/*

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

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);

}

constexpr Bitboard AllSquares = ~Bitboard(0);

constexpr Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;

constexpr Bitboard FileABB = 0x0101010101010101ULL;

constexpr Bitboard FileBBB = FileABB << 1;

constexpr Bitboard FileCBB = FileABB << 2;

constexpr Bitboard FileDBB = FileABB << 3;

constexpr Bitboard FileEBB = FileABB << 4;

constexpr Bitboard FileFBB = FileABB << 5;

constexpr Bitboard FileGBB = FileABB << 6;

constexpr Bitboard FileHBB = FileABB << 7;

constexpr Bitboard Rank1BB = 0xFF;

constexpr Bitboard Rank2BB = Rank1BB << (8 * 1);

constexpr Bitboard Rank3BB = Rank1BB << (8 * 2);

constexpr Bitboard Rank4BB = Rank1BB << (8 * 3);

constexpr Bitboard Rank5BB = Rank1BB << (8 * 4);

constexpr Bitboard Rank6BB = Rank1BB << (8 * 5);

constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);

constexpr 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) {

assert(s >= SQ_A1 && s <= SQ_H8);

return b & SquareBB[s];

}

inline Bitboard operator|(Bitboard b, Square s) {

assert(s >= SQ_A1 && s <= SQ_H8);

return b | SquareBB[s];

}

inline Bitboard operator^(Bitboard b, Square s) {

assert(s >= SQ_A1 && s <= SQ_H8);

return b ^ SquareBB[s];

}

inline Bitboard& operator|=(Bitboard& b, Square s) {

assert(s >= SQ_A1 && s <= SQ_H8);

return b |= SquareBB[s];

}

inline Bitboard& operator^=(Bitboard& b, Square s) {

assert(s >= SQ_A1 && s <= SQ_H8);

return b ^= SquareBB[s];

}

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) {

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 == 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

: 0;

}

/// pawn_attacks_bb() returns the pawn attacks for the given color from the

/// squares in the given bitboard.

template<Color C>

constexpr Bitboard pawn_attacks_bb(Bitboard b) {

return C == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)

: shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);

}

/// double_pawn_attacks_bb() returns the pawn attacks for the given color

/// from the squares in the given bitboard.

template<Color C>

constexpr Bitboard double_pawn_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(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 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__) // GCC, Clang, ICC

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(_MSC_VER) // MSVC

#ifdef _WIN64 // MSVC, WIN64

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 // MSVC, WIN32

inline Square lsb(Bitboard b) {

assert(b);

unsigned long idx;

if (b & 0xffffffff) {

_BitScanForward(&idx, int32_t(b));

return Square(idx);

} else {

_BitScanForward(&idx, int32_t(b >> 32));

return Square(idx + 32);

}

}

inline Square msb(Bitboard b) {

assert(b);

unsigned long idx;

if (b >> 32) {

_BitScanReverse(&idx, int32_t(b >> 32));

return Square(idx + 32);

} else {

_BitScanReverse(&idx, int32_t(b));

return Square(idx);

}

}

#endif

#else // Compiler is neither GCC nor MSVC compatible

#error "Compiler not supported."

#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