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.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 Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
52 Bitboard enemies = pos.pieces(~us);
54 assert(!pos.in_check());
55 assert(pos.piece_on(kfrom) == make_piece(us, KING));
56 assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
58 // Unimpeded rule: All the squares between the king's initial and final squares
59 // (including the final square), and all the squares between the rook's initial
60 // and final squares (including the final square), must be vacant except for
61 // the king and castling rook.
62 for (Square s = std::min(rfrom, rto), e = std::max(rfrom, rto); s <= e; s++)
63 if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
66 for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
67 if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
68 ||(pos.attackers_to(s) & enemies))
71 // Because we generate only legal castling moves we need to verify that
72 // when moving the castling rook we do not discover some hidden checker.
73 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
74 if ( pos.is_chess960()
75 && (pos.attackers_to(kto, pos.occupied_squares() ^ rfrom) & enemies))
78 (*mlist++).move = make_castle(kfrom, rfrom);
80 if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
87 template<Square Delta>
88 inline Bitboard move_pawns(Bitboard p) {
90 return Delta == DELTA_N ? p << 8
91 : Delta == DELTA_S ? p >> 8
92 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
93 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
94 : Delta == DELTA_NW ? (p & ~FileABB) << 7
95 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : 0;
99 template<MoveType Type, Square Delta>
100 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
102 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
106 Square to = pop_1st_bit(&b);
108 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
109 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
111 if (Type == MV_QUIET || Type == MV_EVASION || Type == MV_NON_EVASION)
113 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
114 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
115 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
118 // Knight-promotion is the only one that can give a direct check not
119 // already included in the queen-promotion.
120 if (Type == MV_QUIET_CHECK && (StepAttacksBB[W_KNIGHT][to] & ksq))
121 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
123 (void)ksq; // Silence a warning under MSVC
130 template<Color Us, MoveType Type>
131 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
133 // Compute our parametrized parameters at compile time, named according to
134 // the point of view of white side.
135 const Color Them = (Us == WHITE ? BLACK : WHITE);
136 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
137 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
138 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
139 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
140 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
141 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
143 Bitboard b1, b2, dc1, dc2, emptySquares;
145 Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
146 Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
148 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
149 Type == MV_CAPTURE ? target : pos.pieces(Them));
151 // Single and double pawn pushes, no promotions
152 if (Type != MV_CAPTURE)
154 emptySquares = (Type == MV_QUIET ? target : ~pos.occupied_squares());
156 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
157 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
159 if (Type == MV_EVASION) // Consider only blocking squares
165 if (Type == MV_QUIET_CHECK)
167 b1 &= pos.attacks_from<PAWN>(ksq, Them);
168 b2 &= pos.attacks_from<PAWN>(ksq, Them);
170 // Add pawn pushes which give discovered check. This is possible only
171 // if the pawn is not on the same file as the enemy king, because we
172 // don't generate captures. Note that a possible discovery check
173 // promotion has been already generated among captures.
174 if (pawnsNotOn7 & target) // Target is dc bitboard
176 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
177 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
184 SERIALIZE_PAWNS(b1, UP);
185 SERIALIZE_PAWNS(b2, UP + UP);
188 // Promotions and underpromotions
189 if (pawnsOn7 && (Type != MV_EVASION || (target & TRank8BB)))
191 if (Type == MV_CAPTURE)
192 emptySquares = ~pos.occupied_squares();
194 if (Type == MV_EVASION)
195 emptySquares &= target;
197 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
198 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
199 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
202 // Standard and en-passant captures
203 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
205 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
206 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
208 SERIALIZE_PAWNS(b1, RIGHT);
209 SERIALIZE_PAWNS(b2, LEFT);
211 if (pos.ep_square() != SQ_NONE)
213 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
215 // An en passant capture can be an evasion only if the checking piece
216 // is the double pushed pawn and so is in the target. Otherwise this
217 // is a discovery check and we are forced to do otherwise.
218 if (Type == MV_EVASION && !(target & (pos.ep_square() - UP)))
221 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
226 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
234 template<PieceType Pt>
235 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist,
236 Color us, const CheckInfo& ci) {
237 assert(Pt != KING && Pt != PAWN);
241 const Square* pl = pos.piece_list(us, Pt);
245 target = ci.checkSq[Pt] & ~pos.occupied_squares(); // Non capture checks only
250 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
251 && !(PseudoAttacks[Pt][from] & target))
254 if (ci.dcCandidates && (ci.dcCandidates & from))
257 b = pos.attacks_from<Pt>(from) & target;
259 } while (*++pl != SQ_NONE);
266 template<PieceType Pt>
267 FORCE_INLINE MoveStack* generate_moves(const Position& pos, MoveStack* mlist,
268 Color us, Bitboard target) {
269 assert(Pt != KING && Pt != PAWN);
273 const Square* pl = pos.piece_list(us, Pt);
278 b = pos.attacks_from<Pt>(from) & target;
280 } while (*++pl != SQ_NONE);
287 FORCE_INLINE MoveStack* generate_moves<KING>(const Position& pos, MoveStack* mlist,
288 Color us, Bitboard target) {
289 Square from = pos.king_square(us);
290 Bitboard b = pos.attacks_from<KING>(from) & target;
298 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
299 /// promotions. Returns a pointer to the end of the move list.
301 /// generate<MV_QUIET> generates all pseudo-legal non-captures and
302 /// underpromotions. Returns a pointer to the end of the move list.
304 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
305 /// non-captures. Returns a pointer to the end of the move list.
307 template<MoveType Type>
308 MoveStack* generate(const Position& pos, MoveStack* mlist) {
310 assert(Type == MV_CAPTURE || Type == MV_QUIET || Type == MV_NON_EVASION);
311 assert(!pos.in_check());
313 Color us = pos.side_to_move();
316 if (Type == MV_CAPTURE)
317 target = pos.pieces(~us);
319 else if (Type == MV_QUIET)
320 target = ~pos.occupied_squares();
322 else if (Type == MV_NON_EVASION)
323 target = pos.pieces(~us) | ~pos.occupied_squares();
325 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
326 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
328 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
329 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
330 mlist = generate_moves<ROOK>(pos, mlist, us, target);
331 mlist = generate_moves<QUEEN>(pos, mlist, us, target);
332 mlist = generate_moves<KING>(pos, mlist, us, target);
334 if (Type != MV_CAPTURE && pos.can_castle(us))
336 mlist = generate_castle<KING_SIDE, false>(pos, mlist, us);
337 mlist = generate_castle<QUEEN_SIDE, false>(pos, mlist, us);
343 // Explicit template instantiations
344 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
345 template MoveStack* generate<MV_QUIET>(const Position& pos, MoveStack* mlist);
346 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
349 /// generate<MV_QUIET_CHECK> generates all pseudo-legal non-captures and knight
350 /// underpromotions that give check. Returns a pointer to the end of the move list.
352 MoveStack* generate<MV_QUIET_CHECK>(const Position& pos, MoveStack* mlist) {
354 assert(!pos.in_check());
356 Color us = pos.side_to_move();
358 Bitboard dc = ci.dcCandidates;
362 Square from = pop_1st_bit(&dc);
363 PieceType pt = type_of(pos.piece_on(from));
366 continue; // Will be generated togheter with direct checks
368 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.occupied_squares();
371 b &= ~PseudoAttacks[QUEEN][ci.ksq];
376 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_QUIET_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq)
377 : generate_pawn_moves<BLACK, MV_QUIET_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq));
379 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, ci);
380 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, ci);
381 mlist = generate_direct_checks<ROOK>(pos, mlist, us, ci);
382 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, ci);
384 if (pos.can_castle(us))
386 mlist = generate_castle<KING_SIDE, true>(pos, mlist, us);
387 mlist = generate_castle<QUEEN_SIDE, true>(pos, mlist, us);
394 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
395 /// to move is in check. Returns a pointer to the end of the move list.
397 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
399 assert(pos.in_check());
402 Square from, checksq;
404 Color us = pos.side_to_move();
405 Square ksq = pos.king_square(us);
406 Bitboard sliderAttacks = 0;
407 Bitboard checkers = pos.checkers();
411 // Find squares attacked by slider checkers, we will remove them from the king
412 // evasions so to skip known illegal moves avoiding useless legality check later.
417 checksq = pop_1st_bit(&b);
419 assert(color_of(pos.piece_on(checksq)) == ~us);
421 switch (type_of(pos.piece_on(checksq)))
423 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
424 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
426 // If queen and king are far or not on a diagonal line we can safely
427 // remove all the squares attacked in the other direction becuase are
428 // not reachable by the king anyway.
429 if (squares_between(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
430 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
432 // Otherwise we need to use real rook attacks to check if king is safe
433 // to move in the other direction. For example: king in B2, queen in A1
434 // a knight in B1, and we can safely move to C1.
436 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
443 // Generate evasions for king, capture and non capture moves
444 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
448 // Generate evasions for other pieces only if not under a double check
452 // Blocking evasions or captures of the checking piece
453 target = squares_between(checksq, ksq) | checkers;
455 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_EVASION>(pos, mlist, target)
456 : generate_pawn_moves<BLACK, MV_EVASION>(pos, mlist, target));
458 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
459 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
460 mlist = generate_moves<ROOK>(pos, mlist, us, target);
461 return generate_moves<QUEEN>(pos, mlist, us, target);
465 /// generate<MV_LEGAL> generates all the legal moves in the given position
468 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
470 MoveStack *last, *cur = mlist;
471 Bitboard pinned = pos.pinned_pieces();
473 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
474 : generate<MV_NON_EVASION>(pos, mlist);
476 if (!pos.pl_move_is_legal(cur->move, pinned))
477 cur->move = (--last)->move;