/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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 BITBOARD_H_INCLUDED
#define BITBOARD_H_INCLUDED
#include <string>
#include "types.h"
namespace Bitbases {
void init();
bool probe(Square wksq, Square wpsq, Square bksq, Color us);
}
namespace Bitboards {
void init();
const std::string pretty(Bitboard b);
}
const Bitboard AllSquares = ~Bitboard(0);
const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
const Bitboard FileABB = 0x0101010101010101ULL;
const Bitboard FileBBB = FileABB << 1;
const Bitboard FileCBB = FileABB << 2;
const Bitboard FileDBB = FileABB << 3;
const Bitboard FileEBB = FileABB << 4;
const Bitboard FileFBB = FileABB << 5;
const Bitboard FileGBB = FileABB << 6;
const Bitboard FileHBB = FileABB << 7;
const Bitboard Rank1BB = 0xFF;
const Bitboard Rank2BB = Rank1BB << (8 * 1);
const Bitboard Rank3BB = Rank1BB << (8 * 2);
const Bitboard Rank4BB = Rank1BB << (8 * 3);
const Bitboard Rank5BB = Rank1BB << (8 * 4);
const Bitboard Rank6BB = Rank1BB << (8 * 5);
const Bitboard Rank7BB = Rank1BB << (8 * 6);
const Bitboard Rank8BB = Rank1BB << (8 * 7);
extern int SquareDistance[SQUARE_NB][SQUARE_NB];
extern Bitboard SquareBB[SQUARE_NB];
extern Bitboard FileBB[FILE_NB];
extern Bitboard RankBB[RANK_NB];
extern Bitboard AdjacentFilesBB[FILE_NB];
extern Bitboard ForwardRanksBB[COLOR_NB][RANK_NB];
extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
extern Bitboard DistanceRingBB[SQUARE_NB][8];
extern Bitboard ForwardFileBB[COLOR_NB][SQUARE_NB];
extern Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
extern Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
/// Magic holds all magic bitboards relevant data for a single square
struct Magic {
Bitboard mask;
Bitboard magic;
Bitboard* attacks;
unsigned shift;
// Compute the attack's index using the 'magic bitboards' approach
unsigned index(Bitboard occupied) const {
if (HasPext)
return unsigned(pext(occupied, mask));
if (Is64Bit)
return unsigned(((occupied & mask) * magic) >> shift);
unsigned lo = unsigned(occupied) & unsigned(mask);
unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
}
};
extern Magic RookMagics[SQUARE_NB];
extern Magic BishopMagics[SQUARE_NB];
/// Overloads of bitwise operators between a Bitboard and a Square for testing
/// whether a given bit is set in a bitboard, and for setting and clearing bits.
inline Bitboard operator&(Bitboard b, Square s) {
return b & SquareBB[s];
}
inline Bitboard operator|(Bitboard b, Square s) {
return b | SquareBB[s];
}
inline Bitboard operator^(Bitboard b, Square s) {
return b ^ SquareBB[s];
}
inline Bitboard& operator|=(Bitboard& b, Square s) {
return b |= SquareBB[s];
}
inline Bitboard& operator^=(Bitboard& b, Square s) {
return b ^= SquareBB[s];
}
constexpr bool more_than_one(Bitboard b) {
return b & (b - 1);
}
/// rank_bb() and file_bb() return a bitboard representing all the squares on
/// the given file or rank.
inline Bitboard rank_bb(Rank r) {
return RankBB[r];
}
inline Bitboard rank_bb(Square s) {
return RankBB[rank_of(s)];
}
inline Bitboard file_bb(File f) {
return FileBB[f];
}
inline Bitboard file_bb(Square s) {
return FileBB[file_of(s)];
}
/// shift() moves a bitboard one step along direction D. Mainly for pawns
template<Direction D>
constexpr Bitboard shift(Bitboard b) {
return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
: D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == SOUTH_EAST ? (b & ~FileHBB) >> 7
: D == NORTH_WEST ? (b & ~FileABB) << 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
: 0;
}
/// adjacent_files_bb() returns a bitboard representing all the squares on the
/// adjacent files of the given one.
inline Bitboard adjacent_files_bb(File f) {
return AdjacentFilesBB[f];
}
/// between_bb() returns a bitboard representing all the squares between the two
/// given ones. For instance, between_bb(SQ_C4, SQ_F7) returns a bitboard with
/// the bits for square d5 and e6 set. If s1 and s2 are not on the same rank, file
/// or diagonal, 0 is returned.
inline Bitboard between_bb(Square s1, Square s2) {
return BetweenBB[s1][s2];
}
/// forward_ranks_bb() returns a bitboard representing all the squares on all the ranks
/// in front of the given one, from the point of view of the given color. For
/// instance, forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
inline Bitboard forward_ranks_bb(Color c, Square s) {
return ForwardRanksBB[c][rank_of(s)];
}
/// forward_file_bb() returns a bitboard representing all the squares along the line
/// in front of the given one, from the point of view of the given color:
/// ForwardFileBB[c][s] = forward_ranks_bb(c, s) & file_bb(s)
inline Bitboard forward_file_bb(Color c, Square s) {
return ForwardFileBB[c][s];
}
/// pawn_attack_span() returns a bitboard representing all the squares that can be
/// attacked by a pawn of the given color when it moves along its file, starting
/// from the given square:
/// PawnAttackSpan[c][s] = forward_ranks_bb(c, s) & adjacent_files_bb(file_of(s));
inline Bitboard pawn_attack_span(Color c, Square s) {
return PawnAttackSpan[c][s];
}
/// passed_pawn_mask() returns a bitboard mask which can be used to test if a
/// pawn of the given color and on the given square is a passed pawn:
/// PassedPawnMask[c][s] = pawn_attack_span(c, s) | forward_file_bb(c, s)
inline Bitboard passed_pawn_mask(Color c, Square s) {
return PassedPawnMask[c][s];
}
/// aligned() returns true if the squares s1, s2 and s3 are aligned either on a
/// straight or on a diagonal line.
inline bool aligned(Square s1, Square s2, Square s3) {
return LineBB[s1][s2] & s3;
}
/// distance() functions return the distance between x and y, defined as the
/// number of steps for a king in x to reach y. Works with squares, ranks, files.
template<typename T> inline int distance(T x, T y) { return x < y ? y - x : x - y; }
template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
template<typename T1, typename T2> inline int distance(T2 x, T2 y);
template<> inline int distance<File>(Square x, Square y) { return distance(file_of(x), file_of(y)); }
template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_of(x), rank_of(y)); }
/// attacks_bb() returns a bitboard representing all the squares attacked by a
/// piece of type Pt (bishop or rook) placed on 's'.
template<PieceType Pt>
inline Bitboard attacks_bb(Square s, Bitboard occupied) {
const Magic& m = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
return m.attacks[m.index(occupied)];
}
inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
assert(pt != PAWN);
switch (pt)
{
case BISHOP: return attacks_bb<BISHOP>(s, occupied);
case ROOK : return attacks_bb< ROOK>(s, occupied);
case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
default : return PseudoAttacks[pt][s];
}
}
/// popcount() counts the number of non-zero bits in a bitboard
inline int popcount(Bitboard b) {
#ifndef USE_POPCNT
extern uint8_t PopCnt16[1 << 16];
union { Bitboard bb; uint16_t u[4]; } v = { b };
return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
#elif defined(_MSC_VER) || defined(__INTEL_COMPILER)
return (int)_mm_popcnt_u64(b);
#else // Assumed gcc or compatible compiler
return __builtin_popcountll(b);
#endif
}
/// lsb() and msb() return the least/most significant bit in a non-zero bitboard
#if defined(__GNUC__)
inline Square lsb(Bitboard b) {
assert(b);
return Square(__builtin_ctzll(b));
}
inline Square msb(Bitboard b) {
assert(b);
return Square(63 ^ __builtin_clzll(b));
}
#elif defined(_WIN64) && defined(_MSC_VER)
inline Square lsb(Bitboard b) {
assert(b);
unsigned long idx;
_BitScanForward64(&idx, b);
return (Square) idx;
}
inline Square msb(Bitboard b) {
assert(b);
unsigned long idx;
_BitScanReverse64(&idx, b);
return (Square) idx;
}
#else
#define NO_BSF // Fallback on software implementation for other cases
Square lsb(Bitboard b);
Square msb(Bitboard b);
#endif
/// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
inline Square pop_lsb(Bitboard* b) {
const Square s = lsb(*b);
*b &= *b - 1;
return s;
}
/// frontmost_sq() and backmost_sq() return the square corresponding to the
/// most/least advanced bit relative to the given color.
inline Square frontmost_sq(Color c, Bitboard b) { return c == WHITE ? msb(b) : lsb(b); }
inline Square backmost_sq(Color c, Bitboard b) { return c == WHITE ? lsb(b) : msb(b); }
#endif // #ifndef BITBOARD_H_INCLUDED