2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 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/>.
25 // Simple macro to wrap a very common while loop, no facny, no flexibility,
26 // hardcoded list name 'mlist' and from square 'from'.
27 #define SERIALIZE_MOVES(b) while (b) (*mlist++).move = make_move(from, pop_1st_bit(&b))
29 // Version used for pawns, where the 'from' square is given as a delta from the 'to' square
30 #define SERIALIZE_MOVES_D(b, d) while (b) { to = pop_1st_bit(&b); (*mlist++).move = make_move(to + (d), to); }
39 template<CastlingSide>
40 MoveStack* generate_castle_moves(const Position&, MoveStack*, Color us);
42 template<Color, MoveType>
43 MoveStack* generate_pawn_moves(const Position&, MoveStack*, Bitboard, Square);
45 template<PieceType Pt>
46 inline MoveStack* generate_discovered_checks(const Position& pos, MoveStack* mlist, Square from) {
50 Bitboard b = pos.attacks_from<Pt>(from) & pos.empty_squares();
53 Square ksq = pos.king_square(opposite_color(pos.side_to_move()));
54 b &= ~QueenPseudoAttacks[ksq];
60 template<PieceType Pt>
61 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
62 Bitboard dc, Square ksq) {
67 const Square* pl = pos.piece_list(us, Pt);
69 if ((from = *pl++) == SQ_NONE)
72 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
76 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
77 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
78 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
81 if (dc && bit_is_set(dc, from))
84 b = pos.attacks_from<Pt>(from) & checkSqs;
87 } while ((from = *pl++) != SQ_NONE);
93 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
95 return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
96 : generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
99 template<PieceType Pt, MoveType Type>
100 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
103 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_EVASION);
105 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
106 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
109 template<PieceType Pt>
110 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
114 const Square* pl = pos.piece_list(us, Pt);
120 b = pos.attacks_from<Pt>(from) & target;
122 } while (*++pl != SQ_NONE);
128 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
131 Square from = pos.king_square(us);
133 b = pos.attacks_from<KING>(from) & target;
141 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
142 /// promotions. Returns a pointer to the end of the move list.
144 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
145 /// underpromotions. Returns a pointer to the end of the move list.
147 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
148 /// non-captures. Returns a pointer to the end of the move list.
150 template<MoveType Type>
151 MoveStack* generate(const Position& pos, MoveStack* mlist) {
154 assert(!pos.in_check());
156 Color us = pos.side_to_move();
159 if (Type == MV_CAPTURE || Type == MV_NON_EVASION)
160 target = pos.pieces(opposite_color(us));
161 else if (Type == MV_NON_CAPTURE)
162 target = pos.empty_squares();
166 if (Type == MV_NON_EVASION)
168 mlist = generate_piece_moves<PAWN, MV_CAPTURE>(pos, mlist, us, target);
169 mlist = generate_piece_moves<PAWN, MV_NON_CAPTURE>(pos, mlist, us, pos.empty_squares());
170 target |= pos.empty_squares();
173 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
175 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
176 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
177 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
178 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
179 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
181 if (Type != MV_CAPTURE && pos.can_castle(us))
183 if (pos.can_castle(us == WHITE ? WHITE_OO : BLACK_OO))
184 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
186 if (pos.can_castle(us == WHITE ? WHITE_OOO : BLACK_OOO))
187 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
193 // Explicit template instantiations
194 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
195 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
196 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
199 /// generate_non_capture_checks() generates all pseudo-legal non-captures and knight
200 /// underpromotions that give check. Returns a pointer to the end of the move list.
202 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
205 assert(!pos.in_check());
209 Color us = pos.side_to_move();
210 Square ksq = pos.king_square(opposite_color(us));
212 assert(pos.piece_on(ksq) == make_piece(opposite_color(us), KING));
214 // Discovered non-capture checks
215 b = dc = pos.discovered_check_candidates(us);
219 from = pop_1st_bit(&b);
220 switch (piece_type(pos.piece_on(from)))
222 case PAWN: /* Will be generated togheter with pawns direct checks */ break;
223 case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
224 case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
225 case ROOK: mlist = generate_discovered_checks<ROOK>(pos, mlist, from); break;
226 case KING: mlist = generate_discovered_checks<KING>(pos, mlist, from); break;
227 default: assert(false); break;
231 // Direct non-capture checks
232 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
233 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
234 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
235 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
236 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
240 /// generate_evasions() generates all pseudo-legal check evasions when
241 /// the side to move is in check. Returns a pointer to the end of the move list.
243 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
246 assert(pos.in_check());
249 Square from, checksq;
251 Color us = pos.side_to_move();
252 Square ksq = pos.king_square(us);
253 Bitboard checkers = pos.checkers();
254 Bitboard sliderAttacks = EmptyBoardBB;
256 assert(pos.piece_on(ksq) == make_piece(us, KING));
259 // Find squares attacked by slider checkers, we will remove
260 // them from the king evasions set so to early skip known
261 // illegal moves and avoid an useless legality check later.
266 checksq = pop_1st_bit(&b);
268 assert(piece_color(pos.piece_on(checksq)) == opposite_color(us));
270 switch (piece_type(pos.piece_on(checksq)))
272 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
273 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
275 // If queen and king are far we can safely remove all the squares attacked
276 // in the other direction becuase are not reachable by the king anyway.
277 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
278 sliderAttacks |= QueenPseudoAttacks[checksq];
280 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
281 // use real rook attacks to check if king is safe to move in the other direction.
282 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
284 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
291 // Generate evasions for king, capture and non capture moves
292 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
296 // Generate evasions for other pieces only if not double check
300 // Find squares where a blocking evasion or a capture of the
301 // checker piece is possible.
302 target = squares_between(checksq, ksq) | checkers;
304 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
305 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
306 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
307 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
308 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
312 /// generate<MV_LEGAL> computes a complete list of legal moves in the current position
315 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
319 MoveStack *last, *cur = mlist;
320 Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
322 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
323 : generate<MV_NON_EVASION>(pos, mlist);
325 // Remove illegal moves from the list
327 if (!pos.pl_move_is_legal(cur->move, pinned))
328 cur->move = (--last)->move;
338 template<Square Delta>
339 inline Bitboard move_pawns(Bitboard p) {
341 return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
342 Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
343 Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
346 template<MoveType Type, Square Delta>
347 inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
349 const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
354 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
355 b = move_pawns<Delta>(pawns) & target & ~TFileABB;
356 SERIALIZE_MOVES_D(b, -Delta);
360 template<Color Us, MoveType Type, Square Delta>
361 inline MoveStack* generate_promotions(const Position& pos, MoveStack* mlist, Bitboard pawnsOn7, Bitboard target) {
363 const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
368 // Promotions and under-promotions, both captures and non-captures
369 b = move_pawns<Delta>(pawnsOn7) & target;
371 if (Delta != DELTA_N && Delta != DELTA_S)
376 to = pop_1st_bit(&b);
378 if (Type == MV_CAPTURE || Type == MV_EVASION)
379 (*mlist++).move = make_promotion_move(to - Delta, to, QUEEN);
381 if (Type == MV_NON_CAPTURE || Type == MV_EVASION)
383 (*mlist++).move = make_promotion_move(to - Delta, to, ROOK);
384 (*mlist++).move = make_promotion_move(to - Delta, to, BISHOP);
385 (*mlist++).move = make_promotion_move(to - Delta, to, KNIGHT);
388 // This is the only possible under promotion that can give a check
389 // not already included in the queen-promotion.
390 if ( Type == MV_CHECK
391 && bit_is_set(pos.attacks_from<KNIGHT>(to), pos.king_square(opposite_color(Us))))
392 (*mlist++).move = make_promotion_move(to - Delta, to, KNIGHT);
393 else (void)pos; // Silence a warning under MSVC
398 template<Color Us, MoveType Type>
399 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
401 // Calculate our parametrized parameters at compile time, named
402 // according to the point of view of white side.
403 const Color Them = (Us == WHITE ? BLACK : WHITE);
404 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
405 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
406 const Square TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
407 const Square TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
408 const Square TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
411 Bitboard b1, b2, dc1, dc2, pawnPushes, emptySquares;
412 Bitboard pawns = pos.pieces(PAWN, Us);
413 Bitboard pawnsOn7 = pawns & TRank7BB;
414 Bitboard enemyPieces = (Type == MV_CAPTURE ? target : pos.pieces(Them));
416 // Pre-calculate pawn pushes before changing emptySquares definition
417 if (Type != MV_CAPTURE)
419 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
420 pawnPushes = move_pawns<TDELTA_N>(pawns & ~TRank7BB) & emptySquares;
423 if (Type == MV_EVASION)
425 emptySquares &= target; // Only blocking squares
426 enemyPieces &= target; // Capture only the checker piece
429 // Promotions and underpromotions
432 if (Type == MV_CAPTURE)
433 emptySquares = pos.empty_squares();
436 mlist = generate_promotions<Us, Type, TDELTA_NE>(pos, mlist, pawnsOn7, enemyPieces);
437 mlist = generate_promotions<Us, Type, TDELTA_NW>(pos, mlist, pawnsOn7, enemyPieces);
438 mlist = generate_promotions<Us, Type, TDELTA_N >(pos, mlist, pawnsOn7, emptySquares);
442 if (Type == MV_CAPTURE || Type == MV_EVASION)
444 mlist = generate_pawn_captures<Type, TDELTA_NE>(mlist, pawns, enemyPieces);
445 mlist = generate_pawn_captures<Type, TDELTA_NW>(mlist, pawns, enemyPieces);
448 // Single and double pawn pushes
449 if (Type != MV_CAPTURE)
451 b1 = (Type != MV_EVASION ? pawnPushes : pawnPushes & emptySquares);
452 b2 = move_pawns<TDELTA_N>(pawnPushes & TRank3BB) & emptySquares;
454 if (Type == MV_CHECK)
456 // Consider only pawn moves which give direct checks
457 b1 &= pos.attacks_from<PAWN>(ksq, Them);
458 b2 &= pos.attacks_from<PAWN>(ksq, Them);
460 // Add pawn moves which gives discovered check. This is possible only
461 // if the pawn is not on the same file as the enemy king, because we
462 // don't generate captures.
463 if (pawns & target) // For CHECK type target is dc bitboard
465 dc1 = move_pawns<TDELTA_N>(pawns & target & ~file_bb(ksq)) & emptySquares;
466 dc2 = move_pawns<TDELTA_N>(dc1 & TRank3BB) & emptySquares;
472 SERIALIZE_MOVES_D(b1, -TDELTA_N);
473 SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
476 // En passant captures
477 if ((Type == MV_CAPTURE || Type == MV_EVASION) && pos.ep_square() != SQ_NONE)
479 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
480 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
482 // An en passant capture can be an evasion only if the checking piece
483 // is the double pushed pawn and so is in the target. Otherwise this
484 // is a discovery check and we are forced to do otherwise.
485 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - TDELTA_N))
488 b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
490 assert(b1 != EmptyBoardBB);
494 to = pop_1st_bit(&b1);
495 (*mlist++).move = make_ep_move(to, pos.ep_square());
501 template<CastlingSide Side>
502 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
504 CastleRight f = CastleRight((Side == KING_SIDE ? WHITE_OO : WHITE_OOO) << us);
505 Color them = opposite_color(us);
507 // After castling, the rook and king's final positions are exactly the same
508 // in Chess960 as they would be in standard chess.
509 Square kfrom = pos.king_square(us);
510 Square rfrom = pos.castle_rook_square(f);
511 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
512 Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
514 assert(!pos.in_check());
515 assert(pos.piece_on(kfrom) == make_piece(us, KING));
516 assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
518 // Unimpeded rule: All the squares between the king's initial and final squares
519 // (including the final square), and all the squares between the rook's initial
520 // and final squares (including the final square), must be vacant except for
521 // the king and castling rook.
522 for (Square s = Min(kfrom, kto); s <= Max(kfrom, kto); s++)
523 if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
524 ||(pos.attackers_to(s) & pos.pieces(them)))
527 for (Square s = Min(rfrom, rto); s <= Max(rfrom, rto); s++)
528 if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
531 // Because we generate only legal castling moves we need to verify that
532 // when moving the castling rook we do not discover some hidden checker.
533 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
534 if (pos.is_chess960())
536 Bitboard occ = pos.occupied_squares();
537 clear_bit(&occ, rfrom);
538 if (pos.attackers_to(kto, occ) & pos.pieces(them))
542 (*mlist++).move = make_castle_move(kfrom, rfrom);