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/>.
26 /// Simple macro to wrap a very common while loop, no facny, no flexibility,
27 /// hardcoded names 'mlist' and 'from'.
28 #define SERIALIZE(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
30 /// Version used for pawns, where the 'from' square is given as a delta from the 'to' square
31 #define SERIALIZE_PAWNS(b, d) while (b) { Square to = pop_1st_bit(&b); \
32 (*mlist++).move = make_move(to - (d), to); }
35 enum CastlingSide { KING_SIDE, QUEEN_SIDE };
37 template<CastlingSide Side, bool OnlyChecks>
38 MoveStack* generate_castle(const Position& pos, MoveStack* mlist, Color us) {
40 const CastleRight CR[] = { Side ? WHITE_OOO : WHITE_OO,
41 Side ? BLACK_OOO : BLACK_OO };
43 if (pos.castle_impeded(CR[us]) || !pos.can_castle(CR[us]))
46 // After castling, the rook and king final positions are the same in Chess960
47 // as they would be in standard chess.
48 Square kfrom = pos.king_square(us);
49 Square rfrom = pos.castle_rook_square(CR[us]);
50 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
51 Bitboard enemies = pos.pieces(~us);
53 assert(!pos.in_check());
54 assert(pos.piece_on(kfrom) == make_piece(us, KING));
55 assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
57 for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
58 if ( s != kfrom // We are not in check
59 && (pos.attackers_to(s) & enemies))
62 // Because we generate only legal castling moves we need to verify that
63 // when moving the castling rook we do not discover some hidden checker.
64 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
65 if ( pos.is_chess960()
66 && (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
69 (*mlist++).move = make_castle(kfrom, rfrom);
71 if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
78 template<Square Delta>
79 inline Bitboard move_pawns(Bitboard p) {
81 return Delta == DELTA_N ? p << 8
82 : Delta == DELTA_S ? p >> 8
83 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
84 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
85 : Delta == DELTA_NW ? (p & ~FileABB) << 7
86 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : 0;
90 template<MoveType Type, Square Delta>
91 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
93 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
97 Square to = pop_1st_bit(&b);
99 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
100 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
102 if (Type == MV_QUIET || Type == MV_EVASION || Type == MV_NON_EVASION)
104 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
105 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
106 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
109 // Knight-promotion is the only one that can give a direct check not
110 // already included in the queen-promotion.
111 if (Type == MV_QUIET_CHECK && (StepAttacksBB[W_KNIGHT][to] & ksq))
112 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
114 (void)ksq; // Silence a warning under MSVC
121 template<Color Us, MoveType Type>
122 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
124 // Compute our parametrized parameters at compile time, named according to
125 // the point of view of white side.
126 const Color Them = (Us == WHITE ? BLACK : WHITE);
127 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
128 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
129 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
130 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
131 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
132 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
134 Bitboard b1, b2, dc1, dc2, emptySquares;
136 Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
137 Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
139 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
140 Type == MV_CAPTURE ? target : pos.pieces(Them));
142 // Single and double pawn pushes, no promotions
143 if (Type != MV_CAPTURE)
145 emptySquares = (Type == MV_QUIET ? target : ~pos.pieces());
147 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
148 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
150 if (Type == MV_EVASION) // Consider only blocking squares
156 if (Type == MV_QUIET_CHECK)
158 b1 &= pos.attacks_from<PAWN>(ksq, Them);
159 b2 &= pos.attacks_from<PAWN>(ksq, Them);
161 // Add pawn pushes which give discovered check. This is possible only
162 // if the pawn is not on the same file as the enemy king, because we
163 // don't generate captures. Note that a possible discovery check
164 // promotion has been already generated among captures.
165 if (pawnsNotOn7 & target) // Target is dc bitboard
167 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
168 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
175 SERIALIZE_PAWNS(b1, UP);
176 SERIALIZE_PAWNS(b2, UP + UP);
179 // Promotions and underpromotions
180 if (pawnsOn7 && (Type != MV_EVASION || (target & TRank8BB)))
182 if (Type == MV_CAPTURE)
183 emptySquares = ~pos.pieces();
185 if (Type == MV_EVASION)
186 emptySquares &= target;
188 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
189 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
190 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
193 // Standard and en-passant captures
194 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
196 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
197 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
199 SERIALIZE_PAWNS(b1, RIGHT);
200 SERIALIZE_PAWNS(b2, LEFT);
202 if (pos.ep_square() != SQ_NONE)
204 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
206 // An en passant capture can be an evasion only if the checking piece
207 // is the double pushed pawn and so is in the target. Otherwise this
208 // is a discovery check and we are forced to do otherwise.
209 if (Type == MV_EVASION && !(target & (pos.ep_square() - UP)))
212 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
217 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
225 template<PieceType Pt>
226 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist,
227 Color us, const CheckInfo& ci) {
228 assert(Pt != KING && Pt != PAWN);
232 const Square* pl = pos.piece_list(us, Pt);
236 target = ci.checkSq[Pt] & ~pos.pieces(); // Non capture checks only
241 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
242 && !(PseudoAttacks[Pt][from] & target))
245 if (ci.dcCandidates && (ci.dcCandidates & from))
248 b = pos.attacks_from<Pt>(from) & target;
250 } while (*++pl != SQ_NONE);
257 template<PieceType Pt>
258 FORCE_INLINE MoveStack* generate_moves(const Position& pos, MoveStack* mlist,
259 Color us, Bitboard target) {
260 assert(Pt != KING && Pt != PAWN);
264 const Square* pl = pos.piece_list(us, Pt);
269 b = pos.attacks_from<Pt>(from) & target;
271 } while (*++pl != SQ_NONE);
278 FORCE_INLINE MoveStack* generate_moves<KING>(const Position& pos, MoveStack* mlist,
279 Color us, Bitboard target) {
280 Square from = pos.king_square(us);
281 Bitboard b = pos.attacks_from<KING>(from) & target;
289 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
290 /// promotions. Returns a pointer to the end of the move list.
292 /// generate<MV_QUIET> generates all pseudo-legal non-captures and
293 /// underpromotions. Returns a pointer to the end of the move list.
295 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
296 /// non-captures. Returns a pointer to the end of the move list.
298 template<MoveType Type>
299 MoveStack* generate(const Position& pos, MoveStack* mlist) {
301 assert(Type == MV_CAPTURE || Type == MV_QUIET || Type == MV_NON_EVASION);
302 assert(!pos.in_check());
304 Color us = pos.side_to_move();
307 if (Type == MV_CAPTURE)
308 target = pos.pieces(~us);
310 else if (Type == MV_QUIET)
311 target = ~pos.pieces();
313 else if (Type == MV_NON_EVASION)
314 target = ~pos.pieces(us);
316 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
317 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
319 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
320 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
321 mlist = generate_moves<ROOK>(pos, mlist, us, target);
322 mlist = generate_moves<QUEEN>(pos, mlist, us, target);
323 mlist = generate_moves<KING>(pos, mlist, us, target);
325 if (Type != MV_CAPTURE && pos.can_castle(us))
327 mlist = generate_castle<KING_SIDE, false>(pos, mlist, us);
328 mlist = generate_castle<QUEEN_SIDE, false>(pos, mlist, us);
334 // Explicit template instantiations
335 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
336 template MoveStack* generate<MV_QUIET>(const Position& pos, MoveStack* mlist);
337 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
340 /// generate<MV_QUIET_CHECK> generates all pseudo-legal non-captures and knight
341 /// underpromotions that give check. Returns a pointer to the end of the move list.
343 MoveStack* generate<MV_QUIET_CHECK>(const Position& pos, MoveStack* mlist) {
345 assert(!pos.in_check());
347 Color us = pos.side_to_move();
349 Bitboard dc = ci.dcCandidates;
353 Square from = pop_1st_bit(&dc);
354 PieceType pt = type_of(pos.piece_on(from));
357 continue; // Will be generated togheter with direct checks
359 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
362 b &= ~PseudoAttacks[QUEEN][ci.ksq];
367 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_QUIET_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq)
368 : generate_pawn_moves<BLACK, MV_QUIET_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq));
370 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, ci);
371 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, ci);
372 mlist = generate_direct_checks<ROOK>(pos, mlist, us, ci);
373 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, ci);
375 if (pos.can_castle(us))
377 mlist = generate_castle<KING_SIDE, true>(pos, mlist, us);
378 mlist = generate_castle<QUEEN_SIDE, true>(pos, mlist, us);
385 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
386 /// to move is in check. Returns a pointer to the end of the move list.
388 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
390 assert(pos.in_check());
393 Square from, checksq;
395 Color us = pos.side_to_move();
396 Square ksq = pos.king_square(us);
397 Bitboard sliderAttacks = 0;
398 Bitboard checkers = pos.checkers();
402 // Find squares attacked by slider checkers, we will remove them from the king
403 // evasions so to skip known illegal moves avoiding useless legality check later.
408 checksq = pop_1st_bit(&b);
410 assert(color_of(pos.piece_on(checksq)) == ~us);
412 switch (type_of(pos.piece_on(checksq)))
414 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
415 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
417 // If queen and king are far or not on a diagonal line we can safely
418 // remove all the squares attacked in the other direction becuase are
419 // not reachable by the king anyway.
420 if (squares_between(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
421 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
423 // Otherwise we need to use real rook attacks to check if king is safe
424 // to move in the other direction. For example: king in B2, queen in A1
425 // a knight in B1, and we can safely move to C1.
427 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
434 // Generate evasions for king, capture and non capture moves
435 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
439 // Generate evasions for other pieces only if not under a double check
443 // Blocking evasions or captures of the checking piece
444 target = squares_between(checksq, ksq) | checkers;
446 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_EVASION>(pos, mlist, target)
447 : generate_pawn_moves<BLACK, MV_EVASION>(pos, mlist, target));
449 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
450 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
451 mlist = generate_moves<ROOK>(pos, mlist, us, target);
452 return generate_moves<QUEEN>(pos, mlist, us, target);
456 /// generate<MV_LEGAL> generates all the legal moves in the given position
459 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
461 MoveStack *last, *cur = mlist;
462 Bitboard pinned = pos.pinned_pieces();
464 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
465 : generate<MV_NON_EVASION>(pos, mlist);
467 if (!pos.pl_move_is_legal(cur->move, pinned))
468 cur->move = (--last)->move;