2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #if !defined(POSITION_H_INCLUDED)
21 #define POSITION_H_INCLUDED
23 // Disable a silly and noisy warning from MSVC compiler
26 // Forcing value to bool 'true' or 'false' (performance warning)
27 #pragma warning(disable: 4800)
\r
37 #include "direction.h"
49 /// FEN string for the initial position:
50 const std::string StartPosition =
51 "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
53 /// Maximum number of plies per game (220 should be enough, because the
54 /// maximum search depth is 100, and during position setup we reset the
55 /// move counter for every non-reversible move):
56 const int MaxGameLength = 220;
63 /// Castle rights, encoded as bit fields:
67 WHITE_OO = 1, BLACK_OO = 2,
68 WHITE_OOO = 4, BLACK_OOO = 8,
73 /// The UndoInfo struct stores information we need to restore a Position
74 /// object to its previous state when we retract a move. Whenever a move
75 /// is made on the board (by calling Position::do_move), an UndoInfo object
76 /// must be passed as a parameter. When the move is unmade (by calling
77 /// Position::undo_move), the same UndoInfo object must be passed again.
83 Key key, pawnKey, materialKey;
87 Value mgValue, egValue;
91 /// The position data structure. A position consists of the following data:
93 /// * For each piece type, a bitboard representing the squares occupied
94 /// by pieces of that type.
95 /// * For each color, a bitboard representing the squares occupiecd by
96 /// pieces of that color.
97 /// * A bitboard of all occupied squares.
98 /// * A bitboard of all checking pieces.
99 /// * A 64-entry array of pieces, indexed by the squares of the board.
100 /// * The current side to move.
101 /// * Information about the castling rights for both sides.
102 /// * The initial files of the kings and both pairs of rooks. This is
103 /// used to implement the Chess960 castling rules.
104 /// * The en passant square (which is SQ_NONE if no en passant capture is
106 /// * The squares of the kings for both sides.
107 /// * The last move played.
108 /// * Hash keys for the position itself, the current pawn structure, and
109 /// the current material situation.
110 /// * Hash keys for all previous positions in the game (for detecting
111 /// repetition draws.
112 /// * A counter for detecting 50 move rule draws.
116 friend class MaterialInfo;
121 Position(const Position &pos);
122 Position(const std::string &fen);
125 void from_fen(const std::string &fen);
126 const std::string to_fen() const;
130 void copy(const Position &pos);
131 void flipped_copy(const Position &pos);
133 // The piece on a given square
134 Piece piece_on(Square s) const;
135 PieceType type_of_piece_on(Square s) const;
136 Color color_of_piece_on(Square s) const;
137 bool square_is_empty(Square s) const;
138 bool square_is_occupied(Square s) const;
139 Value midgame_value_of_piece_on(Square s) const;
140 Value endgame_value_of_piece_on(Square s) const;
143 Color side_to_move() const;
145 // Bitboard representation of the position
146 Bitboard empty_squares() const;
147 Bitboard occupied_squares() const;
148 Bitboard pieces_of_color(Color c) const;
149 Bitboard pieces_of_type(PieceType pt) const;
150 Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
151 Bitboard pawns() const;
152 Bitboard knights() const;
153 Bitboard bishops() const;
154 Bitboard rooks() const;
155 Bitboard queens() const;
156 Bitboard kings() const;
157 Bitboard rooks_and_queens() const;
158 Bitboard bishops_and_queens() const;
159 Bitboard sliders() const;
160 Bitboard pawns(Color c) const;
161 Bitboard knights(Color c) const;
162 Bitboard bishops(Color c) const;
163 Bitboard rooks(Color c) const;
164 Bitboard queens(Color c) const;
165 Bitboard kings(Color c) const;
166 Bitboard rooks_and_queens(Color c) const;
167 Bitboard bishops_and_queens(Color c) const;
168 Bitboard sliders_of_color(Color c) const;
170 // Number of pieces of each color and type
171 int piece_count(Color c, PieceType pt) const;
172 int pawn_count(Color c) const;
173 int knight_count(Color c) const;
174 int bishop_count(Color c) const;
175 int rook_count(Color c) const;
176 int queen_count(Color c) const;
178 // The en passant square:
179 Square ep_square() const;
181 // Current king position for each color
182 Square king_square(Color c) const;
185 bool can_castle_kingside(Color c) const;
186 bool can_castle_queenside(Color c) const;
187 bool can_castle(Color c) const;
188 Square initial_kr_square(Color c) const;
189 Square initial_qr_square(Color c) const;
192 Bitboard sliding_attacks(Square s, Direction d) const;
193 Bitboard ray_attacks(Square s, SignedDirection d) const;
194 Bitboard pawn_attacks(Color c, Square s) const;
195 Bitboard white_pawn_attacks(Square s) const;
196 Bitboard black_pawn_attacks(Square s) const;
197 Bitboard knight_attacks(Square s) const;
198 Bitboard bishop_attacks(Square s) const;
199 Bitboard rook_attacks(Square s) const;
200 Bitboard queen_attacks(Square s) const;
201 Bitboard king_attacks(Square s) const;
203 // Bitboards for pinned pieces and discovered check candidates
204 Bitboard discovered_check_candidates(Color c) const;
205 Bitboard pinned_pieces(Color c) const;
208 Bitboard checkers() const;
211 Square piece_list(Color c, PieceType pt, int index) const;
212 Square pawn_list(Color c, int index) const;
213 Square knight_list(Color c, int index) const;
214 Square bishop_list(Color c, int index) const;
215 Square rook_list(Color c, int index) const;
216 Square queen_list(Color c, int index) const;
218 // Attack information for a given square
219 bool square_is_attacked(Square s, Color c) const;
220 Bitboard attacks_to(Square s) const;
221 Bitboard attacks_to(Square s, Color c) const;
222 bool is_check() const;
223 bool piece_attacks_square(Square f, Square t) const;
224 bool white_pawn_attacks_square(Square f, Square t) const;
225 bool black_pawn_attacks_square(Square f, Square t) const;
226 bool knight_attacks_square(Square f, Square t) const;
227 bool bishop_attacks_square(Square f, Square t) const;
228 bool rook_attacks_square(Square f, Square t) const;
229 bool queen_attacks_square(Square f, Square t) const;
230 bool king_attacks_square(Square f, Square t) const;
232 // Properties of moves
233 bool move_is_legal(Move m) const;
234 bool move_is_legal(Move m, Bitboard pinned) const;
235 bool move_is_check(Move m) const;
236 bool move_is_check(Move m, Bitboard dcCandidates) const;
237 bool move_is_capture(Move m) const;
238 bool move_is_pawn_push_to_7th(Move m) const;
239 bool move_is_passed_pawn_push(Move m) const;
240 bool move_was_passed_pawn_push(Move m) const;
241 bool move_attacks_square(Move m, Square s) const;
243 // Information about pawns
244 bool pawn_is_passed(Color c, Square s) const;
245 bool pawn_is_isolated(Color c, Square s) const;
246 bool pawn_is_doubled(Color c, Square s) const;
248 // Open and half-open files
249 bool file_is_open(File f) const;
250 bool file_is_half_open(Color c, File f) const;
253 bool square_is_weak(Square s, Color c) const;
255 // Doing and undoing moves
256 void backup(UndoInfo &u) const;
257 void restore(const UndoInfo &u);
258 void do_move(Move m, UndoInfo &u);
259 void do_move(Move m, UndoInfo &u, Bitboard dcCandidates);
260 void undo_move(Move m, const UndoInfo &u);
261 void do_null_move(UndoInfo &u);
262 void undo_null_move(const UndoInfo &u);
264 // Static exchange evaluation
265 int see(Square from, Square to) const;
266 int see(Move m) const;
268 // Accessing hash keys
270 Key get_pawn_key() const;
271 Key get_material_key() const;
273 // Incremental evaluation
274 Value mg_value() const;
275 Value eg_value() const;
276 Value non_pawn_material(Color c) const;
277 Phase game_phase() const;
279 // Game termination checks
281 bool is_draw() const;
283 // Check if one side threatens a mate in one
284 bool has_mate_threat(Color c);
286 // Number of plies since the last non-reversible move
287 int rule_50_counter() const;
289 // Other properties of the position
290 bool opposite_colored_bishops() const;
291 bool has_pawn_on_7th(Color c) const;
293 // Reset the gamePly variable to 0
294 void reset_game_ply();
296 // Position consistency check, for debugging
299 // Static member functions:
300 static void init_zobrist();
301 static void init_piece_square_tables();
304 // Initialization helper functions (used while setting up a position)
306 void put_piece(Piece p, Square s);
307 void allow_oo(Color c);
308 void allow_ooo(Color c);
310 // Helper functions for doing and undoing moves
311 void do_castle_move(Move m);
312 void do_promotion_move(Move m, UndoInfo &u);
313 void do_ep_move(Move m);
314 void undo_castle_move(Move m);
315 void undo_promotion_move(Move m, const UndoInfo &u);
316 void undo_ep_move(Move m);
317 void find_checkers();
319 // Computing hash keys from scratch (for initialization and debugging)
320 Key compute_key() const;
321 Key compute_pawn_key() const;
322 Key compute_material_key() const;
324 // Computing incremental evaluation scores and material counts
325 Value mg_pst(Color c, PieceType pt, Square s) const;
326 Value eg_pst(Color c, PieceType pt, Square s) const;
327 Value compute_mg_value() const;
328 Value compute_eg_value() const;
329 Value compute_non_pawn_material(Color c) const;
332 Bitboard byColorBB[2], byTypeBB[8];
339 int pieceCount[2][8]; // [color][pieceType]
342 Square pieceList[2][8][16]; // [color][pieceType][index]
348 File initialKFile, initialKRFile, initialQRFile;
350 Square kingSquare[2];
352 Key key, pawnKey, materialKey, history[MaxGameLength];
354 Value mgValue, egValue;
358 static int castleRightsMask[64];
359 static Key zobrist[2][8][64];
360 static Key zobEp[64];
361 static Key zobCastle[16];
362 static Key zobMaterial[2][8][16];
363 static Key zobSideToMove;
364 static Value MgPieceSquareTable[16][64];
365 static Value EgPieceSquareTable[16][64];
370 //// Inline functions
373 inline Piece Position::piece_on(Square s) const {
377 inline Color Position::color_of_piece_on(Square s) const {
378 return color_of_piece(this->piece_on(s));
381 inline PieceType Position::type_of_piece_on(Square s) const {
382 return type_of_piece(this->piece_on(s));
385 inline bool Position::square_is_empty(Square s) const {
386 return this->piece_on(s) == EMPTY;
389 inline bool Position::square_is_occupied(Square s) const {
390 return !this->square_is_empty(s);
393 inline Value Position::midgame_value_of_piece_on(Square s) const {
394 return piece_value_midgame(this->piece_on(s));
397 inline Value Position::endgame_value_of_piece_on(Square s) const {
398 return piece_value_endgame(this->piece_on(s));
401 inline Color Position::side_to_move() const {
405 inline Bitboard Position::occupied_squares() const {
409 inline Bitboard Position::empty_squares() const {
410 return ~(this->occupied_squares());
413 inline Bitboard Position::pieces_of_color(Color c) const {
417 inline Bitboard Position::pieces_of_type(PieceType pt) const {
421 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt)
423 return this->pieces_of_color(c) & this->pieces_of_type(pt);
426 inline Bitboard Position::pawns() const {
427 return this->pieces_of_type(PAWN);
430 inline Bitboard Position::knights() const {
431 return this->pieces_of_type(KNIGHT);
434 inline Bitboard Position::bishops() const {
435 return this->pieces_of_type(BISHOP);
438 inline Bitboard Position::rooks() const {
439 return this->pieces_of_type(ROOK);
442 inline Bitboard Position::queens() const {
443 return this->pieces_of_type(QUEEN);
446 inline Bitboard Position::kings() const {
447 return this->pieces_of_type(KING);
450 inline Bitboard Position::rooks_and_queens() const {
451 return this->rooks() | this->queens();
454 inline Bitboard Position::bishops_and_queens() const {
455 return this->bishops() | this->queens();
458 inline Bitboard Position::sliders() const {
459 return this->bishops() | this->queens() | this->rooks();
462 inline Bitboard Position::pawns(Color c) const {
463 return this->pieces_of_color_and_type(c, PAWN);
466 inline Bitboard Position::knights(Color c) const {
467 return this->pieces_of_color_and_type(c, KNIGHT);
470 inline Bitboard Position::bishops(Color c) const {
471 return this->pieces_of_color_and_type(c, BISHOP);
474 inline Bitboard Position::rooks(Color c) const {
475 return this->pieces_of_color_and_type(c, ROOK);
478 inline Bitboard Position::queens(Color c) const {
479 return this->pieces_of_color_and_type(c, QUEEN);
482 inline Bitboard Position::kings(Color c) const {
483 return this->pieces_of_color_and_type(c, KING);
486 inline Bitboard Position::rooks_and_queens(Color c) const {
487 return this->rooks_and_queens() & this->pieces_of_color(c);
490 inline Bitboard Position::bishops_and_queens(Color c) const {
491 return this->bishops_and_queens() & this->pieces_of_color(c);
494 inline Bitboard Position::sliders_of_color(Color c) const {
495 return this->sliders() & this->pieces_of_color(c);
498 inline int Position::piece_count(Color c, PieceType pt) const {
499 return pieceCount[c][pt];
502 inline int Position::pawn_count(Color c) const {
503 return this->piece_count(c, PAWN);
506 inline int Position::knight_count(Color c) const {
507 return this->piece_count(c, KNIGHT);
510 inline int Position::bishop_count(Color c) const {
511 return this->piece_count(c, BISHOP);
514 inline int Position::rook_count(Color c) const {
515 return this->piece_count(c, ROOK);
518 inline int Position::queen_count(Color c) const {
519 return this->piece_count(c, QUEEN);
522 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
523 return pieceList[c][pt][index];
526 inline Square Position::pawn_list(Color c, int index) const {
527 return this->piece_list(c, PAWN, index);
530 inline Square Position::knight_list(Color c, int index) const {
531 return this->piece_list(c, KNIGHT, index);
534 inline Square Position::bishop_list(Color c, int index) const {
535 return this->piece_list(c, BISHOP, index);
538 inline Square Position::rook_list(Color c, int index) const {
539 return this->piece_list(c, ROOK, index);
542 inline Square Position::queen_list(Color c, int index) const {
543 return this->piece_list(c, QUEEN, index);
546 inline Square Position::ep_square() const {
550 inline Square Position::king_square(Color c) const {
551 return kingSquare[c];
554 inline bool Position::can_castle_kingside(Color side) const {
555 return castleRights & (1+int(side));
558 inline bool Position::can_castle_queenside(Color side) const {
559 return castleRights & (4+4*int(side));
562 inline bool Position::can_castle(Color side) const {
563 return can_castle_kingside(side) || can_castle_queenside(side);
566 inline Square Position::initial_kr_square(Color c) const {
567 return relative_square(c, make_square(initialKRFile, RANK_1));
570 inline Square Position::initial_qr_square(Color c) const {
571 return relative_square(c, make_square(initialQRFile, RANK_1));
574 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
575 return StepAttackBB[pawn_of_color(c)][s];
578 inline Bitboard Position::white_pawn_attacks(Square s) const {
579 return this->pawn_attacks(WHITE, s);
582 inline Bitboard Position::black_pawn_attacks(Square s) const {
583 return this->pawn_attacks(BLACK, s);
586 inline Bitboard Position::knight_attacks(Square s) const {
587 return StepAttackBB[KNIGHT][s];
590 inline Bitboard Position::rook_attacks(Square s) const {
591 return rook_attacks_bb(s, this->occupied_squares());
594 inline Bitboard Position::bishop_attacks(Square s) const {
595 return bishop_attacks_bb(s, this->occupied_squares());
598 inline Bitboard Position::queen_attacks(Square s) const {
599 return this->rook_attacks(s) | this->bishop_attacks(s);
602 inline Bitboard Position::king_attacks(Square s) const {
603 return StepAttackBB[KING][s];
606 inline Bitboard Position::checkers() const {
610 inline bool Position::is_check() const {
611 return this->checkers() != EmptyBoardBB;
614 inline bool Position::white_pawn_attacks_square(Square f, Square t) const {
615 return bit_is_set(this->white_pawn_attacks(f), t);
618 inline bool Position::black_pawn_attacks_square(Square f, Square t) const {
619 return bit_is_set(this->black_pawn_attacks(f), t);
622 inline bool Position::knight_attacks_square(Square f, Square t) const {
623 return bit_is_set(this->knight_attacks(f), t);
626 inline bool Position::bishop_attacks_square(Square f, Square t) const {
627 return bit_is_set(this->bishop_attacks(f), t);
630 inline bool Position::rook_attacks_square(Square f, Square t) const {
631 return bit_is_set(this->rook_attacks(f), t);
634 inline bool Position::queen_attacks_square(Square f, Square t) const {
635 return bit_is_set(this->queen_attacks(f), t);
638 inline bool Position::king_attacks_square(Square f, Square t) const {
639 return bit_is_set(this->king_attacks(f), t);
642 inline bool Position::pawn_is_passed(Color c, Square s) const {
643 return !(this->pawns(opposite_color(c)) & passed_pawn_mask(c, s));
646 inline bool Position::pawn_is_isolated(Color c, Square s) const {
647 return !(this->pawns(c) & neighboring_files_bb(s));
650 inline bool Position::pawn_is_doubled(Color c, Square s) const {
651 return this->pawns(c) & squares_behind(c, s);
654 inline bool Position::file_is_open(File f) const {
655 return !(this->pawns() & file_bb(f));
658 inline bool Position::file_is_half_open(Color c, File f) const {
659 return !(this->pawns(c) & file_bb(f));
662 inline bool Position::square_is_weak(Square s, Color c) const {
663 return !(this->pawns(c) & outpost_mask(opposite_color(c), s));
666 inline Key Position::get_key() const {
670 inline Key Position::get_pawn_key() const {
674 inline Key Position::get_material_key() const {
678 inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
679 return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
682 inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
683 return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
686 inline Value Position::mg_value() const {
690 inline Value Position::eg_value() const {
694 inline Value Position::non_pawn_material(Color c) const {
695 return npMaterial[c];
698 inline Phase Position::game_phase() const {
700 // The purpose of the Value(325) terms below is to make sure the difference
701 // between MidgameLimit and EndgameLimit is a power of 2, which should make
702 // the division at the end of the function a bit faster.
704 static const Value MidgameLimit =
705 2*QueenValueMidgame+2*RookValueMidgame+6*BishopValueMidgame+Value(325);
706 static const Value EndgameLimit = 4*RookValueMidgame-Value(325);
707 Value npm = this->non_pawn_material(WHITE) + this->non_pawn_material(BLACK);
709 if(npm >= MidgameLimit)
710 return PHASE_MIDGAME;
711 else if(npm <= EndgameLimit)
712 return PHASE_ENDGAME;
714 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
717 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
718 Color c = this->side_to_move();
720 this->piece_on(move_from(m)) == pawn_of_color(c) &&
721 pawn_rank(c, move_to(m)) == RANK_7;
724 inline bool Position::move_is_passed_pawn_push(Move m) const {
725 Color c = this->side_to_move();
727 this->piece_on(move_from(m)) == pawn_of_color(c) &&
728 this->pawn_is_passed(c, move_to(m));
731 inline bool Position::move_was_passed_pawn_push(Move m) const {
732 Color c = opposite_color(this->side_to_move());
734 this->piece_on(move_to(m)) == pawn_of_color(c) &&
735 this->pawn_is_passed(c, move_to(m));
738 inline int Position::rule_50_counter() const {
742 inline bool Position::opposite_colored_bishops() const {
744 this->bishop_count(WHITE) == 1 && this->bishop_count(BLACK) == 1 &&
745 square_color(this->bishop_list(WHITE, 0)) !=
746 square_color(this->bishop_list(BLACK, 0));
749 inline bool Position::has_pawn_on_7th(Color c) const {
750 return this->pawns(c) & relative_rank_bb(c, RANK_7);
754 #endif // !defined(POSITION_H_INCLUDED)