File: position.h

package info (click to toggle)
stockfish 12-2
  • links: PTS
  • area: main
  • in suites: bullseye, sid
  • size: 21,436 kB
  • sloc: cpp: 9,020; makefile: 740; ansic: 199; sh: 193
file content (447 lines) | stat: -rw-r--r-- 12,873 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)

  Stockfish is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef POSITION_H_INCLUDED
#define POSITION_H_INCLUDED

#include <cassert>
#include <deque>
#include <memory> // For std::unique_ptr
#include <string>

#include "bitboard.h"
#include "evaluate.h"
#include "types.h"

#include "nnue/nnue_accumulator.h"


/// StateInfo struct stores information needed to restore a Position object to
/// its previous state when we retract a move. Whenever a move is made on the
/// board (by calling Position::do_move), a StateInfo object must be passed.

struct StateInfo {

  // Copied when making a move
  Key    pawnKey;
  Key    materialKey;
  Value  nonPawnMaterial[COLOR_NB];
  int    castlingRights;
  int    rule50;
  int    pliesFromNull;
  Square epSquare;

  // Not copied when making a move (will be recomputed anyhow)
  Key        key;
  Bitboard   checkersBB;
  Piece      capturedPiece;
  StateInfo* previous;
  Bitboard   blockersForKing[COLOR_NB];
  Bitboard   pinners[COLOR_NB];
  Bitboard   checkSquares[PIECE_TYPE_NB];
  int        repetition;

  // Used by NNUE
  Eval::NNUE::Accumulator accumulator;
  DirtyPiece dirtyPiece;
};


/// A list to keep track of the position states along the setup moves (from the
/// start position to the position just before the search starts). Needed by
/// 'draw by repetition' detection. Use a std::deque because pointers to
/// elements are not invalidated upon list resizing.
typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;


/// Position class stores information regarding the board representation as
/// pieces, side to move, hash keys, castling info, etc. Important methods are
/// do_move() and undo_move(), used by the search to update node info when
/// traversing the search tree.
class Thread;

class Position {
public:
  static void init();

  Position() = default;
  Position(const Position&) = delete;
  Position& operator=(const Position&) = delete;

  // FEN string input/output
  Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
  Position& set(const std::string& code, Color c, StateInfo* si);
  const std::string fen() const;

  // Position representation
  Bitboard pieces(PieceType pt) const;
  Bitboard pieces(PieceType pt1, PieceType pt2) const;
  Bitboard pieces(Color c) const;
  Bitboard pieces(Color c, PieceType pt) const;
  Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
  Piece piece_on(Square s) const;
  Square ep_square() const;
  bool empty(Square s) const;
  template<PieceType Pt> int count(Color c) const;
  template<PieceType Pt> int count() const;
  template<PieceType Pt> const Square* squares(Color c) const;
  template<PieceType Pt> Square square(Color c) const;
  bool is_on_semiopen_file(Color c, Square s) const;

  // Castling
  CastlingRights castling_rights(Color c) const;
  bool can_castle(CastlingRights cr) const;
  bool castling_impeded(CastlingRights cr) const;
  Square castling_rook_square(CastlingRights cr) const;

  // Checking
  Bitboard checkers() const;
  Bitboard blockers_for_king(Color c) const;
  Bitboard check_squares(PieceType pt) const;
  Bitboard pinners(Color c) const;
  bool is_discovery_check_on_king(Color c, Move m) const;

  // Attacks to/from a given square
  Bitboard attackers_to(Square s) const;
  Bitboard attackers_to(Square s, Bitboard occupied) const;
  Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;

  // Properties of moves
  bool legal(Move m) const;
  bool pseudo_legal(const Move m) const;
  bool capture(Move m) const;
  bool capture_or_promotion(Move m) const;
  bool gives_check(Move m) const;
  bool advanced_pawn_push(Move m) const;
  Piece moved_piece(Move m) const;
  Piece captured_piece() const;

  // Piece specific
  bool pawn_passed(Color c, Square s) const;
  bool opposite_bishops() const;
  int  pawns_on_same_color_squares(Color c, Square s) const;

  // Doing and undoing moves
  void do_move(Move m, StateInfo& newSt);
  void do_move(Move m, StateInfo& newSt, bool givesCheck);
  void undo_move(Move m);
  void do_null_move(StateInfo& newSt);
  void undo_null_move();

  // Static Exchange Evaluation
  bool see_ge(Move m, Value threshold = VALUE_ZERO) const;

  // Accessing hash keys
  Key key() const;
  Key key_after(Move m) const;
  Key material_key() const;
  Key pawn_key() const;

  // Other properties of the position
  Color side_to_move() const;
  int game_ply() const;
  bool is_chess960() const;
  Thread* this_thread() const;
  bool is_draw(int ply) const;
  bool has_game_cycle(int ply) const;
  bool has_repeated() const;
  int rule50_count() const;
  Score psq_score() const;
  Value non_pawn_material(Color c) const;
  Value non_pawn_material() const;

  // Position consistency check, for debugging
  bool pos_is_ok() const;
  void flip();

  // Used by NNUE
  StateInfo* state() const;

private:
  // Initialization helpers (used while setting up a position)
  void set_castling_right(Color c, Square rfrom);
  void set_state(StateInfo* si) const;
  void set_check_info(StateInfo* si) const;

  // Other helpers
  void put_piece(Piece pc, Square s);
  void remove_piece(Square s);
  void move_piece(Square from, Square to);
  template<bool Do>
  void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);

  // Data members
  Piece board[SQUARE_NB];
  Bitboard byTypeBB[PIECE_TYPE_NB];
  Bitboard byColorBB[COLOR_NB];
  int pieceCount[PIECE_NB];
  Square pieceList[PIECE_NB][16];
  int index[SQUARE_NB];
  int castlingRightsMask[SQUARE_NB];
  Square castlingRookSquare[CASTLING_RIGHT_NB];
  Bitboard castlingPath[CASTLING_RIGHT_NB];
  int gamePly;
  Color sideToMove;
  Score psq;
  Thread* thisThread;
  StateInfo* st;
  bool chess960;
};

namespace PSQT {
  extern Score psq[PIECE_NB][SQUARE_NB];
}

extern std::ostream& operator<<(std::ostream& os, const Position& pos);

inline Color Position::side_to_move() const {
  return sideToMove;
}

inline Piece Position::piece_on(Square s) const {
  assert(is_ok(s));
  return board[s];
}

inline bool Position::empty(Square s) const {
  return piece_on(s) == NO_PIECE;
}

inline Piece Position::moved_piece(Move m) const {
  return piece_on(from_sq(m));
}

inline Bitboard Position::pieces(PieceType pt = ALL_PIECES) const {
  return byTypeBB[pt];
}

inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
  return pieces(pt1) | pieces(pt2);
}

inline Bitboard Position::pieces(Color c) const {
  return byColorBB[c];
}

inline Bitboard Position::pieces(Color c, PieceType pt) const {
  return pieces(c) & pieces(pt);
}

inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
  return pieces(c) & (pieces(pt1) | pieces(pt2));
}

template<PieceType Pt> inline int Position::count(Color c) const {
  return pieceCount[make_piece(c, Pt)];
}

template<PieceType Pt> inline int Position::count() const {
  return count<Pt>(WHITE) + count<Pt>(BLACK);
}

template<PieceType Pt> inline const Square* Position::squares(Color c) const {
  return pieceList[make_piece(c, Pt)];
}

template<PieceType Pt> inline Square Position::square(Color c) const {
  assert(pieceCount[make_piece(c, Pt)] == 1);
  return squares<Pt>(c)[0];
}

inline Square Position::ep_square() const {
  return st->epSquare;
}

inline bool Position::is_on_semiopen_file(Color c, Square s) const {
  return !(pieces(c, PAWN) & file_bb(s));
}

inline bool Position::can_castle(CastlingRights cr) const {
  return st->castlingRights & cr;
}

inline CastlingRights Position::castling_rights(Color c) const {
  return c & CastlingRights(st->castlingRights);
}

inline bool Position::castling_impeded(CastlingRights cr) const {
  assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);

  return pieces() & castlingPath[cr];
}

inline Square Position::castling_rook_square(CastlingRights cr) const {
  assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);

  return castlingRookSquare[cr];
}

inline Bitboard Position::attackers_to(Square s) const {
  return attackers_to(s, pieces());
}

inline Bitboard Position::checkers() const {
  return st->checkersBB;
}

inline Bitboard Position::blockers_for_king(Color c) const {
  return st->blockersForKing[c];
}

inline Bitboard Position::pinners(Color c) const {
  return st->pinners[c];
}

inline Bitboard Position::check_squares(PieceType pt) const {
  return st->checkSquares[pt];
}

inline bool Position::is_discovery_check_on_king(Color c, Move m) const {
  return st->blockersForKing[c] & from_sq(m);
}

inline bool Position::pawn_passed(Color c, Square s) const {
  return !(pieces(~c, PAWN) & passed_pawn_span(c, s));
}

inline bool Position::advanced_pawn_push(Move m) const {
  return   type_of(moved_piece(m)) == PAWN
        && relative_rank(sideToMove, to_sq(m)) > RANK_5;
}

inline int Position::pawns_on_same_color_squares(Color c, Square s) const {
  return popcount(pieces(c, PAWN) & ((DarkSquares & s) ? DarkSquares : ~DarkSquares));
}

inline Key Position::key() const {
  return st->key;
}

inline Key Position::pawn_key() const {
  return st->pawnKey;
}

inline Key Position::material_key() const {
  return st->materialKey;
}

inline Score Position::psq_score() const {
  return psq;
}

inline Value Position::non_pawn_material(Color c) const {
  return st->nonPawnMaterial[c];
}

inline Value Position::non_pawn_material() const {
  return non_pawn_material(WHITE) + non_pawn_material(BLACK);
}

inline int Position::game_ply() const {
  return gamePly;
}

inline int Position::rule50_count() const {
  return st->rule50;
}

inline bool Position::opposite_bishops() const {
  return   count<BISHOP>(WHITE) == 1
        && count<BISHOP>(BLACK) == 1
        && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
}

inline bool Position::is_chess960() const {
  return chess960;
}

inline bool Position::capture_or_promotion(Move m) const {
  assert(is_ok(m));
  return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
}

inline bool Position::capture(Move m) const {
  assert(is_ok(m));
  // Castling is encoded as "king captures rook"
  return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
}

inline Piece Position::captured_piece() const {
  return st->capturedPiece;
}

inline Thread* Position::this_thread() const {
  return thisThread;
}

inline void Position::put_piece(Piece pc, Square s) {

  board[s] = pc;
  byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
  byColorBB[color_of(pc)] |= s;
  index[s] = pieceCount[pc]++;
  pieceList[pc][index[s]] = s;
  pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
  psq += PSQT::psq[pc][s];
}

inline void Position::remove_piece(Square s) {

  // WARNING: This is not a reversible operation. If we remove a piece in
  // do_move() and then replace it in undo_move() we will put it at the end of
  // the list and not in its original place, it means index[] and pieceList[]
  // are not invariant to a do_move() + undo_move() sequence.
  Piece pc = board[s];
  byTypeBB[ALL_PIECES] ^= s;
  byTypeBB[type_of(pc)] ^= s;
  byColorBB[color_of(pc)] ^= s;
  /* board[s] = NO_PIECE;  Not needed, overwritten by the capturing one */
  Square lastSquare = pieceList[pc][--pieceCount[pc]];
  index[lastSquare] = index[s];
  pieceList[pc][index[lastSquare]] = lastSquare;
  pieceList[pc][pieceCount[pc]] = SQ_NONE;
  pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
  psq -= PSQT::psq[pc][s];
}

inline void Position::move_piece(Square from, Square to) {

  // index[from] is not updated and becomes stale. This works as long as index[]
  // is accessed just by known occupied squares.
  Piece pc = board[from];
  Bitboard fromTo = from | to;
  byTypeBB[ALL_PIECES] ^= fromTo;
  byTypeBB[type_of(pc)] ^= fromTo;
  byColorBB[color_of(pc)] ^= fromTo;
  board[from] = NO_PIECE;
  board[to] = pc;
  index[to] = index[from];
  pieceList[pc][index[to]] = to;
  psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
}

inline void Position::do_move(Move m, StateInfo& newSt) {
  do_move(m, newSt, gives_check(m));
}

inline StateInfo* Position::state() const {

  return st;
}

#endif // #ifndef POSITION_H_INCLUDED