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) 2015-2020 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
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 DistanceRingBB[SQUARE_NB][8];
extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
-extern Bitboard KingFlank[FILE_NB];
/// Magic holds all magic bitboards relevant data for a single square
extern Magic RookMagics[SQUARE_NB];
extern Magic BishopMagics[SQUARE_NB];
+inline Bitboard square_bb(Square s) {
+ assert(is_ok(s));
+ return SquareBB[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 square_bb(Square s) {
- assert(s >= SQ_A1 && s <= SQ_H8);
- return SquareBB[s];
-}
-
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^( Bitboard b, Square s) { return b ^ square_bb(s); }
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 s, Square s2) { return square_bb(s) | 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);
+constexpr bool opposite_colors(Square s1, Square s2) {
+ return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 1;
}
}
-/// 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) {
return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
+ : D == NORTH+NORTH? b <<16 : D == SOUTH+SOUTH? b >>16
: D == EAST ? (b & ~FileHBB) << 1 : D == WEST ? (b & ~FileABB) >> 1
: D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == NORTH_WEST ? (b & ~FileABB) << 7
: D == SOUTH_EAST ? (b & ~FileHBB) >> 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
/// 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 shift<EAST>(file_bb(f)) | shift<WEST>(file_bb(f));
+inline Bitboard adjacent_files_bb(Square s) {
+ return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
}
-/// 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.
+/// 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 BetweenBB[s1][s2];
+ Bitboard b = LineBB[s1][s2] & ((AllSquares << s1) ^ (AllSquares << s2));
+ return b & (b - 1); //exclude lsb
}
/// 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 c == WHITE ? ~Rank1BB << 8 * (rank_of(s) - RANK_1)
- : ~Rank8BB >> 8 * (RANK_8 - rank_of(s));
+ return c == WHITE ? ~Rank1BB << 8 * relative_rank(WHITE, s)
+ : ~Rank8BB >> 8 * relative_rank(BLACK, s);
}
/// starting from the given square.
inline Bitboard pawn_attack_span(Color c, Square s) {
- return forward_ranks_bb(c, s) & adjacent_files_bb(file_of(s));
+ return forward_ranks_bb(c, s) & adjacent_files_bb(s);
}
/// the given color and on the given square is a passed pawn.
inline Bitboard passed_pawn_span(Color c, Square s) {
- return forward_ranks_bb(c, s) & (adjacent_files_bb(file_of(s)) | file_bb(s));
+ return forward_ranks_bb(c, s) & (adjacent_files_bb(s) | file_bb(s));
}
/// 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.
+/// number of steps for a king in x to reach y.
-template<typename T> inline int distance(T x, T y) { return std::abs(x - y); }
+template<typename T1 = Square> inline int distance(Square x, Square y);
+template<> inline int distance<File>(Square x, Square y) { return std::abs(file_of(x) - file_of(y)); }
+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<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)); }
+inline int edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
+inline int edge_distance(Rank r) { return std::min(r, Rank(RANK_8 - r)); }
+/// Return the target square bitboard if we do not step off the board, empty otherwise
+
+inline Bitboard safe_destination(Square s, int step)
+{
+ Square to = Square(s + step);
+ return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
+}
/// attacks_bb() returns a bitboard representing all the squares attacked by a
/// piece of type Pt (bishop or rook) placed on 's'.
/// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
inline Square pop_lsb(Bitboard* b) {
+ assert(*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); }
+/// frontmost_sq() returns the most advanced square for the given color,
+/// requires a non-zero bitboard.
+inline Square frontmost_sq(Color c, Bitboard b) {
+ assert(b);
+ return c == WHITE ? msb(b) : lsb(b);
+}
#endif // #ifndef BITBOARD_H_INCLUDED