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>
38 MoveStack* generate_castle_moves(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(flip(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())
76 Bitboard occ = pos.occupied_squares();
77 clear_bit(&occ, rfrom);
78 if (pos.attackers_to(kto, occ) & enemies)
82 (*mlist++).move = make_castle(kfrom, rfrom);
88 template<Square Delta>
89 inline Bitboard move_pawns(Bitboard p) {
91 return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
92 Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
93 Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
97 template<Square Delta>
98 inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
100 const Bitboard TFileABB = ( Delta == DELTA_NE
101 || Delta == DELTA_SE ? FileABB : FileHBB);
103 Bitboard b = move_pawns<Delta>(pawns) & target & ~TFileABB;
104 SERIALIZE_PAWNS(b, -Delta);
109 template<MoveType Type, Square Delta>
110 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
112 const Bitboard TFileABB = ( Delta == DELTA_NE
113 || Delta == DELTA_SE ? FileABB : FileHBB);
115 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
117 if (Delta != DELTA_N && Delta != DELTA_S)
122 Square to = pop_1st_bit(&b);
124 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
125 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
127 if (Type == MV_NON_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
129 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
130 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
131 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
134 // Knight-promotion is the only one that can give a check (direct or
135 // discovered) not already included in the queen-promotion.
136 if (Type == MV_NON_CAPTURE_CHECK && bit_is_set(StepAttacksBB[W_KNIGHT][to], ksq))
137 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
139 (void)ksq; // Silence a warning under MSVC
145 template<Color Us, MoveType Type>
146 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
148 // Calculate our parametrized parameters at compile time, named according to
149 // the point of view of white side.
150 const Color Them = (Us == WHITE ? BLACK : WHITE);
151 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
152 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
153 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
154 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
155 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
157 Bitboard b1, b2, dc1, dc2, emptySquares;
159 Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
160 Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
162 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
163 Type == MV_CAPTURE ? target : pos.pieces(Them));
165 // Single and double pawn pushes, no promotions
166 if (Type != MV_CAPTURE)
168 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
170 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
171 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
173 if (Type == MV_EVASION) // Consider only blocking squares
179 if (Type == MV_NON_CAPTURE_CHECK)
181 // Consider only direct checks
182 b1 &= pos.attacks_from<PAWN>(ksq, Them);
183 b2 &= pos.attacks_from<PAWN>(ksq, Them);
185 // Add pawn pushes which give discovered check. This is possible only
186 // if the pawn is not on the same file as the enemy king, because we
187 // don't generate captures. Note that a possible discovery check
188 // promotion has been already generated among captures.
189 if (pawnsNotOn7 & target) // Target is dc bitboard
191 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
192 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
199 SERIALIZE_PAWNS(b1, -UP);
200 SERIALIZE_PAWNS(b2, -UP -UP);
203 // Promotions and underpromotions
206 if (Type == MV_CAPTURE)
207 emptySquares = pos.empty_squares();
209 if (Type == MV_EVASION)
210 emptySquares &= target;
212 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
213 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
214 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
217 // Standard and en-passant captures
218 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
220 mlist = generate_pawn_captures<RIGHT>(mlist, pawnsNotOn7, enemies);
221 mlist = generate_pawn_captures<LEFT >(mlist, pawnsNotOn7, enemies);
223 if (pos.ep_square() != SQ_NONE)
225 assert(rank_of(pos.ep_square()) == (Us == WHITE ? RANK_6 : RANK_3));
227 // An en passant capture can be an evasion only if the checking piece
228 // is the double pushed pawn and so is in the target. Otherwise this
229 // is a discovery check and we are forced to do otherwise.
230 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
233 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
238 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
246 template<PieceType Pt>
247 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
248 Bitboard dc, Square ksq) {
249 assert(Pt != KING && Pt != PAWN);
251 Bitboard checkSqs, b;
253 const Square* pl = pos.piece_list(us, Pt);
255 if ((from = *pl++) == SQ_NONE)
258 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
262 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
263 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
264 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
267 if (dc && bit_is_set(dc, from))
270 b = pos.attacks_from<Pt>(from) & checkSqs;
273 } while ((from = *pl++) != SQ_NONE);
280 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
282 return us == WHITE ? generate_pawn_moves<WHITE, MV_NON_CAPTURE_CHECK>(p, m, dc, ksq)
283 : generate_pawn_moves<BLACK, MV_NON_CAPTURE_CHECK>(p, m, dc, ksq);
287 template<PieceType Pt, MoveType Type>
288 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
291 return us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
292 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE);
296 template<PieceType Pt>
297 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
301 const Square* pl = pos.piece_list(us, Pt);
307 b = pos.attacks_from<Pt>(from) & target;
309 } while (*++pl != SQ_NONE);
316 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
318 Square from = pos.king_square(us);
319 Bitboard b = pos.attacks_from<KING>(from) & target;
327 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
328 /// promotions. Returns a pointer to the end of the move list.
330 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
331 /// underpromotions. Returns a pointer to the end of the move list.
333 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
334 /// non-captures. Returns a pointer to the end of the move list.
336 template<MoveType Type>
337 MoveStack* generate(const Position& pos, MoveStack* mlist) {
339 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
340 assert(!pos.in_check());
342 Color us = pos.side_to_move();
345 if (Type == MV_CAPTURE)
346 target = pos.pieces(flip(us));
348 else if (Type == MV_NON_CAPTURE)
349 target = pos.empty_squares();
351 else if (Type == MV_NON_EVASION)
352 target = pos.pieces(flip(us)) | pos.empty_squares();
354 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
355 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
356 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
357 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
358 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
359 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
361 if (Type != MV_CAPTURE && pos.can_castle(us))
363 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
364 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
370 // Explicit template instantiations
371 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
372 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
373 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
376 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
377 /// underpromotions that give check. Returns a pointer to the end of the move list.
379 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
381 assert(!pos.in_check());
386 Color us = pos.side_to_move();
387 Square ksq = pos.king_square(flip(us));
389 assert(pos.piece_on(ksq) == make_piece(flip(us), KING));
391 b = dc = pos.discovered_check_candidates();
395 from = pop_1st_bit(&b);
396 pt = type_of(pos.piece_on(from));
399 continue; // Will be generated togheter with direct checks
401 b = pos.attacks_from(Piece(pt), from) & pos.empty_squares();
404 b &= ~QueenPseudoAttacks[ksq];
409 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
410 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
411 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
412 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
413 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
417 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
418 /// to move is in check. Returns a pointer to the end of the move list.
420 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
422 assert(pos.in_check());
425 Square from, checksq;
427 Color us = pos.side_to_move();
428 Square ksq = pos.king_square(us);
429 Bitboard checkers = pos.checkers();
430 Bitboard sliderAttacks = 0;
432 assert(pos.piece_on(ksq) == make_piece(us, KING));
435 // Find squares attacked by slider checkers, we will remove them from the king
436 // evasions set so to skip known illegal moves and avoid to do legality check later.
441 checksq = pop_1st_bit(&b);
443 assert(color_of(pos.piece_on(checksq)) == flip(us));
445 switch (type_of(pos.piece_on(checksq)))
447 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
448 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
450 // If queen and king are far we can safely remove all the squares attacked
451 // in the other direction becuase are not reachable by the king anyway.
452 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
453 sliderAttacks |= QueenPseudoAttacks[checksq];
455 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
456 // use real rook attacks to check if king is safe to move in the other direction.
457 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
459 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
466 // Generate evasions for king, capture and non capture moves
467 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
471 // Generate evasions for other pieces only if not under a double check
475 // Target for blocking evasions or captures of the checking piece
476 target = squares_between(checksq, ksq) | checkers;
478 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
479 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
480 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
481 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
482 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
486 /// generate<MV_LEGAL> generates all the legal moves in the given position
489 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
491 MoveStack *last, *cur = mlist;
492 Bitboard pinned = pos.pinned_pieces();
494 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
495 : generate<MV_NON_EVASION>(pos, mlist);
497 if (!pos.pl_move_is_legal(cur->move, pinned))
498 cur->move = (--last)->move;