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 EdgeFileBB = ( Delta == DELTA_NE
103 || Delta == DELTA_SE ? FileABB : FileHBB);
107 b = move_pawns<Delta>(pawns) & target & ~EdgeFileBB;
108 SERIALIZE_MOVES_D(b, -Delta);
113 template<MoveType Type, Square Delta>
114 inline MoveStack* generate_promotions(const Position& pos, MoveStack* mlist, Bitboard pawnsOn7, Bitboard target) {
116 const Bitboard EdgeFileBB = ( 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 under promotion is the only one that can give a check not
141 // already included in the queen-promotion.
142 if (Type == MV_CHECK)
144 Square ksq = pos.king_square(Delta > 0 ? BLACK : WHITE);
145 if (bit_is_set(pos.attacks_from<KNIGHT>(to), ksq))
146 (*mlist++).move = make_promotion(to - Delta, to, KNIGHT);
149 (void)pos; // Silence a warning under MSVC
155 template<Color Us, MoveType Type>
156 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
158 // Calculate our parametrized parameters at compile time, named
159 // according to the point of view of white side.
160 const Color Them = (Us == WHITE ? BLACK : WHITE);
161 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
162 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
163 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
164 const Square RIGHT_UP = (Us == WHITE ? DELTA_NE : DELTA_SW);
165 const Square LEFT_UP = (Us == WHITE ? DELTA_NW : DELTA_SE);
168 Bitboard b1, b2, dc1, dc2, pawnPushes, emptySquares;
169 Bitboard pawns = pos.pieces(PAWN, Us);
170 Bitboard pawnsOn7 = pawns & TRank7BB;
171 Bitboard enemyPieces = (Type == MV_CAPTURE ? target : pos.pieces(Them));
173 // Pre-calculate pawn pushes before changing emptySquares definition
174 if (Type != MV_CAPTURE)
176 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
177 pawnPushes = move_pawns<UP>(pawns & ~TRank7BB) & emptySquares;
180 if (Type == MV_EVASION)
182 emptySquares &= target; // Only blocking squares
183 enemyPieces &= target; // Capture only the checker piece
186 // Promotions and underpromotions
189 if (Type == MV_CAPTURE)
190 emptySquares = pos.empty_squares();
193 mlist = generate_promotions<Type, RIGHT_UP>(pos, mlist, pawnsOn7, enemyPieces);
194 mlist = generate_promotions<Type, LEFT_UP>(pos, mlist, pawnsOn7, enemyPieces);
195 mlist = generate_promotions<Type, UP>(pos, mlist, pawnsOn7, emptySquares);
199 if (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
201 mlist = generate_pawn_captures<RIGHT_UP>(mlist, pawns, enemyPieces);
202 mlist = generate_pawn_captures<LEFT_UP>(mlist, pawns, enemyPieces);
205 // Single and double pawn pushes
206 if (Type != MV_CAPTURE)
208 b1 = (Type != MV_EVASION ? pawnPushes : pawnPushes & emptySquares);
209 b2 = move_pawns<UP>(pawnPushes & TRank3BB) & emptySquares;
211 if (Type == MV_CHECK)
213 // Consider only pawn moves which give direct checks
214 b1 &= pos.attacks_from<PAWN>(ksq, Them);
215 b2 &= pos.attacks_from<PAWN>(ksq, Them);
217 // Add pawn moves which gives discovered check. This is possible only
218 // if the pawn is not on the same file as the enemy king, because we
219 // don't generate captures.
220 if (pawns & target) // For CHECK type target is dc bitboard
222 dc1 = move_pawns<UP>(pawns & target & ~file_bb(ksq)) & emptySquares;
223 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
229 SERIALIZE_MOVES_D(b1, -UP);
230 SERIALIZE_MOVES_D(b2, -UP -UP);
233 // En passant captures
234 if ( (Type == MV_CAPTURE || Type == MV_EVASION || Type == MV_NON_EVASION)
235 && pos.ep_square() != SQ_NONE)
237 assert(Us != WHITE || rank_of(pos.ep_square()) == RANK_6);
238 assert(Us != BLACK || rank_of(pos.ep_square()) == RANK_3);
240 // An en passant capture can be an evasion only if the checking piece
241 // is the double pushed pawn and so is in the target. Otherwise this
242 // is a discovery check and we are forced to do otherwise.
243 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
246 b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
252 to = pop_1st_bit(&b1);
253 (*mlist++).move = make_enpassant(to, pos.ep_square());
260 template<PieceType Pt>
261 inline MoveStack* generate_discovered_checks(const Position& pos, MoveStack* mlist, Square from) {
263 assert(Pt != QUEEN && Pt != PAWN);
265 Bitboard b = pos.attacks_from<Pt>(from) & pos.empty_squares();
268 b &= ~QueenPseudoAttacks[pos.king_square(flip(pos.side_to_move()))];
275 template<PieceType Pt>
276 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
277 Bitboard dc, Square ksq) {
278 assert(Pt != KING && Pt != PAWN);
280 Bitboard checkSqs, b;
282 const Square* pl = pos.piece_list(us, Pt);
284 if ((from = *pl++) == SQ_NONE)
287 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
291 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
292 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
293 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
296 if (dc && bit_is_set(dc, from))
299 b = pos.attacks_from<Pt>(from) & checkSqs;
302 } while ((from = *pl++) != SQ_NONE);
309 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
311 return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
312 : generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
316 template<PieceType Pt, MoveType Type>
317 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
320 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
321 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
325 template<PieceType Pt>
326 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
330 const Square* pl = pos.piece_list(us, Pt);
336 b = pos.attacks_from<Pt>(from) & target;
338 } while (*++pl != SQ_NONE);
345 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
348 Square from = pos.king_square(us);
350 b = pos.attacks_from<KING>(from) & target;
358 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
359 /// promotions. Returns a pointer to the end of the move list.
361 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
362 /// underpromotions. Returns a pointer to the end of the move list.
364 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
365 /// non-captures. Returns a pointer to the end of the move list.
367 template<MoveType Type>
368 MoveStack* generate(const Position& pos, MoveStack* mlist) {
370 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
371 assert(!pos.in_check());
373 Color us = pos.side_to_move();
376 if (Type == MV_CAPTURE)
377 target = pos.pieces(flip(us));
379 else if (Type == MV_NON_CAPTURE)
380 target = pos.empty_squares();
382 else if (Type == MV_NON_EVASION)
383 target = pos.pieces(flip(us)) | pos.empty_squares();
385 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
386 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
387 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
388 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
389 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
390 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
392 if (Type != MV_CAPTURE && pos.can_castle(us))
394 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
395 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
401 // Explicit template instantiations
402 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
403 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
404 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
407 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
408 /// underpromotions that give check. Returns a pointer to the end of the move list.
410 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
412 assert(!pos.in_check());
416 Color us = pos.side_to_move();
417 Square ksq = pos.king_square(flip(us));
419 assert(pos.piece_on(ksq) == make_piece(flip(us), KING));
421 // Discovered non-capture checks
422 b = dc = pos.discovered_check_candidates();
426 from = pop_1st_bit(&b);
427 switch (type_of(pos.piece_on(from)))
429 case PAWN: /* Will be generated togheter with pawns direct checks */ break;
430 case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
431 case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
432 case ROOK: mlist = generate_discovered_checks<ROOK>(pos, mlist, from); break;
433 case KING: mlist = generate_discovered_checks<KING>(pos, mlist, from); break;
434 default: assert(false); break;
438 // Direct non-capture checks
439 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
440 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
441 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
442 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
443 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
447 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
448 /// to move is in check. Returns a pointer to the end of the move list.
450 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
452 assert(pos.in_check());
455 Square from, checksq;
457 Color us = pos.side_to_move();
458 Square ksq = pos.king_square(us);
459 Bitboard checkers = pos.checkers();
460 Bitboard sliderAttacks = 0;
462 assert(pos.piece_on(ksq) == make_piece(us, KING));
465 // Find squares attacked by slider checkers, we will remove
466 // them from the king evasions set so to early skip known
467 // illegal moves and avoid an useless legality check later.
472 checksq = pop_1st_bit(&b);
474 assert(color_of(pos.piece_on(checksq)) == flip(us));
476 switch (type_of(pos.piece_on(checksq)))
478 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
479 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
481 // If queen and king are far we can safely remove all the squares attacked
482 // in the other direction becuase are not reachable by the king anyway.
483 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
484 sliderAttacks |= QueenPseudoAttacks[checksq];
486 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
487 // use real rook attacks to check if king is safe to move in the other direction.
488 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
490 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
497 // Generate evasions for king, capture and non capture moves
498 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
502 // Generate evasions for other pieces only if not double check
506 // Find squares where a blocking evasion or a capture of the
507 // checker piece is possible.
508 target = squares_between(checksq, ksq) | checkers;
510 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
511 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
512 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
513 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
514 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
518 /// generate<MV_LEGAL> computes a complete list of legal moves in the current position
521 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
523 MoveStack *last, *cur = mlist;
524 Bitboard pinned = pos.pinned_pieces();
526 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
527 : generate<MV_NON_EVASION>(pos, mlist);
529 // Remove illegal moves from the list
531 if (!pos.pl_move_is_legal(cur->move, pinned))
532 cur->move = (--last)->move;