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/>.
28 // Simple macro to wrap a very common while loop, no facny, no flexibility,
29 // hardcoded list name 'mlist' and from square 'from'.
30 #define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
32 // Version used for pawns, where the 'from' square is given as a delta from the 'to' square
33 #define SERIALIZE_MOVES_D(b, d) while (b) { to = pop_1st_bit(&b); (*mlist++).move = make_move(to + (d), to); }
37 enum CastlingSide { KING_SIDE, QUEEN_SIDE };
39 template<CastlingSide Side>
40 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
42 const CastleRight CR[] = { Side ? WHITE_OOO : WHITE_OO,
43 Side ? BLACK_OOO : BLACK_OO };
45 if (!pos.can_castle(CR[us]))
48 // After castling, the rook and king final positions are the same in Chess960
49 // as they would be in standard chess.
50 Square kfrom = pos.king_square(us);
51 Square rfrom = pos.castle_rook_square(CR[us]);
52 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
53 Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
54 Bitboard enemies = pos.pieces(flip(us));
56 assert(!pos.in_check());
57 assert(pos.piece_on(kfrom) == make_piece(us, KING));
58 assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
60 // Unimpeded rule: All the squares between the king's initial and final squares
61 // (including the final square), and all the squares between the rook's initial
62 // and final squares (including the final square), must be vacant except for
63 // the king and castling rook.
64 for (Square s = std::min(rfrom, rto), e = std::max(rfrom, rto); s <= e; s++)
65 if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
68 for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
69 if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
70 ||(pos.attackers_to(s) & enemies))
73 // Because we generate only legal castling moves we need to verify that
74 // when moving the castling rook we do not discover some hidden checker.
75 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
76 if (pos.is_chess960())
78 Bitboard occ = pos.occupied_squares();
79 clear_bit(&occ, rfrom);
80 if (pos.attackers_to(kto, occ) & enemies)
84 (*mlist++).move = make_castle(kfrom, rfrom);
90 template<Square Delta>
91 inline Bitboard move_pawns(Bitboard p) {
93 return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
94 Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
95 Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
99 template<Square Delta>
100 inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
102 const Bitboard TFileABB = ( Delta == DELTA_NE
103 || Delta == DELTA_SE ? FileABB : FileHBB);
107 b = move_pawns<Delta>(pawns) & target & ~TFileABB;
108 SERIALIZE_MOVES_D(b, -Delta);
113 template<MoveType Type, Square Delta>
114 inline MoveStack* generate_promotions(MoveStack* mlist, Bitboard pawnsOn7, Bitboard target, Square ksq) {
116 const Bitboard TFileABB = ( Delta == DELTA_NE
117 || Delta == DELTA_SE ? FileABB : FileHBB);
121 b = move_pawns<Delta>(pawnsOn7) & target;
123 if (Delta != DELTA_N && Delta != DELTA_S)
128 to = pop_1st_bit(&b);
130 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
131 (*mlist++).move = make_promotion(to - Delta, to, QUEEN);
133 if (Type == MV_NON_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
135 (*mlist++).move = make_promotion(to - Delta, to, ROOK);
136 (*mlist++).move = make_promotion(to - Delta, to, BISHOP);
137 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
140 // Knight-promotion is the only one that can give a check (direct or
141 // discovered) not already included in the queen-promotion.
142 if ( Type == MV_CHECK
143 && bit_is_set(StepAttacksBB[W_KNIGHT][to], ksq))
144 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
146 (void)ksq; // Silence a warning under MSVC
152 template<Color Us, MoveType Type>
153 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
155 // Calculate our parametrized parameters at compile time, named according to
156 // the point of view of white side.
157 const Color Them = (Us == WHITE ? BLACK : WHITE);
158 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
159 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
160 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
161 const Square RIGHT = (Us == WHITE ? DELTA_NE : DELTA_SW);
162 const Square LEFT = (Us == WHITE ? DELTA_NW : DELTA_SE);
165 Bitboard b1, b2, dc1, dc2, emptySquares;
167 Bitboard pawns = pos.pieces(PAWN, Us);
168 Bitboard pawnsOn7 = pawns & TRank7BB;
169 Bitboard pawnsNotOn7 = pawns & ~TRank7BB;
171 Bitboard enemies = (Type == MV_EVASION ? pos.pieces(Them) & target:
172 Type == MV_CAPTURE ? target : pos.pieces(Them));
174 // Single and double pawn pushes, no promotions
175 if (Type != MV_CAPTURE)
177 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
179 b1 = move_pawns<UP>(pawnsNotOn7) & emptySquares;
180 b2 = move_pawns<UP>(b1 & TRank3BB) & emptySquares;
182 if (Type == MV_EVASION)
184 b1 &= target; // Consider only blocking squares
188 if (Type == MV_CHECK)
190 // Consider only direct checks
191 b1 &= pos.attacks_from<PAWN>(ksq, Them);
192 b2 &= pos.attacks_from<PAWN>(ksq, Them);
194 // Add pawn pushes which give discovered check. This is possible only
195 // if the pawn is not on the same file as the enemy king, because we
196 // don't generate captures. Note that a possible discovery check
197 // promotion has been already generated among captures.
198 if (pawnsNotOn7 & target) // For CHECK type target is dc bitboard
200 dc1 = move_pawns<UP>(pawnsNotOn7 & target) & emptySquares & ~file_bb(ksq);
201 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
208 SERIALIZE_MOVES_D(b1, -UP);
209 SERIALIZE_MOVES_D(b2, -UP -UP);
212 // Promotions and underpromotions
215 if (Type == MV_CAPTURE)
216 emptySquares = pos.empty_squares();
218 if (Type == MV_EVASION)
219 emptySquares &= target;
221 mlist = generate_promotions<Type, RIGHT>(mlist, pawnsOn7, enemies, ksq);
222 mlist = generate_promotions<Type, LEFT>(mlist, pawnsOn7, enemies, ksq);
223 mlist = generate_promotions<Type, UP>(mlist, pawnsOn7, emptySquares, ksq);
226 // Standard and en-passant captures
227 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
229 mlist = generate_pawn_captures<RIGHT>(mlist, pawnsNotOn7, enemies);
230 mlist = generate_pawn_captures<LEFT >(mlist, pawnsNotOn7, enemies);
232 if (pos.ep_square() != SQ_NONE)
234 assert(rank_of(pos.ep_square()) == (Us == WHITE ? RANK_6 : RANK_3));
236 // An en passant capture can be an evasion only if the checking piece
237 // is the double pushed pawn and so is in the target. Otherwise this
238 // is a discovery check and we are forced to do otherwise.
239 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
242 b1 = pawnsNotOn7 & pos.attacks_from<PAWN>(pos.ep_square(), Them);
247 (*mlist++).move = make_enpassant(pop_1st_bit(&b1), pos.ep_square());
255 template<PieceType Pt>
256 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
257 Bitboard dc, Square ksq) {
258 assert(Pt != KING && Pt != PAWN);
260 Bitboard checkSqs, b;
262 const Square* pl = pos.piece_list(us, Pt);
264 if ((from = *pl++) == SQ_NONE)
267 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
271 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
272 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
273 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
276 if (dc && bit_is_set(dc, from))
279 b = pos.attacks_from<Pt>(from) & checkSqs;
282 } while ((from = *pl++) != SQ_NONE);
289 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
291 return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
292 : generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
296 template<PieceType Pt, MoveType Type>
297 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
300 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
301 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
305 template<PieceType Pt>
306 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
310 const Square* pl = pos.piece_list(us, Pt);
316 b = pos.attacks_from<Pt>(from) & target;
318 } while (*++pl != SQ_NONE);
325 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
328 Square from = pos.king_square(us);
330 b = pos.attacks_from<KING>(from) & target;
338 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
339 /// promotions. Returns a pointer to the end of the move list.
341 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
342 /// underpromotions. Returns a pointer to the end of the move list.
344 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
345 /// non-captures. Returns a pointer to the end of the move list.
347 template<MoveType Type>
348 MoveStack* generate(const Position& pos, MoveStack* mlist) {
350 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
351 assert(!pos.in_check());
353 Color us = pos.side_to_move();
356 if (Type == MV_CAPTURE)
357 target = pos.pieces(flip(us));
359 else if (Type == MV_NON_CAPTURE)
360 target = pos.empty_squares();
362 else if (Type == MV_NON_EVASION)
363 target = pos.pieces(flip(us)) | pos.empty_squares();
365 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
366 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
367 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
368 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
369 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
370 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
372 if (Type != MV_CAPTURE && pos.can_castle(us))
374 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
375 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
381 // Explicit template instantiations
382 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
383 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
384 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
387 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
388 /// underpromotions that give check. Returns a pointer to the end of the move list.
390 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
392 assert(!pos.in_check());
397 Color us = pos.side_to_move();
398 Square ksq = pos.king_square(flip(us));
400 assert(pos.piece_on(ksq) == make_piece(flip(us), KING));
402 // Discovered non-capture checks
403 b = dc = pos.discovered_check_candidates();
407 from = pop_1st_bit(&b);
408 pt = type_of(pos.piece_on(from));
411 continue; // Will be generated togheter with direct checks
413 b = pos.attacks_from(Piece(pt), from) & pos.empty_squares();
416 b &= ~QueenPseudoAttacks[ksq];
421 // Direct non-capture checks
422 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
423 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
424 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
425 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
426 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
430 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
431 /// to move is in check. Returns a pointer to the end of the move list.
433 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
435 assert(pos.in_check());
438 Square from, checksq;
440 Color us = pos.side_to_move();
441 Square ksq = pos.king_square(us);
442 Bitboard checkers = pos.checkers();
443 Bitboard sliderAttacks = 0;
445 assert(pos.piece_on(ksq) == make_piece(us, KING));
448 // Find squares attacked by slider checkers, we will remove
449 // them from the king evasions set so to early skip known
450 // illegal moves and avoid an useless legality check later.
455 checksq = pop_1st_bit(&b);
457 assert(color_of(pos.piece_on(checksq)) == flip(us));
459 switch (type_of(pos.piece_on(checksq)))
461 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
462 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
464 // If queen and king are far we can safely remove all the squares attacked
465 // in the other direction becuase are not reachable by the king anyway.
466 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
467 sliderAttacks |= QueenPseudoAttacks[checksq];
469 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
470 // use real rook attacks to check if king is safe to move in the other direction.
471 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
473 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
480 // Generate evasions for king, capture and non capture moves
481 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
485 // Generate evasions for other pieces only if not double check
489 // Find squares where a blocking evasion or a capture of the
490 // checker piece is possible.
491 target = squares_between(checksq, ksq) | checkers;
493 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
494 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
495 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
496 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
497 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
501 /// generate<MV_LEGAL> computes a complete list of legal moves in the current position
504 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
506 MoveStack *last, *cur = mlist;
507 Bitboard pinned = pos.pinned_pieces();
509 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
510 : generate<MV_NON_EVASION>(pos, mlist);
512 // Remove illegal moves from the list
514 if (!pos.pl_move_is_legal(cur->move, pinned))
515 cur->move = (--last)->move;