKing = pos.occupied_squares();
232 clear_bit(&b_noKing, ksq);
234 // Find squares attacked by slider checkers, we will
235 // remove them from king evasions set so to avoid a couple
236 // of cycles in the slow king evasions legality check loop
237 // and to be able to use attackers_to().
238 Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
241 from = pop_1st_bit(&b);
242 sliderAttacks |= bishop_attacks_bb(from, b_noKing);
245 b = checkers & pos.pieces(ROOK, QUEEN);
248 from = pop_1st_bit(&b);
249 sliderAttacks |= rook_attacks_bb(from, b_noKing);
252 // Generate evasions for king, both captures and non captures
253 Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
254 Bitboard enemy = pos.pieces_of_color(them);
257 to = pop_1st_bit(&b1);
258 // Note that we can use attackers_to() only because we
259 // have already removed slider checkers attacked squares.
260 if (!(pos.attackers_to(to) & enemy))
261 (*mlist++).move = make_move(ksq, to);
264 // Generate evasions for other pieces only if not double check. We use a
265 // simple bit twiddling hack here rather than calling count_1s in order to
266 // save some time (we know that pos.checkers() has at most two nonzero bits).
267 if (!(checkers & (checkers - 1))) // Only one bit set?
269 Square checksq = first_1(checkers);
271 assert(pos.color_of_piece_on(checksq) == them);
273 // Generate captures of the checking piece
276 b1 = pos.attacks_from<PAWN>(checksq, them) & pos.pieces(PAWN, us) & ~pinned;
279 from = pop_1st_bit(&b1);
280 if (relative_rank(us, checksq) == RANK_8)
282 (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
283 (*mlist++).move = make_promotion_move(from, checksq, ROOK);
284 (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
285 (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
287 (*mlist++).move = make_move(from, checksq);
291 b1 = ( (pos.attacks_from<KNIGHT>(checksq) & pos.pieces(KNIGHT, us))
292 | (pos.attacks_from<BISHOP>(checksq) & pos.pieces(BISHOP, QUEEN, us))
293 | (pos.attacks_from<ROOK>(checksq) & pos.pieces(ROOK, QUEEN, us)) ) & ~pinned;
297 from = pop_1st_bit(&b1);
298 (*mlist++).move = make_move(from, checksq);
301 // Blocking check evasions are possible only if the checking piece is a slider
304 Bitboard blockSquares = squares_between(checksq, ksq);
306 assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
310 mlist = generate_piece_moves<PAWN>(pos, mlist, us, blockSquares, pinned);
311 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, blockSquares, pinned);
312 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, blockSquares, pinned);
313 mlist = generate_piece_moves<ROOK>(pos, mlist, us, blockSquares, pinned);
314 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, blockSquares, pinned);
318 // Finally, the special case of en passant captures. An en passant
319 // capture can only be a check evasion if the check is not a discovered
320 // check. If pos.ep_square() is set, the last move made must have been
321 // a double pawn push. If, furthermore, the checking piece is a pawn,
322 // an en passant check evasion may be possible.
323 if (pos.ep_square() != SQ_NONE && (checkers & pos.pieces(PAWN, them)))
325 to = pos.ep_square();
326 b1 = pos.attacks_from<PAWN>(to, them) & pos.pieces(PAWN, us);
328 // The checking pawn cannot be a discovered (bishop) check candidate
329 // otherwise we were in check also before last double push move.
330 assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
331 assert(count_1s(b1) == 1 || count_1s(b1) == 2);
336 from = pop_1st_bit(&b1);
337 // Move is always legal because checking pawn is not a discovered
338 // check candidate and our capturing pawn has been already tested
339 // against pinned pieces.
340 (*mlist++).move = make_ep_move(from, to);
348 /// generate_legal_moves() computes a complete list of legal moves in the
349 /// current position. This function is not very fast, and should be used
350 /// only in situations where performance is unimportant. It wouldn't be
351 /// very hard to write an efficient legal move generator, but for the moment
352 /// we don't need it.
354 MoveStack* generate_legal_moves(const Position& pos, MoveStack* mlist) {
358 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
361 return generate_evasions(pos, mlist, pinned);
363 // Generate pseudo-legal moves
364 MoveStack* last = generate_captures(pos, mlist);
365 last = generate_noncaptures(pos, last);
367 // Remove illegal moves from the list
368 for (MoveStack* cur = mlist; cur != last; cur++)
369 if (!pos.pl_move_is_legal(cur->move, pinned))
371 cur->move = (--last)->move;
378 /// move_is_legal() takes a position and a (not necessarily pseudo-legal)
379 /// move and a pinned pieces bitboard as input, and tests whether
380 /// the move is legal. If the move is legal, the move itself is
381 /// returned. If not, the function returns false. This function must
382 /// only be used when the side to move is not in check.
384 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
387 assert(!pos.is_check());
388 assert(move_is_ok(m));
389 assert(pinned == pos.pinned_pieces(pos.side_to_move()));
391 Color us = pos.side_to_move();
392 Square from = move_from(m);
393 Piece pc = pos.piece_on(from);
395 // If the from square is not occupied by a piece belonging to the side to
396 // move, the move is obviously not legal.
397 if (color_of_piece(pc) != us)
400 Color them = opposite_color(us);
401 Square to = move_to(m);
406 // The piece must be a pawn and destination square must be the
407 // en passant square.
408 if ( type_of_piece(pc) != PAWN
409 || to != pos.ep_square())
412 assert(pos.square_is_empty(to));
413 assert(pos.piece_on(to - pawn_push(us)) == piece_of_color_and_type(them, PAWN));
415 // The move is pseudo-legal, check if it is also legal
416 return pos.pl_move_is_legal(m, pinned);
420 if (move_is_short_castle(m))
422 // The piece must be a king and side to move must still have
423 // the right to castle kingside.
424 if ( type_of_piece(pc) != KING
425 ||!pos.can_castle_kingside(us))
428 assert(from == pos.king_square(us));
429 assert(to == pos.initial_kr_square(us));
430 assert(pos.piece_on(to) == piece_of_color_and_type(us, ROOK));
432 Square g1 = relative_square(us, SQ_G1);
433 Square f1 = relative_square(us, SQ_F1);
435 bool illegal = false;
437 // Check if any of the squares between king and rook
438 // is occupied or under attack.
439 for (s = Min(from, g1); s <= Max(from, g1); s++)
440 if ( (s != from && s != to && !pos.square_is_empty(s))
441 ||(pos.attackers_to(s) & pos.pieces_of_color(them)))
444 // Check if any of the squares between king and rook
446 for (s = Min(to, f1); s <= Max(to, f1); s++)
447 if (s != from && s != to && !pos.square_is_empty(s))
453 if (move_is_long_castle(m))
455 // The piece must be a king and side to move must still have
456 // the right to castle kingside.
457 if ( type_of_piece(pc) != KING
458 ||!pos.can_castle_queenside(us))
461 assert(from == pos.king_square(us));
462 assert(to == pos.initial_qr_square(us));
463 assert(pos.piece_on(to) == piece_of_color_and_type(us, ROOK));
465 Square c1 = relative_square(us, SQ_C1);
466 Square d1 = relative_square(us, SQ_D1);
468 bool illegal = false;
470 for (s = Min(from, c1); s <= Max(from, c1); s++)
471 if( (s != from && s != to && !pos.square_is_empty(s))
472 ||(pos.attackers_to(s) & pos.pieces_of_color(them)))
475 for (s = Min(to, d1); s <= Max(to, d1); s++)
476 if(s != from && s != to && !pos.square_is_empty(s))
479 if ( square_file(to) == FILE_B
480 && ( pos.piece_on(to + DELTA_W) == piece_of_color_and_type(them, ROOK)
481 || pos.piece_on(to + DELTA_W) == piece_of_color_and_type(them, QUEEN)))
489 // The destination square cannot be occupied by a friendly piece
490 if (pos.color_of_piece_on(to) == us)
493 // Proceed according to the type of the moving piece.
494 if (type_of_piece(pc) == PAWN)
496 // Move direction must be compatible with pawn color
497 int direction = to - from;
498 if ((us == WHITE) != (direction > 0))
501 // If the destination square is on the 8/1th rank, the move must
503 if ( ( (square_rank(to) == RANK_8 && us == WHITE)
504 ||(square_rank(to) == RANK_1 && us != WHITE))
505 && !move_is_promotion(m))
508 // Proceed according to the square delta between the source and
509 // destionation squares.
516 // Capture. The destination square must be occupied by an enemy
517 // piece (en passant captures was handled earlier).
518 if (pos.color_of_piece_on(to) != them)
524 // Pawn push. The destination square must be empty.
525 if (!pos.square_is_empty(to))
530 // Double white pawn push. The destination square must be on the fourth
531 // rank, and both the destination square and the square between the
532 // source and destination squares must be empty.
533 if ( square_rank(to) != RANK_4
534 || !pos.square_is_empty(to)
535 || !pos.square_is_empty(from + DELTA_N))
540 // Double black pawn push. The destination square must be on the fifth
541 // rank, and both the destination square and the square between the
542 // source and destination squares must be empty.
543 if ( square_rank(to) != RANK_5
544 || !pos.square_is_empty(to)
545 || !pos.square_is_empty(from + DELTA_S))
552 // The move is pseudo-legal, check if it is also legal
553 return pos.pl_move_is_legal(m, pinned);
556 // Luckly we can handle all the other pieces in one go
557 return ( bit_is_set(pos.attacks_from(pc, from), to)
558 && pos.pl_move_is_legal(m, pinned)
559 && !move_is_promotion(m));
563 /// Another version of move_is_legal(), which takes only a position and a move
564 /// as input. This function does not require that the side to move is not in
565 /// check. It is not optimized for speed, and is only used for verifying move
566 /// legality when building a PV from the transposition table.
568 bool move_is_legal(const Position& pos, const Move m) {
570 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
572 return move_is_legal(pos, m, pinned);
577 MoveStack* last = generate_evasions(p, mlist, pinned);
578 for (MoveStack* cur = mlist; cur != last; cur++)
589 template<PieceType Piece>
590 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
595 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
597 from = pos.piece_list(us, Piece, i);
598 b = pos.attacks_from<Piece>(from) & target;
604 template<PieceType Piece>
605 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist,
606 Color us, Bitboard target, Bitboard pinned) {
610 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
612 from = pos.piece_list(us, Piece, i);
613 if (pinned && bit_is_set(pinned, from))
616 b = pos.attacks_from<Piece>(from) & target;
623 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
626 Square from = pos.king_square(us);
628 b = pos.attacks_from<KING>(from) & target;
633 template<Color Us, SquareDelta Diagonal>
634 MoveStack* generate_pawn_captures_diagonal(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion) {
636 // Calculate our parametrized parameters at compile time
637 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
638 const Bitboard TFileABB = (Diagonal == DELTA_NE ? FileABB : FileHBB);
639 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
640 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
641 const SquareDelta TTDELTA_NE = (Diagonal == DELTA_NE ? TDELTA_NE : TDELTA_NW);
645 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
646 Bitboard b1 = move_pawns<Us, Diagonal>(pawns) & ~TFileABB & enemyPieces;
648 // Capturing promotions
651 Bitboard b2 = b1 & TRank8BB;
655 to = pop_1st_bit(&b2);
656 (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, QUEEN);
660 // Capturing non-promotions
661 SERIALIZE_MOVES_D(b1, -TTDELTA_NE);
666 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist) {
668 // Calculate our parametrized parameters at compile time
669 const Color Them = (Us == WHITE ? BLACK : WHITE);
670 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
671 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
672 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
675 Bitboard pawns = pos.pieces(PAWN, Us);
676 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
677 bool possiblePromotion = (pawns & TRank7BB);
679 // Standard captures and capturing promotions in both directions
680 mlist = generate_pawn_captures_diagonal<Us, DELTA_NE>(mlist, pawns, enemyPieces, possiblePromotion);
681 mlist = generate_pawn_captures_diagonal<Us, DELTA_NW>(mlist, pawns, enemyPieces, possiblePromotion);
683 // Non-capturing promotions
684 if (possiblePromotion)
686 Bitboard b1 = move_pawns<Us, DELTA_N>(pawns) & pos.empty_squares() & TRank8BB;
689 to = pop_1st_bit(&b1);
690 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
694 // En passant captures
695 if (pos.ep_square() != SQ_NONE)
697 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
698 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
700 Bitboard b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
701 assert(b1 != EmptyBoardBB);
705 to = pop_1st_bit(&b1);
706 (*mlist++).move = make_ep_move(to, pos.ep_square());
712 template<Color Us, bool GenerateChecks>
713 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist, Bitboard dc, Square ksq) {
715 // Calculate our parametrized parameters at compile time
716 const Color Them = (Us == WHITE ? BLACK : WHITE);
717 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
718 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
719 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
720 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
721 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
722 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
724 Bitboard b1, b2, dcPawns1, dcPawns2;
726 Bitboard pawns = pos.pieces(PAWN, Us);
727 Bitboard emptySquares = pos.empty_squares();
729 if (pawns & TRank7BB) // There is some promotion candidate ?
731 // When generating checks consider under-promotion moves (both captures
732 // and non captures) only if can give a discovery check.
733 Bitboard pp = GenerateChecks ? pawns & dc & EmptyBoardBB: pawns;
734 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
736 // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
737 b1 = move_pawns<Us, DELTA_NE>(pp) & ~FileABB & enemyPieces & TRank8BB;
740 to = pop_1st_bit(&b1);
741 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
742 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
743 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
746 // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
747 b1 = move_pawns<Us, DELTA_NW>(pp) & ~FileHBB & enemyPieces & TRank8BB;
750 to = pop_1st_bit(&b1);
751 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
752 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
753 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
756 // Underpromotion pawn pushes
757 b1 = move_pawns<Us, DELTA_N>(pp) & emptySquares & TRank8BB;
760 to = pop_1st_bit(&b1);
761 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
762 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
763 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
767 dcPawns1 = dcPawns2 = EmptyBoardBB;
768 if (GenerateChecks && (dc & pawns))
770 // Pawn moves which gives discovered check. This is possible only if the
771 // pawn is not on the same file as the enemy king, because we don't
772 // generate captures.
773 dcPawns1 = move_pawns<Us, DELTA_N>(pawns & dc & ~file_bb(ksq)) & emptySquares & ~TRank8BB;
774 dcPawns2 = move_pawns<Us, DELTA_N>(dcPawns1 & TRank3BB) & emptySquares;
777 // Single pawn pushes
778 b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & ~TRank8BB;
779 b2 = GenerateChecks ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns1 : b1;
780 SERIALIZE_MOVES_D(b2, -TDELTA_N);
782 // Double pawn pushes
783 b1 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
784 b2 = GenerateChecks ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns2 : b1;
785 SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
789 template<PieceType Piece>
790 MoveStack* generate_piece_checks(const Position& pos, MoveStack* mlist, Color us,
791 Bitboard dc, Square ksq) {
793 Bitboard target = pos.pieces(Piece, us);
796 Bitboard b = target & dc;
799 Square from = pop_1st_bit(&b);
800 Bitboard bb = pos.attacks_from<Piece>(from) & pos.empty_squares();
802 bb &= ~QueenPseudoAttacks[ksq];
809 Bitboard checkSqs = pos.attacks_from<Piece>(ksq) & pos.empty_squares();
810 if (Piece == KING || !checkSqs)
815 Square from = pop_1st_bit(&b);
816 if ( (Piece == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
817 || (Piece == ROOK && !(RookPseudoAttacks[from] & checkSqs))
818 || (Piece == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
821 Bitboard bb = pos.attacks_from<Piece>(from) & checkSqs;
828 MoveStack* generate_pawn_blocking_evasions(const Position& pos, Bitboard pinned,
829 Bitboard blockSquares, MoveStack* mlist) {
831 // Calculate our parametrized parameters at compile time
832 const Rank TRANK_8 = (Us == WHITE ? RANK_8 : RANK_1);
833 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
834 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
838 // Find non-pinned pawns and push them one square
839 Bitboard b1 = move_pawns<Us, DELTA_N>(pos.pieces(PAWN, Us) & ~pinned);
841 // We don't have to AND with empty squares here,
842 // because the blocking squares will always be empty.
843 Bitboard b2 = b1 & blockSquares;
846 to = pop_1st_bit(&b2);
848 assert(pos.piece_on(to) == EMPTY);
850 if (square_rank(to) == TRANK_8)
852 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
853 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
854 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
855 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
857 (*mlist++).move = make_move(to - TDELTA_N, to);
860 // Double pawn pushes
861 b2 = b1 & pos.empty_squares() & TRank3BB;
862 b2 = move_pawns<Us, DELTA_N>(b2) & blockSquares;
865 to = pop_1st_bit(&b2);
867 assert(pos.piece_on(to) == EMPTY);
868 assert(Us != WHITE || square_rank(to) == RANK_4);
869 assert(Us != BLACK || square_rank(to) == RANK_5);
871 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
876 template<CastlingSide Side>
877 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
879 Color us = pos.side_to_move();
881 if ( (Side == KING_SIDE && pos.can_castle_kingside(us))
882 ||(Side == QUEEN_SIDE && pos.can_castle_queenside(us)))
884 Color them = opposite_color(us);
885 Square ksq = pos.king_square(us);
887 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
889 Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
890 Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
891 Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
893 bool illegal = false;
895 assert(pos.piece_on(rsq) == piece_of_color_and_type(us, ROOK));
897 // It is a bit complicated to correctly handle Chess960
898 for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
899 if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
900 ||(pos.attackers_to(s) & pos.pieces_of_color(them)))
903 for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
904 if (s != ksq && s != rsq && pos.square_is_occupied(s))
907 if ( Side == QUEEN_SIDE
908 && square_file(rsq) == FILE_B
909 && ( pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, ROOK)
910 || pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, QUEEN)))
914 (*mlist++).move = make_castle_move(ksq, rsq);
919 bool castling_is_check(const Position& pos, CastlingSide side) {
921 // After castling opponent king is attacked by the castled rook?
922 File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
923 Color us = pos.side_to_move();
924 Square ksq = pos.king_square(us);
925 Bitboard occ = pos.occupied_squares();
927 clear_bit(&occ, ksq); // Remove our king from the board
928 Square rsq = make_square(rookFile, square_rank(ksq));
929 return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));