X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.h;h=21dc6e44087a36e5c527d0d9a15b78119aa48463;hp=9fbcbf724b2bc7704ac3548724189b9757f8076e;hb=29b5842da8d5477c0aea924cfd364c9e619456a2;hpb=d6618d73258fb3973648d335966ab0f11666e4bb
diff --git a/src/bitboard.h b/src/bitboard.h
index 9fbcbf72..21dc6e44 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -1,183 +1,128 @@
/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ 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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
- Glaurung is free software: you can redistribute it and/or modify
+ 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.
-
- Glaurung is distributed in the hope that it will be useful,
+
+ 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 .
*/
-
-#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
-
-
-// Check for 64 bits for different compilers: Intel, MSVC and gcc
-#if defined(__x86_64) || defined(_WIN64) || (__SIZEOF_INT__ > 4)
-#define IS_64BIT
-#endif
+#include "types.h"
-#if !defined(AUTO_CONFIGURATION) || defined(IS_64BIT)
+namespace Bitbases {
-//#define USE_COMPACT_ROOK_ATTACKS
-//#define USE_32BIT_ATTACKS
-#define USE_FOLDED_BITSCAN
+void init();
+bool probe(Square wksq, Square wpsq, Square bksq, Color us);
-#define BITCOUNT_SWAR_64
-//#define BITCOUNT_SWAR_32
-//#define BITCOUNT_LOOP
+}
-#else
+namespace Bitboards {
-#define USE_32BIT_ATTACKS
-#define USE_FOLDED_BITSCAN
-#define BITCOUNT_SWAR_32
+void init();
+const std::string pretty(Bitboard b);
-#endif
+}
-////
-//// Includes
-////
+const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
-#include "direction.h"
-#include "piece.h"
-#include "square.h"
-#include "types.h"
+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;
+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);
-////
-//// Types
-////
+extern int SquareDistance[SQUARE_NB][SQUARE_NB];
-typedef uint64_t Bitboard;
+extern Bitboard RookMasks [SQUARE_NB];
+extern Bitboard RookMagics [SQUARE_NB];
+extern Bitboard* RookAttacks[SQUARE_NB];
+extern unsigned RookShifts [SQUARE_NB];
+extern Bitboard BishopMasks [SQUARE_NB];
+extern Bitboard BishopMagics [SQUARE_NB];
+extern Bitboard* BishopAttacks[SQUARE_NB];
+extern unsigned BishopShifts [SQUARE_NB];
-////
-//// Constants and variables
-////
+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];
-const Bitboard EmptyBoardBB = 0ULL;
-const Bitboard WhiteSquaresBB = 0x55AA55AA55AA55AAULL;
-const Bitboard BlackSquaresBB = 0xAA55AA55AA55AA55ULL;
+/// 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.
-extern const Bitboard SquaresByColorBB[2];
+inline Bitboard operator&(Bitboard b, Square s) {
+ return b & SquareBB[s];
+}
-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];
-
-extern Bitboard SetMaskBB[64];
-extern Bitboard ClearMaskBB[64];
-
-extern Bitboard StepAttackBB[16][64];
-extern Bitboard RayBB[64][8];
-extern Bitboard BetweenBB[64][64];
-
-extern Bitboard PassedPawnMask[2][64];
-extern Bitboard OutpostMask[2][64];
-
-#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 const uint64_t BMult[64];
-extern const int BShift[64];
-extern Bitboard BMask[64];
-extern int BAttackIndex[64];
-extern Bitboard BAttacks[0x1480];
-
-extern Bitboard BishopPseudoAttacks[64];
-extern Bitboard RookPseudoAttacks[64];
-extern Bitboard QueenPseudoAttacks[64];
-
-
-////
-//// Inline functions
-////
-
-/// Functions for testing whether a given bit is set in a bitboard, and for
-/// setting and clearing bits.
-
-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) {
@@ -185,255 +130,212 @@ 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.
+/// shift_bb() moves a bitboard one step along direction Delta. Mainly for pawns
-inline Bitboard neighboring_files_bb(File f) {
- return NeighboringFilesBB[f];
+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;
}
-inline Bitboard neighboring_files_bb(Square s) {
- return neighboring_files_bb(square_file(s));
-}
-
-
-/// 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.
-inline Bitboard this_and_neighboring_files_bb(File f) {
- return ThisAndNeighboringFilesBB[f];
-}
+/// 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(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.
+/// 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);
-#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);
+inline Bitboard pawn_attack_span(Color c, Square s) {
+ return PawnAttackSpan[c][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 rook_attacks_bb(Square s, Bitboard blockers) {
- return file_attacks_bb(s, blockers) | rank_attacks_bb(s, blockers);
-}
+/// 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)
-#elif defined(USE_32BIT_ATTACKS)
-
-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])];
+/// 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;
}
-#endif
-#if defined(USE_32BIT_ATTACKS)
+/// 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.
-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])];
-}
+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]; }
-#else // defined(USE_32BIT_ATTACKS)
+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)); }
-inline Bitboard bishop_attacks_bb(Square s, Bitboard blockers) {
- Bitboard b = blockers & BMask[s];
- return BAttacks[BAttackIndex[s] + ((b * BMult[s]) >> BShift[s])];
-}
-#endif // defined(USE_32BIT_ATTACKS)
+/// 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
+inline unsigned magic_index(Square s, Bitboard occupied) {
-inline Bitboard queen_attacks_bb(Square s, Bitboard blockers) {
- return rook_attacks_bb(s, blockers) | bishop_attacks_bb(s, blockers);
-}
+ 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_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.
+ if (Is64Bit)
+ return unsigned(((occupied & Masks[s]) * Magics[s]) >> Shifts[s]);
-inline Bitboard squares_between(Square s1, Square s2) {
- return BetweenBB[s1][s2];
+ 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];
}
+template
+inline Bitboard attacks_bb(Square s, Bitboard occupied) {
+ return (Pt == ROOK ? RookAttacks : BishopAttacks)[s][magic_index(s, occupied)];
+}
-/// 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.
+inline Bitboard attacks_bb(Piece pc, Square s, Bitboard occupied) {
-inline Bitboard squares_in_front_of(Color c, Square s) {
- return in_front_bb(c, s) & file_bb(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];
+ }
}
-/// squares_behind is similar to squares_in_front, but returns the squares
-/// behind the square instead of in front of the square.
+/// popcount() counts the number of non-zero bits in a bitboard
-inline Bitboard squares_behind(Color c, Square s) {
- return in_front_bb(opposite_color(c), s) & file_bb(s);
-}
+inline int popcount(Bitboard b) {
+#ifndef USE_POPCNT
-/// 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.
+ 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]];
-inline Bitboard passed_pawn_mask(Color c, Square s) {
- return PassedPawnMask[c][s];
-}
+#elif defined(_MSC_VER) && defined(__INTEL_COMPILER)
+ return _mm_popcnt_u64(b);
-/// 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.
+#elif defined(_MSC_VER)
-inline Bitboard outpost_mask(Color c, Square s) {
- return OutpostMask[c][s];
-}
+ return (int)__popcnt64(b);
+#else // Assumed gcc or compatible compiler
-/// 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.
+ return __builtin_popcountll(b);
-inline Bitboard isolated_pawn_mask(Square s) {
- return neighboring_files_bb(s);
+#endif
}
-/// count_1s() counts the number of nonzero bits in a bitboard.
+/// lsb() and msb() return the least/most significant bit in a non-zero bitboard
-#if defined(BITCOUNT_LOOP)
+#if defined(__GNUC__)
-inline int count_1s(Bitboard b) {
- int r;
- for(r = 0; b; r++, b &= b - 1);
- return r;
+inline Square lsb(Bitboard b) {
+ assert(b);
+ return Square(__builtin_ctzll(b));
}
-inline int count_1s_max_15(Bitboard b) {
- return count_1s(b);
+inline Square msb(Bitboard b) {
+ assert(b);
+ return Square(63 - __builtin_clzll(b));
}
-#elif defined(BITCOUNT_SWAR_32)
-
-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);
+#elif defined(_WIN64) && defined(_MSC_VER)
+
+inline Square lsb(Bitboard b) {
+ assert(b);
+ unsigned long idx;
+ _BitScanForward64(&idx, 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);
+inline Square msb(Bitboard b) {
+ assert(b);
+ unsigned long idx;
+ _BitScanReverse64(&idx, b);
+ return (Square) idx;
}
-#elif defined(BITCOUNT_SWAR_64)
+#else
+
+#define NO_BSF // Fallback on software implementation for other cases
-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);
-}
+Square lsb(Bitboard b);
+Square msb(Bitboard b);
+
+#endif
-inline int count_1s_max_15(Bitboard b) {
- b -= (b>>1) & 0x5555555555555555ULL;
- b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
- b *= 0x1111111111111111ULL;
- return int(b >> 60);
-}
-#endif // BITCOUNT
+/// 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;
+}
-////
-//// Prototypes
-////
-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