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) 2015-2016 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, const CheckInfo* ci) {
31 static const 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 Square K = Chess960 ? kto > kfrom ? DELTA_W : DELTA_E
46 : KingSide ? DELTA_W : DELTA_E;
48 for (Square s = kto; s != kfrom; s += K)
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, *ci))
63 (void)ci; // Silence a warning under MSVC
70 template<GenType Type, Square Delta>
71 ExtMove* make_promotions(ExtMove* moveList, Square to, const CheckInfo* ci) {
73 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
74 *moveList++ = make<PROMOTION>(to - Delta, to, QUEEN);
76 if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
78 *moveList++ = make<PROMOTION>(to - Delta, to, ROOK);
79 *moveList++ = make<PROMOTION>(to - Delta, to, BISHOP);
80 *moveList++ = make<PROMOTION>(to - Delta, to, KNIGHT);
83 // Knight promotion is the only promotion that can give a direct check
84 // that's not already included in the queen promotion.
85 if (Type == QUIET_CHECKS && (StepAttacksBB[W_KNIGHT][to] & ci->ksq))
86 *moveList++ = make<PROMOTION>(to - Delta, to, KNIGHT);
88 (void)ci; // Silence a warning under MSVC
94 template<Color Us, GenType Type>
95 ExtMove* generate_pawn_moves(const Position& pos, ExtMove* moveList,
96 Bitboard target, const CheckInfo* ci) {
98 // Compute our parametrized parameters at compile time, named according to
99 // the point of view of white side.
100 const Color Them = (Us == WHITE ? BLACK : WHITE);
101 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
102 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
103 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
104 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
105 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
106 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
108 Bitboard emptySquares;
110 Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
111 Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
113 Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
114 Type == CAPTURES ? target : pos.pieces(Them));
116 // Single and double pawn pushes, no promotions
117 if (Type != CAPTURES)
119 emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
121 Bitboard b1 = shift_bb<Up>(pawnsNotOn7) & emptySquares;
122 Bitboard b2 = shift_bb<Up>(b1 & TRank3BB) & emptySquares;
124 if (Type == EVASIONS) // Consider only blocking squares
130 if (Type == QUIET_CHECKS)
132 b1 &= pos.attacks_from<PAWN>(ci->ksq, Them);
133 b2 &= pos.attacks_from<PAWN>(ci->ksq, Them);
135 // Add pawn pushes which give discovered check. This is possible only
136 // if the pawn is not on the same file as the enemy king, because we
137 // don't generate captures. Note that a possible discovery check
138 // promotion has been already generated amongst the captures.
139 if (pawnsNotOn7 & ci->dcCandidates)
141 Bitboard dc1 = shift_bb<Up>(pawnsNotOn7 & ci->dcCandidates) & emptySquares & ~file_bb(ci->ksq);
142 Bitboard dc2 = shift_bb<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_bb<Right>(pawnsOn7) & enemies;
172 Bitboard b2 = shift_bb<Left >(pawnsOn7) & enemies;
173 Bitboard b3 = shift_bb<Up >(pawnsOn7) & emptySquares;
176 moveList = make_promotions<Type, Right>(moveList, pop_lsb(&b1), ci);
179 moveList = make_promotions<Type, Left >(moveList, pop_lsb(&b2), ci);
182 moveList = make_promotions<Type, Up >(moveList, pop_lsb(&b3), ci);
185 // Standard and en-passant captures
186 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
188 Bitboard b1 = shift_bb<Right>(pawnsNotOn7) & enemies;
189 Bitboard b2 = shift_bb<Left >(pawnsNotOn7) & enemies;
193 Square to = pop_lsb(&b1);
194 *moveList++ = make_move(to - Right, to);
199 Square to = pop_lsb(&b2);
200 *moveList++ = make_move(to - Left, to);
203 if (pos.ep_square() != SQ_NONE)
205 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
207 // An en passant capture can be an evasion only if the checking piece
208 // is the double pushed pawn and so is in the target. Otherwise this
209 // is a discovery check and we are forced to do otherwise.
210 if (Type == EVASIONS && !(target & (pos.ep_square() - Up)))
213 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
218 *moveList++ = make<ENPASSANT>(pop_lsb(&b1), pos.ep_square());
226 template<PieceType Pt, bool Checks>
227 ExtMove* generate_moves(const Position& pos, ExtMove* moveList, Color us,
228 Bitboard target, const CheckInfo* ci) {
230 assert(Pt != KING && Pt != PAWN);
232 const Square* pl = pos.squares<Pt>(us);
234 for (Square from = *pl; from != SQ_NONE; from = *++pl)
238 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
239 && !(PseudoAttacks[Pt][from] & target & ci->checkSquares[Pt]))
242 if (ci->dcCandidates & from)
246 Bitboard b = pos.attacks_from<Pt>(from) & target;
249 b &= ci->checkSquares[Pt];
252 *moveList++ = make_move(from, pop_lsb(&b));
259 template<Color Us, GenType Type>
260 ExtMove* generate_all(const Position& pos, ExtMove* moveList, Bitboard target,
261 const CheckInfo* ci = nullptr) {
263 const bool Checks = Type == QUIET_CHECKS;
265 moveList = generate_pawn_moves<Us, Type>(pos, moveList, target, ci);
266 moveList = generate_moves<KNIGHT, Checks>(pos, moveList, Us, target, ci);
267 moveList = generate_moves<BISHOP, Checks>(pos, moveList, Us, target, ci);
268 moveList = generate_moves< ROOK, Checks>(pos, moveList, Us, target, ci);
269 moveList = generate_moves< QUEEN, Checks>(pos, moveList, Us, target, ci);
271 if (Type != QUIET_CHECKS && Type != EVASIONS)
273 Square ksq = pos.square<KING>(Us);
274 Bitboard b = pos.attacks_from<KING>(ksq) & target;
276 *moveList++ = make_move(ksq, pop_lsb(&b));
279 if (Type != CAPTURES && Type != EVASIONS && pos.can_castle(Us))
281 if (pos.is_chess960())
283 moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, true>(pos, moveList, Us, ci);
284 moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, true>(pos, moveList, Us, ci);
288 moveList = generate_castling<MakeCastling<Us, KING_SIDE>::right, Checks, false>(pos, moveList, Us, ci);
289 moveList = generate_castling<MakeCastling<Us, QUEEN_SIDE>::right, Checks, false>(pos, moveList, Us, ci);
299 /// generate<CAPTURES> generates all pseudo-legal captures and queen
300 /// promotions. Returns a pointer to the end of the move list.
302 /// generate<QUIETS> generates all pseudo-legal non-captures and
303 /// underpromotions. Returns a pointer to the end of the move list.
305 /// generate<NON_EVASIONS> generates all pseudo-legal captures and
306 /// non-captures. Returns a pointer to the end of the move list.
308 template<GenType Type>
309 ExtMove* generate(const Position& pos, ExtMove* moveList) {
311 assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
312 assert(!pos.checkers());
314 Color us = pos.side_to_move();
316 Bitboard target = Type == CAPTURES ? pos.pieces(~us)
317 : Type == QUIETS ? ~pos.pieces()
318 : Type == NON_EVASIONS ? ~pos.pieces(us) : 0;
320 return us == WHITE ? generate_all<WHITE, Type>(pos, moveList, target)
321 : generate_all<BLACK, Type>(pos, moveList, target);
324 // Explicit template instantiations
325 template ExtMove* generate<CAPTURES>(const Position&, ExtMove*);
326 template ExtMove* generate<QUIETS>(const Position&, ExtMove*);
327 template ExtMove* generate<NON_EVASIONS>(const Position&, ExtMove*);
330 /// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
331 /// underpromotions that give check. Returns a pointer to the end of the move list.
333 ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
335 assert(!pos.checkers());
337 Color us = pos.side_to_move();
339 Bitboard dc = ci.dcCandidates;
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(Piece(pt), from) & ~pos.pieces();
352 b &= ~PseudoAttacks[QUEEN][ci.ksq];
355 *moveList++ = make_move(from, pop_lsb(&b));
358 return us == WHITE ? generate_all<WHITE, QUIET_CHECKS>(pos, moveList, ~pos.pieces(), &ci)
359 : generate_all<BLACK, QUIET_CHECKS>(pos, moveList, ~pos.pieces(), &ci);
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 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
407 Square ksq = pos.square<KING>(pos.side_to_move());
408 ExtMove* cur = moveList;
410 moveList = pos.checkers() ? generate<EVASIONS >(pos, moveList)
411 : generate<NON_EVASIONS>(pos, moveList);
412 while (cur != moveList)
413 if ( (pinned || from_sq(*cur) == ksq || type_of(*cur) == ENPASSANT)
414 && !pos.legal(*cur, pinned))
415 *cur = (--moveList)->move;