2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #ifndef BITBOARD_H_INCLUDED
22 #define BITBOARD_H_INCLUDED
31 bool probe(Square wksq, Square wpsq, Square bksq, Color us);
38 const std::string pretty(Bitboard b);
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 extern uint8_t PopCnt16[1 << 16];
69 extern uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
71 extern Bitboard SquareBB[SQUARE_NB];
72 extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
73 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
74 extern Bitboard DistanceRingBB[SQUARE_NB][8];
75 extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
76 extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
77 extern Bitboard KingFlank[FILE_NB];
80 /// Magic holds all magic bitboards relevant data for a single square
87 // Compute the attack's index using the 'magic bitboards' approach
88 unsigned index(Bitboard occupied) const {
91 return unsigned(pext(occupied, mask));
94 return unsigned(((occupied & mask) * magic) >> shift);
96 unsigned lo = unsigned(occupied) & unsigned(mask);
97 unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
98 return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
102 extern Magic RookMagics[SQUARE_NB];
103 extern Magic BishopMagics[SQUARE_NB];
106 /// Overloads of bitwise operators between a Bitboard and a Square for testing
107 /// whether a given bit is set in a bitboard, and for setting and clearing bits.
109 inline Bitboard operator&(Bitboard b, Square s) {
110 assert(s >= SQ_A1 && s <= SQ_H8);
111 return b & SquareBB[s];
114 inline Bitboard operator|(Bitboard b, Square s) {
115 assert(s >= SQ_A1 && s <= SQ_H8);
116 return b | SquareBB[s];
119 inline Bitboard operator^(Bitboard b, Square s) {
120 assert(s >= SQ_A1 && s <= SQ_H8);
121 return b ^ SquareBB[s];
124 inline Bitboard& operator|=(Bitboard& b, Square s) {
125 assert(s >= SQ_A1 && s <= SQ_H8);
126 return b |= SquareBB[s];
129 inline Bitboard& operator^=(Bitboard& b, Square s) {
130 assert(s >= SQ_A1 && s <= SQ_H8);
131 return b ^= SquareBB[s];
134 constexpr bool more_than_one(Bitboard b) {
138 inline bool opposite_colors(Square s1, Square s2) {
139 return bool(DarkSquares & s1) != bool(DarkSquares & s2);
143 /// rank_bb() and file_bb() return a bitboard representing all the squares on
144 /// the given file or rank.
146 inline Bitboard rank_bb(Rank r) {
147 return Rank1BB << (8 * r);
150 inline Bitboard rank_bb(Square s) {
151 return rank_bb(rank_of(s));
154 inline Bitboard file_bb(File f) {
158 inline Bitboard file_bb(Square s) {
159 return file_bb(file_of(s));
163 /// shift() moves a bitboard one step along direction D
165 template<Direction D>
166 constexpr Bitboard shift(Bitboard b) {
167 return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
168 : D == EAST ? (b & ~FileHBB) << 1 : D == WEST ? (b & ~FileABB) >> 1
169 : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == NORTH_WEST ? (b & ~FileABB) << 7
170 : D == SOUTH_EAST ? (b & ~FileHBB) >> 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
175 /// pawn_attacks_bb() returns the squares attacked by pawns of the given color
176 /// from the squares in the given bitboard.
179 constexpr Bitboard pawn_attacks_bb(Bitboard b) {
180 return C == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)
181 : shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
185 /// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the
186 /// given color from the squares in the given bitboard.
189 constexpr Bitboard pawn_double_attacks_bb(Bitboard b) {
190 return C == WHITE ? shift<NORTH_WEST>(b) & shift<NORTH_EAST>(b)
191 : shift<SOUTH_WEST>(b) & shift<SOUTH_EAST>(b);
195 /// adjacent_files_bb() returns a bitboard representing all the squares on the
196 /// adjacent files of the given one.
198 inline Bitboard adjacent_files_bb(File f) {
199 return shift<EAST>(file_bb(f)) | shift<WEST>(file_bb(f));
203 /// between_bb() returns a bitboard representing all the squares between the two
204 /// given ones. For instance, between_bb(SQ_C4, SQ_F7) returns a bitboard with
205 /// the bits for square d5 and e6 set. If s1 and s2 are not on the same rank,
206 /// file or diagonal, 0 is returned.
208 inline Bitboard between_bb(Square s1, Square s2) {
209 return BetweenBB[s1][s2];
213 /// forward_ranks_bb() returns a bitboard representing the squares on the ranks
214 /// in front of the given one, from the point of view of the given color. For instance,
215 /// forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
217 inline Bitboard forward_ranks_bb(Color c, Square s) {
218 return c == WHITE ? ~Rank1BB << 8 * (rank_of(s) - RANK_1)
219 : ~Rank8BB >> 8 * (RANK_8 - rank_of(s));
223 /// forward_file_bb() returns a bitboard representing all the squares along the
224 /// line in front of the given one, from the point of view of the given color.
226 inline Bitboard forward_file_bb(Color c, Square s) {
227 return forward_ranks_bb(c, s) & file_bb(s);
231 /// pawn_attack_span() returns a bitboard representing all the squares that can
232 /// be attacked by a pawn of the given color when it moves along its file,
233 /// starting from the given square.
235 inline Bitboard pawn_attack_span(Color c, Square s) {
236 return forward_ranks_bb(c, s) & adjacent_files_bb(file_of(s));
240 /// passed_pawn_span() returns a bitboard which can be used to test if a pawn of
241 /// the given color and on the given square is a passed pawn.
243 inline Bitboard passed_pawn_span(Color c, Square s) {
244 return forward_ranks_bb(c, s) & (adjacent_files_bb(file_of(s)) | file_bb(s));
248 /// aligned() returns true if the squares s1, s2 and s3 are aligned either on a
249 /// straight or on a diagonal line.
251 inline bool aligned(Square s1, Square s2, Square s3) {
252 return LineBB[s1][s2] & s3;
256 /// distance() functions return the distance between x and y, defined as the
257 /// number of steps for a king in x to reach y. Works with squares, ranks, files.
259 template<typename T> inline int distance(T x, T y) { return std::abs(x - y); }
260 template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
262 template<typename T1, typename T2> inline int distance(T2 x, T2 y);
263 template<> inline int distance<File>(Square x, Square y) { return distance(file_of(x), file_of(y)); }
264 template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_of(x), rank_of(y)); }
267 /// attacks_bb() returns a bitboard representing all the squares attacked by a
268 /// piece of type Pt (bishop or rook) placed on 's'.
270 template<PieceType Pt>
271 inline Bitboard attacks_bb(Square s, Bitboard occupied) {
273 const Magic& m = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
274 return m.attacks[m.index(occupied)];
277 inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
283 case BISHOP: return attacks_bb<BISHOP>(s, occupied);
284 case ROOK : return attacks_bb< ROOK>(s, occupied);
285 case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
286 default : return PseudoAttacks[pt][s];
291 /// popcount() counts the number of non-zero bits in a bitboard
293 inline int popcount(Bitboard b) {
297 union { Bitboard bb; uint16_t u[4]; } v = { b };
298 return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
300 #elif defined(_MSC_VER) || defined(__INTEL_COMPILER)
302 return (int)_mm_popcnt_u64(b);
304 #else // Assumed gcc or compatible compiler
306 return __builtin_popcountll(b);
312 /// lsb() and msb() return the least/most significant bit in a non-zero bitboard
314 #if defined(__GNUC__) // GCC, Clang, ICC
316 inline Square lsb(Bitboard b) {
318 return Square(__builtin_ctzll(b));
321 inline Square msb(Bitboard b) {
323 return Square(63 ^ __builtin_clzll(b));
326 #elif defined(_MSC_VER) // MSVC
328 #ifdef _WIN64 // MSVC, WIN64
330 inline Square lsb(Bitboard b) {
333 _BitScanForward64(&idx, b);
337 inline Square msb(Bitboard b) {
340 _BitScanReverse64(&idx, b);
346 inline Square lsb(Bitboard b) {
350 if (b & 0xffffffff) {
351 _BitScanForward(&idx, int32_t(b));
354 _BitScanForward(&idx, int32_t(b >> 32));
355 return Square(idx + 32);
359 inline Square msb(Bitboard b) {
364 _BitScanReverse(&idx, int32_t(b >> 32));
365 return Square(idx + 32);
367 _BitScanReverse(&idx, int32_t(b));
374 #else // Compiler is neither GCC nor MSVC compatible
376 #error "Compiler not supported."
381 /// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
383 inline Square pop_lsb(Bitboard* b) {
384 const Square s = lsb(*b);
390 /// frontmost_sq() and backmost_sq() return the square corresponding to the
391 /// most/least advanced bit relative to the given color.
393 inline Square frontmost_sq(Color c, Bitboard b) { return c == WHITE ? msb(b) : lsb(b); }
394 inline Square backmost_sq(Color c, Bitboard b) { return c == WHITE ? lsb(b) : msb(b); }
396 #endif // #ifndef BITBOARD_H_INCLUDED