X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.h;h=6b277cd5a703eeee500c416cf70ffa38c3d09704;hp=bc1900196d45cbc0c901158506096460195b426d;hb=54b5b528d9ef6c4f14a2000eead9a5c0686f899e;hpb=279ed7ed4883666a209c76864b0218d85e1494ee diff --git a/src/bitboard.h b/src/bitboard.h index bc190019..aa4e1711 100644 --- a/src/bitboard.h +++ b/src/bitboard.h @@ -1,13 +1,14 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008 Marco Costalba + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, 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 @@ -17,172 +18,111 @@ along with this program. If not, see . */ - -#if !defined(BITBOARD_H_INCLUDED) +#ifndef BITBOARD_H_INCLUDED #define BITBOARD_H_INCLUDED +#include -//// -//// Defines -//// - -// Comment following define if you prefer manually adjust -// platform macros defined below -#define AUTO_CONFIGURATION - -// Quiet a warning on Intel compiler -#if !defined(__SIZEOF_INT__ ) -#define __SIZEOF_INT__ 0 -#endif - -// Check for 64 bits for different compilers: Intel, MSVC and gcc -#if defined(__x86_64) || defined(_WIN64) || (__SIZEOF_INT__ > 4) -#define IS_64BIT -#endif - -#if !defined(AUTO_CONFIGURATION) || defined(IS_64BIT) - -//#define USE_COMPACT_ROOK_ATTACKS -//#define USE_32BIT_ATTACKS -#define USE_FOLDED_BITSCAN - -#define BITCOUNT_SWAR_64 -//#define BITCOUNT_SWAR_32 -//#define BITCOUNT_LOOP - -#else - -#define USE_32BIT_ATTACKS -#define USE_FOLDED_BITSCAN -#define BITCOUNT_SWAR_32 - -#endif - -//// -//// Includes -//// - -#include "direction.h" -#include "piece.h" -#include "square.h" #include "types.h" +namespace Bitbases { -//// -//// Types -//// - -typedef uint64_t Bitboard; +void init(); +bool probe(Square wksq, Square wpsq, Square bksq, Color us); +} -//// -//// Constants and variables -//// +namespace Bitboards { -const Bitboard EmptyBoardBB = 0ULL; +void init(); +const std::string pretty(Bitboard b); -const Bitboard WhiteSquaresBB = 0x55AA55AA55AA55AAULL; -const Bitboard BlackSquaresBB = 0xAA55AA55AA55AA55ULL; +} -extern const Bitboard SquaresByColorBB[2]; +const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL; const Bitboard FileABB = 0x0101010101010101ULL; -const Bitboard FileBBB = 0x0202020202020202ULL; -const Bitboard FileCBB = 0x0404040404040404ULL; -const Bitboard FileDBB = 0x0808080808080808ULL; -const Bitboard FileEBB = 0x1010101010101010ULL; -const Bitboard FileFBB = 0x2020202020202020ULL; -const Bitboard FileGBB = 0x4040404040404040ULL; -const Bitboard FileHBB = 0x8080808080808080ULL; - -extern const Bitboard FileBB[8]; -extern const Bitboard NeighboringFilesBB[8]; -extern const Bitboard ThisAndNeighboringFilesBB[8]; - -const Bitboard Rank1BB = 0xFFULL; -const Bitboard Rank2BB = 0xFF00ULL; -const Bitboard Rank3BB = 0xFF0000ULL; -const Bitboard Rank4BB = 0xFF000000ULL; -const Bitboard Rank5BB = 0xFF00000000ULL; -const Bitboard Rank6BB = 0xFF0000000000ULL; -const Bitboard Rank7BB = 0xFF000000000000ULL; -const Bitboard Rank8BB = 0xFF00000000000000ULL; - -extern const Bitboard RankBB[8]; -extern const Bitboard RelativeRankBB[2][8]; -extern const Bitboard InFrontBB[2][8]; +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; -extern Bitboard SetMaskBB[64]; -extern Bitboard ClearMaskBB[64]; +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); -extern Bitboard StepAttackBB[16][64]; -extern Bitboard RayBB[64][8]; -extern Bitboard BetweenBB[64][64]; +extern int SquareDistance[SQUARE_NB][SQUARE_NB]; -extern Bitboard PassedPawnMask[2][64]; -extern Bitboard OutpostMask[2][64]; +extern Bitboard RookMasks [SQUARE_NB]; +extern Bitboard RookMagics [SQUARE_NB]; +extern Bitboard* RookAttacks[SQUARE_NB]; +extern unsigned RookShifts [SQUARE_NB]; -#if defined(USE_COMPACT_ROOK_ATTACKS) -extern Bitboard RankAttacks[8][64], FileAttacks[8][64]; -#else -extern const uint64_t RMult[64]; -extern const int RShift[64]; -extern Bitboard RMask[64]; -extern int RAttackIndex[64]; -extern Bitboard RAttacks[0x19000]; -#endif // defined(USE_COMPACT_ROOK_ATTACKS) +extern Bitboard BishopMasks [SQUARE_NB]; +extern Bitboard BishopMagics [SQUARE_NB]; +extern Bitboard* BishopAttacks[SQUARE_NB]; +extern unsigned BishopShifts [SQUARE_NB]; -extern const uint64_t BMult[64]; -extern const int BShift[64]; -extern Bitboard BMask[64]; -extern int BAttackIndex[64]; -extern Bitboard BAttacks[0x1480]; +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 DistanceRingBB[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 BishopPseudoAttacks[64]; -extern Bitboard RookPseudoAttacks[64]; -extern Bitboard QueenPseudoAttacks[64]; +/// 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 functions -//// - -/// Functions 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 set_mask_bb(Square s) { - // return 1ULL << s; - return SetMaskBB[s]; +inline Bitboard operator|(Bitboard b, Square s) { + return b | SquareBB[s]; } -inline Bitboard clear_mask_bb(Square s) { - // return ~set_mask_bb(s); - return ClearMaskBB[s]; +inline Bitboard operator^(Bitboard b, Square s) { + return b ^ SquareBB[s]; } -inline Bitboard bit_is_set(Bitboard b, Square s) { - return b & set_mask_bb(s); +inline Bitboard& operator|=(Bitboard& b, Square s) { + return b |= SquareBB[s]; } -inline void set_bit(Bitboard *b, Square s) { - *b |= set_mask_bb(s); +inline Bitboard& operator^=(Bitboard& b, Square s) { + return b ^= SquareBB[s]; } -inline void clear_bit(Bitboard *b, Square s) { - *b &= clear_mask_bb(s); +inline bool more_than_one(Bitboard b) { + return b & (b - 1); } -/// rank_bb() and file_bb() gives a bitboard containing all squares on a given -/// file or rank. It is also possible to pass a square as input to these -/// functions. +/// 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 rank_bb(square_rank(s)); + return RankBB[rank_of(s)]; } inline Bitboard file_bb(File f) { @@ -190,255 +130,211 @@ inline Bitboard file_bb(File f) { } inline Bitboard file_bb(Square s) { - return file_bb(square_file(s)); + return FileBB[file_of(s)]; } -/// neighboring_files_bb takes a file or a square as input, and returns a -/// bitboard representing all squares on the neighboring files. - -inline Bitboard neighboring_files_bb(File f) { - return NeighboringFilesBB[f]; -} +/// shift_bb() moves a bitboard one step along direction Delta. Mainly for pawns -inline Bitboard neighboring_files_bb(Square s) { - return neighboring_files_bb(square_file(s)); +template +inline Bitboard shift_bb(Bitboard b) { + 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 + : 0; } -/// this_and_neighboring_files_bb takes a file or a square as input, and -/// returns a bitboard representing all squares on the given and neighboring -/// files. +/// adjacent_files_bb() returns a bitboard representing all the squares on the +/// adjacent files of the given one. -inline Bitboard this_and_neighboring_files_bb(File f) { - return ThisAndNeighboringFilesBB[f]; -} - -inline Bitboard this_and_neighboring_files_bb(Square s) { - return this_and_neighboring_files_bb(square_file(s)); +inline Bitboard adjacent_files_bb(File f) { + return AdjacentFilesBB[f]; } -/// relative_rank_bb() takes a color and a rank as input, and returns a bitboard -/// representing all squares on the given rank from the given color's point of -/// view. For instance, relative_rank_bb(WHITE, 7) gives all squares on the -/// 7th rank, while relative_rank_bb(BLACK, 7) gives all squares on the 2nd -/// rank. +/// 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 relative_rank_bb(Color c, Rank r) { - return RelativeRankBB[c][r]; +inline Bitboard between_bb(Square s1, Square s2) { + return BetweenBB[s1][s2]; } -/// in_front_bb() takes a color and a rank or square as input, and returns a -/// bitboard representing all the squares on all ranks in front of the rank -/// (or square), from the given color's point of view. For instance, -/// in_front_bb(WHITE, RANK_5) will give all squares on ranks 6, 7 and 8, while -/// in_front_bb(BLACK, SQ_D3) will give all squares on ranks 1 and 2. +/// in_front_bb() returns a bitboard representing all the squares on all the ranks +/// in front of the given one, from the point of view of the given color. For +/// instance, in_front_bb(BLACK, RANK_3) will return the squares on ranks 1 and 2. inline Bitboard in_front_bb(Color c, Rank r) { return InFrontBB[c][r]; } -inline Bitboard in_front_bb(Color c, Square s) { - return in_front_bb(c, square_rank(s)); -} - -/// ray_bb() gives a bitboard representing all squares along the ray in a -/// given direction from a given square. +/// forward_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: +/// ForwardBB[c][s] = in_front_bb(c, s) & file_bb(s) -inline Bitboard ray_bb(Square s, SignedDirection d) { - return RayBB[s][d]; +inline Bitboard forward_bb(Color c, Square s) { + return ForwardBB[c][s]; } -/// Functions for computing sliding attack bitboards. rook_attacks_bb(), -/// bishop_attacks_bb() and queen_attacks_bb() all take a square and a -/// bitboard of occupied squares as input, and return a bitboard representing -/// all squares attacked by a rook, bishop or queen on the given square. - -#if defined(USE_COMPACT_ROOK_ATTACKS) - -inline Bitboard file_attacks_bb(Square s, Bitboard blockers) { - Bitboard b = (blockers >> square_file(s)) & 0x01010101010100ULL; - return - FileAttacks[square_rank(s)][(b*0xd6e8802041d0c441ULL)>>58] & 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: +/// PawnAttackSpan[c][s] = in_front_bb(c, s) & adjacent_files_bb(s); -inline Bitboard rank_attacks_bb(Square s, Bitboard blockers) { - Bitboard b = (blockers >> ((s & 56) + 1)) & 63; - return RankAttacks[square_file(s)][b] & rank_bb(s); +inline Bitboard pawn_attack_span(Color c, Square s) { + return PawnAttackSpan[c][s]; } -inline Bitboard rook_attacks_bb(Square s, Bitboard blockers) { - return file_attacks_bb(s, blockers) | rank_attacks_bb(s, blockers); -} -#elif defined(USE_32BIT_ATTACKS) +/// 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_bb(c, s) -inline Bitboard rook_attacks_bb(Square s, Bitboard blockers) { - Bitboard b = blockers & RMask[s]; - return RAttacks[RAttackIndex[s] + - (unsigned(int(b) * int(RMult[s]) ^ - int(b >> 32) * int(RMult[s] >> 32)) - >> RShift[s])]; +inline Bitboard passed_pawn_mask(Color c, Square s) { + return PassedPawnMask[c][s]; } -#else -inline Bitboard rook_attacks_bb(Square s, Bitboard blockers) { - Bitboard b = blockers & RMask[s]; - return RAttacks[RAttackIndex[s] + ((b * RMult[s]) >> RShift[s])]; +/// squares_of_color() returns a bitboard representing all the squares of the +/// same color of the given one. + +inline Bitboard squares_of_color(Square s) { + return DarkSquares & s ? DarkSquares : ~DarkSquares; } -#endif -#if defined(USE_32BIT_ATTACKS) +/// aligned() returns true if the squares s1, s2 and s3 are aligned either on a +/// straight or on a diagonal line. -inline Bitboard bishop_attacks_bb(Square s, Bitboard blockers) { - Bitboard b = blockers & BMask[s]; - return BAttacks[BAttackIndex[s] + - (unsigned(int(b) * int(BMult[s]) ^ - int(b >> 32) * int(BMult[s] >> 32)) - >> BShift[s])]; +inline bool aligned(Square s1, Square s2, Square s3) { + return LineBB[s1][s2] & s3; } -#else // defined(USE_32BIT_ATTACKS) -inline Bitboard bishop_attacks_bb(Square s, Bitboard blockers) { - Bitboard b = blockers & BMask[s]; - return BAttacks[BAttackIndex[s] + ((b * BMult[s]) >> BShift[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. -#endif // defined(USE_32BIT_ATTACKS) +template inline int distance(T x, T y) { return x < y ? y - x : x - y; } +template<> inline int distance(Square x, Square y) { return SquareDistance[x][y]; } -inline Bitboard queen_attacks_bb(Square s, Bitboard blockers) { - return rook_attacks_bb(s, blockers) | bishop_attacks_bb(s, blockers); -} +template inline int distance(T2 x, T2 y); +template<> inline int distance(Square x, Square y) { return distance(file_of(x), file_of(y)); } +template<> inline int distance(Square x, Square y) { return distance(rank_of(x), rank_of(y)); } -/// squares_between returns a bitboard representing all squares between -/// two squares. For instance, squares_between(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, EmptyBoardBB is returned. +/// attacks_bb() returns a bitboard representing all the squares attacked by a +/// piece of type Pt (bishop or rook) placed on 's'. The helper magic_index() +/// looks up the index using the 'magic bitboards' approach. +template +FORCE_INLINE unsigned magic_index(Square s, Bitboard occupied) { -inline Bitboard squares_between(Square s1, Square s2) { - return BetweenBB[s1][s2]; -} + Bitboard* const Masks = Pt == ROOK ? RookMasks : BishopMasks; + Bitboard* const Magics = Pt == ROOK ? RookMagics : BishopMagics; + unsigned* const Shifts = Pt == ROOK ? RookShifts : BishopShifts; + if (HasPext) + return unsigned(pext(occupied, Masks[s])); -/// squares_in_front_of 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. For instance, -/// squares_in_front_of(BLACK, SQ_E4) returns a bitboard with the squares -/// e3, e2 and e1 set. + if (Is64Bit) + return unsigned(((occupied & Masks[s]) * Magics[s]) >> Shifts[s]); -inline Bitboard squares_in_front_of(Color c, Square s) { - return in_front_bb(c, s) & file_bb(s); + unsigned lo = unsigned(occupied) & unsigned(Masks[s]); + unsigned hi = unsigned(occupied >> 32) & unsigned(Masks[s] >> 32); + return (lo * unsigned(Magics[s]) ^ hi * unsigned(Magics[s] >> 32)) >> Shifts[s]; } - -/// squares_behind is similar to squares_in_front, but returns the squares -/// behind the square instead of in front of the square. - -inline Bitboard squares_behind(Color c, Square s) { - return in_front_bb(opposite_color(c), s) & file_bb(s); +template +inline Bitboard attacks_bb(Square s, Bitboard occupied) { + return (Pt == ROOK ? RookAttacks : BishopAttacks)[s][magic_index(s, occupied)]; } +inline Bitboard attacks_bb(Piece pc, Square s, Bitboard occupied) { -/// 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. - -inline Bitboard passed_pawn_mask(Color c, Square s) { - return PassedPawnMask[c][s]; + switch (type_of(pc)) + { + case BISHOP: return attacks_bb(s, occupied); + case ROOK : return attacks_bb(s, occupied); + case QUEEN : return attacks_bb(s, occupied) | attacks_bb(s, occupied); + default : return StepAttacksBB[pc][s]; + } } -/// outpost_mask takes a color and a square as input, and returns a bitboard -/// mask which can be used to test whether a piece on the square can possibly -/// be driven away by an enemy pawn. - -inline Bitboard outpost_mask(Color c, Square s) { - return OutpostMask[c][s]; -} +/// lsb() and msb() return the least/most significant bit in a non-zero bitboard +#ifdef USE_BSFQ -/// isolated_pawn_mask takes a square as input, and returns a bitboard mask -/// which can be used to test whether a pawn on the given square is isolated. +# if defined(_MSC_VER) && !defined(__INTEL_COMPILER) -inline Bitboard isolated_pawn_mask(Square s) { - return neighboring_files_bb(s); +FORCE_INLINE Square lsb(Bitboard b) { + unsigned long idx; + _BitScanForward64(&idx, b); + return (Square) idx; } +FORCE_INLINE Square msb(Bitboard b) { + unsigned long idx; + _BitScanReverse64(&idx, b); + return (Square) idx; +} -/// count_1s() counts the number of nonzero bits in a bitboard. +# elif defined(__arm__) -#if defined(BITCOUNT_LOOP) +FORCE_INLINE int lsb32(uint32_t v) { + __asm__("rbit %0, %1" : "=r"(v) : "r"(v)); + return __builtin_clz(v); +} -inline int count_1s(Bitboard b) { - int r; - for(r = 0; b; r++, b &= b - 1); - return r; +FORCE_INLINE Square msb(Bitboard b) { + return (Square) (63 - __builtin_clzll(b)); } -inline int count_1s_max_15(Bitboard b) { - return count_1s(b); +FORCE_INLINE Square lsb(Bitboard b) { + return (Square) (uint32_t(b) ? lsb32(uint32_t(b)) : 32 + lsb32(uint32_t(b >> 32))); } -#elif defined(BITCOUNT_SWAR_32) +# else // Assumed gcc or compatible compiler -inline int count_1s(Bitboard b) { - unsigned w = unsigned(b >> 32), v = unsigned(b); - v = v - ((v >> 1) & 0x55555555); - w = w - ((w >> 1) & 0x55555555); - v = (v & 0x33333333) + ((v >> 2) & 0x33333333); - w = (w & 0x33333333) + ((w >> 2) & 0x33333333); - v = (v + (v >> 4)) & 0x0F0F0F0F; - w = (w + (w >> 4)) & 0x0F0F0F0F; - v = ((v+w) * 0x01010101) >> 24; // mul is fast on amd procs - return int(v); +FORCE_INLINE Square lsb(Bitboard b) { // Assembly code by Heinz van Saanen + Bitboard idx; + __asm__("bsfq %1, %0": "=r"(idx): "rm"(b) ); + return (Square) idx; } -inline int count_1s_max_15(Bitboard b) { - unsigned w = unsigned(b >> 32), v = unsigned(b); - v = v - ((v >> 1) & 0x55555555); - w = w - ((w >> 1) & 0x55555555); - v = (v & 0x33333333) + ((v >> 2) & 0x33333333); - w = (w & 0x33333333) + ((w >> 2) & 0x33333333); - v = ((v+w) * 0x11111111) >> 28; - return int(v); +FORCE_INLINE Square msb(Bitboard b) { + Bitboard idx; + __asm__("bsrq %1, %0": "=r"(idx): "rm"(b) ); + return (Square) idx; } -#elif defined(BITCOUNT_SWAR_64) +# endif -inline int count_1s(Bitboard b) { - b -= ((b>>1) & 0x5555555555555555ULL); - b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL); - b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL; - b *= 0x0101010101010101ULL; - return int(b >> 56); -} +#else // ifdef(USE_BSFQ) -inline int count_1s_max_15(Bitboard b) { - b -= (b>>1) & 0x5555555555555555ULL; - b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL); - b *= 0x1111111111111111ULL; - return int(b >> 60); -} +Square lsb(Bitboard b); +Square msb(Bitboard b); -#endif // BITCOUNT +#endif -//// -//// Prototypes -//// +/// pop_lsb() finds and clears the least significant bit in a non-zero bitboard + +FORCE_INLINE Square pop_lsb(Bitboard* b) { + const Square s = lsb(*b); + *b &= *b - 1; + return s; +} + -extern void print_bitboard(Bitboard b); -extern void init_bitboards(); -extern Square first_1(Bitboard b); -extern Square pop_1st_bit(Bitboard *b); +/// 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 // !defined(BITBOARD_H_INCLUDED) +#endif // #ifndef BITBOARD_H_INCLUDED