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stockfish/src/nnue/evaluate_nnue.cpp

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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2021 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/>.
*/
// Code for calculating NNUE evaluation function
#include <iostream>
#include <set>
#include "../evaluate.h"
#include "../position.h"
#include "../misc.h"
#include "../uci.h"
#include "../types.h"
#include "evaluate_nnue.h"
namespace Stockfish::Eval::NNUE {
// Input feature converter
LargePagePtr<FeatureTransformer> feature_transformer;
// Evaluation function
AlignedPtr<Network> network;
// Evaluation function file name
std::string fileName;
namespace Detail {
// Initialize the evaluation function parameters
template <typename T>
void Initialize(AlignedPtr<T>& pointer) {
pointer.reset(reinterpret_cast<T*>(std_aligned_alloc(alignof(T), sizeof(T))));
std::memset(pointer.get(), 0, sizeof(T));
}
template <typename T>
void Initialize(LargePagePtr<T>& pointer) {
static_assert(alignof(T) <= 4096, "aligned_large_pages_alloc() may fail for such a big alignment requirement of T");
pointer.reset(reinterpret_cast<T*>(aligned_large_pages_alloc(sizeof(T))));
std::memset(pointer.get(), 0, sizeof(T));
}
// Read evaluation function parameters
template <typename T>
bool ReadParameters(std::istream& stream, T& reference) {
std::uint32_t header;
header = read_little_endian<std::uint32_t>(stream);
if (!stream || header != T::GetHashValue()) return false;
return reference.ReadParameters(stream);
}
} // namespace Detail
// Initialize the evaluation function parameters
void Initialize() {
Detail::Initialize(feature_transformer);
Detail::Initialize(network);
}
// Read network header
bool ReadHeader(std::istream& stream, std::uint32_t* hash_value, std::string* architecture)
{
std::uint32_t version, size;
version = read_little_endian<std::uint32_t>(stream);
*hash_value = read_little_endian<std::uint32_t>(stream);
size = read_little_endian<std::uint32_t>(stream);
if (!stream || version != kVersion) return false;
architecture->resize(size);
stream.read(&(*architecture)[0], size);
return !stream.fail();
}
// Read network parameters
bool ReadParameters(std::istream& stream) {
std::uint32_t hash_value;
std::string architecture;
if (!ReadHeader(stream, &hash_value, &architecture)) return false;
if (hash_value != kHashValue) return false;
if (!Detail::ReadParameters(stream, *feature_transformer)) return false;
if (!Detail::ReadParameters(stream, *network)) return false;
return stream && stream.peek() == std::ios::traits_type::eof();
}
// Evaluation function. Perform differential calculation.
Value evaluate(const Position& pos) {
// We manually align the arrays on the stack because with gcc < 9.3
// overaligning stack variables with alignas() doesn't work correctly.
constexpr uint64_t alignment = kCacheLineSize;
#if defined(ALIGNAS_ON_STACK_VARIABLES_BROKEN)
TransformedFeatureType transformed_features_unaligned[
FeatureTransformer::kBufferSize + alignment / sizeof(TransformedFeatureType)];
char buffer_unaligned[Network::kBufferSize + alignment];
auto* transformed_features = align_ptr_up<alignment>(&transformed_features_unaligned[0]);
auto* buffer = align_ptr_up<alignment>(&buffer_unaligned[0]);
#else
alignas(alignment)
TransformedFeatureType transformed_features[FeatureTransformer::kBufferSize];
alignas(alignment) char buffer[Network::kBufferSize];
#endif
ASSERT_ALIGNED(transformed_features, alignment);
ASSERT_ALIGNED(buffer, alignment);
feature_transformer->Transform(pos, transformed_features);
const auto output = network->Propagate(transformed_features, buffer);
return static_cast<Value>(output[0] / FV_SCALE);
}
// Load eval, from a file stream or a memory stream
bool load_eval(std::string name, std::istream& stream) {
Initialize();
fileName = name;
return ReadParameters(stream);
}
} // namespace Stockfish::Eval::NNUE