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bitboard.h
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141 lines (107 loc) · 3.28 KB
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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2025 The Stockfish developers (see AUTHORS file)
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 <algorithm>
#include <cassert>
#include <cmath>
#include <cstring>
#include <cstdint>
#include <cstdlib>
#include <string>
#include "types.h"
namespace Stockfish {
// Counts the number of non-zero bits in a bitboard.
inline int popcount(Bitboard b) {
#ifndef USE_POPCNT
b = b - ((b >> 1) & 0x5555555555555555ULL);
b = (b & 0x3333333333333333ULL) + ((b >> 2) & 0x3333333333333333ULL);
b = (b + (b >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
return (b * 0x0101010101010101ULL) >> 56;
#elif defined(_MSC_VER)
return int(_mm_popcnt_u64(b));
#else // Assumed gcc or compatible compiler
return __builtin_popcountll(b);
#endif
}
// Returns the least significant bit in a non-zero bitboard.
inline Square lsb(Bitboard b) {
assert(b);
#if defined(__GNUC__) // GCC, Clang, ICX
return Square(__builtin_ctzll(b));
#elif defined(_MSC_VER)
#ifdef _WIN64 // MSVC, WIN64
unsigned long idx;
_BitScanForward64(&idx, b);
return Square(idx);
#else // MSVC, WIN32
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);
}
#endif
#else // Compiler is neither GCC nor MSVC compatible
#error "Compiler not supported."
#endif
}
// Returns the most significant bit in a non-zero bitboard.
inline Square msb(Bitboard b) {
assert(b);
#if defined(__GNUC__) // GCC, Clang, ICX
return Square(63 ^ __builtin_clzll(b));
#elif defined(_MSC_VER)
#ifdef _WIN64 // MSVC, WIN64
unsigned long idx;
_BitScanReverse64(&idx, b);
return Square(idx);
#else // MSVC, WIN32
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
}
// Returns the bitboard of the least significant
// square of a non-zero bitboard. It is equivalent to square_bb(lsb(bb)).
inline Bitboard least_significant_square_bb(Bitboard b) {
assert(b);
return b & -b;
}
// 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;
}
} // namespace Stockfish
#endif // #ifndef BITBOARD_H_INCLUDED