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/>.
29 // Simple macro to wrap a very common while loop, no facny, no flexibility,
30 // hardcoded list name 'mlist' and from square 'from'.
31 #define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
34 //// Local definitions
50 bool castling_is_check(const Position&, CastlingSide);
53 template<CastlingSide Side>
54 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist);
56 template<Color Us, Rank, Bitboard, SquareDelta>
57 MoveStack* generate_pawn_blocking_evasions(const Position&, Bitboard, Bitboard, MoveStack*);
60 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist);
62 template<Color Us, SquareDelta Diagonal>
63 MoveStack* generate_pawn_captures_diagonal(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces);
66 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist);
69 MoveStack* generate_pawn_checks(const Position&, Bitboard, Square, MoveStack*);
71 template<Color Us, SquareDelta Direction>
72 inline Bitboard move_pawns(Bitboard p) {
74 if (Direction == DELTA_N)
75 return Us == WHITE ? p << 8 : p >> 8;
76 else if (Direction == DELTA_NE)
77 return Us == WHITE ? p << 9 : p >> 7;
78 else if (Direction == DELTA_NW)
79 return Us == WHITE ? p << 7 : p >> 9;
84 // Template generate_piece_checks() with specializations
86 MoveStack* generate_piece_checks(const Position&, MoveStack*, Color, Bitboard, Square);
89 inline MoveStack* generate_piece_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
91 return (us == WHITE ? generate_pawn_checks<WHITE>(p, dc, ksq, m)
92 : generate_pawn_checks<BLACK>(p, dc, ksq, m));
95 // Template generate_piece_moves() with specializations and overloads
97 MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard);
100 MoveStack* generate_piece_moves<KING>(const Position&, MoveStack*, Color, Bitboard);
102 template<PieceType Piece, MoveType Type>
103 inline MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us) {
105 assert(Piece == PAWN);
108 return (us == WHITE ? generate_pawn_captures<WHITE>(p, m)
109 : generate_pawn_captures<BLACK>(p, m));
111 return (us == WHITE ? generate_pawn_noncaptures<WHITE>(p, m)
112 : generate_pawn_noncaptures<BLACK>(p, m));
116 MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard, Bitboard);
119 inline MoveStack* generate_piece_moves<PAWN>(const Position& p, MoveStack* m,
120 Color us, Bitboard t, Bitboard pnd) {
122 return generate_pawn_blocking_evasions<WHITE, RANK_8, Rank3BB, DELTA_N>(p, pnd, t, m);
124 return generate_pawn_blocking_evasions<BLACK, RANK_1, Rank6BB, DELTA_S>(p, pnd, t, m);
134 /// generate_captures generates() all pseudo-legal captures and queen
135 /// promotions. The return value is the number of moves generated.
137 int 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));
144 MoveStack* mlist_start = mlist;
146 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
147 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
148 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
149 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
150 mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us);
151 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
152 return int(mlist - mlist_start);
156 /// generate_noncaptures() generates all pseudo-legal non-captures and
157 /// underpromotions. The return value is the number of moves generated.
159 int generate_noncaptures(const Position& pos, MoveStack* mlist) {
162 assert(!pos.is_check());
164 Color us = pos.side_to_move();
165 Bitboard target = pos.empty_squares();
166 MoveStack* mlist_start = mlist;
168 mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us);
169 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
170 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
171 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
172 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
173 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
174 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
175 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
176 return int(mlist - mlist_start);
180 /// generate_non_capture_checks() generates all pseudo-legal non-capturing,
181 /// non-promoting checks. It returns the number of generated moves.
183 int generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
186 assert(!pos.is_check());
188 Color us = pos.side_to_move();
189 Square ksq = pos.king_square(opposite_color(us));
190 MoveStack* mlist_start = mlist;
192 assert(pos.piece_on(ksq) == piece_of_color_and_type(opposite_color(us), KING));
195 mlist = generate_piece_checks<PAWN>(pos, mlist, us, dc, ksq);
196 mlist = generate_piece_checks<KNIGHT>(pos, mlist, us, dc, ksq);
197 mlist = generate_piece_checks<BISHOP>(pos, mlist, us, dc, ksq);
198 mlist = generate_piece_checks<ROOK>(pos, mlist, us, dc, ksq);
199 mlist = generate_piece_checks<QUEEN>(pos, mlist, us, dc, ksq);
200 mlist = generate_piece_checks<KING>(pos, mlist, us, dc, ksq);
202 // Castling moves that give check. Very rare but nice to have!
203 if ( pos.can_castle_queenside(us)
204 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
205 && castling_is_check(pos, QUEEN_SIDE))
206 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
208 if ( pos.can_castle_kingside(us)
209 && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
210 && castling_is_check(pos, KING_SIDE))
211 mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
213 return int(mlist - mlist_start);
217 /// generate_evasions() generates all check evasions when the side to move is
218 /// in check. Unlike the other move generation functions, this one generates
219 /// only legal moves. It returns the number of generated moves.
221 int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
224 assert(pos.is_check());
227 Color us = pos.side_to_move();
228 Color them = opposite_color(us);
229 Square ksq = pos.king_square(us);
230 MoveStack* mlist_start = mlist;
232 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
234 // The bitboard of occupied pieces without our king
235 Bitboard b_noKing = pos.occupied_squares();
236 clear_bit(&b_noKing, ksq);
238 // Find squares attacked by slider checkers, we will
239 // remove them from king evasions set so to avoid a couple
240 // of cycles in the slow king evasions legality check loop
241 // and to be able to use square_is_attacked().
242 Bitboard checkers = pos.checkers();
243 Bitboard checkersAttacks = EmptyBoardBB;
244 Bitboard b = checkers & (pos.queens() | pos.bishops());
247 from = pop_1st_bit(&b);
248 checkersAttacks |= bishop_attacks_bb(from, b_noKing);
251 b = checkers & (pos.queens() | pos.rooks());
254 from = pop_1st_bit(&b);
255 checkersAttacks |= rook_attacks_bb(from, b_noKing);
258 // Generate evasions for king
259 Bitboard b1 = pos.piece_attacks<KING>(ksq) & ~pos.pieces_of_color(us) & ~checkersAttacks;
262 to = pop_1st_bit(&b1);
263 // Note that we can use square_is_attacked() only because we
264 // have already removed slider checkers.
265 if (!pos.square_is_attacked(to, them))
266 (*mlist++).move = make_move(ksq, to);
269 // Generate evasions for other pieces only if not double check. We use a
270 // simple bit twiddling hack here rather than calling count_1s in order to
271 // save some time (we know that pos.checkers() has at most two nonzero bits).
272 if (!(checkers & (checkers - 1))) // Only one bit set?
274 Square checksq = first_1(checkers);
276 assert(pos.color_of_piece_on(checksq) == them);
278 // Generate captures of the checking piece
281 b1 = pos.pawn_attacks(them, checksq) & pos.pawns(us) & ~pinned;
284 from = pop_1st_bit(&b1);
285 if (relative_rank(us, checksq) == RANK_8)
287 (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
288 (*mlist++).move = make_promotion_move(from, checksq, ROOK);
289 (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
290 (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
292 (*mlist++).move = make_move(from, checksq);
296 b1 = ( (pos.piece_attacks<KNIGHT>(checksq) & pos.knights(us))
297 | (pos.piece_attacks<BISHOP>(checksq) & pos.bishops_and_queens(us))
298 | (pos.piece_attacks<ROOK>(checksq) & pos.rooks_and_queens(us)) ) & ~pinned;
302 from = pop_1st_bit(&b1);
303 (*mlist++).move = make_move(from, checksq);
306 // Blocking check evasions are possible only if the checking piece is
308 if (checkers & pos.sliders())
310 Bitboard blockSquares = squares_between(checksq, ksq);
312 assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
314 if (blockSquares != EmptyBoardBB)
316 mlist = generate_piece_moves<PAWN>(pos, mlist, us, blockSquares, pinned);
317 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, blockSquares, pinned);
318 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, blockSquares, pinned);
319 mlist = generate_piece_moves<ROOK>(pos, mlist, us, blockSquares, pinned);
320 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, blockSquares, pinned);
324 // Finally, the special case of en passant captures. An en passant
325 // capture can only be a check evasion if the check is not a discovered
326 // check. If pos.ep_square() is set, the last move made must have been
327 // a double pawn push. If, furthermore, the checking piece is a pawn,
328 // an en passant check evasion may be possible.
329 if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them)))
331 to = pos.ep_square();
332 b1 = pos.pawn_attacks(them, to) & pos.pawns(us);
334 // The checking pawn cannot be a discovered (bishop) check candidate
335 // otherwise we were in check also before last double push move.
336 assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
337 assert(count_1s(b1) == 1 || count_1s(b1) == 2);
342 from = pop_1st_bit(&b1);
343 // Move is always legal because checking pawn is not a discovered
344 // check candidate and our capturing pawn has been already tested
345 // against pinned pieces.
346 (*mlist++).move = make_ep_move(from, to);
350 return int(mlist - mlist_start);
354 /// generate_legal_moves() computes a complete list of legal moves in the
355 /// current position. This function is not very fast, and should be used
356 /// only in situations where performance is unimportant. It wouldn't be
357 /// very hard to write an efficient legal move generator, but for the moment
358 /// we don't need it.
360 int generate_legal_moves(const Position& pos, MoveStack* mlist) {
364 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
367 return generate_evasions(pos, mlist, pinned);
369 // Generate pseudo-legal moves
370 int n = generate_captures(pos, mlist);
371 n += generate_noncaptures(pos, mlist + n);
373 // Remove illegal moves from the list
374 for (int i = 0; i < n; i++)
375 if (!pos.pl_move_is_legal(mlist[i].move, pinned))
376 mlist[i--].move = mlist[--n].move;
382 /// move_is_legal() takes a position and a (not necessarily pseudo-legal)
383 /// move and a pinned pieces bitboard as input, and tests whether
384 /// the move is legal. If the move is legal, the move itself is
385 /// returned. If not, the function returns false. This function must
386 /// only be used when the side to move is not in check.
388 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
391 assert(!pos.is_check());
392 assert(move_is_ok(m));
393 assert(pinned == pos.pinned_pieces(pos.side_to_move()));
395 Color us = pos.side_to_move();
396 Color them = opposite_color(us);
397 Square from = move_from(m);
398 Piece pc = pos.piece_on(from);
400 // If the from square is not occupied by a piece belonging to the side to
401 // move, the move is obviously not legal.
402 if (color_of_piece(pc) != us)
405 Square to = move_to(m);
410 // The piece must be a pawn and destination square must be the
411 // en passant square.
412 if ( type_of_piece(pc) != PAWN
413 || to != pos.ep_square())
416 assert(pos.square_is_empty(to));
417 assert(pos.piece_on(to - pawn_push(us)) == piece_of_color_and_type(them, PAWN));
419 // The move is pseudo-legal, check if it is also legal
420 return pos.pl_move_is_legal(m, pinned);
424 if (move_is_short_castle(m))
426 // The piece must be a king and side to move must still have
427 // the right to castle kingside.
428 if ( type_of_piece(pc) != KING
429 ||!pos.can_castle_kingside(us))
432 assert(from == pos.king_square(us));
433 assert(to == pos.initial_kr_square(us));
434 assert(pos.piece_on(to) == piece_of_color_and_type(us, ROOK));
436 Square g1 = relative_square(us, SQ_G1);
437 Square f1 = relative_square(us, SQ_F1);
439 bool illegal = false;
441 // Check if any of the squares between king and rook
442 // is occupied or under attack.
443 for (s = Min(from, g1); s <= Max(from, g1); s++)
444 if ( (s != from && s != to && !pos.square_is_empty(s))
445 || pos.square_is_attacked(s, them))
448 // Check if any of the squares between king and rook
450 for (s = Min(to, f1); s <= Max(to, f1); s++)
451 if (s != from && s != to && !pos.square_is_empty(s))
457 if (move_is_long_castle(m))
459 // The piece must be a king and side to move must still have
460 // the right to castle kingside.
461 if ( type_of_piece(pc) != KING
462 ||!pos.can_castle_queenside(us))
465 assert(from == pos.king_square(us));
466 assert(to == pos.initial_qr_square(us));
467 assert(pos.piece_on(to) == piece_of_color_and_type(us, ROOK));
469 Square c1 = relative_square(us, SQ_C1);
470 Square d1 = relative_square(us, SQ_D1);
472 bool illegal = false;
474 for (s = Min(from, c1); s <= Max(from, c1); s++)
475 if( (s != from && s != to && !pos.square_is_empty(s))
476 || pos.square_is_attacked(s, them))
479 for (s = Min(to, d1); s <= Max(to, d1); s++)
480 if(s != from && s != to && !pos.square_is_empty(s))
483 if ( square_file(to) == FILE_B
484 && ( pos.piece_on(to + DELTA_W) == piece_of_color_and_type(them, ROOK)
485 || pos.piece_on(to + DELTA_W) == piece_of_color_and_type(them, QUEEN)))
493 // The destination square cannot be occupied by a friendly piece
494 if (pos.color_of_piece_on(to) == us)
497 // Proceed according to the type of the moving piece.
498 if (type_of_piece(pc) == PAWN)
500 // Move direction must be compatible with pawn color
501 int direction = to - from;
502 if ((us == WHITE) != (direction > 0))
505 // If the destination square is on the 8/1th rank, the move must
507 if ( ( (square_rank(to) == RANK_8 && us == WHITE)
508 ||(square_rank(to) == RANK_1 && us != WHITE))
509 && !move_promotion(m))
512 // Proceed according to the square delta between the source and
513 // destionation squares.
520 // Capture. The destination square must be occupied by an enemy
521 // piece (en passant captures was handled earlier).
522 if (pos.color_of_piece_on(to) != them)
528 // Pawn push. The destination square must be empty.
529 if (!pos.square_is_empty(to))
534 // Double white pawn push. The destination square must be on the fourth
535 // rank, and both the destination square and the square between the
536 // source and destination squares must be empty.
537 if ( square_rank(to) != RANK_4
538 || !pos.square_is_empty(to)
539 || !pos.square_is_empty(from + DELTA_N))
544 // Double black pawn push. The destination square must be on the fifth
545 // rank, and both the destination square and the square between the
546 // source and destination squares must be empty.
547 if ( square_rank(to) != RANK_5
548 || !pos.square_is_empty(to)
549 || !pos.square_is_empty(from + DELTA_S))
556 // The move is pseudo-legal, check if it is also legal
557 return pos.pl_move_is_legal(m, pinned);
560 // Luckly we can handle all the other pieces in one go
561 return ( pos.piece_attacks_square(pos.piece_on(from), from, to)
562 && pos.pl_move_is_legal(m, pinned)
563 && !move_promotion(m));
569 template<PieceType Piece>
570 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
575 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
577 from = pos.piece_list(us, Piece, i);
578 b = pos.piece_attacks<Piece>(from) & target;
584 template<PieceType Piece>
585 MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist,
586 Color us, Bitboard target, Bitboard pinned) {
590 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
592 from = pos.piece_list(us, Piece, i);
593 if (pinned && bit_is_set(pinned, from))
596 b = pos.piece_attacks<Piece>(from) & target;
603 MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
606 Square from = pos.king_square(us);
608 b = pos.piece_attacks<KING>(from) & target;
613 template<Color Us, SquareDelta Diagonal>
614 MoveStack* generate_pawn_captures_diagonal(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces) {
616 // Calculate our parametrized parameters at compile time
617 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
618 const Bitboard TFileABB = (Diagonal == DELTA_NE ? FileABB : FileHBB);
619 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
620 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
621 const SquareDelta TTDELTA_NE = (Diagonal == DELTA_NE ? TDELTA_NE : TDELTA_NW);
625 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
626 Bitboard b1 = move_pawns<Us, Diagonal>(pawns) & ~TFileABB & enemyPieces;
628 // Capturing promotions
629 Bitboard b2 = b1 & TRank8BB;
632 to = pop_1st_bit(&b2);
633 (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, QUEEN);
636 // Capturing non-promotions
640 to = pop_1st_bit(&b2);
641 (*mlist++).move = make_move(to - TTDELTA_NE, to);
647 MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist) {
649 // Calculate our parametrized parameters at compile time
650 const Color Them = (Us == WHITE ? BLACK : WHITE);
651 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
652 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
655 Bitboard pawns = pos.pawns(Us);
656 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
658 // Standard captures and capturing promotions in both directions
659 mlist = generate_pawn_captures_diagonal<Us, DELTA_NE>(mlist, pawns, enemyPieces);
660 mlist = generate_pawn_captures_diagonal<Us, DELTA_NW>(mlist, pawns, enemyPieces);
662 // Non-capturing promotions
663 Bitboard b1 = move_pawns<Us, DELTA_N>(pawns) & pos.empty_squares() & TRank8BB;
666 to = pop_1st_bit(&b1);
667 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
670 // En passant captures
671 if (pos.ep_square() != SQ_NONE)
673 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
674 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
676 b1 = pawns & pos.pawn_attacks(Them, pos.ep_square());
677 assert(b1 != EmptyBoardBB);
681 to = pop_1st_bit(&b1);
682 (*mlist++).move = make_ep_move(to, pos.ep_square());
689 MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist) {
691 // Calculate our parametrized parameters at compile time
692 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
693 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
694 const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
695 const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
696 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
700 Bitboard pawns = pos.pawns(Us);
701 Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
702 Bitboard emptySquares = pos.empty_squares();
704 // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
705 b1 = move_pawns<Us, DELTA_NE>(pawns) & ~FileABB & enemyPieces & TRank8BB;
708 to = pop_1st_bit(&b1);
709 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
710 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
711 (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
714 // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
715 b1 = move_pawns<Us, DELTA_NW>(pawns) & ~FileHBB & enemyPieces & TRank8BB;
718 to = pop_1st_bit(&b1);
719 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
720 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
721 (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
724 // Single pawn pushes
725 b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares;
729 to = pop_1st_bit(&b2);
730 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
731 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
732 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
737 to = pop_1st_bit(&b2);
738 (*mlist++).move = make_move(to - TDELTA_N, to);
741 // Double pawn pushes
742 b2 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
745 to = pop_1st_bit(&b2);
746 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
753 MoveStack* generate_pawn_checks(const Position& pos, Bitboard dc, Square ksq, MoveStack* mlist)
755 // Calculate our parametrized parameters at compile time
756 const Color Them = (Us == WHITE ? BLACK : WHITE);
757 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
758 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
759 const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
762 Bitboard empty = pos.empty_squares();
763 Bitboard pawns = pos.pawns(Us);
767 // Pawn moves which gives discovered check. This is possible only if the
768 // pawn is not on the same file as the enemy king, because we don't
769 // generate captures.
770 b1 = pawns & ~file_bb(ksq);
772 // Discovered checks, single pawn pushes, no promotions
773 b2 = b3 = move_pawns<Us, DELTA_N>(b1 & dc) & empty & ~TRank8BB;
776 Square to = pop_1st_bit(&b3);
777 (*mlist++).move = make_move(to - TDELTA_N, to);
780 // Discovered checks, double pawn pushes
781 b3 = move_pawns<Us, DELTA_N>(b2 & TRank3BB) & empty;
784 Square to = pop_1st_bit(&b3);
785 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
789 // Direct checks. These are possible only for pawns on neighboring files
790 // of the enemy king.
791 b1 = pawns & neighboring_files_bb(ksq) & ~dc;
793 // Direct checks, single pawn pushes
794 b2 = move_pawns<Us, DELTA_N>(b1) & empty;
795 b3 = b2 & pos.pawn_attacks(Them, ksq);
798 Square to = pop_1st_bit(&b3);
799 (*mlist++).move = make_move(to - TDELTA_N, to);
802 // Direct checks, double pawn pushes
803 b3 = move_pawns<Us, DELTA_N>(b2 & TRank3BB) & empty & pos.pawn_attacks(Them, ksq);
806 Square to = pop_1st_bit(&b3);
807 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
812 template<PieceType Piece>
813 MoveStack* generate_piece_checks(const Position& pos, MoveStack* mlist, Color us,
814 Bitboard dc, Square ksq) {
816 Bitboard target = pos.pieces_of_color_and_type(us, Piece);
819 Bitboard b = target & dc;
822 Square from = pop_1st_bit(&b);
823 Bitboard bb = pos.piece_attacks<Piece>(from) & pos.empty_squares();
825 bb &= ~QueenPseudoAttacks[ksq];
832 if (Piece == KING || !b)
835 Bitboard checkSqs = pos.piece_attacks<Piece>(ksq) & pos.empty_squares();
841 Square from = pop_1st_bit(&b);
842 if ( (Piece == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
843 || (Piece == ROOK && !(RookPseudoAttacks[from] & checkSqs))
844 || (Piece == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
847 Bitboard bb = pos.piece_attacks<Piece>(from) & checkSqs;
853 template<Color Us, Rank TRANK_8, Bitboard TRank3BB, SquareDelta TDELTA_N>
854 MoveStack* generate_pawn_blocking_evasions(const Position& pos, Bitboard pinned,
855 Bitboard blockSquares, MoveStack* mlist) {
858 // Find non-pinned pawns and push them one square
859 Bitboard b1 = move_pawns<Us, DELTA_N>(pos.pawns(Us) & ~pinned);
861 // We don't have to AND with empty squares here,
862 // because the blocking squares will always be empty.
863 Bitboard b2 = b1 & blockSquares;
866 to = pop_1st_bit(&b2);
868 assert(pos.piece_on(to) == EMPTY);
870 if (square_rank(to) == TRANK_8)
872 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
873 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
874 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
875 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
877 (*mlist++).move = make_move(to - TDELTA_N, to);
880 // Double pawn pushes
881 b2 = b1 & pos.empty_squares() & TRank3BB;
882 b2 = move_pawns<Us, DELTA_N>(b2) & blockSquares;
885 to = pop_1st_bit(&b2);
887 assert(pos.piece_on(to) == EMPTY);
888 assert(Us != WHITE || square_rank(to) == RANK_4);
889 assert(Us != BLACK || square_rank(to) == RANK_5);
891 (*mlist++).move = make_move(to - TDELTA_N - TDELTA_N, to);
896 template<CastlingSide Side>
897 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
899 Color us = pos.side_to_move();
901 if ( (Side == KING_SIDE && pos.can_castle_kingside(us))
902 ||(Side == QUEEN_SIDE && pos.can_castle_queenside(us)))
904 Color them = opposite_color(us);
905 Square ksq = pos.king_square(us);
907 assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
909 Square rsq = (Side == KING_SIDE ? pos.initial_kr_square(us) : pos.initial_qr_square(us));
910 Square s1 = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
911 Square s2 = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
913 bool illegal = false;
915 assert(pos.piece_on(rsq) == piece_of_color_and_type(us, ROOK));
917 // It is a bit complicated to correctly handle Chess960
918 for (s = Min(ksq, s1); s <= Max(ksq, s1); s++)
919 if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
920 || pos.square_is_attacked(s, them))
923 for (s = Min(rsq, s2); s <= Max(rsq, s2); s++)
924 if (s != ksq && s != rsq && pos.square_is_occupied(s))
927 if ( Side == QUEEN_SIDE
928 && square_file(rsq) == FILE_B
929 && ( pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, ROOK)
930 || pos.piece_on(relative_square(us, SQ_A1)) == piece_of_color_and_type(them, QUEEN)))
934 (*mlist++).move = make_castle_move(ksq, rsq);
939 bool castling_is_check(const Position& pos, CastlingSide side) {
941 // After castling opponent king is attacked by the castled rook?
942 File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
943 Color us = pos.side_to_move();
944 Square ksq = pos.king_square(us);
945 Bitboard occ = pos.occupied_squares();
947 clear_bit(&occ, ksq); // Remove our king from the board
948 Square rsq = make_square(rookFile, square_rank(ksq));
949 return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));