2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
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/>.
27 // Simple macro to wrap a very common while loop, no facny, no flexibility,
28 // hardcoded list name 'mlist' and from square 'from'.
29 #define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
31 // Version used for pawns, where the 'from' square is given as a delta from the 'to' square
32 #define SERIALIZE_MOVES_D(b, d) while (b) { to = pop_1st_bit(&b); (*mlist++).move = make_move(to + (d), to); }
41 template<CastlingSide>
42 MoveStack* generate_castle_moves(const Position&, MoveStack*, Color us);
44 template<Color, MoveType>
45 MoveStack* generate_pawn_moves(const Position&, MoveStack*, Bitboard, Square);
47 template<PieceType Pt>
48 inline MoveStack* generate_discovered_checks(const Position& pos, MoveStack* mlist, Square from) {
50 assert(Pt != QUEEN && Pt != PAWN);
52 Bitboard b = pos.attacks_from<Pt>(from) & pos.empty_squares();
55 b &= ~QueenPseudoAttacks[pos.king_square(flip(pos.side_to_move()))];
61 template<PieceType Pt>
62 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
63 Bitboard dc, Square ksq) {
64 assert(Pt != KING && Pt != PAWN);
68 const Square* pl = pos.piece_list(us, Pt);
70 if ((from = *pl++) == SQ_NONE)
73 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
77 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
78 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
79 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
82 if (dc && bit_is_set(dc, from))
85 b = pos.attacks_from<Pt>(from) & checkSqs;
88 } while ((from = *pl++) != SQ_NONE);
94 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
96 return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
97 : generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
100 template<PieceType Pt, MoveType Type>
101 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
104 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
105 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
108 template<PieceType Pt>
109 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
113 const Square* pl = pos.piece_list(us, Pt);
119 b = pos.attacks_from<Pt>(from) & target;
121 } while (*++pl != SQ_NONE);
127 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
130 Square from = pos.king_square(us);
132 b = pos.attacks_from<KING>(from) & target;
140 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
141 /// promotions. Returns a pointer to the end of the move list.
143 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
144 /// underpromotions. Returns a pointer to the end of the move list.
146 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
147 /// non-captures. Returns a pointer to the end of the move list.
149 template<MoveType Type>
150 MoveStack* generate(const Position& pos, MoveStack* mlist) {
152 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
153 assert(!pos.in_check());
155 Color us = pos.side_to_move();
158 if (Type == MV_CAPTURE)
159 target = pos.pieces(flip(us));
161 else if (Type == MV_NON_CAPTURE)
162 target = pos.empty_squares();
164 else if (Type == MV_NON_EVASION)
165 target = pos.pieces(flip(us)) | pos.empty_squares();
167 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
168 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
169 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
170 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
171 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
172 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
174 if (Type != MV_CAPTURE && pos.can_castle(us))
176 if (pos.can_castle(us == WHITE ? WHITE_OO : BLACK_OO))
177 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
179 if (pos.can_castle(us == WHITE ? WHITE_OOO : BLACK_OOO))
180 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
186 // Explicit template instantiations
187 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
188 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
189 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
192 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
193 /// underpromotions that give check. Returns a pointer to the end of the move list.
195 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
197 assert(!pos.in_check());
201 Color us = pos.side_to_move();
202 Square ksq = pos.king_square(flip(us));
204 assert(pos.piece_on(ksq) == make_piece(flip(us), KING));
206 // Discovered non-capture checks
207 b = dc = pos.discovered_check_candidates();
211 from = pop_1st_bit(&b);
212 switch (type_of(pos.piece_on(from)))
214 case PAWN: /* Will be generated togheter with pawns direct checks */ break;
215 case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
216 case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
217 case ROOK: mlist = generate_discovered_checks<ROOK>(pos, mlist, from); break;
218 case KING: mlist = generate_discovered_checks<KING>(pos, mlist, from); break;
219 default: assert(false); break;
223 // Direct non-capture checks
224 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
225 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
226 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
227 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
228 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
232 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
233 /// to move is in check. Returns a pointer to the end of the move list.
235 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
237 assert(pos.in_check());
240 Square from, checksq;
242 Color us = pos.side_to_move();
243 Square ksq = pos.king_square(us);
244 Bitboard checkers = pos.checkers();
245 Bitboard sliderAttacks = 0;
247 assert(pos.piece_on(ksq) == make_piece(us, KING));
250 // Find squares attacked by slider checkers, we will remove
251 // them from the king evasions set so to early skip known
252 // illegal moves and avoid an useless legality check later.
257 checksq = pop_1st_bit(&b);
259 assert(color_of(pos.piece_on(checksq)) == flip(us));
261 switch (type_of(pos.piece_on(checksq)))
263 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
264 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
266 // If queen and king are far we can safely remove all the squares attacked
267 // in the other direction becuase are not reachable by the king anyway.
268 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
269 sliderAttacks |= QueenPseudoAttacks[checksq];
271 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
272 // use real rook attacks to check if king is safe to move in the other direction.
273 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
275 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
282 // Generate evasions for king, capture and non capture moves
283 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
287 // Generate evasions for other pieces only if not double check
291 // Find squares where a blocking evasion or a capture of the
292 // checker piece is possible.
293 target = squares_between(checksq, ksq) | checkers;
295 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
296 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
297 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
298 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
299 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
303 /// generate<MV_LEGAL> computes a complete list of legal moves in the current position
306 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
308 MoveStack *last, *cur = mlist;
309 Bitboard pinned = pos.pinned_pieces();
311 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
312 : generate<MV_NON_EVASION>(pos, mlist);
314 // Remove illegal moves from the list
316 if (!pos.pl_move_is_legal(cur->move, pinned))
317 cur->move = (--last)->move;
327 template<Square Delta>
328 inline Bitboard move_pawns(Bitboard p) {
330 return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
331 Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
332 Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
335 template<Square Delta>
336 inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
338 const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
343 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
344 b = move_pawns<Delta>(pawns) & target & ~TFileABB;
345 SERIALIZE_MOVES_D(b, -Delta);
349 template<MoveType Type, Square Delta>
350 inline MoveStack* generate_promotions(const Position& pos, MoveStack* mlist, Bitboard pawnsOn7, Bitboard target) {
352 const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
357 // Promotions and under-promotions, both captures and non-captures
358 b = move_pawns<Delta>(pawnsOn7) & target;
360 if (Delta != DELTA_N && Delta != DELTA_S)
365 to = pop_1st_bit(&b);
367 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
368 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
370 if (Type == MV_NON_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
372 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
373 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
374 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
377 // This is the only possible under promotion that can give a check
378 // not already included in the queen-promotion.
379 if ( Type == MV_CHECK
380 && bit_is_set(pos.attacks_from<KNIGHT>(to), pos.king_square(Delta > 0 ? BLACK : WHITE)))
381 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
382 else (void)pos; // Silence a warning under MSVC
387 template<Color Us, MoveType Type>
388 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
390 // Calculate our parametrized parameters at compile time, named
391 // according to the point of view of white side.
392 const Color Them = (Us == WHITE ? BLACK : WHITE);
393 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
394 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
395 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
396 const Square RIGHT_UP = (Us == WHITE ? DELTA_NE : DELTA_SW);
397 const Square LEFT_UP = (Us == WHITE ? DELTA_NW : DELTA_SE);
400 Bitboard b1, b2, dc1, dc2, pawnPushes, emptySquares;
401 Bitboard pawns = pos.pieces(PAWN, Us);
402 Bitboard pawnsOn7 = pawns & TRank7BB;
403 Bitboard enemyPieces = (Type == MV_CAPTURE ? target : pos.pieces(Them));
405 // Pre-calculate pawn pushes before changing emptySquares definition
406 if (Type != MV_CAPTURE)
408 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
409 pawnPushes = move_pawns<UP>(pawns & ~TRank7BB) & emptySquares;
412 if (Type == MV_EVASION)
414 emptySquares &= target; // Only blocking squares
415 enemyPieces &= target; // Capture only the checker piece
418 // Promotions and underpromotions
421 if (Type == MV_CAPTURE)
422 emptySquares = pos.empty_squares();
425 mlist = generate_promotions<Type, RIGHT_UP>(pos, mlist, pawnsOn7, enemyPieces);
426 mlist = generate_promotions<Type, LEFT_UP>(pos, mlist, pawnsOn7, enemyPieces);
427 mlist = generate_promotions<Type, UP>(pos, mlist, pawnsOn7, emptySquares);
431 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
433 mlist = generate_pawn_captures<RIGHT_UP>(mlist, pawns, enemyPieces);
434 mlist = generate_pawn_captures<LEFT_UP>(mlist, pawns, enemyPieces);
437 // Single and double pawn pushes
438 if (Type != MV_CAPTURE)
440 b1 = (Type != MV_EVASION ? pawnPushes : pawnPushes & emptySquares);
441 b2 = move_pawns<UP>(pawnPushes & TRank3BB) & emptySquares;
443 if (Type == MV_CHECK)
445 // Consider only pawn moves which give direct checks
446 b1 &= pos.attacks_from<PAWN>(ksq, Them);
447 b2 &= pos.attacks_from<PAWN>(ksq, Them);
449 // Add pawn moves which gives discovered check. This is possible only
450 // if the pawn is not on the same file as the enemy king, because we
451 // don't generate captures.
452 if (pawns & target) // For CHECK type target is dc bitboard
454 dc1 = move_pawns<UP>(pawns & target & ~file_bb(ksq)) & emptySquares;
455 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
461 SERIALIZE_MOVES_D(b1, -UP);
462 SERIALIZE_MOVES_D(b2, -UP -UP);
465 // En passant captures
466 if ( (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
467 && pos.ep_square() != SQ_NONE)
469 assert(Us != WHITE || rank_of(pos.ep_square()) == RANK_6);
470 assert(Us != BLACK || rank_of(pos.ep_square()) == RANK_3);
472 // An en passant capture can be an evasion only if the checking piece
473 // is the double pushed pawn and so is in the target. Otherwise this
474 // is a discovery check and we are forced to do otherwise.
475 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
478 b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
484 to = pop_1st_bit(&b1);
485 (*mlist++).move = make_enpassant(to, pos.ep_square());
491 template<CastlingSide Side>
492 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
494 CastleRight f = CastleRight((Side == KING_SIDE ? WHITE_OO : WHITE_OOO) << us);
495 Color them = flip(us);
497 // After castling, the rook and king's final positions are exactly the same
498 // in Chess960 as they would be in standard chess.
499 Square kfrom = pos.king_square(us);
500 Square rfrom = pos.castle_rook_square(f);
501 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
502 Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
504 assert(!pos.in_check());
505 assert(pos.piece_on(kfrom) == make_piece(us, KING));
506 assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
508 // Unimpeded rule: All the squares between the king's initial and final squares
509 // (including the final square), and all the squares between the rook's initial
510 // and final squares (including the final square), must be vacant except for
511 // the king and castling rook.
512 for (Square s = std::min(kfrom, kto); s <= std::max(kfrom, kto); s++)
513 if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
514 ||(pos.attackers_to(s) & pos.pieces(them)))
517 for (Square s = std::min(rfrom, rto); s <= std::max(rfrom, rto); s++)
518 if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
521 // Because we generate only legal castling moves we need to verify that
522 // when moving the castling rook we do not discover some hidden checker.
523 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
524 if (pos.is_chess960())
526 Bitboard occ = pos.occupied_squares();
527 clear_bit(&occ, rfrom);
528 if (pos.attackers_to(kto, occ) & pos.pieces(them))
532 (*mlist++).move = make_castle(kfrom, rfrom);