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
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 template<CastlingRight Cr, bool Checks, bool Chess960>
28 ExtMove* generate_castling(const Position& pos, ExtMove* moveList, Color us, const CheckInfo* ci) {
30 static const bool KingSide = (Cr == WHITE_OO || Cr == BLACK_OO);
32 if (pos.castling_impeded(Cr) || !pos.can_castle(Cr))
35 // After castling, the rook and king final positions are the same in Chess960
36 // as they would be in standard chess.
37 Square kfrom = pos.king_square(us);
38 Square rfrom = pos.castling_rook_square(Cr);
39 Square kto = relative_square(us, KingSide ? SQ_G1 : SQ_C1);
40 Bitboard enemies = pos.pieces(~us);
42 assert(!pos.checkers());
44 const Square K = Chess960 ? kto > kfrom ? DELTA_W : DELTA_E
45 : KingSide ? DELTA_W : DELTA_E;
47 for (Square s = kto; s != kfrom; s += K)
48 if (pos.attackers_to(s) & enemies)
51 // Because we generate only legal castling moves we need to verify that
52 // when moving the castling rook we do not discover some hidden checker.
53 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
54 if (Chess960 && (attacks_bb<ROOK>(kto, pos.pieces() ^ rfrom) & pos.pieces(~us, ROOK, QUEEN)))
57 Move m = make<CASTLING>(kfrom, rfrom);
59 if (Checks && !pos.gives_check(m, *ci))
64 return (void)ci, moveList; // Silence a warning under MSVC
68 template<GenType Type, Square Delta>
69 ExtMove* make_promotions(ExtMove* moveList, Square to, const CheckInfo* ci) {
71 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
72 *moveList++ = make<PROMOTION>(to - Delta, to, QUEEN);
74 if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
76 *moveList++ = make<PROMOTION>(to - Delta, to, ROOK);
77 *moveList++ = make<PROMOTION>(to - Delta, to, BISHOP);
78 *moveList++ = make<PROMOTION>(to - Delta, 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 && (StepAttacksBB[W_KNIGHT][to] & ci->ksq))
84 *moveList++ = make<PROMOTION>(to - Delta, to, KNIGHT);
86 return (void)ci, moveList; // Silence a warning under MSVC
90 template<Color Us, GenType Type>
91 ExtMove* generate_pawn_moves(const Position& pos, ExtMove* moveList,
92 Bitboard target, const CheckInfo* ci) {
94 // Compute our parametrized parameters at compile time, named according to
95 // the point of view of white side.
96 const Color Them = (Us == WHITE ? BLACK : WHITE);
97 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
98 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
99 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
100 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
101 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
102 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
104 Bitboard emptySquares;
106 Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
107 Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
109 Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
110 Type == CAPTURES ? target : pos.pieces(Them));
112 // Single and double pawn pushes, no promotions
113 if (Type != CAPTURES)
115 emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
117 Bitboard b1 = shift_bb<Up>(pawnsNotOn7) & emptySquares;
118 Bitboard b2 = shift_bb<Up>(b1 & TRank3BB) & emptySquares;
120 if (Type == EVASIONS) // Consider only blocking squares
126 if (Type == QUIET_CHECKS)
128 b1 &= pos.attacks_from<PAWN>(ci->ksq, Them);
129 b2 &= pos.attacks_from<PAWN>(ci->ksq, Them);
131 // Add pawn pushes which give discovered check. This is possible only
132 // if the pawn is not on the same file as the enemy king, because we
133 // don't generate captures. Note that a possible discovery check
134 // promotion has been already generated amongst the captures.
135 if (pawnsNotOn7 & ci->dcCandidates)
137 Bitboard dc1 = shift_bb<Up>(pawnsNotOn7 & ci->dcCandidates) & emptySquares & ~file_bb(ci->ksq);
138 Bitboard dc2 = shift_bb<Up>(dc1 & TRank3BB) & emptySquares;
147 Square to = pop_lsb(&b1);
148 *moveList++ = make_move(to - Up, to);
153 Square to = pop_lsb(&b2);
154 *moveList++ = make_move(to - Up - Up, to);
158 // Promotions and underpromotions
159 if (pawnsOn7 && (Type != EVASIONS || (target & TRank8BB)))
161 if (Type == CAPTURES)
162 emptySquares = ~pos.pieces();
164 if (Type == EVASIONS)
165 emptySquares &= target;
167 Bitboard b1 = shift_bb<Right>(pawnsOn7) & enemies;
168 Bitboard b2 = shift_bb<Left >(pawnsOn7) & enemies;
169 Bitboard b3 = shift_bb<Up >(pawnsOn7) & emptySquares;
172 moveList = make_promotions<Type, Right>(moveList, pop_lsb(&b1), ci);
175 moveList = make_promotions<Type, Left >(moveList, pop_lsb(&b2), ci);
178 moveList = make_promotions<Type, Up >(moveList, pop_lsb(&b3), ci);
181 // Standard and en-passant captures
182 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
184 Bitboard b1 = shift_bb<Right>(pawnsNotOn7) & enemies;
185 Bitboard b2 = shift_bb<Left >(pawnsNotOn7) & enemies;
189 Square to = pop_lsb(&b1);
190 *moveList++ = make_move(to - Right, to);
195 Square to = pop_lsb(&b2);
196 *moveList++ = make_move(to - Left, to);
199 if (pos.ep_square() != SQ_NONE)
201 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
203 // An en passant capture can be an evasion only if the checking piece
204 // is the double pushed pawn and so is in the target. Otherwise this
205 // is a discovery check and we are forced to do otherwise.
206 if (Type == EVASIONS && !(target & (pos.ep_square() - Up)))
209 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
214 *moveList++ = make<ENPASSANT>(pop_lsb(&b1), pos.ep_square());
222 template<PieceType Pt, bool Checks>
223 ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Color us,
224 Bitboard target, const CheckInfo* ci) {
226 assert(Pt != KING && Pt != PAWN);
228 const Square* pl = pos.list<Pt>(us);
230 for (Square from = *pl; from != SQ_NONE; from = *++pl)
234 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
235 && !(PseudoAttacks[Pt][from] & target & ci->checkSquares[Pt]))
238 if (ci->dcCandidates && (ci->dcCandidates & from))
242 Bitboard b = pos.attacks_from<Pt>(from) & target;
245 b &= ci->checkSquares[Pt];
248 *moveList++ = make_move(from, pop_lsb(&b));
255 template<Color Us, GenType Type>
256 ExtMove* generate_all(const Position& pos, ExtMove* moveList, Bitboard target,
257 const CheckInfo* ci = nullptr) {
259 const bool Checks = Type == QUIET_CHECKS;
261 moveList = generate_pawn_moves<Us, Type>(pos, moveList, target, ci);
262 moveList = generate_moves<KNIGHT, Checks>(pos, moveList, Us, target, ci);
263 moveList = generate_moves<BISHOP, Checks>(pos, moveList, Us, target, ci);
264 moveList = generate_moves< ROOK, Checks>(pos, moveList, Us, target, ci);
265 moveList = generate_moves< QUEEN, Checks>(pos, moveList, Us, target, ci);
267 if (Type != QUIET_CHECKS && Type != EVASIONS)
269 Square ksq = pos.king_square(Us);
270 Bitboard b = pos.attacks_from<KING>(ksq) & target;
272 *moveList++ = make_move(ksq, pop_lsb(&b));
275 if (Type != CAPTURES && Type != EVASIONS && pos.can_castle(Us))
277 if (pos.is_chess960())
279 moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, true>(pos, moveList, Us, ci);
280 moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, true>(pos, moveList, Us, ci);
284 moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, false>(pos, moveList, Us, ci);
285 moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, false>(pos, moveList, Us, ci);
295 /// generate<CAPTURES> generates all pseudo-legal captures and queen
296 /// promotions. Returns a pointer to the end of the move list.
298 /// generate<QUIETS> generates all pseudo-legal non-captures and
299 /// underpromotions. Returns a pointer to the end of the move list.
301 /// generate<NON_EVASIONS> generates all pseudo-legal captures and
302 /// non-captures. Returns a pointer to the end of the move list.
304 template<GenType Type>
305 ExtMove* generate(const Position& pos, ExtMove* moveList) {
307 assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
308 assert(!pos.checkers());
310 Color us = pos.side_to_move();
312 Bitboard target = Type == CAPTURES ? pos.pieces(~us)
313 : Type == QUIETS ? ~pos.pieces()
314 : Type == NON_EVASIONS ? ~pos.pieces(us) : 0;
316 return us == WHITE ? generate_all<WHITE, Type>(pos, moveList, target)
317 : generate_all<BLACK, Type>(pos, moveList, target);
320 // Explicit template instantiations
321 template ExtMove* generate<CAPTURES>(const Position&, ExtMove*);
322 template ExtMove* generate<QUIETS>(const Position&, ExtMove*);
323 template ExtMove* generate<NON_EVASIONS>(const Position&, ExtMove*);
326 /// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
327 /// underpromotions that give check. Returns a pointer to the end of the move list.
329 ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
331 assert(!pos.checkers());
333 Color us = pos.side_to_move();
335 Bitboard dc = ci.dcCandidates;
339 Square from = pop_lsb(&dc);
340 PieceType pt = type_of(pos.piece_on(from));
343 continue; // Will be generated together with direct checks
345 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
348 b &= ~PseudoAttacks[QUEEN][ci.ksq];
351 *moveList++ = make_move(from, pop_lsb(&b));
354 return us == WHITE ? generate_all<WHITE, QUIET_CHECKS>(pos, moveList, ~pos.pieces(), &ci)
355 : generate_all<BLACK, QUIET_CHECKS>(pos, moveList, ~pos.pieces(), &ci);
359 /// generate<EVASIONS> generates all pseudo-legal check evasions when the side
360 /// to move is in check. Returns a pointer to the end of the move list.
362 ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
364 assert(pos.checkers());
366 Color us = pos.side_to_move();
367 Square ksq = pos.king_square(us);
368 Bitboard sliderAttacks = 0;
369 Bitboard sliders = pos.checkers() & ~pos.pieces(KNIGHT, PAWN);
371 // Find all the squares attacked by slider checkers. We will remove them from
372 // the king evasions in order to skip known illegal moves, which avoids any
373 // useless legality checks later on.
376 Square checksq = pop_lsb(&sliders);
377 sliderAttacks |= LineBB[checksq][ksq] ^ checksq;
380 // Generate evasions for king, capture and non capture moves
381 Bitboard b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
383 *moveList++ = make_move(ksq, pop_lsb(&b));
385 if (more_than_one(pos.checkers()))
386 return moveList; // Double check, only a king move can save the day
388 // Generate blocking evasions or captures of the checking piece
389 Square checksq = lsb(pos.checkers());
390 Bitboard target = between_bb(checksq, ksq) | checksq;
392 return us == WHITE ? generate_all<WHITE, EVASIONS>(pos, moveList, target)
393 : generate_all<BLACK, EVASIONS>(pos, moveList, target);
397 /// generate<LEGAL> generates all the legal moves in the given position
400 ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
402 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
403 Square ksq = pos.king_square(pos.side_to_move());
404 ExtMove* cur = moveList;
406 moveList = pos.checkers() ? generate<EVASIONS >(pos, moveList)
407 : generate<NON_EVASIONS>(pos, moveList);
408 while (cur != moveList)
409 if ( (pinned || from_sq(*cur) == ksq || type_of(*cur) == ENPASSANT)
410 && !pos.legal(*cur, pinned))
411 *cur = (--moveList)->move;