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/>.
25 /// Simple macro to wrap a very common while loop, no facny, no flexibility,
26 /// hardcoded names 'mlist' and 'from'.
27 #define SERIALIZE(b) while (b) (*mlist++).move = make_move(from, pop_lsb(&b))
29 /// Version used for pawns, where the 'from' square is given as a delta from the 'to' square
30 #define SERIALIZE_PAWNS(b, d) while (b) { Square to = pop_lsb(&b); \
31 (*mlist++).move = make_move(to - (d), to); }
34 template<CastlingSide Side, bool Checks, bool Chess960>
35 MoveStack* generate_castle(const Position& pos, MoveStack* mlist, Color us) {
37 if (pos.castle_impeded(us, Side) || !pos.can_castle(make_castle_right(us, Side)))
40 // After castling, the rook and king final positions are the same in Chess960
41 // as they would be in standard chess.
42 Square kfrom = pos.king_square(us);
43 Square rfrom = pos.castle_rook_square(us, Side);
44 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
45 Bitboard enemies = pos.pieces(~us);
47 assert(!pos.checkers());
49 const int K = Chess960 ? kto > kfrom ? -1 : 1
50 : Side == KING_SIDE ? -1 : 1;
52 for (Square s = kto; s != kfrom; s += (Square)K)
53 if (pos.attackers_to(s) & enemies)
56 // Because we generate only legal castling moves we need to verify that
57 // when moving the castling rook we do not discover some hidden checker.
58 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
59 if (Chess960 && (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
62 (*mlist++).move = make<CASTLE>(kfrom, rfrom);
64 if (Checks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
71 template<Square Delta>
72 inline Bitboard move_pawns(Bitboard p) {
74 return Delta == DELTA_N ? p << 8
75 : Delta == DELTA_S ? p >> 8
76 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
77 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
78 : Delta == DELTA_NW ? (p & ~FileABB) << 7
79 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : 0;
83 template<GenType Type, Square Delta>
84 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7,
85 Bitboard target, const CheckInfo* ci) {
87 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
91 Square to = pop_lsb(&b);
93 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
94 (*mlist++).move = make<PROMOTION>(to - Delta, to, QUEEN);
96 if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
98 (*mlist++).move = make<PROMOTION>(to - Delta, to, ROOK);
99 (*mlist++).move = make<PROMOTION>(to - Delta, to, BISHOP);
100 (*mlist++).move = make<PROMOTION>(to - Delta, to, KNIGHT);
103 // Knight-promotion is the only one that can give a direct check not
104 // already included in the queen-promotion.
105 if (Type == QUIET_CHECKS && (StepAttacksBB[W_KNIGHT][to] & ci->ksq))
106 (*mlist++).move = make<PROMOTION>(to - Delta, to, KNIGHT);
108 (void)ci; // Silence a warning under MSVC
115 template<Color Us, GenType Type>
116 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist,
117 Bitboard target, const CheckInfo* ci) {
119 // Compute our parametrized parameters at compile time, named according to
120 // the point of view of white side.
121 const Color Them = (Us == WHITE ? BLACK : WHITE);
122 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
123 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
124 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
125 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
126 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
127 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
129 Bitboard b1, b2, dc1, dc2, emptySquares;
131 Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
132 Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
134 Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
135 Type == CAPTURES ? target : pos.pieces(Them));
137 // Single and double pawn pushes, no promotions
138 if (Type != CAPTURES)
140 emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
142 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
143 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
145 if (Type == EVASIONS) // Consider only blocking squares
151 if (Type == QUIET_CHECKS)
153 b1 &= pos.attacks_from<PAWN>(ci->ksq, Them);
154 b2 &= pos.attacks_from<PAWN>(ci->ksq, Them);
156 // Add pawn pushes which give discovered check. This is possible only
157 // if the pawn is not on the same file as the enemy king, because we
158 // don't generate captures. Note that a possible discovery check
159 // promotion has been already generated among captures.
160 if (pawnsNotOn7 & ci->dcCandidates)
162 dc1 = move_pawns<UP>(pawnsNotOn7 & ci->dcCandidates) & emptySquares & ~file_bb(ci->ksq);
163 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
170 SERIALIZE_PAWNS(b1, UP);
171 SERIALIZE_PAWNS(b2, UP + UP);
174 // Promotions and underpromotions
175 if (pawnsOn7 && (Type != EVASIONS || (target & TRank8BB)))
177 if (Type == CAPTURES)
178 emptySquares = ~pos.pieces();
180 if (Type == EVASIONS)
181 emptySquares &= target;
183 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ci);
184 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ci);
185 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ci);
188 // Standard and en-passant captures
189 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
191 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
192 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
194 SERIALIZE_PAWNS(b1, RIGHT);
195 SERIALIZE_PAWNS(b2, LEFT);
197 if (pos.ep_square() != SQ_NONE)
199 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
201 // An en passant capture can be an evasion only if the checking piece
202 // is the double pushed pawn and so is in the target. Otherwise this
203 // is a discovery check and we are forced to do otherwise.
204 if (Type == EVASIONS && !(target & (pos.ep_square() - UP)))
207 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
212 (*mlist++).move = make<ENPASSANT>(pop_lsb(&b1), pos.ep_square());
220 template<PieceType Pt, bool Checks> FORCE_INLINE
221 MoveStack* generate_moves(const Position& pos, MoveStack* mlist, Color us,
222 Bitboard target, const CheckInfo* ci) {
224 assert(Pt != KING && Pt != PAWN);
226 const Square* pl = pos.piece_list(us, Pt);
228 for (Square from = *pl; from != SQ_NONE; from = *++pl)
232 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
233 && !(PseudoAttacks[Pt][from] & target & ci->checkSq[Pt]))
236 if (ci->dcCandidates && (ci->dcCandidates & from))
240 Bitboard b = pos.attacks_from<Pt>(from) & target;
243 b &= ci->checkSq[Pt];
252 FORCE_INLINE MoveStack* generate_king_moves(const Position& pos, MoveStack* mlist,
253 Color us, Bitboard target) {
254 Square from = pos.king_square(us);
255 Bitboard b = pos.attacks_from<KING>(from) & target;
261 template<GenType Type> FORCE_INLINE
262 MoveStack* generate_all_moves(const Position& pos, MoveStack* mlist, Color us,
263 Bitboard target, const CheckInfo* ci = NULL) {
265 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target, ci)
266 : generate_pawn_moves<BLACK, Type>(pos, mlist, target, ci));
268 mlist = generate_moves<KNIGHT, Type == QUIET_CHECKS>(pos, mlist, us, target, ci);
269 mlist = generate_moves<BISHOP, Type == QUIET_CHECKS>(pos, mlist, us, target, ci);
270 mlist = generate_moves<ROOK, Type == QUIET_CHECKS>(pos, mlist, us, target, ci);
271 mlist = generate_moves<QUEEN, Type == QUIET_CHECKS>(pos, mlist, us, target, ci);
273 if (Type != QUIET_CHECKS && Type != EVASIONS)
274 mlist = generate_king_moves(pos, mlist, us, target);
276 if (Type != CAPTURES && Type != EVASIONS && pos.can_castle(us))
278 if (pos.is_chess960())
280 mlist = generate_castle<KING_SIDE, Type == QUIET_CHECKS, true>(pos, mlist, us);
281 mlist = generate_castle<QUEEN_SIDE, Type == QUIET_CHECKS, true>(pos, mlist, us);
285 mlist = generate_castle<KING_SIDE, Type == QUIET_CHECKS, false>(pos, mlist, us);
286 mlist = generate_castle<QUEEN_SIDE, Type == QUIET_CHECKS, false>(pos, mlist, us);
297 /// generate<CAPTURES> generates all pseudo-legal captures and queen
298 /// promotions. Returns a pointer to the end of the move list.
300 /// generate<QUIETS> generates all pseudo-legal non-captures and
301 /// underpromotions. Returns a pointer to the end of the move list.
303 /// generate<NON_EVASIONS> generates all pseudo-legal captures and
304 /// non-captures. Returns a pointer to the end of the move list.
306 template<GenType Type>
307 MoveStack* generate(const Position& pos, MoveStack* mlist) {
309 assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
310 assert(!pos.checkers());
312 Color us = pos.side_to_move();
315 if (Type == CAPTURES)
316 target = pos.pieces(~us);
318 else if (Type == QUIETS)
319 target = ~pos.pieces();
321 else if (Type == NON_EVASIONS)
322 target = ~pos.pieces(us);
324 return generate_all_moves<Type>(pos, mlist, us, target);
327 // Explicit template instantiations
328 template MoveStack* generate<CAPTURES>(const Position&, MoveStack*);
329 template MoveStack* generate<QUIETS>(const Position&, MoveStack*);
330 template MoveStack* generate<NON_EVASIONS>(const Position&, MoveStack*);
333 /// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
334 /// underpromotions that give check. Returns a pointer to the end of the move list.
336 MoveStack* generate<QUIET_CHECKS>(const Position& pos, MoveStack* mlist) {
338 assert(!pos.checkers());
340 Color us = pos.side_to_move();
342 Bitboard dc = ci.dcCandidates;
346 Square from = pop_lsb(&dc);
347 PieceType pt = type_of(pos.piece_on(from));
350 continue; // Will be generated togheter with direct checks
352 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
355 b &= ~PseudoAttacks[QUEEN][ci.ksq];
360 return generate_all_moves<QUIET_CHECKS>(pos, mlist, us, ~pos.pieces(), &ci);
364 /// generate<EVASIONS> generates all pseudo-legal check evasions when the side
365 /// to move is in check. Returns a pointer to the end of the move list.
367 MoveStack* generate<EVASIONS>(const Position& pos, MoveStack* mlist) {
369 assert(pos.checkers());
371 Square from, checksq;
373 Color us = pos.side_to_move();
374 Square ksq = pos.king_square(us);
375 Bitboard sliderAttacks = 0;
376 Bitboard b = pos.checkers();
378 assert(pos.checkers());
380 // Find squares attacked by slider checkers, we will remove them from the king
381 // evasions so to skip known illegal moves avoiding useless legality check later.
385 checksq = pop_lsb(&b);
387 assert(color_of(pos.piece_on(checksq)) == ~us);
389 switch (type_of(pos.piece_on(checksq)))
391 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
392 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
394 // If queen and king are far or not on a diagonal line we can safely
395 // remove all the squares attacked in the other direction becuase are
396 // not reachable by the king anyway.
397 if (between_bb(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
398 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
400 // Otherwise we need to use real rook attacks to check if king is safe
401 // to move in the other direction. For example: king in B2, queen in A1
402 // a knight in B1, and we can safely move to C1.
404 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
411 // Generate evasions for king, capture and non capture moves
412 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
417 return mlist; // Double check, only a king move can save the day
419 // Generate blocking evasions or captures of the checking piece
420 Bitboard target = between_bb(checksq, ksq) | pos.checkers();
422 return generate_all_moves<EVASIONS>(pos, mlist, us, target);
426 /// generate<LEGAL> generates all the legal moves in the given position
429 MoveStack* generate<LEGAL>(const Position& pos, MoveStack* mlist) {
431 MoveStack *end, *cur = mlist;
432 Bitboard pinned = pos.pinned_pieces();
433 Square ksq = pos.king_square(pos.side_to_move());
435 end = pos.checkers() ? generate<EVASIONS>(pos, mlist)
436 : generate<NON_EVASIONS>(pos, mlist);
438 if ( (pinned || from_sq(cur->move) == ksq || type_of(cur->move) == ENPASSANT)
439 && !pos.pl_move_is_legal(cur->move, pinned))
440 cur->move = (--end)->move;