X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.h;h=15ec4153362d82d1339e9657e19190cf2e118005;hp=ecff5c3abd84a7ff5b6365ebf5329b4fcb09cef7;hb=1f3bd968bb194a1f42af661cca9ec445c13978e8;hpb=5f2bf91ad18069e77e5c0e32c387b2200abd94d9 diff --git a/src/bitboard.h b/src/bitboard.h index ecff5c3a..15ec4153 100644 --- a/src/bitboard.h +++ b/src/bitboard.h @@ -1,14 +1,14 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, 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 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 @@ -21,318 +21,431 @@ #ifndef BITBOARD_H_INCLUDED #define BITBOARD_H_INCLUDED +#include + #include "types.h" -namespace Bitboards { +namespace Bitbases { void init(); -const std::string pretty(Bitboard b); +bool probe(Square wksq, Square wpsq, Square bksq, Color us); } -namespace Bitbases { +namespace Bitboards { -void init_kpk(); -bool probe_kpk(Square wksq, Square wpsq, Square bksq, Color us); +void init(); +const std::string pretty(Bitboard b); } -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; +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; -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); +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); -CACHE_LINE_ALIGNMENT +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); -extern Bitboard RMasks[SQUARE_NB]; -extern Bitboard RMagics[SQUARE_NB]; -extern Bitboard* RAttacks[SQUARE_NB]; -extern unsigned RShifts[SQUARE_NB]; +constexpr Bitboard KingFlank[FILE_NB] = { + QueenSide ^ FileDBB, QueenSide, QueenSide, + CenterFiles, CenterFiles, + KingSide, KingSide, KingSide ^ FileEBB +}; -extern Bitboard BMasks[SQUARE_NB]; -extern Bitboard BMagics[SQUARE_NB]; -extern Bitboard* BAttacks[SQUARE_NB]; -extern unsigned BShifts[SQUARE_NB]; +extern uint8_t PopCnt16[1 << 16]; +extern uint8_t 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 InFrontBB[COLOR_NB][RANK_NB]; -extern Bitboard StepAttacksBB[PIECE_NB][SQUARE_NB]; -extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB]; extern Bitboard LineBB[SQUARE_NB][SQUARE_NB]; -extern Bitboard DistanceRingsBB[SQUARE_NB][8]; -extern Bitboard ForwardBB[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]; -extern int SquareDistance[SQUARE_NB][SQUARE_NB]; -const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL; +/// 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]; + +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 operator&(Bitboard b, Square s) { - return b & 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|=(Bitboard& b, Square s) { - return b |= SquareBB[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^=(Bitboard& b, Square s) { - return b ^= SquareBB[s]; -} +inline Bitboard operator|(Square s1, Square s2) { return square_bb(s1) | s2; } -inline Bitboard operator|(Bitboard b, Square s) { - return b | SquareBB[s]; +constexpr bool more_than_one(Bitboard b) { + return b & (b - 1); } -inline Bitboard operator^(Bitboard b, Square s) { - return b ^ SquareBB[s]; +/// Counts the occupation of the bitboard depending on the occupation of SQ_A1 +/// as in `b & (1ULL << SQ_A1) ? more_than_two(b) : more_than_one(b)` + +constexpr bool conditional_more_than_two(Bitboard b) { + return b & (b - 1) & (b - 2); } -inline bool more_than_one(Bitboard b) { - return b & (b - 1); +constexpr bool opposite_colors(Square s1, Square s2) { + return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 1; } -inline int square_distance(Square s1, Square s2) { - return SquareDistance[s1][s2]; + +/// rank_bb() and file_bb() return a bitboard representing all the squares on +/// the given file or rank. + +constexpr Bitboard rank_bb(Rank r) { + return Rank1BB << (8 * r); } -inline int file_distance(Square s1, Square s2) { - return abs(file_of(s1) - file_of(s2)); +constexpr Bitboard rank_bb(Square s) { + return rank_bb(rank_of(s)); } -inline int rank_distance(Square s1, Square s2) { - return abs(rank_of(s1) - rank_of(s2)); +constexpr Bitboard file_bb(File f) { + return FileABB << f; } +constexpr Bitboard file_bb(Square s) { + return file_bb(file_of(s)); +} -/// shift_bb() moves bitboard one step along direction Delta. Mainly for pawns. -template -inline Bitboard shift_bb(Bitboard b) { +/// shift() moves a bitboard one or two steps as specified by the direction D - return Delta == DELTA_N ? b << 8 : Delta == DELTA_S ? b >> 8 - : Delta == DELTA_NE ? (b & ~FileHBB) << 9 : Delta == DELTA_SE ? (b & ~FileHBB) >> 7 - : Delta == DELTA_NW ? (b & ~FileABB) << 7 : Delta == DELTA_SW ? (b & ~FileABB) >> 9 +template +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 : 0; } -/// rank_bb() and file_bb() take a file or a square as input and return -/// a bitboard representing all squares on the given file or rank. +/// pawn_attacks_bb() returns the squares attacked by pawns of the given color +/// from the squares in the given bitboard. -inline Bitboard rank_bb(Rank r) { - return RankBB[r]; +template +constexpr Bitboard pawn_attacks_bb(Bitboard b) { + return C == WHITE ? shift(b) | shift(b) + : shift(b) | shift(b); } -inline Bitboard rank_bb(Square s) { - return RankBB[rank_of(s)]; -} +inline Bitboard pawn_attacks_bb(Color c, Square s) { -inline Bitboard file_bb(File f) { - return FileBB[f]; + assert(is_ok(s)); + return PawnAttacks[c][s]; } -inline Bitboard file_bb(Square s) { - return FileBB[file_of(s)]; + +/// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the +/// given color from the squares in the given bitboard. + +template +constexpr Bitboard pawn_double_attacks_bb(Bitboard b) { + return C == WHITE ? shift(b) & shift(b) + : shift(b) & shift(b); } -/// adjacent_files_bb() takes a file as input and returns a bitboard representing -/// all squares on the adjacent files. +/// adjacent_files_bb() returns a bitboard representing all the squares on the +/// adjacent files of a given square. -inline Bitboard adjacent_files_bb(File f) { - return AdjacentFilesBB[f]; +constexpr Bitboard adjacent_files_bb(Square s) { + return shift(file_bb(s)) | shift(file_bb(s)); } -/// in_front_bb() takes a color and a rank as input, and returns a bitboard -/// representing all the squares on all ranks in front of the rank, from the -/// given color's point of view. For instance, in_front_bb(BLACK, RANK_3) will -/// give all squares on ranks 1 and 2. +/// 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 in_front_bb(Color c, Rank r) { - return InFrontBB[c][r]; + assert(is_ok(s1) && is_ok(s2)); + return LineBB[s1][s2]; } -/// between_bb() returns a bitboard representing all squares between two squares. -/// 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 line, 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 } -/// forward_bb() takes a color and a square as input, and returns a bitboard -/// representing all squares along the line in front of the square, from the -/// point of view of the given color. Definition of the table is: -/// ForwardBB[c][s] = in_front_bb(c, s) & file_bb(s) +/// 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. -inline Bitboard forward_bb(Color c, Square s) { - return ForwardBB[c][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); } -/// pawn_attack_span() takes a color and a square as input, and returns a bitboard -/// representing all squares that can be attacked by a pawn of the given color -/// when it moves along its file starting from the given square. Definition is: -/// PawnAttackSpan[c][s] = in_front_bb(c, s) & adjacent_files_bb(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 pawn_attack_span(Color c, Square s) { - return PawnAttackSpan[c][s]; +constexpr Bitboard forward_file_bb(Color c, Square s) { + return forward_ranks_bb(c, s) & file_bb(s); } -/// passed_pawn_mask() takes a color and a square as input, and returns a -/// bitboard mask which can be used to test if a pawn of the given color on -/// the given square is a passed pawn. Definition of the table is: -/// PassedPawnMask[c][s] = pawn_attack_span(c, s) | forward_bb(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. -inline Bitboard passed_pawn_mask(Color c, Square s) { - return PassedPawnMask[c][s]; +constexpr Bitboard pawn_attack_span(Color c, Square s) { + return forward_ranks_bb(c, s) & adjacent_files_bb(s); } -/// squares_of_color() returns a bitboard representing all squares with the same -/// color of the given square. +/// 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 squares_of_color(Square s) { - return DarkSquares & s ? DarkSquares : ~DarkSquares; +constexpr Bitboard passed_pawn_span(Color c, Square s) { + return pawn_attack_span(c, s) | forward_file_bb(c, s); } -/// aligned() returns true if the squares s1, s2 and s3 are aligned -/// either on a straight or on a diagonal line. +/// 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; } -/// Functions for computing sliding attack bitboards. Function attacks_bb() takes -/// a square and a bitboard of occupied squares as input, and returns a bitboard -/// representing all squares attacked by Pt (bishop or rook) on the given square. -template -FORCE_INLINE unsigned magic_index(Square s, Bitboard occ) { +/// distance() functions return the distance between x and y, defined as the +/// number of steps for a king in x to reach y. + +template inline int distance(Square x, Square y); +template<> inline int distance(Square x, Square y) { return std::abs(file_of(x) - file_of(y)); } +template<> inline int distance(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); } +template<> inline int distance(Square x, Square y) { return SquareDistance[x][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)); } + + +/// 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); +} - Bitboard* const Masks = Pt == ROOK ? RMasks : BMasks; - Bitboard* const Magics = Pt == ROOK ? RMagics : BMagics; - unsigned* const Shifts = Pt == ROOK ? RShifts : BShifts; - if (Is64Bit) - return unsigned(((occ & Masks[s]) * Magics[s]) >> Shifts[s]); +/// attacks_bb(Square) returns the pseudo attacks of the give piece type +/// assuming an empty board. - unsigned lo = unsigned(occ) & unsigned(Masks[s]); - unsigned hi = unsigned(occ >> 32) & unsigned(Masks[s] >> 32); - return (lo * unsigned(Magics[s]) ^ hi * unsigned(Magics[s] >> 32)) >> Shifts[s]; +template +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 -inline Bitboard attacks_bb(Square s, Bitboard occ) { - return (Pt == ROOK ? RAttacks : BAttacks)[s][magic_index(s, occ)]; +inline Bitboard attacks_bb(Square s, Bitboard 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(s, occupied) | attacks_bb(s, occupied); + default : return PseudoAttacks[Pt][s]; + } } -inline Bitboard attacks_bb(Piece p, Square s, Bitboard occ) { +inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) { + + assert((pt != PAWN) && (is_ok(s))); - switch (type_of(p)) + switch (pt) { - case BISHOP: return attacks_bb(s, occ); - case ROOK : return attacks_bb(s, occ); - case QUEEN : return attacks_bb(s, occ) | attacks_bb(s, occ); - default : return StepAttacksBB[p][s]; + case BISHOP: return attacks_bb(s, occupied); + case ROOK : return attacks_bb< ROOK>(s, occupied); + case QUEEN : return attacks_bb(s, occupied) | attacks_bb(s, occupied); + default : return PseudoAttacks[pt][s]; } } -/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard. -/// pop_lsb() finds and clears the least significant bit in a nonzero bitboard. -#ifdef USE_BSFQ +/// popcount() counts the number of non-zero bits in a bitboard -# if defined(_MSC_VER) && !defined(__INTEL_COMPILER) +inline int popcount(Bitboard b) { -FORCE_INLINE Square lsb(Bitboard b) { - unsigned long index; - _BitScanForward64(&index, b); - return (Square) index; -} +#ifndef USE_POPCNT -FORCE_INLINE Square msb(Bitboard b) { - unsigned long index; - _BitScanReverse64(&index, b); - return (Square) index; -} + 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 -# elif defined(__arm__) + return __builtin_popcountll(b); -FORCE_INLINE int lsb32(uint32_t v) { - __asm__("rbit %0, %1" : "=r"(v) : "r"(v)); - return __builtin_clz(v); +#endif } -FORCE_INLINE Square msb(Bitboard b) { - return (Square) (63 - __builtin_clzll(b)); + +/// 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)); } -FORCE_INLINE Square lsb(Bitboard b) { - return (Square) (uint32_t(b) ? lsb32(uint32_t(b)) : 32 + lsb32(uint32_t(b >> 32))); +inline Square msb(Bitboard b) { + assert(b); + return Square(63 ^ __builtin_clzll(b)); } -# else +#elif defined(_MSC_VER) // MSVC + +#ifdef _WIN64 // MSVC, WIN64 -FORCE_INLINE Square lsb(Bitboard b) { // Assembly code by Heinz van Saanen - Bitboard index; - __asm__("bsfq %1, %0": "=r"(index): "rm"(b) ); - return (Square) index; +inline Square lsb(Bitboard b) { + assert(b); + unsigned long idx; + _BitScanForward64(&idx, b); + return (Square) idx; } -FORCE_INLINE Square msb(Bitboard b) { - Bitboard index; - __asm__("bsrq %1, %0": "=r"(index): "rm"(b) ); - return (Square) index; +inline Square msb(Bitboard b) { + assert(b); + unsigned long idx; + _BitScanReverse64(&idx, b); + return (Square) idx; } -# endif +#else // MSVC, WIN32 -FORCE_INLINE Square pop_lsb(Bitboard* b) { - const Square s = lsb(*b); - *b &= *b - 1; - return s; +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); + } } -#else // if defined(USE_BSFQ) +inline Square msb(Bitboard b) { + assert(b); + unsigned long idx; -extern Square msb(Bitboard b); -extern Square lsb(Bitboard b); -extern Square pop_lsb(Bitboard* b); + if (b >> 32) { + _BitScanReverse(&idx, int32_t(b >> 32)); + return Square(idx + 32); + } else { + _BitScanReverse(&idx, int32_t(b)); + return Square(idx); + } +} #endif -/// frontmost_sq() and backmost_sq() find the square corresponding to the -/// most/least advanced bit relative to the given color. +#else // Compiler is neither GCC nor MSVC compatible + +#error "Compiler not supported." + +#endif -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); } + +/// 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() 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