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_lsb(&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_lsb(&b); \
32 (*mlist++).move = make_move(to - (d), to); }
35 template<CastlingSide Side, bool OnlyChecks>
36 MoveStack* generate_castle(const Position& pos, MoveStack* mlist, Color us) {
38 if (pos.castle_impeded(us, Side) || !pos.can_castle(make_castle_right(us, Side)))
41 // After castling, the rook and king final positions are the same in Chess960
42 // as they would be in standard chess.
43 Square kfrom = pos.king_square(us);
44 Square rfrom = pos.castle_rook_square(us, Side);
45 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
46 Bitboard enemies = pos.pieces(~us);
48 assert(!pos.in_check());
50 for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
51 if ( s != kfrom // We are not in check
52 && (pos.attackers_to(s) & enemies))
55 // Because we generate only legal castling moves we need to verify that
56 // when moving the castling rook we do not discover some hidden checker.
57 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
58 if ( pos.is_chess960()
59 && (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
62 (*mlist++).move = make<CASTLE>(kfrom, rfrom);
64 if (OnlyChecks && !pos.move_gives_check((mlist - 1)->move, CheckInfo(pos)))
71 template<Square Delta>
72 inline Bitboard move_pawns(Bitboard p) {
74 return Delta == DELTA_N ? p << 8
75 : Delta == DELTA_S ? p >> 8
76 : Delta == DELTA_NE ? (p & ~FileHBB) << 9
77 : Delta == DELTA_SE ? (p & ~FileHBB) >> 7
78 : Delta == DELTA_NW ? (p & ~FileABB) << 7
79 : Delta == DELTA_SW ? (p & ~FileABB) >> 9 : 0;
83 template<GenType Type, Square Delta>
84 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
86 Bitboard b = move_pawns<Delta>(pawnsOn7) & target;
90 Square to = pop_lsb(&b);
92 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
93 (*mlist++).move = make<PROMOTION>(to - Delta, to, QUEEN);
95 if (Type == QUIETS || Type == EVASIONS || Type == NON_EVASIONS)
97 (*mlist++).move = make<PROMOTION>(to - Delta, to, ROOK);
98 (*mlist++).move = make<PROMOTION>(to - Delta, to, BISHOP);
99 (*mlist++).move = make<PROMOTION>(to - Delta, to, KNIGHT);
102 // Knight-promotion is the only one that can give a direct check not
103 // already included in the queen-promotion.
104 if (Type == QUIET_CHECKS && (StepAttacksBB[W_KNIGHT][to] & ksq))
105 (*mlist++).move = make<PROMOTION>(to - Delta, to, KNIGHT);
107 (void)ksq; // Silence a warning under MSVC
114 template<Color Us, GenType Type>
115 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq = SQ_NONE) {
117 // Compute our parametrized parameters at compile time, named according to
118 // the point of view of white side.
119 const Color Them = (Us == WHITE ? BLACK : WHITE);
120 const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
121 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
122 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
123 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
124 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
125 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
127 Bitboard b1, b2, dc1, dc2, emptySquares;
129 Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
130 Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
132 Bitboard enemies = (Type == EVASIONS ? pos.pieces(Them) & target:
133 Type == CAPTURES ? target : pos.pieces(Them));
135 // Single and double pawn pushes, no promotions
136 if (Type != CAPTURES)
138 emptySquares = (Type == QUIETS ? target : ~pos.pieces());
140 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
141 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
143 if (Type == EVASIONS) // Consider only blocking squares
149 if (Type == QUIET_CHECKS)
151 b1 &= pos.attacks_from<PAWN>(ksq, Them);
152 b2 &= pos.attacks_from<PAWN>(ksq, Them);
154 // Add pawn pushes which give discovered check. This is possible only
155 // if the pawn is not on the same file as the enemy king, because we
156 // don't generate captures. Note that a possible discovery check
157 // promotion has been already generated among captures.
158 if (pawnsNotOn7 & target) // Target is dc bitboard
160 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
161 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
168 SERIALIZE_PAWNS(b1, UP);
169 SERIALIZE_PAWNS(b2, UP + UP);
172 // Promotions and underpromotions
173 if (pawnsOn7 && (Type != EVASIONS || (target & TRank8BB)))
175 if (Type == CAPTURES)
176 emptySquares = ~pos.pieces();
178 if (Type == EVASIONS)
179 emptySquares &= target;
181 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
182 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
183 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
186 // Standard and en-passant captures
187 if (Type == CAPTURES || Type == EVASIONS || Type == NON_EVASIONS)
189 b1 = move_pawns<RIGHT>(pawnsNotOn7) & enemies;
190 b2 = move_pawns<LEFT >(pawnsNotOn7) & enemies;
192 SERIALIZE_PAWNS(b1, RIGHT);
193 SERIALIZE_PAWNS(b2, LEFT);
195 if (pos.ep_square() != SQ_NONE)
197 assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
199 // An en passant capture can be an evasion only if the checking piece
200 // is the double pushed pawn and so is in the target. Otherwise this
201 // is a discovery check and we are forced to do otherwise.
202 if (Type == EVASIONS && !(target & (pos.ep_square() - UP)))
205 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
210 (*mlist++).move = make<ENPASSANT>(pop_lsb(&b1), pos.ep_square());
218 template<PieceType Pt>
219 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist,
220 Color us, const CheckInfo& ci) {
221 assert(Pt != KING && Pt != PAWN);
225 const Square* pl = pos.piece_list(us, Pt);
229 target = ci.checkSq[Pt] & ~pos.pieces(); // Non capture checks only
234 if ( (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
235 && !(PseudoAttacks[Pt][from] & target))
238 if (ci.dcCandidates && (ci.dcCandidates & from))
241 b = pos.attacks_from<Pt>(from) & target;
243 } while (*++pl != SQ_NONE);
250 template<PieceType Pt>
251 FORCE_INLINE MoveStack* generate_moves(const Position& pos, MoveStack* mlist,
252 Color us, Bitboard target) {
253 assert(Pt != KING && Pt != PAWN);
257 const Square* pl = pos.piece_list(us, Pt);
262 b = pos.attacks_from<Pt>(from) & target;
264 } while (*++pl != SQ_NONE);
271 FORCE_INLINE MoveStack* generate_moves<KING>(const Position& pos, MoveStack* mlist,
272 Color us, Bitboard target) {
273 Square from = pos.king_square(us);
274 Bitboard b = pos.attacks_from<KING>(from) & target;
282 /// generate<CAPTURES> generates all pseudo-legal captures and queen
283 /// promotions. Returns a pointer to the end of the move list.
285 /// generate<QUIETS> generates all pseudo-legal non-captures and
286 /// underpromotions. Returns a pointer to the end of the move list.
288 /// generate<NON_EVASIONS> generates all pseudo-legal captures and
289 /// non-captures. Returns a pointer to the end of the move list.
291 template<GenType Type>
292 MoveStack* generate(const Position& pos, MoveStack* mlist) {
294 assert(Type == CAPTURES || Type == QUIETS || Type == NON_EVASIONS);
295 assert(!pos.in_check());
297 Color us = pos.side_to_move();
300 if (Type == CAPTURES)
301 target = pos.pieces(~us);
303 else if (Type == QUIETS)
304 target = ~pos.pieces();
306 else if (Type == NON_EVASIONS)
307 target = ~pos.pieces(us);
309 mlist = (us == WHITE ? generate_pawn_moves<WHITE, Type>(pos, mlist, target)
310 : generate_pawn_moves<BLACK, Type>(pos, mlist, target));
312 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
313 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
314 mlist = generate_moves<ROOK>(pos, mlist, us, target);
315 mlist = generate_moves<QUEEN>(pos, mlist, us, target);
316 mlist = generate_moves<KING>(pos, mlist, us, target);
318 if (Type != CAPTURES && pos.can_castle(us))
320 mlist = generate_castle<KING_SIDE, false>(pos, mlist, us);
321 mlist = generate_castle<QUEEN_SIDE, false>(pos, mlist, us);
327 // Explicit template instantiations
328 template MoveStack* generate<CAPTURES>(const Position& pos, MoveStack* mlist);
329 template MoveStack* generate<QUIETS>(const Position& pos, MoveStack* mlist);
330 template MoveStack* generate<NON_EVASIONS>(const Position& pos, MoveStack* mlist);
333 /// generate<QUIET_CHECKS> generates all pseudo-legal non-captures and knight
334 /// underpromotions that give check. Returns a pointer to the end of the move list.
336 MoveStack* generate<QUIET_CHECKS>(const Position& pos, MoveStack* mlist) {
338 assert(!pos.in_check());
340 Color us = pos.side_to_move();
342 Bitboard dc = ci.dcCandidates;
346 Square from = pop_lsb(&dc);
347 PieceType pt = type_of(pos.piece_on(from));
350 continue; // Will be generated togheter with direct checks
352 Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
355 b &= ~PseudoAttacks[QUEEN][ci.ksq];
360 mlist = (us == WHITE ? generate_pawn_moves<WHITE, QUIET_CHECKS>(pos, mlist, ci.dcCandidates, ci.ksq)
361 : generate_pawn_moves<BLACK, QUIET_CHECKS>(pos, mlist, ci.dcCandidates, ci.ksq));
363 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, ci);
364 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, ci);
365 mlist = generate_direct_checks<ROOK>(pos, mlist, us, ci);
366 mlist = generate_direct_checks<QUEEN>(pos, mlist, us, ci);
368 if (pos.can_castle(us))
370 mlist = generate_castle<KING_SIDE, true>(pos, mlist, us);
371 mlist = generate_castle<QUEEN_SIDE, true>(pos, mlist, us);
378 /// generate<EVASIONS> generates all pseudo-legal check evasions when the side
379 /// to move is in check. Returns a pointer to the end of the move list.
381 MoveStack* generate<EVASIONS>(const Position& pos, MoveStack* mlist) {
383 assert(pos.in_check());
386 Square from, checksq;
388 Color us = pos.side_to_move();
389 Square ksq = pos.king_square(us);
390 Bitboard sliderAttacks = 0;
391 Bitboard checkers = pos.checkers();
395 // Find squares attacked by slider checkers, we will remove them from the king
396 // evasions so to skip known illegal moves avoiding useless legality check later.
401 checksq = pop_lsb(&b);
403 assert(color_of(pos.piece_on(checksq)) == ~us);
405 switch (type_of(pos.piece_on(checksq)))
407 case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
408 case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
410 // If queen and king are far or not on a diagonal line we can safely
411 // remove all the squares attacked in the other direction becuase are
412 // not reachable by the king anyway.
413 if (between_bb(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
414 sliderAttacks |= PseudoAttacks[QUEEN][checksq];
416 // Otherwise we need to use real rook attacks to check if king is safe
417 // to move in the other direction. For example: king in B2, queen in A1
418 // a knight in B1, and we can safely move to C1.
420 sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
427 // Generate evasions for king, capture and non capture moves
428 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
432 // Generate evasions for other pieces only if not under a double check
436 // Blocking evasions or captures of the checking piece
437 target = between_bb(checksq, ksq) | checkers;
439 mlist = (us == WHITE ? generate_pawn_moves<WHITE, EVASIONS>(pos, mlist, target)
440 : generate_pawn_moves<BLACK, EVASIONS>(pos, mlist, target));
442 mlist = generate_moves<KNIGHT>(pos, mlist, us, target);
443 mlist = generate_moves<BISHOP>(pos, mlist, us, target);
444 mlist = generate_moves<ROOK>(pos, mlist, us, target);
445 return generate_moves<QUEEN>(pos, mlist, us, target);
449 /// generate<LEGAL> generates all the legal moves in the given position
452 MoveStack* generate<LEGAL>(const Position& pos, MoveStack* mlist) {
454 MoveStack *last, *cur = mlist;
455 Bitboard pinned = pos.pinned_pieces();
457 last = pos.in_check() ? generate<EVASIONS>(pos, mlist)
458 : generate<NON_EVASIONS>(pos, mlist);
460 if (!pos.pl_move_is_legal(cur->move, pinned))
461 cur->move = (--last)->move;