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) {
51 Bitboard b = pos.attacks_from<Pt>(from) & pos.empty_squares();
54 b &= ~QueenPseudoAttacks[pos.king_square(opposite_color(pos.side_to_move()))];
60 template<PieceType Pt>
61 inline MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
62 Bitboard dc, Square ksq) {
68 const Square* pl = pos.piece_list(us, Pt);
70 if ((from = *pl++) == SQ_NONE)
73 checkSqs = pos.attacks_from<Pt>(ksq) & pos.empty_squares();
77 if ( (Pt == QUEEN && !(QueenPseudoAttacks[from] & checkSqs))
78 || (Pt == ROOK && !(RookPseudoAttacks[from] & checkSqs))
79 || (Pt == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
82 if (dc && bit_is_set(dc, from))
85 b = pos.attacks_from<Pt>(from) & checkSqs;
88 } while ((from = *pl++) != SQ_NONE);
94 FORCE_INLINE MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
96 return (us == WHITE ? generate_pawn_moves<WHITE, MV_CHECK>(p, m, dc, ksq)
97 : generate_pawn_moves<BLACK, MV_CHECK>(p, m, dc, ksq));
100 template<PieceType Pt, MoveType Type>
101 FORCE_INLINE MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
104 assert(Type == MV_CAPTURE || Type == MV_NON_CAPTURE || Type == MV_EVASION);
106 return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
107 : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
110 template<PieceType Pt>
111 FORCE_INLINE MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
115 const Square* pl = pos.piece_list(us, Pt);
121 b = pos.attacks_from<Pt>(from) & target;
123 } while (*++pl != SQ_NONE);
129 FORCE_INLINE MoveStack* generate_piece_moves<KING>(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
132 Square from = pos.king_square(us);
134 b = pos.attacks_from<KING>(from) & target;
142 /// generate<MV_CAPTURE> generates all pseudo-legal captures and queen
143 /// promotions. Returns a pointer to the end of the move list.
145 /// generate<MV_NON_CAPTURE> generates all pseudo-legal non-captures and
146 /// underpromotions. Returns a pointer to the end of the move list.
148 /// generate<MV_NON_EVASION> generates all pseudo-legal captures and
149 /// non-captures. Returns a pointer to the end of the move list.
151 template<MoveType Type>
152 MoveStack* generate(const Position& pos, MoveStack* mlist) {
155 assert(!pos.in_check());
157 Color us = pos.side_to_move();
160 if (Type == MV_CAPTURE || Type == MV_NON_EVASION)
161 target = pos.pieces(opposite_color(us));
162 else if (Type == MV_NON_CAPTURE)
163 target = pos.empty_squares();
167 if (Type == MV_NON_EVASION)
169 mlist = generate_piece_moves<PAWN, MV_CAPTURE>(pos, mlist, us, target);
170 mlist = generate_piece_moves<PAWN, MV_NON_CAPTURE>(pos, mlist, us, pos.empty_squares());
171 target |= pos.empty_squares();
174 mlist = generate_piece_moves<PAWN, Type>(pos, mlist, us, target);
176 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
177 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
178 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
179 mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
180 mlist = generate_piece_moves<KING>(pos, mlist, us, target);
182 if (Type != MV_CAPTURE && pos.can_castle(us))
184 if (pos.can_castle(us == WHITE ? WHITE_OO : BLACK_OO))
185 mlist = generate_castle_moves<KING_SIDE>(pos, mlist, us);
187 if (pos.can_castle(us == WHITE ? WHITE_OOO : BLACK_OOO))
188 mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist, us);
194 // Explicit template instantiations
195 template MoveStack* generate<MV_CAPTURE>(const Position& pos, MoveStack* mlist);
196 template MoveStack* generate<MV_NON_CAPTURE>(const Position& pos, MoveStack* mlist);
197 template MoveStack* generate<MV_NON_EVASION>(const Position& pos, MoveStack* mlist);
200 /// generate_non_capture_checks() generates all pseudo-legal non-captures and knight
201 /// underpromotions that give check. Returns a pointer to the end of the move list.
203 MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist) {
206 assert(!pos.in_check());
210 Color us = pos.side_to_move();
211 Square ksq = pos.king_square(opposite_color(us));
213 assert(pos.piece_on(ksq) == make_piece(opposite_color(us), KING));
215 // Discovered non-capture checks
216 b = dc = pos.discovered_check_candidates();
220 from = pop_1st_bit(&b);
221 switch (piece_type(pos.piece_on(from)))
223 case PAWN: /* Will be generated togheter with pawns direct checks */ break;
224 case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
225 case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
226 case ROOK: mlist = generate_discovered_checks<ROOK>(pos, mlist, from); break;
227 case KING: mlist = generate_discovered_checks<KING>(pos, mlist, from); break;
228 default: assert(false); break;
232 // Direct non-capture checks
233 mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
234 mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
235 mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
236 mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
237 return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
241 /// generate_evasions() generates all pseudo-legal check evasions when
242 /// the side to move is in check. Returns a pointer to the end of the move list.
244 MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
247 assert(pos.in_check());
250 Square from, checksq;
252 Color us = pos.side_to_move();
253 Square ksq = pos.king_square(us);
254 Bitboard checkers = pos.checkers();
255 Bitboard sliderAttacks = EmptyBoardBB;
257 assert(pos.piece_on(ksq) == make_piece(us, KING));
260 // Find squares attacked by slider checkers, we will remove
261 // them from the king evasions set so to early skip known
262 // illegal moves and avoid an useless legality check later.
267 checksq = pop_1st_bit(&b);
269 assert(piece_color(pos.piece_on(checksq)) == opposite_color(us));
271 switch (piece_type(pos.piece_on(checksq)))
273 case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
274 case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
276 // If queen and king are far we can safely remove all the squares attacked
277 // in the other direction becuase are not reachable by the king anyway.
278 if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
279 sliderAttacks |= QueenPseudoAttacks[checksq];
281 // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
282 // use real rook attacks to check if king is safe to move in the other direction.
283 // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
285 sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
292 // Generate evasions for king, capture and non capture moves
293 b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
297 // Generate evasions for other pieces only if not double check
301 // Find squares where a blocking evasion or a capture of the
302 // checker piece is possible.
303 target = squares_between(checksq, ksq) | checkers;
305 mlist = generate_piece_moves<PAWN, MV_EVASION>(pos, mlist, us, target);
306 mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
307 mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
308 mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
309 return generate_piece_moves<QUEEN>(pos, mlist, us, target);
313 /// generate<MV_LEGAL> computes a complete list of legal moves in the current position
316 MoveStack* generate<MV_LEGAL>(const Position& pos, MoveStack* mlist) {
320 MoveStack *last, *cur = mlist;
321 Bitboard pinned = pos.pinned_pieces();
323 last = pos.in_check() ? generate<MV_EVASION>(pos, mlist)
324 : generate<MV_NON_EVASION>(pos, mlist);
326 // Remove illegal moves from the list
328 if (!pos.pl_move_is_legal(cur->move, pinned))
329 cur->move = (--last)->move;
339 template<Square Delta>
340 inline Bitboard move_pawns(Bitboard p) {
342 return Delta == DELTA_N ? p << 8 : Delta == DELTA_S ? p >> 8 :
343 Delta == DELTA_NE ? p << 9 : Delta == DELTA_SE ? p >> 7 :
344 Delta == DELTA_NW ? p << 7 : Delta == DELTA_SW ? p >> 9 : p;
347 template<MoveType Type, Square Delta>
348 inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard target) {
350 const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
355 // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
356 b = move_pawns<Delta>(pawns) & target & ~TFileABB;
357 SERIALIZE_MOVES_D(b, -Delta);
361 template<MoveType Type, Square Delta>
362 inline MoveStack* generate_promotions(const Position& pos, MoveStack* mlist, Bitboard pawnsOn7, Bitboard target) {
364 const Bitboard TFileABB = (Delta == DELTA_NE || Delta == DELTA_SE ? FileABB : FileHBB);
369 // Promotions and under-promotions, both captures and non-captures
370 b = move_pawns<Delta>(pawnsOn7) & target;
372 if (Delta != DELTA_N && Delta != DELTA_S)
377 to = pop_1st_bit(&b);
379 if (Type == MV_CAPTURE || Type == MV_EVASION)
380 (*mlist++).move = make_promotion_move(to - Delta, to, QUEEN);
382 if (Type == MV_NON_CAPTURE || Type == MV_EVASION)
384 (*mlist++).move = make_promotion_move(to - Delta, to, ROOK);
385 (*mlist++).move = make_promotion_move(to - Delta, to, BISHOP);
386 (*mlist++).move = make_promotion_move(to - Delta, to, KNIGHT);
389 // This is the only possible under promotion that can give a check
390 // not already included in the queen-promotion.
391 if ( Type == MV_CHECK
392 && bit_is_set(pos.attacks_from<KNIGHT>(to), pos.king_square(Delta > 0 ? BLACK : WHITE)))
393 (*mlist++).move = make_promotion_move(to - Delta, to, KNIGHT);
394 else (void)pos; // Silence a warning under MSVC
399 template<Color Us, MoveType Type>
400 MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
402 // Calculate our parametrized parameters at compile time, named
403 // according to the point of view of white side.
404 const Color Them = (Us == WHITE ? BLACK : WHITE);
405 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
406 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
407 const Square UP = (Us == WHITE ? DELTA_N : DELTA_S);
408 const Square RIGHT_UP = (Us == WHITE ? DELTA_NE : DELTA_SW);
409 const Square LEFT_UP = (Us == WHITE ? DELTA_NW : DELTA_SE);
412 Bitboard b1, b2, dc1, dc2, pawnPushes, emptySquares;
413 Bitboard pawns = pos.pieces(PAWN, Us);
414 Bitboard pawnsOn7 = pawns & TRank7BB;
415 Bitboard enemyPieces = (Type == MV_CAPTURE ? target : pos.pieces(Them));
417 // Pre-calculate pawn pushes before changing emptySquares definition
418 if (Type != MV_CAPTURE)
420 emptySquares = (Type == MV_NON_CAPTURE ? target : pos.empty_squares());
421 pawnPushes = move_pawns<UP>(pawns & ~TRank7BB) & emptySquares;
424 if (Type == MV_EVASION)
426 emptySquares &= target; // Only blocking squares
427 enemyPieces &= target; // Capture only the checker piece
430 // Promotions and underpromotions
433 if (Type == MV_CAPTURE)
434 emptySquares = pos.empty_squares();
437 mlist = generate_promotions<Type, RIGHT_UP>(pos, mlist, pawnsOn7, enemyPieces);
438 mlist = generate_promotions<Type, LEFT_UP>(pos, mlist, pawnsOn7, enemyPieces);
439 mlist = generate_promotions<Type, UP>(pos, mlist, pawnsOn7, emptySquares);
443 if (Type == MV_CAPTURE || Type == MV_EVASION)
445 mlist = generate_pawn_captures<Type, RIGHT_UP>(mlist, pawns, enemyPieces);
446 mlist = generate_pawn_captures<Type, LEFT_UP>(mlist, pawns, enemyPieces);
449 // Single and double pawn pushes
450 if (Type != MV_CAPTURE)
452 b1 = (Type != MV_EVASION ? pawnPushes : pawnPushes & emptySquares);
453 b2 = move_pawns<UP>(pawnPushes & TRank3BB) & emptySquares;
455 if (Type == MV_CHECK)
457 // Consider only pawn moves which give direct checks
458 b1 &= pos.attacks_from<PAWN>(ksq, Them);
459 b2 &= pos.attacks_from<PAWN>(ksq, Them);
461 // Add pawn moves which gives discovered check. This is possible only
462 // if the pawn is not on the same file as the enemy king, because we
463 // don't generate captures.
464 if (pawns & target) // For CHECK type target is dc bitboard
466 dc1 = move_pawns<UP>(pawns & target & ~file_bb(ksq)) & emptySquares;
467 dc2 = move_pawns<UP>(dc1 & TRank3BB) & emptySquares;
473 SERIALIZE_MOVES_D(b1, -UP);
474 SERIALIZE_MOVES_D(b2, -UP -UP);
477 // En passant captures
478 if ((Type == MV_CAPTURE || Type == MV_EVASION) && pos.ep_square() != SQ_NONE)
480 assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
481 assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
483 // An en passant capture can be an evasion only if the checking piece
484 // is the double pushed pawn and so is in the target. Otherwise this
485 // is a discovery check and we are forced to do otherwise.
486 if (Type == MV_EVASION && !bit_is_set(target, pos.ep_square() - UP))
489 b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
491 assert(b1 != EmptyBoardBB);
495 to = pop_1st_bit(&b1);
496 (*mlist++).move = make_ep_move(to, pos.ep_square());
502 template<CastlingSide Side>
503 MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, Color us) {
505 CastleRight f = CastleRight((Side == KING_SIDE ? WHITE_OO : WHITE_OOO) << us);
506 Color them = opposite_color(us);
508 // After castling, the rook and king's final positions are exactly the same
509 // in Chess960 as they would be in standard chess.
510 Square kfrom = pos.king_square(us);
511 Square rfrom = pos.castle_rook_square(f);
512 Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
513 Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
515 assert(!pos.in_check());
516 assert(pos.piece_on(kfrom) == make_piece(us, KING));
517 assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
519 // Unimpeded rule: All the squares between the king's initial and final squares
520 // (including the final square), and all the squares between the rook's initial
521 // and final squares (including the final square), must be vacant except for
522 // the king and castling rook.
523 for (Square s = Min(kfrom, kto); s <= Max(kfrom, kto); s++)
524 if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
525 ||(pos.attackers_to(s) & pos.pieces(them)))
528 for (Square s = Min(rfrom, rto); s <= Max(rfrom, rto); s++)
529 if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
532 // Because we generate only legal castling moves we need to verify that
533 // when moving the castling rook we do not discover some hidden checker.
534 // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
535 if (pos.is_chess960())
537 Bitboard occ = pos.occupied_squares();
538 clear_bit(&occ, rfrom);
539 if (pos.attackers_to(kto, occ) & pos.pieces(them))
543 (*mlist++).move = make_castle_move(kfrom, rfrom);