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_discovered_checks(const Position& pos, MoveStack* mlist, Square from) {
258 assert(Pt != QUEEN && Pt != PAWN);
260 Bitboard b = pos.attacks_from<Pt>(from) & pos.empty_squares();
263 b &= ~QueenPseudoAttacks[pos.king_square(flip(pos.side_to_move()))];
270 template<PieceType Pt>
271 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
272 Bitboard dc, Square ksq) {
273 assert(Pt != KING && Pt != PAWN);
275 Bitboard checkSqs, b;
277 const Square* pl = pos.piece_list(us, Pt);
279 if ((from = *pl++) == SQ_NONE)
282 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
286 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
287 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
288 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
291 if (dc && bit_is_set(dc, from))
294 b = pos.attacks_from<Pt>(from) & checkSqs;
297 } while ((from = *pl++) != SQ_NONE);
304 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
306 return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
307 : generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
311 template<PieceType Pt, MoveType Type>
312 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
315 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
316 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
320 template<PieceType Pt>
321 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
325 const Square* pl = pos.piece_list(us, Pt);
331 b = pos.attacks_from<Pt>(from) & target;
333 } while (*++pl != SQ_NONE);
340 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
343 Square from = pos.king_square(us);
345 b = pos.attacks_from<KING>(from) & target;
353 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
354 /// promotions. Returns a pointer to the end of the move list.
356 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
357 /// underpromotions. Returns a pointer to the end of the move list.
359 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
360 /// non-captures. Returns a pointer to the end of the move list.
362 template<MoveType Type>
363 MoveStack* generate(const Position& pos, MoveStack* mlist) {
365 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_NON_EVASION);
366 assert(!pos.in_check());
368 Color us = pos.side_to_move();
371 if (Type == MV_CAPTURE)
372 target = pos.pieces(flip(us));
374 else if (Type == MV_NON_CAPTURE)
375 target = pos.empty_squares();
377 else if (Type == MV_NON_EVASION)
378 target = pos.pieces(flip(us)) | pos.empty_squares();
380 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
381 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
382 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
383 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
384 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
385 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
387 if (Type != MV_CAPTURE && pos.can_castle(us))
389 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
390 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
396 // Explicit template instantiations
397 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
398 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
399 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
402 /// generate<MV_NON_CAPTURE_CHECK> generates all pseudo-legal non-captures and knight
403 /// underpromotions that give check. Returns a pointer to the end of the move list.
405 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
407 assert(!pos.in_check());
411 Color us = pos.side_to_move();
412 Square ksq = pos.king_square(flip(us));
414 assert(pos.piece_on(ksq) == make_piece(flip(us), KING));
416 // Discovered non-capture checks
417 b = dc = pos.discovered_check_candidates();
421 from = pop_1st_bit(&b);
422 switch (type_of(pos.piece_on(from)))
424 case PAWN: /* Will be generated togheter with pawns direct checks */ break;
425 case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
426 case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
427 case ROOK: mlist = generate_discovered_checks<ROOK>(pos, mlist, from); break;
428 case KING: mlist = generate_discovered_checks<KING>(pos, mlist, from); break;
429 default: assert(false); break;
433 // Direct non-capture checks
434 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
435 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
436 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
437 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
438 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
442 /// generate<MV_EVASION> generates all pseudo-legal check evasions when the side
443 /// to move is in check. Returns a pointer to the end of the move list.
445 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
447 assert(pos.in_check());
450 Square from, checksq;
452 Color us = pos.side_to_move();
453 Square ksq = pos.king_square(us);
454 Bitboard checkers = pos.checkers();
455 Bitboard sliderAttacks = 0;
457 assert(pos.piece_on(ksq) == make_piece(us, KING));
460 // Find squares attacked by slider checkers, we will remove
461 // them from the king evasions set so to early skip known
462 // illegal moves and avoid an useless legality check later.
467 checksq = pop_1st_bit(&b);
469 assert(color_of(pos.piece_on(checksq)) == flip(us));
471 switch (type_of(pos.piece_on(checksq)))
473 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
474 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
476 // If queen and king are far we can safely remove all the squares attacked
477 // in the other direction becuase are not reachable by the king anyway.
478 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
479 sliderAttacks |= QueenPseudoAttacks[checksq];
481 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
482 // use real rook attacks to check if king is safe to move in the other direction.
483 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
485 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
492 // Generate evasions for king, capture and non capture moves
493 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
497 // Generate evasions for other pieces only if not double check
501 // Find squares where a blocking evasion or a capture of the
502 // checker piece is possible.
503 target = squares_between(checksq, ksq) | checkers;
505 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
506 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
507 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
508 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
509 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
513 /// generate<MV_LEGAL> computes a complete list of legal moves in the current position
516 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
518 MoveStack *last, *cur = mlist;
519 Bitboard pinned = pos.pinned_pieces();
521 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
522 : generate<MV_NON_EVASION>(pos, mlist);
524 // Remove illegal moves from the list
526 if (!pos.pl_move_is_legal(cur->move, pinned))
527 cur->move = (--last)->move;