2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
5 Stockfish 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 Stockfish 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/>.
19 #ifndef BITBOARD_H_INCLUDED
20 #define BITBOARD_H_INCLUDED
31 bool probe(Square wksq, Square wpsq, Square bksq, Color us);
33 } // namespace Stockfish::Bitbases
38 std::string pretty(Bitboard b);
40 } // namespace Stockfish::Bitboards
42 constexpr Bitboard AllSquares = ~Bitboard(0);
43 constexpr Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
45 constexpr Bitboard FileABB = 0x0101010101010101ULL;
46 constexpr Bitboard FileBBB = FileABB << 1;
47 constexpr Bitboard FileCBB = FileABB << 2;
48 constexpr Bitboard FileDBB = FileABB << 3;
49 constexpr Bitboard FileEBB = FileABB << 4;
50 constexpr Bitboard FileFBB = FileABB << 5;
51 constexpr Bitboard FileGBB = FileABB << 6;
52 constexpr Bitboard FileHBB = FileABB << 7;
54 constexpr Bitboard Rank1BB = 0xFF;
55 constexpr Bitboard Rank2BB = Rank1BB << (8 * 1);
56 constexpr Bitboard Rank3BB = Rank1BB << (8 * 2);
57 constexpr Bitboard Rank4BB = Rank1BB << (8 * 3);
58 constexpr Bitboard Rank5BB = Rank1BB << (8 * 4);
59 constexpr Bitboard Rank6BB = Rank1BB << (8 * 5);
60 constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);
61 constexpr Bitboard Rank8BB = Rank1BB << (8 * 7);
63 constexpr Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
64 constexpr Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
65 constexpr Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
66 constexpr Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
68 constexpr Bitboard KingFlank[FILE_NB] = {
69 QueenSide ^ FileDBB, QueenSide, QueenSide,
70 CenterFiles, CenterFiles,
71 KingSide, KingSide, KingSide ^ FileEBB
74 extern uint8_t PopCnt16[1 << 16];
75 extern uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
77 extern Bitboard SquareBB[SQUARE_NB];
78 extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
79 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
80 extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
81 extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
84 /// Magic holds all magic bitboards relevant data for a single square
91 // Compute the attack's index using the 'magic bitboards' approach
92 unsigned index(Bitboard occupied) const {
95 return unsigned(pext(occupied, mask));
98 return unsigned(((occupied & mask) * magic) >> shift);
100 unsigned lo = unsigned(occupied) & unsigned(mask);
101 unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
102 return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
106 extern Magic RookMagics[SQUARE_NB];
107 extern Magic BishopMagics[SQUARE_NB];
109 inline Bitboard square_bb(Square s) {
115 /// Overloads of bitwise operators between a Bitboard and a Square for testing
116 /// whether a given bit is set in a bitboard, and for setting and clearing bits.
118 inline Bitboard operator&( Bitboard b, Square s) { return b & square_bb(s); }
119 inline Bitboard operator|( Bitboard b, Square s) { return b | square_bb(s); }
120 inline Bitboard operator^( Bitboard b, Square s) { return b ^ square_bb(s); }
121 inline Bitboard& operator|=(Bitboard& b, Square s) { return b |= square_bb(s); }
122 inline Bitboard& operator^=(Bitboard& b, Square s) { return b ^= square_bb(s); }
124 inline Bitboard operator&(Square s, Bitboard b) { return b & s; }
125 inline Bitboard operator|(Square s, Bitboard b) { return b | s; }
126 inline Bitboard operator^(Square s, Bitboard b) { return b ^ s; }
128 inline Bitboard operator|(Square s1, Square s2) { return square_bb(s1) | s2; }
130 constexpr bool more_than_one(Bitboard b) {
135 constexpr bool opposite_colors(Square s1, Square s2) {
136 return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 1;
140 /// rank_bb() and file_bb() return a bitboard representing all the squares on
141 /// the given file or rank.
143 constexpr Bitboard rank_bb(Rank r) {
144 return Rank1BB << (8 * r);
147 constexpr Bitboard rank_bb(Square s) {
148 return rank_bb(rank_of(s));
151 constexpr Bitboard file_bb(File f) {
155 constexpr Bitboard file_bb(Square s) {
156 return file_bb(file_of(s));
160 /// shift() moves a bitboard one or two steps as specified by the direction D
162 template<Direction D>
163 constexpr Bitboard shift(Bitboard b) {
164 return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
165 : D == NORTH+NORTH? b <<16 : D == SOUTH+SOUTH? b >>16
166 : D == EAST ? (b & ~FileHBB) << 1 : D == WEST ? (b & ~FileABB) >> 1
167 : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == NORTH_WEST ? (b & ~FileABB) << 7
168 : D == SOUTH_EAST ? (b & ~FileHBB) >> 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
173 /// pawn_attacks_bb() returns the squares attacked by pawns of the given color
174 /// from the squares in the given bitboard.
177 constexpr Bitboard pawn_attacks_bb(Bitboard b) {
178 return C == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)
179 : shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
182 inline Bitboard pawn_attacks_bb(Color c, Square s) {
185 return PawnAttacks[c][s];
189 /// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the
190 /// given color from the squares in the given bitboard.
193 constexpr Bitboard pawn_double_attacks_bb(Bitboard b) {
194 return C == WHITE ? shift<NORTH_WEST>(b) & shift<NORTH_EAST>(b)
195 : shift<SOUTH_WEST>(b) & shift<SOUTH_EAST>(b);
199 /// adjacent_files_bb() returns a bitboard representing all the squares on the
200 /// adjacent files of a given square.
202 constexpr Bitboard adjacent_files_bb(Square s) {
203 return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
207 /// line_bb() returns a bitboard representing an entire line (from board edge
208 /// to board edge) that intersects the two given squares. If the given squares
209 /// are not on a same file/rank/diagonal, the function returns 0. For instance,
210 /// line_bb(SQ_C4, SQ_F7) will return a bitboard with the A2-G8 diagonal.
212 inline Bitboard line_bb(Square s1, Square s2) {
214 assert(is_ok(s1) && is_ok(s2));
216 return LineBB[s1][s2];
220 /// between_bb(s1, s2) returns a bitboard representing the squares in the semi-open
221 /// segment between the squares s1 and s2 (excluding s1 but including s2). If the
222 /// given squares are not on a same file/rank/diagonal, it returns s2. For instance,
223 /// between_bb(SQ_C4, SQ_F7) will return a bitboard with squares D5, E6 and F7, but
224 /// between_bb(SQ_E6, SQ_F8) will return a bitboard with the square F8. This trick
225 /// allows to generate non-king evasion moves faster: the defending piece must either
226 /// interpose itself to cover the check or capture the checking piece.
228 inline Bitboard between_bb(Square s1, Square s2) {
230 assert(is_ok(s1) && is_ok(s2));
232 return BetweenBB[s1][s2];
236 /// forward_ranks_bb() returns a bitboard representing the squares on the ranks in
237 /// front of the given one, from the point of view of the given color. For instance,
238 /// forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
240 constexpr Bitboard forward_ranks_bb(Color c, Square s) {
241 return c == WHITE ? ~Rank1BB << 8 * relative_rank(WHITE, s)
242 : ~Rank8BB >> 8 * relative_rank(BLACK, s);
246 /// forward_file_bb() returns a bitboard representing all the squares along the
247 /// line in front of the given one, from the point of view of the given color.
249 constexpr Bitboard forward_file_bb(Color c, Square s) {
250 return forward_ranks_bb(c, s) & file_bb(s);
254 /// pawn_attack_span() returns a bitboard representing all the squares that can
255 /// be attacked by a pawn of the given color when it moves along its file, starting
256 /// from the given square.
258 constexpr Bitboard pawn_attack_span(Color c, Square s) {
259 return forward_ranks_bb(c, s) & adjacent_files_bb(s);
263 /// passed_pawn_span() returns a bitboard which can be used to test if a pawn of
264 /// the given color and on the given square is a passed pawn.
266 constexpr Bitboard passed_pawn_span(Color c, Square s) {
267 return pawn_attack_span(c, s) | forward_file_bb(c, s);
271 /// aligned() returns true if the squares s1, s2 and s3 are aligned either on a
272 /// straight or on a diagonal line.
274 inline bool aligned(Square s1, Square s2, Square s3) {
275 return line_bb(s1, s2) & s3;
279 /// distance() functions return the distance between x and y, defined as the
280 /// number of steps for a king in x to reach y.
282 template<typename T1 = Square> inline int distance(Square x, Square y);
283 template<> inline int distance<File>(Square x, Square y) { return std::abs(file_of(x) - file_of(y)); }
284 template<> inline int distance<Rank>(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); }
285 template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
287 inline int edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
288 inline int edge_distance(Rank r) { return std::min(r, Rank(RANK_8 - r)); }
291 /// attacks_bb(Square) returns the pseudo attacks of the give piece type
292 /// assuming an empty board.
294 template<PieceType Pt>
295 inline Bitboard attacks_bb(Square s) {
297 assert((Pt != PAWN) && (is_ok(s)));
299 return PseudoAttacks[Pt][s];
303 /// attacks_bb(Square, Bitboard) returns the attacks by the given piece
304 /// assuming the board is occupied according to the passed Bitboard.
305 /// Sliding piece attacks do not continue passed an occupied square.
307 template<PieceType Pt>
308 inline Bitboard attacks_bb(Square s, Bitboard occupied) {
310 assert((Pt != PAWN) && (is_ok(s)));
314 case BISHOP: return BishopMagics[s].attacks[BishopMagics[s].index(occupied)];
315 case ROOK : return RookMagics[s].attacks[ RookMagics[s].index(occupied)];
316 case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
317 default : return PseudoAttacks[Pt][s];
321 inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
323 assert((pt != PAWN) && (is_ok(s)));
327 case BISHOP: return attacks_bb<BISHOP>(s, occupied);
328 case ROOK : return attacks_bb< ROOK>(s, occupied);
329 case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
330 default : return PseudoAttacks[pt][s];
335 /// popcount() counts the number of non-zero bits in a bitboard
337 inline int popcount(Bitboard b) {
341 union { Bitboard bb; uint16_t u[4]; } v = { b };
342 return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
344 #elif defined(_MSC_VER) || defined(__INTEL_COMPILER)
346 return (int)_mm_popcnt_u64(b);
348 #else // Assumed gcc or compatible compiler
350 return __builtin_popcountll(b);
356 /// lsb() and msb() return the least/most significant bit in a non-zero bitboard
358 #if defined(__GNUC__) // GCC, Clang, ICC
360 inline Square lsb(Bitboard b) {
362 return Square(__builtin_ctzll(b));
365 inline Square msb(Bitboard b) {
367 return Square(63 ^ __builtin_clzll(b));
370 #elif defined(_MSC_VER) // MSVC
372 #ifdef _WIN64 // MSVC, WIN64
374 inline Square lsb(Bitboard b) {
377 _BitScanForward64(&idx, b);
381 inline Square msb(Bitboard b) {
384 _BitScanReverse64(&idx, b);
390 inline Square lsb(Bitboard b) {
394 if (b & 0xffffffff) {
395 _BitScanForward(&idx, int32_t(b));
398 _BitScanForward(&idx, int32_t(b >> 32));
399 return Square(idx + 32);
403 inline Square msb(Bitboard b) {
408 _BitScanReverse(&idx, int32_t(b >> 32));
409 return Square(idx + 32);
411 _BitScanReverse(&idx, int32_t(b));
418 #else // Compiler is neither GCC nor MSVC compatible
420 #error "Compiler not supported."
424 /// least_significant_square_bb() returns the bitboard of the least significant
425 /// square of a non-zero bitboard. It is equivalent to square_bb(lsb(bb)).
427 inline Bitboard least_significant_square_bb(Bitboard b) {
432 /// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
434 inline Square pop_lsb(Bitboard& b) {
436 const Square s = lsb(b);
442 /// frontmost_sq() returns the most advanced square for the given color,
443 /// requires a non-zero bitboard.
444 inline Square frontmost_sq(Color c, Bitboard b) {
446 return c == WHITE ? msb(b) : lsb(b);
449 } // namespace Stockfish
451 #endif // #ifndef BITBOARD_H_INCLUDED