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 OnlyChecks>
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.in_check());
49 for (Square s = kto; s != kfrom; s += (Square)(Side == KING_SIDE ? -1 : 1))
50 if (pos.attackers_to(s) & enemies)
53 // Because we generate only legal castling moves we need to verify that
54 // when moving the castling rook we do not discover some hidden checker.
55 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
56 if ( pos.is_chess960()
57 && (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
60 (*mlist++).move = make<CASTLE>(kfrom, rfrom);
62 if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
69 template<Square Delta>
70 inline Bitboard move_pawns(Bitboard p) {
72 return Delta == DELTA_N ? p << 8
73 : Delta == DELTA_S ? p >> 8
74 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
75 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
76 : Delta == DELTA_NW ? (p & ~FileABB) << 7
77 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : 0;
81 template<GenType Type, Square Delta>
82 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
84 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
88 Square to = pop_lsb(&b);
90 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
91 (*mlist++).move = make<PROMOTION>(to - Delta, to, QUEEN);
93 if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
95 (*mlist++).move = make<PROMOTION>(to - Delta, to, ROOK);
96 (*mlist++).move = make<PROMOTION>(to - Delta, to, BISHOP);
97 (*mlist++).move = make<PROMOTION>(to - Delta, to, KNIGHT);
100 // Knight-promotion is the only one that can give a direct check not
101 // already included in the queen-promotion.
102 if (Type == QUIET_CHECKS && (StepAttacksBB[W_KNIGHT][to] & ksq))
103 (*mlist++).move = make<PROMOTION>(to - Delta, to, KNIGHT);
105 (void)ksq; // Silence a warning under MSVC
112 template<Color Us, GenType Type>
113 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
115 // Compute our parametrized parameters at compile time, named according to
116 // the point of view of white side.
117 const Color Them = (Us == WHITE ? BLACK : WHITE);
118 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
119 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
120 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
121 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
122 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
123 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
125 Bitboard b1, b2, dc1, dc2, emptySquares;
127 Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
128 Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
130 Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
131 Type == CAPTURES ? target : pos.pieces(Them));
133 // Single and double pawn pushes, no promotions
134 if (Type != CAPTURES)
136 emptySquares = (Type == QUIETS ? target : ~pos.pieces());
138 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
139 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
141 if (Type == EVASIONS) // Consider only blocking squares
147 if (Type == QUIET_CHECKS)
149 b1 &= pos.attacks_from<PAWN>(ksq, Them);
150 b2 &= pos.attacks_from<PAWN>(ksq, Them);
152 // Add pawn pushes which give discovered check. This is possible only
153 // if the pawn is not on the same file as the enemy king, because we
154 // don't generate captures. Note that a possible discovery check
155 // promotion has been already generated among captures.
156 if (pawnsNotOn7 & target) // Target is dc bitboard
158 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
159 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
166 SERIALIZE_PAWNS(b1, UP);
167 SERIALIZE_PAWNS(b2, UP + UP);
170 // Promotions and underpromotions
171 if (pawnsOn7 && (Type != EVASIONS || (target & TRank8BB)))
173 if (Type == CAPTURES)
174 emptySquares = ~pos.pieces();
176 if (Type == EVASIONS)
177 emptySquares &= target;
179 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
180 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
181 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
184 // Standard and en-passant captures
185 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
187 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
188 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
190 SERIALIZE_PAWNS(b1, RIGHT);
191 SERIALIZE_PAWNS(b2, LEFT);
193 if (pos.ep_square() != SQ_NONE)
195 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
197 // An en passant capture can be an evasion only if the checking piece
198 // is the double pushed pawn and so is in the target. Otherwise this
199 // is a discovery check and we are forced to do otherwise.
200 if (Type == EVASIONS && !(target & (pos.ep_square() - UP)))
203 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
208 (*mlist++).move = make<ENPASSANT>(pop_lsb(&b1), pos.ep_square());
216 template<PieceType Pt, bool OnlyChecks> FORCE_INLINE
217 MoveStack* generate_moves(const Position& pos, MoveStack* mlist, Color us,
218 Bitboard target, const CheckInfo* ci = NULL) {
220 assert(Pt != KING && Pt != PAWN);
222 const Square* pl = pos.piece_list(us, Pt);
224 for (Square from = *pl; from != SQ_NONE; from = *++pl)
228 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
229 && !(PseudoAttacks[Pt][from] & target & ci->checkSq[Pt]))
232 if (ci->dcCandidates && (ci->dcCandidates & from))
236 Bitboard b = pos.attacks_from<Pt>(from) & target;
239 b &= ci->checkSq[Pt];
247 template<> FORCE_INLINE
248 MoveStack* generate_moves<KING, false>(const Position& pos, MoveStack* mlist, Color us,
249 Bitboard target, const CheckInfo*) {
250 Square from = pos.king_square(us);
251 Bitboard b = pos.attacks_from<KING>(from) & target;
259 /// generate<CAPTURES> generates all pseudo-legal captures and queen
260 /// promotions. Returns a pointer to the end of the move list.
262 /// generate<QUIETS> generates all pseudo-legal non-captures and
263 /// underpromotions. Returns a pointer to the end of the move list.
265 /// generate<NON_EVASIONS> generates all pseudo-legal captures and
266 /// non-captures. Returns a pointer to the end of the move list.
268 template<GenType Type>
269 MoveStack* generate(const Position& pos, MoveStack* mlist) {
271 assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
272 assert(!pos.in_check());
274 Color us = pos.side_to_move();
277 if (Type == CAPTURES)
278 target = pos.pieces(~us);
280 else if (Type == QUIETS)
281 target = ~pos.pieces();
283 else if (Type == NON_EVASIONS)
284 target = ~pos.pieces(us);
286 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
287 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
289 mlist = generate_moves<KNIGHT, false>(pos, mlist, us, target);
290 mlist = generate_moves<BISHOP, false>(pos, mlist, us, target);
291 mlist = generate_moves<ROOK, false>(pos, mlist, us, target);
292 mlist = generate_moves<QUEEN, false>(pos, mlist, us, target);
293 mlist = generate_moves<KING, false>(pos, mlist, us, target);
295 if (Type != CAPTURES && pos.can_castle(us))
297 mlist = generate_castle<KING_SIDE, false>(pos, mlist, us);
298 mlist = generate_castle<QUEEN_SIDE, false>(pos, mlist, us);
304 // Explicit template instantiations
305 template MoveStack* generate<CAPTURES>(const Position& pos, MoveStack* mlist);
306 template MoveStack* generate<QUIETS>(const Position& pos, MoveStack* mlist);
307 template MoveStack* generate<NON_EVASIONS>(const Position& pos, MoveStack* mlist);
310 /// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
311 /// underpromotions that give check. Returns a pointer to the end of the move list.
313 MoveStack* generate<QUIET_CHECKS>(const Position& pos, MoveStack* mlist) {
315 assert(!pos.in_check());
317 Color us = pos.side_to_move();
319 Bitboard empty = ~pos.pieces();
320 Bitboard dc = ci.dcCandidates;
324 Square from = pop_lsb(&dc);
325 PieceType pt = type_of(pos.piece_on(from));
328 continue; // Will be generated togheter with direct checks
330 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
333 b &= ~PseudoAttacks[QUEEN][ci.ksq];
338 mlist = (us == WHITE ? generate_pawn_moves<WHITE, QUIET_CHECKS>(pos, mlist, ci.dcCandidates, ci.ksq)
339 : generate_pawn_moves<BLACK, QUIET_CHECKS>(pos, mlist, ci.dcCandidates, ci.ksq));
341 mlist = generate_moves<KNIGHT, true>(pos, mlist, us, empty, &ci);
342 mlist = generate_moves<BISHOP, true>(pos, mlist, us, empty, &ci);
343 mlist = generate_moves<ROOK, true>(pos, mlist, us, empty, &ci);
344 mlist = generate_moves<QUEEN, true>(pos, mlist, us, empty, &ci);
346 if (pos.can_castle(us))
348 mlist = generate_castle<KING_SIDE, true>(pos, mlist, us);
349 mlist = generate_castle<QUEEN_SIDE, true>(pos, mlist, us);
356 /// generate<EVASIONS> generates all pseudo-legal check evasions when the side
357 /// to move is in check. Returns a pointer to the end of the move list.
359 MoveStack* generate<EVASIONS>(const Position& pos, MoveStack* mlist) {
361 assert(pos.in_check());
364 Square from, checksq;
366 Color us = pos.side_to_move();
367 Square ksq = pos.king_square(us);
368 Bitboard sliderAttacks = 0;
369 Bitboard checkers = pos.checkers();
373 // Find squares attacked by slider checkers, we will remove them from the king
374 // evasions so to skip known illegal moves avoiding useless legality check later.
379 checksq = pop_lsb(&b);
381 assert(color_of(pos.piece_on(checksq)) == ~us);
383 switch (type_of(pos.piece_on(checksq)))
385 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
386 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
388 // If queen and king are far or not on a diagonal line we can safely
389 // remove all the squares attacked in the other direction becuase are
390 // not reachable by the king anyway.
391 if (between_bb(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
392 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
394 // Otherwise we need to use real rook attacks to check if king is safe
395 // to move in the other direction. For example: king in B2, queen in A1
396 // a knight in B1, and we can safely move to C1.
398 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
405 // Generate evasions for king, capture and non capture moves
406 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
410 // Generate evasions for other pieces only if not under a double check
414 // Blocking evasions or captures of the checking piece
415 target = between_bb(checksq, ksq) | checkers;
417 mlist = (us == WHITE ? generate_pawn_moves<WHITE, EVASIONS>(pos, mlist, target)
418 : generate_pawn_moves<BLACK, EVASIONS>(pos, mlist, target));
420 mlist = generate_moves<KNIGHT, false>(pos, mlist, us, target);
421 mlist = generate_moves<BISHOP, false>(pos, mlist, us, target);
422 mlist = generate_moves<ROOK, false>(pos, mlist, us, target);
423 return generate_moves<QUEEN, false>(pos, mlist, us, target);
427 /// generate<LEGAL> generates all the legal moves in the given position
430 MoveStack* generate<LEGAL>(const Position& pos, MoveStack* mlist) {
432 MoveStack *end, *cur = mlist;
433 Bitboard pinned = pos.pinned_pieces();
435 end = pos.in_check() ? generate<EVASIONS>(pos, mlist)
436 : generate<NON_EVASIONS>(pos, mlist);
438 if (!pos.pl_move_is_legal(cur->move, pinned))
439 cur->move = (--end)->move;