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 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);
+constexpr bool opposite_colors(Square s1, Square s2) {
+ return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 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) {
+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) {
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
: shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
}
+inline Bitboard pawn_attacks_bb(Color c, Square s) {
+
+ assert(is_ok(s));
+ return PawnAttacks[c][s];
+}
+
/// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the
/// given color from the squares in the given bitboard.
/// adjacent_files_bb() returns a bitboard representing all the squares on the
-/// adjacent files of the given one.
+/// adjacent files of a given square.
+
+constexpr Bitboard adjacent_files_bb(Square s) {
+ return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(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.
+
+inline Bitboard line_bb(Square s1, Square s2) {
-inline Bitboard adjacent_files_bb(File f) {
- return shift<EAST>(file_bb(f)) | shift<WEST>(file_bb(f));
+ assert(is_ok(s1) && is_ok(s2));
+ return LineBB[s1][s2];
}
-/// 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 a bitboard representing squares that are linearly
+/// between the two given squares (excluding the given squares). If the given
+/// squares are not on a same file/rank/diagonal, we return 0. For instance,
+/// between_bb(SQ_C4, SQ_F7) will return a bitboard with squares D5 and E6.
inline Bitboard between_bb(Square s1, Square s2) {
- return BetweenBB[s1][s2];
+ Bitboard b = line_bb(s1, s2) & ((AllSquares << s1) ^ (AllSquares << s2));
+ return b & (b - 1); //exclude lsb
}
/// 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 c == WHITE ? ~Rank1BB << 8 * (rank_of(s) - RANK_1)
- : ~Rank8BB >> 8 * (RANK_8 - rank_of(s));
+constexpr Bitboard forward_ranks_bb(Color c, Square s) {
+ return c == WHITE ? ~Rank1BB << 8 * relative_rank(WHITE, s)
+ : ~Rank8BB >> 8 * relative_rank(BLACK, 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.
-inline Bitboard forward_file_bb(Color c, Square s) {
+constexpr 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.
+/// 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(file_of(s));
+constexpr Bitboard pawn_attack_span(Color c, Square s) {
+ return forward_ranks_bb(c, s) & adjacent_files_bb(s);
}
/// 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.
-inline Bitboard passed_pawn_span(Color c, Square s) {
- return forward_ranks_bb(c, s) & (adjacent_files_bb(file_of(s)) | file_bb(s));
+constexpr Bitboard passed_pawn_span(Color c, Square s) {
+ return pawn_attack_span(c, s) | forward_file_bb(c, s);
}
/// 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;
}
/// 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)); }
-/// attacks_bb() returns a bitboard representing all the squares attacked by a
-/// piece of type Pt (bishop or rook) placed on 's'.
+/// safe_destination() returns the bitboard of target square for the given step
+/// from the given square. If the step is off the board, returns empty bitboard.
+
+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(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(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)
{
/// 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
projects / stockfish / blobdiff