/*
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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2004-2023 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
#ifndef BITBOARD_H_INCLUDED
#define BITBOARD_H_INCLUDED
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
#include <string>
#include "types.h"
-namespace Bitbases {
-
-void init();
-bool probe(Square wksq, Square wpsq, Square bksq, Color us);
-
-}
+namespace Stockfish {
namespace Bitboards {
void init();
-const std::string pretty(Bitboard b);
-
-}
+std::string pretty(Bitboard b);
-constexpr Bitboard AllSquares = ~Bitboard(0);
-constexpr Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
+} // namespace Stockfish::Bitboards
constexpr Bitboard FileABB = 0x0101010101010101ULL;
constexpr Bitboard FileBBB = FileABB << 1;
constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);
constexpr Bitboard Rank8BB = Rank1BB << (8 * 7);
-constexpr Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
-constexpr Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
-constexpr Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
-constexpr Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
-
-constexpr Bitboard KingFlank[FILE_NB] = {
- QueenSide ^ FileDBB, QueenSide, QueenSide,
- CenterFiles, CenterFiles,
- KingSide, KingSide, KingSide ^ FileEBB
-};
-
extern uint8_t PopCnt16[1 << 16];
extern uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
-extern Bitboard SquareBB[SQUARE_NB];
+extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
extern Magic BishopMagics[SQUARE_NB];
inline Bitboard square_bb(Square s) {
- assert(s >= SQ_A1 && s <= SQ_H8);
- return SquareBB[s];
+ assert(is_ok(s));
+ return (1ULL << s);
}
+
/// 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 |= square_bb(s); }
inline Bitboard& operator^=(Bitboard& b, Square s) { return b ^= square_bb(s); }
+inline Bitboard operator&(Square s, Bitboard b) { return b & s; }
+inline Bitboard operator|(Square s, Bitboard b) { return b | s; }
+inline Bitboard operator^(Square s, Bitboard b) { return b ^ s; }
+
+inline Bitboard operator|(Square s1, Square s2) { return square_bb(s1) | s2; }
+
constexpr bool more_than_one(Bitboard b) {
return b & (b - 1);
}
-inline bool opposite_colors(Square s1, Square s2) {
- return bool(DarkSquares & s1) != bool(DarkSquares & s2);
-}
-
/// rank_bb() and file_bb() return a bitboard representing all the squares on
/// the given file or rank.
-inline Bitboard rank_bb(Rank r) {
+constexpr Bitboard rank_bb(Rank r) {
return Rank1BB << (8 * r);
}
-inline Bitboard rank_bb(Square s) {
+constexpr Bitboard rank_bb(Square s) {
return rank_bb(rank_of(s));
}
-inline Bitboard file_bb(File f) {
+constexpr Bitboard file_bb(File f) {
return FileABB << f;
}
-inline Bitboard file_bb(Square s) {
+constexpr Bitboard file_bb(Square s) {
return file_bb(file_of(s));
}
-/// shift() moves a bitboard one step along direction D
+/// shift() moves a bitboard one or two steps as specified by the direction D
template<Direction D>
constexpr Bitboard shift(Bitboard b) {
: shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
}
+inline Bitboard pawn_attacks_bb(Color c, Square s) {
-/// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the
-/// given color from the squares in the given bitboard.
-
-template<Color C>
-constexpr Bitboard pawn_double_attacks_bb(Bitboard b) {
- return C == WHITE ? shift<NORTH_WEST>(b) & shift<NORTH_EAST>(b)
- : shift<SOUTH_WEST>(b) & shift<SOUTH_EAST>(b);
-}
-
-
-/// adjacent_files_bb() returns a bitboard representing all the squares on the
-/// adjacent files of the given one.
-
-inline Bitboard adjacent_files_bb(Square s) {
- return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
+ assert(is_ok(s));
+ return PawnAttacks[c][s];
}
+/// line_bb() returns a bitboard representing an entire line (from board edge
+/// to board edge) that intersects the two given squares. If the given squares
+/// are not on a same file/rank/diagonal, the function returns 0. For instance,
+/// line_bb(SQ_C4, SQ_F7) will return a bitboard with the A2-G8 diagonal.
-/// between_bb() returns squares that are linearly between the given squares
-/// If the given squares are not on a same file/rank/diagonal, return 0.
-
-inline Bitboard between_bb(Square s1, Square s2) {
- return LineBB[s1][s2] & ( (AllSquares << (s1 + (s1 < s2)))
- ^(AllSquares << (s2 + !(s1 < s2))));
-}
-
+inline Bitboard line_bb(Square s1, Square s2) {
-/// forward_ranks_bb() returns a bitboard representing the squares on 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.
+ assert(is_ok(s1) && is_ok(s2));
-inline Bitboard forward_ranks_bb(Color c, Square s) {
- return c == WHITE ? ~Rank1BB << 8 * (rank_of(s) - RANK_1)
- : ~Rank8BB >> 8 * (RANK_8 - rank_of(s));
+ return LineBB[s1][s2];
}
-/// 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.
-
-inline Bitboard forward_file_bb(Color c, Square s) {
- return forward_ranks_bb(c, s) & file_bb(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.
-
-inline Bitboard pawn_attack_span(Color c, Square s) {
- return forward_ranks_bb(c, s) & adjacent_files_bb(s);
-}
+/// between_bb(s1, s2) returns a bitboard representing the squares in the semi-open
+/// segment between the squares s1 and s2 (excluding s1 but including s2). If the
+/// given squares are not on a same file/rank/diagonal, it returns s2. For instance,
+/// between_bb(SQ_C4, SQ_F7) will return a bitboard with squares D5, E6 and F7, but
+/// between_bb(SQ_E6, SQ_F8) will return a bitboard with the square F8. This trick
+/// allows to generate non-king evasion moves faster: the defending piece must either
+/// interpose itself to cover the check or capture the checking piece.
+inline Bitboard between_bb(Square s1, Square s2) {
-/// passed_pawn_span() returns a bitboard which can be used to test if a pawn of
-/// the given color and on the given square is a passed pawn.
+ assert(is_ok(s1) && is_ok(s2));
-inline Bitboard passed_pawn_span(Color c, Square s) {
- return forward_ranks_bb(c, s) & (adjacent_files_bb(s) | file_bb(s));
+ return BetweenBB[s1][s2];
}
-
/// 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;
+ return line_bb(s1, s2) & s3;
}
template<> inline int distance<Rank>(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); }
template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
-template<class T> constexpr const T& clamp(const T& v, const T& lo, const T& hi) {
- return v < lo ? lo : v > hi ? hi : v;
+inline int edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
+
+/// attacks_bb(Square) returns the pseudo attacks of the give piece type
+/// assuming an empty board.
+
+template<PieceType Pt>
+inline Bitboard attacks_bb(Square s) {
+
+ assert((Pt != PAWN) && (is_ok(s)));
+
+ return PseudoAttacks[Pt][s];
}
-/// attacks_bb() returns a bitboard representing all the squares attacked by a
-/// piece of type Pt (bishop or rook) placed on 's'.
+
+/// attacks_bb(Square, Bitboard) returns the attacks by the given piece
+/// assuming the board is occupied according to the passed Bitboard.
+/// Sliding piece attacks do not continue passed an occupied square.
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)];
+ assert((Pt != PAWN) && (is_ok(s)));
+
+ switch (Pt)
+ {
+ case BISHOP: return BishopMagics[s].attacks[BishopMagics[s].index(occupied)];
+ case ROOK : return RookMagics[s].attacks[ RookMagics[s].index(occupied)];
+ case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
+ default : return PseudoAttacks[Pt][s];
+ }
}
inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
- assert(pt != PAWN);
+ assert((pt != PAWN) && (is_ok(s)));
switch (pt)
{
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)
+#elif defined(_MSC_VER)
return (int)_mm_popcnt_u64(b);
/// lsb() and msb() return the least/most significant bit in a non-zero bitboard
-#if defined(__GNUC__) // GCC, Clang, ICC
+#if defined(__GNUC__) // GCC, Clang, ICX
inline Square lsb(Bitboard b) {
assert(b);
#endif
+/// least_significant_square_bb() returns the bitboard of the least significant
+/// square of a non-zero bitboard. It is equivalent to square_bb(lsb(bb)).
+
+inline Bitboard least_significant_square_bb(Bitboard b) {
+ assert(b);
+ return b & -b;
+}
/// 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;
+inline Square pop_lsb(Bitboard& b) {
+ assert(b);
+ const Square s = lsb(b);
+ b &= b - 1;
return s;
}
-
-/// frontmost_sq() returns the most advanced square for the given color
-inline Square frontmost_sq(Color c, Bitboard b) { return c == WHITE ? msb(b) : lsb(b); }
+} // namespace Stockfish
#endif // #ifndef BITBOARD_H_INCLUDED