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
95 : Delta == DELTA_S ? p >> 8
96 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
97 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
98 : Delta == DELTA_NW ? (p & ~FileABB) << 7
99 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : p;
103 template<MoveType Type, Square Delta>
104 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
106 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
110 Square to = pop_1st_bit(&b);
112 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
113 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
115 if (Type == MV_NON_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
117 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
118 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
119 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
122 // Knight-promotion is the only one that can give a check (direct or
123 // discovered) not already included in the queen-promotion.
124 if (Type == MV_NON_CAPTURE_CHECK && bit_is_set(StepAttacksBB[W_KNIGHT][to], ksq))
125 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
127 (void)ksq; // Silence a warning under MSVC
134 template<Color Us, MoveType Type>
135 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
137 // Calculate our parametrized parameters at compile time, named according to
138 // the point of view of white side.
139 const Color Them = (Us == WHITE ? BLACK : WHITE);
140 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
141 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
142 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
143 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
144 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
145 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
147 Bitboard b1, b2, dc1, dc2, emptySquares;
149 Bitboard pawnsOn7 = pos.pieces(PAWN, Us) & TRank7BB;
150 Bitboard pawnsNotOn7 = pos.pieces(PAWN, Us) & ~TRank7BB;
152 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
153 Type == MV_CAPTURE ? target : pos.pieces(Them));
155 // Single and double pawn pushes, no promotions
156 if (Type != MV_CAPTURE)
158 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
160 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
161 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
163 if (Type == MV_EVASION) // Consider only blocking squares
169 if (Type == MV_NON_CAPTURE_CHECK)
171 b1 &= pos.attacks_from<PAWN>(ksq, Them);
172 b2 &= pos.attacks_from<PAWN>(ksq, Them);
174 // Add pawn pushes which give discovered check. This is possible only
175 // if the pawn is not on the same file as the enemy king, because we
176 // don't generate captures. Note that a possible discovery check
177 // promotion has been already generated among captures.
178 if (pawnsNotOn7 & target) // Target is dc bitboard
180 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
181 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
188 SERIALIZE_PAWNS(b1, -UP);
189 SERIALIZE_PAWNS(b2, -UP -UP);
192 // Promotions and underpromotions
193 if (pawnsOn7 && (Type != MV_EVASION || (target & TRank8BB)))
195 if (Type == MV_CAPTURE)
196 emptySquares = pos.empty_squares();
198 if (Type == MV_EVASION)
199 emptySquares &= target;
201 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
202 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
203 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
206 // Standard and en-passant captures
207 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
209 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
210 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
212 SERIALIZE_PAWNS(b1, -RIGHT);
213 SERIALIZE_PAWNS(b2, -LEFT);
215 if (pos.ep_square() != SQ_NONE)
217 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
219 // An en passant capture can be an evasion only if the checking piece
220 // is the double pushed pawn and so is in the target. Otherwise this
221 // is a discovery check and we are forced to do otherwise.
222 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
225 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
230 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
238 template<PieceType Pt>
239 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist,
240 Color us, const CheckInfo& ci) {
241 assert(Pt != KING && Pt != PAWN);
244 const Square* pl = pos.piece_list(us, Pt);
246 if ((from = *pl++) == SQ_NONE)
249 Bitboard checkSqs = ci.checkSq[Pt] & pos.empty_squares();
253 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
254 && !(PseudoAttacks[Pt][from] & checkSqs))
257 if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
260 Bitboard b = pos.attacks_from<Pt>(from) & checkSqs;
263 } while ((from = *pl++) != SQ_NONE);
269 template<PieceType Pt>
270 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
274 const Square* pl = pos.piece_list(us, Pt);
280 b = pos.attacks_from<Pt>(from) & target;
282 } while (*++pl != SQ_NONE);
290 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
292 Square from = pos.king_square(us);
293 Bitboard b = pos.attacks_from<KING>(from) & target;
301 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
302 /// promotions. Returns a pointer to the end of the move list.
304 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
305 /// underpromotions. Returns a pointer to the end of the move list.
307 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
308 /// non-captures. Returns a pointer to the end of the move list.
310 template<MoveType Type>
311 MoveStack* generate(const Position& pos, MoveStack* mlist) {
313 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
314 assert(!pos.in_check());
316 Color us = pos.side_to_move();
319 if (Type == MV_CAPTURE)
320 target = pos.pieces(~us);
322 else if (Type == MV_NON_CAPTURE)
323 target = pos.empty_squares();
325 else if (Type == MV_NON_EVASION)
326 target = pos.pieces(~us) | pos.empty_squares();
328 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
329 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
331 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
332 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
333 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
334 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
335 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
337 if (Type != MV_CAPTURE && pos.can_castle(us))
339 mlist = generate_castle_moves<KING_SIDE, false>(pos, mlist, us);
340 mlist = generate_castle_moves<QUEEN_SIDE, false>(pos, mlist, us);
346 // Explicit template instantiations
347 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
348 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
349 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
352 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
353 /// underpromotions that give check. Returns a pointer to the end of the move list.
355 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
357 assert(!pos.in_check());
359 Color us = pos.side_to_move();
361 Bitboard dc = ci.dcCandidates;
365 Square from = pop_1st_bit(&dc);
366 PieceType pt = type_of(pos.piece_on(from));
369 continue; // Will be generated togheter with direct checks
371 Bitboard b = pos.attacks_from(Piece(pt), from) & pos.empty_squares();
374 b &= ~PseudoAttacks[QUEEN][ci.ksq];
379 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_NON_CAPTURE_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq)
380 : generate_pawn_moves<BLACK, MV_NON_CAPTURE_CHECK>(pos, mlist, ci.dcCandidates, ci.ksq));
382 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, ci);
383 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, ci);
384 mlist = generate_direct_checks<ROOK>(pos, mlist, us, ci);
385 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, ci);
387 if (pos.can_castle(us))
389 mlist = generate_castle_moves<KING_SIDE, true>(pos, mlist, us);
390 mlist = generate_castle_moves<QUEEN_SIDE, true>(pos, mlist, us);
397 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
398 /// to move is in check. Returns a pointer to the end of the move list.
400 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
402 assert(pos.in_check());
405 Square from, checksq;
407 Color us = pos.side_to_move();
408 Square ksq = pos.king_square(us);
409 Bitboard sliderAttacks = 0;
410 Bitboard checkers = pos.checkers();
414 // Find squares attacked by slider checkers, we will remove them from the king
415 // evasions so to skip known illegal moves avoiding useless legality check later.
420 checksq = pop_1st_bit(&b);
422 assert(color_of(pos.piece_on(checksq)) == ~us);
424 switch (type_of(pos.piece_on(checksq)))
426 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
427 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
429 // If queen and king are far or not on a diagonal line we can safely
430 // remove all the squares attacked in the other direction becuase are
431 // not reachable by the king anyway.
432 if (squares_between(ksq, checksq) || !bit_is_set(PseudoAttacks[BISHOP][checksq], ksq))
433 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
435 // Otherwise we need to use real rook attacks to check if king is safe
436 // to move in the other direction. For example: king in B2, queen in A1
437 // a knight in B1, and we can safely move to C1.
439 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
446 // Generate evasions for king, capture and non capture moves
447 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
451 // Generate evasions for other pieces only if not under a double check
455 // Blocking evasions or captures of the checking piece
456 target = squares_between(checksq, ksq) | checkers;
458 mlist = (us == WHITE ? generate_pawn_moves<WHITE, MV_EVASION>(pos, mlist, target)
459 : generate_pawn_moves<BLACK, MV_EVASION>(pos, mlist, target));
461 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
462 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
463 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
464 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
468 /// generate<MV_LEGAL> generates all the legal moves in the given position
471 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
473 MoveStack *last, *cur = mlist;
474 Bitboard pinned = pos.pinned_pieces();
476 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
477 : generate<MV_NON_EVASION>(pos, mlist);
479 if (!pos.pl_move_is_legal(cur->move, pinned))
480 cur->move = (--last)->move;