2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
28 template<CastlingRight Cr, bool Checks, bool Chess960>
29 ExtMove* generate_castling(const Position& pos, ExtMove* moveList, Color us) {
31 constexpr bool KingSide = (Cr == WHITE_OO || Cr == BLACK_OO);
33 if (pos.castling_impeded(Cr) || !pos.can_castle(Cr))
36 // After castling, the rook and king final positions are the same in Chess960
37 // as they would be in standard chess.
38 Square kfrom = pos.square<KING>(us);
39 Square rfrom = pos.castling_rook_square(Cr);
40 Square kto = relative_square(us, KingSide ? SQ_G1 : SQ_C1);
41 Bitboard enemies = pos.pieces(~us);
43 assert(!pos.checkers());
45 const Direction step = Chess960 ? kto > kfrom ? WEST : EAST
46 : KingSide ? WEST : EAST;
48 for (Square s = kto; s != kfrom; s += step)
49 if (pos.attackers_to(s) & enemies)
52 // Because we generate only legal castling moves we need to verify that
53 // when moving the castling rook we do not discover some hidden checker.
54 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
55 if (Chess960 && (attacks_bb<ROOK>(kto, pos.pieces() ^ rfrom) & pos.pieces(~us, ROOK, QUEEN)))
58 Move m = make<CASTLING>(kfrom, rfrom);
60 if (Checks && !pos.gives_check(m))
68 template<GenType Type, Direction D>
69 ExtMove* make_promotions(ExtMove* moveList, Square to, Square ksq) {
71 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
72 *moveList++ = make<PROMOTION>(to - D, to, QUEEN);
74 if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
76 *moveList++ = make<PROMOTION>(to - D, to, ROOK);
77 *moveList++ = make<PROMOTION>(to - D, to, BISHOP);
78 *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
81 // Knight promotion is the only promotion that can give a direct check
82 // that's not already included in the queen promotion.
83 if (Type == QUIET_CHECKS && (PseudoAttacks[KNIGHT][to] & ksq))
84 *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
86 (void)ksq; // Silence a warning under MSVC
92 template<Color Us, GenType Type>
93 ExtMove* generate_pawn_moves(const Position& pos, ExtMove* moveList, Bitboard target) {
95 // Compute our parametrized parameters at compile time, named according to
96 // the point of view of white side.
97 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
98 constexpr Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
99 constexpr Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
100 constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
101 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
102 constexpr Direction UpRight = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
103 constexpr Direction UpLeft = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
105 Bitboard emptySquares;
107 Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
108 Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
110 Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
111 Type == CAPTURES ? target : pos.pieces(Them));
113 // Single and double pawn pushes, no promotions
114 if (Type != CAPTURES)
116 emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
118 Bitboard b1 = shift<Up>(pawnsNotOn7) & emptySquares;
119 Bitboard b2 = shift<Up>(b1 & TRank3BB) & emptySquares;
121 if (Type == EVASIONS) // Consider only blocking squares
127 if (Type == QUIET_CHECKS)
129 Square ksq = pos.square<KING>(Them);
131 b1 &= pos.attacks_from<PAWN>(ksq, Them);
132 b2 &= pos.attacks_from<PAWN>(ksq, Them);
134 // Add pawn pushes which give discovered check. This is possible only
135 // if the pawn is not on the same file as the enemy king, because we
136 // don't generate captures. Note that a possible discovery check
137 // promotion has been already generated amongst the captures.
138 Bitboard dcCandidates = pos.blockers_for_king(Them);
139 if (pawnsNotOn7 & dcCandidates)
141 Bitboard dc1 = shift<Up>(pawnsNotOn7 & dcCandidates) & emptySquares & ~file_bb(ksq);
142 Bitboard dc2 = shift<Up>(dc1 & TRank3BB) & emptySquares;
151 Square to = pop_lsb(&b1);
152 *moveList++ = make_move(to - Up, to);
157 Square to = pop_lsb(&b2);
158 *moveList++ = make_move(to - Up - Up, to);
162 // Promotions and underpromotions
163 if (pawnsOn7 && (Type != EVASIONS || (target & TRank8BB)))
165 if (Type == CAPTURES)
166 emptySquares = ~pos.pieces();
168 if (Type == EVASIONS)
169 emptySquares &= target;
171 Bitboard b1 = shift<UpRight>(pawnsOn7) & enemies;
172 Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
173 Bitboard b3 = shift<Up >(pawnsOn7) & emptySquares;
175 Square ksq = pos.square<KING>(Them);
178 moveList = make_promotions<Type, UpRight>(moveList, pop_lsb(&b1), ksq);
181 moveList = make_promotions<Type, UpLeft >(moveList, pop_lsb(&b2), ksq);
184 moveList = make_promotions<Type, Up >(moveList, pop_lsb(&b3), ksq);
187 // Standard and en-passant captures
188 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
190 Bitboard b1 = shift<UpRight>(pawnsNotOn7) & enemies;
191 Bitboard b2 = shift<UpLeft >(pawnsNotOn7) & enemies;
195 Square to = pop_lsb(&b1);
196 *moveList++ = make_move(to - UpRight, to);
201 Square to = pop_lsb(&b2);
202 *moveList++ = make_move(to - UpLeft, to);
205 if (pos.ep_square() != SQ_NONE)
207 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
209 // An en passant capture can be an evasion only if the checking piece
210 // is the double pushed pawn and so is in the target. Otherwise this
211 // is a discovery check and we are forced to do otherwise.
212 if (Type == EVASIONS && !(target & (pos.ep_square() - Up)))
215 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
220 *moveList++ = make<ENPASSANT>(pop_lsb(&b1), pos.ep_square());
228 template<PieceType Pt, bool Checks>
229 ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Color us,
232 assert(Pt != KING && Pt != PAWN);
234 const Square* pl = pos.squares<Pt>(us);
236 for (Square from = *pl; from != SQ_NONE; from = *++pl)
240 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
241 && !(PseudoAttacks[Pt][from] & target & pos.check_squares(Pt)))
244 if (pos.blockers_for_king(~us) & from)
248 Bitboard b = pos.attacks_from<Pt>(from) & target;
251 b &= pos.check_squares(Pt);
254 *moveList++ = make_move(from, pop_lsb(&b));
261 template<Color Us, GenType Type>
262 ExtMove* generate_all(const Position& pos, ExtMove* moveList, Bitboard target) {
264 constexpr bool Checks = Type == QUIET_CHECKS;
266 moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
267 moveList = generate_moves<KNIGHT, Checks>(pos, moveList, Us, target);
268 moveList = generate_moves<BISHOP, Checks>(pos, moveList, Us, target);
269 moveList = generate_moves< ROOK, Checks>(pos, moveList, Us, target);
270 moveList = generate_moves< QUEEN, Checks>(pos, moveList, Us, target);
272 if (Type != QUIET_CHECKS && Type != EVASIONS)
274 Square ksq = pos.square<KING>(Us);
275 Bitboard b = pos.attacks_from<KING>(ksq) & target;
277 *moveList++ = make_move(ksq, pop_lsb(&b));
280 if (Type != CAPTURES && Type != EVASIONS && pos.can_castle(Us))
282 if (pos.is_chess960())
284 moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, true>(pos, moveList, Us);
285 moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, true>(pos, moveList, Us);
289 moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, false>(pos, moveList, Us);
290 moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, false>(pos, moveList, Us);
300 /// generate<CAPTURES> generates all pseudo-legal captures and queen
301 /// promotions. Returns a pointer to the end of the move list.
303 /// generate<QUIETS> generates all pseudo-legal non-captures and
304 /// underpromotions. Returns a pointer to the end of the move list.
306 /// generate<NON_EVASIONS> generates all pseudo-legal captures and
307 /// non-captures. Returns a pointer to the end of the move list.
309 template<GenType Type>
310 ExtMove* generate(const Position& pos, ExtMove* moveList) {
312 assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
313 assert(!pos.checkers());
315 Color us = pos.side_to_move();
317 Bitboard target = Type == CAPTURES ? pos.pieces(~us)
318 : Type == QUIETS ? ~pos.pieces()
319 : Type == NON_EVASIONS ? ~pos.pieces(us) : 0;
321 return us == WHITE ? generate_all<WHITE, Type>(pos, moveList, target)
322 : generate_all<BLACK, Type>(pos, moveList, target);
325 // Explicit template instantiations
326 template ExtMove* generate<CAPTURES>(const Position&, ExtMove*);
327 template ExtMove* generate<QUIETS>(const Position&, ExtMove*);
328 template ExtMove* generate<NON_EVASIONS>(const Position&, ExtMove*);
331 /// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
332 /// underpromotions that give check. Returns a pointer to the end of the move list.
334 ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
336 assert(!pos.checkers());
338 Color us = pos.side_to_move();
339 Bitboard dc = pos.blockers_for_king(~us) & pos.pieces(us);
343 Square from = pop_lsb(&dc);
344 PieceType pt = type_of(pos.piece_on(from));
347 continue; // Will be generated together with direct checks
349 Bitboard b = pos.attacks_from(pt, from) & ~pos.pieces();
352 b &= ~PseudoAttacks[QUEEN][pos.square<KING>(~us)];
355 *moveList++ = make_move(from, pop_lsb(&b));
358 return us == WHITE ? generate_all<WHITE, QUIET_CHECKS>(pos, moveList, ~pos.pieces())
359 : generate_all<BLACK, QUIET_CHECKS>(pos, moveList, ~pos.pieces());
363 /// generate<EVASIONS> generates all pseudo-legal check evasions when the side
364 /// to move is in check. Returns a pointer to the end of the move list.
366 ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
368 assert(pos.checkers());
370 Color us = pos.side_to_move();
371 Square ksq = pos.square<KING>(us);
372 Bitboard sliderAttacks = 0;
373 Bitboard sliders = pos.checkers() & ~pos.pieces(KNIGHT, PAWN);
375 // Find all the squares attacked by slider checkers. We will remove them from
376 // the king evasions in order to skip known illegal moves, which avoids any
377 // useless legality checks later on.
380 Square checksq = pop_lsb(&sliders);
381 sliderAttacks |= LineBB[checksq][ksq] ^ checksq;
384 // Generate evasions for king, capture and non capture moves
385 Bitboard b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
387 *moveList++ = make_move(ksq, pop_lsb(&b));
389 if (more_than_one(pos.checkers()))
390 return moveList; // Double check, only a king move can save the day
392 // Generate blocking evasions or captures of the checking piece
393 Square checksq = lsb(pos.checkers());
394 Bitboard target = between_bb(checksq, ksq) | checksq;
396 return us == WHITE ? generate_all<WHITE, EVASIONS>(pos, moveList, target)
397 : generate_all<BLACK, EVASIONS>(pos, moveList, target);
401 /// generate<LEGAL> generates all the legal moves in the given position
404 ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
406 Color us = pos.side_to_move();
407 Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
408 Square ksq = pos.square<KING>(us);
409 ExtMove* cur = moveList;
411 moveList = pos.checkers() ? generate<EVASIONS >(pos, moveList)
412 : generate<NON_EVASIONS>(pos, moveList);
413 while (cur != moveList)
414 if ( (pinned || from_sq(*cur) == ksq || type_of(*cur) == ENPASSANT)
416 *cur = (--moveList)->move;