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_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(~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);
84 if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
91 template<Square Delta>
92 inline Bitboard move_pawns(Bitboard p) {
94 return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
95 Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
96 Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
100 template<Square Delta>
101 inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
103 const Bitboard TFileABB = ( Delta == DELTA_NE
104 || Delta == DELTA_SE ? FileABB : FileHBB);
106 Bitboard b = move_pawns<Delta>(pawns) & target & ~TFileABB;
107 SERIALIZE_PAWNS(b, -Delta);
112 template<MoveType Type, Square Delta>
113 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
115 const Bitboard TFileABB = ( Delta == DELTA_NE
116 || Delta == DELTA_SE ? FileABB : FileHBB);
118 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
120 if (Delta != DELTA_N && Delta != DELTA_S)
125 Square to = pop_1st_bit(&b);
127 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
128 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
130 if (Type == MV_NON_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
132 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
133 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
134 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
137 // Knight-promotion is the only one that can give a check (direct or
138 // discovered) not already included in the queen-promotion.
139 if (Type == MV_NON_CAPTURE_CHECK && bit_is_set(StepAttacksBB[W_KNIGHT][to], ksq))
140 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
142 (void)ksq; // Silence a warning under MSVC
149 template<Color Us, MoveType Type>
150 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
152 // Calculate our parametrized parameters at compile time, named according to
153 // the point of view of white side.
154 const Color Them = (Us == WHITE ? BLACK : WHITE);
155 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
156 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
157 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
158 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
159 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
161 Bitboard b1, b2, dc1, dc2, emptySquares;
163 Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
164 Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
166 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
167 Type == MV_CAPTURE ? target : pos.pieces(Them));
169 // Single and double pawn pushes, no promotions
170 if (Type != MV_CAPTURE)
172 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
174 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
175 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
177 if (Type == MV_EVASION) // Consider only blocking squares
183 if (Type == MV_NON_CAPTURE_CHECK)
185 // Consider only direct checks
186 b1 &= pos.attacks_from<PAWN>(ksq, Them);
187 b2 &= pos.attacks_from<PAWN>(ksq, Them);
189 // Add pawn pushes which give discovered check. This is possible only
190 // if the pawn is not on the same file as the enemy king, because we
191 // don't generate captures. Note that a possible discovery check
192 // promotion has been already generated among captures.
193 if (pawnsNotOn7 & target) // Target is dc bitboard
195 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
196 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
203 SERIALIZE_PAWNS(b1, -UP);
204 SERIALIZE_PAWNS(b2, -UP -UP);
207 // Promotions and underpromotions
210 if (Type == MV_CAPTURE)
211 emptySquares = pos.empty_squares();
213 if (Type == MV_EVASION)
214 emptySquares &= target;
216 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
217 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
218 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
221 // Standard and en-passant captures
222 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
224 mlist = generate_pawn_captures<RIGHT>(mlist, pawnsNotOn7, enemies);
225 mlist = generate_pawn_captures<LEFT >(mlist, pawnsNotOn7, enemies);
227 if (pos.ep_square() != SQ_NONE)
229 assert(rank_of(pos.ep_square()) == (Us == WHITE ? RANK_6 : RANK_3));
231 // An en passant capture can be an evasion only if the checking piece
232 // is the double pushed pawn and so is in the target. Otherwise this
233 // is a discovery check and we are forced to do otherwise.
234 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
237 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
242 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
250 template<PieceType Pt>
251 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist,
252 Color us, const CheckInfo& ci) {
253 assert(Pt != KING && Pt != PAWN);
256 const Square* pl = pos.piece_list(us, Pt);
258 if ((from = *pl++) == SQ_NONE)
261 Bitboard checkSqs = ci.checkSq[Pt] & pos.empty_squares();
265 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
266 && !(PseudoAttacks[Pt][from] & checkSqs))
269 if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
272 Bitboard b = pos.attacks_from<Pt>(from) & checkSqs;
275 } while ((from = *pl++) != SQ_NONE);
281 template<PieceType Pt>
282 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
286 const Square* pl = pos.piece_list(us, Pt);
292 b = pos.attacks_from<Pt>(from) & target;
294 } while (*++pl != SQ_NONE);
302 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
304 Square from = pos.king_square(us);
305 Bitboard b = pos.attacks_from<KING>(from) & target;
313 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
314 /// promotions. Returns a pointer to the end of the move list.
316 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
317 /// underpromotions. Returns a pointer to the end of the move list.
319 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
320 /// non-captures. Returns a pointer to the end of the move list.
322 template<MoveType Type>
323 MoveStack* generate(const Position& pos, MoveStack* mlist) {
325 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
326 assert(!pos.in_check());
328 Color us = pos.side_to_move();
331 if (Type == MV_CAPTURE)
332 target = pos.pieces(~us);
334 else if (Type == MV_NON_CAPTURE)
335 target = pos.empty_squares();
337 else if (Type == MV_NON_EVASION)
338 target = pos.pieces(~us) | pos.empty_squares();
340 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
341 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
343 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
344 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
345 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
346 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
347 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
349 if (Type != MV_CAPTURE && pos.can_castle(us))
351 mlist = generate_castle_moves<KING_SIDE, false>(pos, mlist, us);
352 mlist = generate_castle_moves<QUEEN_SIDE, false>(pos, mlist, us);
358 // Explicit template instantiations
359 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
360 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
361 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
364 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
365 /// underpromotions that give check. Returns a pointer to the end of the move list.
367 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
369 assert(!pos.in_check());
371 Color us = pos.side_to_move();
373 Bitboard dc = ci.dcCandidates;
377 Square from = pop_1st_bit(&dc);
378 PieceType pt = type_of(pos.piece_on(from));
381 continue; // Will be generated togheter with direct checks
383 Bitboard b = pos.attacks_from(Piece(pt), from) & pos.empty_squares();
386 b &= ~PseudoAttacks[QUEEN][ci.ksq];
391 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_NON_CAPTURE_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq)
392 : generate_pawn_moves<BLACK, MV_NON_CAPTURE_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq));
394 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, ci);
395 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, ci);
396 mlist = generate_direct_checks<ROOK>(pos, mlist, us, ci);
397 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, ci);
399 if (pos.can_castle(us))
401 mlist = generate_castle_moves<KING_SIDE, true>(pos, mlist, us);
402 mlist = generate_castle_moves<QUEEN_SIDE, true>(pos, mlist, us);
409 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
410 /// to move is in check. Returns a pointer to the end of the move list.
412 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
414 assert(pos.in_check());
417 Square from, checksq;
419 Color us = pos.side_to_move();
420 Square ksq = pos.king_square(us);
421 Bitboard sliderAttacks = 0;
422 Bitboard checkers = pos.checkers();
426 // Find squares attacked by slider checkers, we will remove them from the king
427 // evasions so to skip known illegal moves avoiding useless legality check later.
432 checksq = pop_1st_bit(&b);
434 assert(color_of(pos.piece_on(checksq)) == ~us);
436 switch (type_of(pos.piece_on(checksq)))
438 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
439 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
441 // If queen and king are far or not on a diagonal line we can safely
442 // remove all the squares attacked in the other direction becuase are
443 // not reachable by the king anyway.
444 if (squares_between(ksq, checksq) || !bit_is_set(PseudoAttacks[BISHOP][checksq], ksq))
445 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
447 // Otherwise we need to use real rook attacks to check if king is safe
448 // to move in the other direction. For example: king in B2, queen in A1
449 // a knight in B1, and we can safely move to C1.
451 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
458 // Generate evasions for king, capture and non capture moves
459 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
463 // Generate evasions for other pieces only if not under a double check
467 // Blocking evasions or captures of the checking piece
468 target = squares_between(checksq, ksq) | checkers;
470 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_EVASION>(pos, mlist, target)
471 : generate_pawn_moves<BLACK, MV_EVASION>(pos, mlist, target));
473 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
474 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
475 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
476 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
480 /// generate<MV_LEGAL> generates all the legal moves in the given position
483 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
485 MoveStack *last, *cur = mlist;
486 Bitboard pinned = pos.pinned_pieces();
488 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
489 : generate<MV_NON_EVASION>(pos, mlist);
491 if (!pos.pl_move_is_legal(cur->move, pinned))
492 cur->move = (--last)->move;