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nnue_common.h
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nnue_common.h
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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2023 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/>.
*/
// Constants used in NNUE evaluation function
#ifndef NNUE_COMMON_H_INCLUDED
#define NNUE_COMMON_H_INCLUDED
#include <cstring>
#include <iostream>
#include "../misc.h" // for IsLittleEndian
#if defined(USE_AVX2)
#include <immintrin.h>
#elif defined(USE_SSE41)
#include <smmintrin.h>
#elif defined(USE_SSSE3)
#include <tmmintrin.h>
#elif defined(USE_SSE2)
#include <emmintrin.h>
#elif defined(USE_MMX)
#include <mmintrin.h>
#elif defined(USE_NEON)
#include <arm_neon.h>
#endif
namespace Stockfish::Eval::NNUE {
// Version of the evaluation file
constexpr std::uint32_t Version = 0x7AF32F20u;
// Constant used in evaluation value calculation
constexpr int OutputScale = 16;
constexpr int WeightScaleBits = 6;
// Size of cache line (in bytes)
constexpr std::size_t CacheLineSize = 64;
constexpr const char Leb128MagicString[] = "COMPRESSED_LEB128";
constexpr const std::size_t Leb128MagicStringSize = sizeof(Leb128MagicString) - 1;
// SIMD width (in bytes)
#if defined(USE_AVX2)
constexpr std::size_t SimdWidth = 32;
#elif defined(USE_SSE2)
constexpr std::size_t SimdWidth = 16;
#elif defined(USE_MMX)
constexpr std::size_t SimdWidth = 8;
#elif defined(USE_NEON)
constexpr std::size_t SimdWidth = 16;
#endif
constexpr std::size_t MaxSimdWidth = 32;
// Type of input feature after conversion
using TransformedFeatureType = std::uint8_t;
using IndexType = std::uint32_t;
// Round n up to be a multiple of base
template <typename IntType>
constexpr IntType ceil_to_multiple(IntType n, IntType base) {
return (n + base - 1) / base * base;
}
// read_little_endian() is our utility to read an integer (signed or unsigned, any size)
// from a stream in little-endian order. We swap the byte order after the read if
// necessary to return a result with the byte ordering of the compiling machine.
template <typename IntType>
inline IntType read_little_endian(std::istream& stream) {
IntType result;
if (IsLittleEndian)
stream.read(reinterpret_cast<char*>(&result), sizeof(IntType));
else
{
std::uint8_t u[sizeof(IntType)];
typename std::make_unsigned<IntType>::type v = 0;
stream.read(reinterpret_cast<char*>(u), sizeof(IntType));
for (std::size_t i = 0; i < sizeof(IntType); ++i)
v = (v << 8) | u[sizeof(IntType) - i - 1];
std::memcpy(&result, &v, sizeof(IntType));
}
return result;
}
// write_little_endian() is our utility to write an integer (signed or unsigned, any size)
// to a stream in little-endian order. We swap the byte order before the write if
// necessary to always write in little endian order, independently of the byte
// ordering of the compiling machine.
template <typename IntType>
inline void write_little_endian(std::ostream& stream, IntType value) {
if (IsLittleEndian)
stream.write(reinterpret_cast<const char*>(&value), sizeof(IntType));
else
{
std::uint8_t u[sizeof(IntType)];
typename std::make_unsigned<IntType>::type v = value;
std::size_t i = 0;
// if constexpr to silence the warning about shift by 8
if constexpr (sizeof(IntType) > 1)
{
for (; i + 1 < sizeof(IntType); ++i)
{
u[i] = (std::uint8_t)v;
v >>= 8;
}
}
u[i] = (std::uint8_t)v;
stream.write(reinterpret_cast<char*>(u), sizeof(IntType));
}
}
// read_little_endian(s, out, N) : read integers in bulk from a little indian stream.
// This reads N integers from stream s and put them in array out.
template <typename IntType>
inline void read_little_endian(std::istream& stream, IntType* out, std::size_t count) {
if (IsLittleEndian)
stream.read(reinterpret_cast<char*>(out), sizeof(IntType) * count);
else
for (std::size_t i = 0; i < count; ++i)
out[i] = read_little_endian<IntType>(stream);
}
// write_little_endian(s, values, N) : write integers in bulk to a little indian stream.
// This takes N integers from array values and writes them on stream s.
template <typename IntType>
inline void write_little_endian(std::ostream& stream, const IntType* values, std::size_t count) {
if (IsLittleEndian)
stream.write(reinterpret_cast<const char*>(values), sizeof(IntType) * count);
else
for (std::size_t i = 0; i < count; ++i)
write_little_endian<IntType>(stream, values[i]);
}
// read_leb_128(s, out, N) : read N signed integers from the stream s, putting them in
// the array out. The stream is assumed to be compressed using the signed LEB128 format.
// See https://en.wikipedia.org/wiki/LEB128 for a description of the compression scheme.
template <typename IntType>
inline void read_leb_128(std::istream& stream, IntType* out, std::size_t count) {
// Check the presence of our LEB128 magic string
char leb128MagicString[Leb128MagicStringSize];
stream.read(leb128MagicString, Leb128MagicStringSize);
assert(strncmp(Leb128MagicString, leb128MagicString, Leb128MagicStringSize) == 0);
static_assert(std::is_signed_v<IntType>, "Not implemented for unsigned types");
const std::uint32_t BUF_SIZE = 4096;
std::uint8_t buf[BUF_SIZE];
auto bytes_left = read_little_endian<std::uint32_t>(stream);
std::uint32_t buf_pos = BUF_SIZE;
for (std::size_t i = 0; i < count; ++i)
{
IntType result = 0;
size_t shift = 0;
do
{
if (buf_pos == BUF_SIZE)
{
stream.read(reinterpret_cast<char*>(buf), std::min(bytes_left, BUF_SIZE));
buf_pos = 0;
}
std::uint8_t byte = buf[buf_pos++];
--bytes_left;
result |= (byte & 0x7f) << shift;
shift += 7;
if ((byte & 0x80) == 0)
{
out[i] = (sizeof(IntType) * 8 <= shift || (byte & 0x40) == 0) ? result
: result | ~((1 << shift) - 1);
break;
}
}
while (shift < sizeof(IntType) * 8);
}
assert(bytes_left == 0);
}
// write_leb_128(s, values, N) : write signed integers to a stream with LEB128 compression.
// This takes N integers from array values, compress them with the LEB128 algorithm and
// writes the result on the stream s.
// See https://en.wikipedia.org/wiki/LEB128 for a description of the compression scheme.
template <typename IntType>
inline void write_leb_128(std::ostream& stream, const IntType* values, std::size_t count) {
// Write our LEB128 magic string
stream.write(Leb128MagicString, Leb128MagicStringSize);
static_assert(std::is_signed_v<IntType>, "Not implemented for unsigned types");
std::uint32_t byte_count = 0;
for (std::size_t i = 0; i < count; ++i)
{
IntType value = values[i];
std::uint8_t byte;
do
{
byte = value & 0x7f;
value >>= 7;
++byte_count;
}
while ((byte & 0x40) == 0 ? value != 0 : value != -1);
}
write_little_endian(stream, byte_count);
const std::uint32_t BUF_SIZE = 4096;
std::uint8_t buf[BUF_SIZE];
std::uint32_t buf_pos = 0;
auto flush = [&]() {
if (buf_pos > 0)
{
stream.write(reinterpret_cast<char*>(buf), buf_pos);
buf_pos = 0;
}
};
auto write = [&](std::uint8_t byte) {
buf[buf_pos++] = byte;
if (buf_pos == BUF_SIZE)
flush();
};
for (std::size_t i = 0; i < count; ++i)
{
IntType value = values[i];
while (true)
{
std::uint8_t byte = value & 0x7f;
value >>= 7;
if ((byte & 0x40) == 0 ? value == 0 : value == -1)
{
write(byte);
break;
}
write(byte | 0x80);
}
}
flush();
}
} // namespace Stockfish::Eval::NNUE
#endif // #ifndef NNUE_COMMON_H_INCLUDED