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) 2015-2018 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 const Bitboard AllSquares = ~Bitboard(0);
43 const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
45 const Bitboard FileABB = 0x0101010101010101ULL;
46 const Bitboard FileBBB = FileABB << 1;
47 const Bitboard FileCBB = FileABB << 2;
48 const Bitboard FileDBB = FileABB << 3;
49 const Bitboard FileEBB = FileABB << 4;
50 const Bitboard FileFBB = FileABB << 5;
51 const Bitboard FileGBB = FileABB << 6;
52 const Bitboard FileHBB = FileABB << 7;
54 const Bitboard Rank1BB = 0xFF;
55 const Bitboard Rank2BB = Rank1BB << (8 * 1);
56 const Bitboard Rank3BB = Rank1BB << (8 * 2);
57 const Bitboard Rank4BB = Rank1BB << (8 * 3);
58 const Bitboard Rank5BB = Rank1BB << (8 * 4);
59 const Bitboard Rank6BB = Rank1BB << (8 * 5);
60 const Bitboard Rank7BB = Rank1BB << (8 * 6);
61 const Bitboard Rank8BB = Rank1BB << (8 * 7);
63 extern int SquareDistance[SQUARE_NB][SQUARE_NB];
65 extern Bitboard SquareBB[SQUARE_NB];
66 extern Bitboard FileBB[FILE_NB];
67 extern Bitboard RankBB[RANK_NB];
68 extern Bitboard AdjacentFilesBB[FILE_NB];
69 extern Bitboard ForwardRanksBB[COLOR_NB][RANK_NB];
70 extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
71 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
72 extern Bitboard DistanceRingBB[SQUARE_NB][8];
73 extern Bitboard ForwardFileBB[COLOR_NB][SQUARE_NB];
74 extern Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
75 extern Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
76 extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
77 extern Bitboard PawnAttacks[COLOR_NB][SQUARE_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 return b & SquareBB[s];
113 inline Bitboard operator|(Bitboard b, Square s) {
114 return b | SquareBB[s];
117 inline Bitboard operator^(Bitboard b, Square s) {
118 return b ^ SquareBB[s];
121 inline Bitboard& operator|=(Bitboard& b, Square s) {
122 return b |= SquareBB[s];
125 inline Bitboard& operator^=(Bitboard& b, Square s) {
126 return b ^= SquareBB[s];
129 constexpr bool more_than_one(Bitboard b) {
133 /// rank_bb() and file_bb() return a bitboard representing all the squares on
134 /// the given file or rank.
136 inline Bitboard rank_bb(Rank r) {
140 inline Bitboard rank_bb(Square s) {
141 return RankBB[rank_of(s)];
144 inline Bitboard file_bb(File f) {
148 inline Bitboard file_bb(Square s) {
149 return FileBB[file_of(s)];
153 /// shift() moves a bitboard one step along direction D. Mainly for pawns
155 template<Direction D>
156 constexpr Bitboard shift(Bitboard b) {
157 return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
158 : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == SOUTH_EAST ? (b & ~FileHBB) >> 7
159 : D == NORTH_WEST ? (b & ~FileABB) << 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
164 /// adjacent_files_bb() returns a bitboard representing all the squares on the
165 /// adjacent files of the given one.
167 inline Bitboard adjacent_files_bb(File f) {
168 return AdjacentFilesBB[f];
172 /// between_bb() returns a bitboard representing all the squares between the two
173 /// given ones. For instance, between_bb(SQ_C4, SQ_F7) returns a bitboard with
174 /// the bits for square d5 and e6 set. If s1 and s2 are not on the same rank, file
175 /// or diagonal, 0 is returned.
177 inline Bitboard between_bb(Square s1, Square s2) {
178 return BetweenBB[s1][s2];
182 /// forward_ranks_bb() returns a bitboard representing all the squares on all the ranks
183 /// in front of the given one, from the point of view of the given color. For
184 /// instance, forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
186 inline Bitboard forward_ranks_bb(Color c, Square s) {
187 return ForwardRanksBB[c][rank_of(s)];
191 /// forward_file_bb() returns a bitboard representing all the squares along the line
192 /// in front of the given one, from the point of view of the given color:
193 /// ForwardFileBB[c][s] = forward_ranks_bb(c, s) & file_bb(s)
195 inline Bitboard forward_file_bb(Color c, Square s) {
196 return ForwardFileBB[c][s];
200 /// pawn_attack_span() returns a bitboard representing all the squares that can be
201 /// attacked by a pawn of the given color when it moves along its file, starting
202 /// from the given square:
203 /// PawnAttackSpan[c][s] = forward_ranks_bb(c, s) & adjacent_files_bb(file_of(s));
205 inline Bitboard pawn_attack_span(Color c, Square s) {
206 return PawnAttackSpan[c][s];
210 /// passed_pawn_mask() returns a bitboard mask which can be used to test if a
211 /// pawn of the given color and on the given square is a passed pawn:
212 /// PassedPawnMask[c][s] = pawn_attack_span(c, s) | forward_file_bb(c, s)
214 inline Bitboard passed_pawn_mask(Color c, Square s) {
215 return PassedPawnMask[c][s];
219 /// aligned() returns true if the squares s1, s2 and s3 are aligned either on a
220 /// straight or on a diagonal line.
222 inline bool aligned(Square s1, Square s2, Square s3) {
223 return LineBB[s1][s2] & s3;
227 /// distance() functions return the distance between x and y, defined as the
228 /// number of steps for a king in x to reach y. Works with squares, ranks, files.
230 template<typename T> inline int distance(T x, T y) { return x < y ? y - x : x - y; }
231 template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
233 template<typename T1, typename T2> inline int distance(T2 x, T2 y);
234 template<> inline int distance<File>(Square x, Square y) { return distance(file_of(x), file_of(y)); }
235 template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_of(x), rank_of(y)); }
238 /// attacks_bb() returns a bitboard representing all the squares attacked by a
239 /// piece of type Pt (bishop or rook) placed on 's'.
241 template<PieceType Pt>
242 inline Bitboard attacks_bb(Square s, Bitboard occupied) {
244 const Magic& m = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
245 return m.attacks[m.index(occupied)];
248 inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
254 case BISHOP: return attacks_bb<BISHOP>(s, occupied);
255 case ROOK : return attacks_bb< ROOK>(s, occupied);
256 case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
257 default : return PseudoAttacks[pt][s];
262 /// popcount() counts the number of non-zero bits in a bitboard
264 inline int popcount(Bitboard b) {
268 extern uint8_t PopCnt16[1 << 16];
269 union { Bitboard bb; uint16_t u[4]; } v = { b };
270 return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
272 #elif defined(_MSC_VER) || defined(__INTEL_COMPILER)
274 return (int)_mm_popcnt_u64(b);
276 #else // Assumed gcc or compatible compiler
278 return __builtin_popcountll(b);
284 /// lsb() and msb() return the least/most significant bit in a non-zero bitboard
286 #if defined(__GNUC__)
288 inline Square lsb(Bitboard b) {
290 return Square(__builtin_ctzll(b));
293 inline Square msb(Bitboard b) {
295 return Square(63 ^ __builtin_clzll(b));
298 #elif defined(_WIN64) && defined(_MSC_VER)
300 inline Square lsb(Bitboard b) {
303 _BitScanForward64(&idx, b);
307 inline Square msb(Bitboard b) {
310 _BitScanReverse64(&idx, b);
316 #define NO_BSF // Fallback on software implementation for other cases
318 Square lsb(Bitboard b);
319 Square msb(Bitboard b);
324 /// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
326 inline Square pop_lsb(Bitboard* b) {
327 const Square s = lsb(*b);
333 /// frontmost_sq() and backmost_sq() return the square corresponding to the
334 /// most/least advanced bit relative to the given color.
336 inline Square frontmost_sq(Color c, Bitboard b) { return c == WHITE ? msb(b) : lsb(b); }
337 inline Square backmost_sq(Color c, Bitboard b) { return c == WHITE ? lsb(b) : msb(b); }
339 #endif // #ifndef BITBOARD_H_INCLUDED