2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
19 // Code for calculating NNUE evaluation function
25 #include "../evaluate.h"
26 #include "../position.h"
30 #include "evaluate_nnue.h"
32 namespace Eval::NNUE {
34 uint32_t kpp_board_index[PIECE_NB][COLOR_NB] = {
35 // convention: W - us, B - them
36 // viewed from other side, W and B are reversed
38 { PS_W_PAWN, PS_B_PAWN },
39 { PS_W_KNIGHT, PS_B_KNIGHT },
40 { PS_W_BISHOP, PS_B_BISHOP },
41 { PS_W_ROOK, PS_B_ROOK },
42 { PS_W_QUEEN, PS_B_QUEEN },
43 { PS_W_KING, PS_B_KING },
46 { PS_B_PAWN, PS_W_PAWN },
47 { PS_B_KNIGHT, PS_W_KNIGHT },
48 { PS_B_BISHOP, PS_W_BISHOP },
49 { PS_B_ROOK, PS_W_ROOK },
50 { PS_B_QUEEN, PS_W_QUEEN },
51 { PS_B_KING, PS_W_KING },
55 // Input feature converter
56 AlignedPtr<FeatureTransformer> feature_transformer;
58 // Evaluation function
59 AlignedPtr<Network> network;
61 // Evaluation function file name
66 // Initialize the evaluation function parameters
68 void Initialize(AlignedPtr<T>& pointer) {
70 pointer.reset(reinterpret_cast<T*>(std_aligned_alloc(alignof(T), sizeof(T))));
71 std::memset(pointer.get(), 0, sizeof(T));
74 // Read evaluation function parameters
76 bool ReadParameters(std::istream& stream, const AlignedPtr<T>& pointer) {
79 header = read_little_endian<std::uint32_t>(stream);
80 if (!stream || header != T::GetHashValue()) return false;
81 return pointer->ReadParameters(stream);
86 // Initialize the evaluation function parameters
89 Detail::Initialize(feature_transformer);
90 Detail::Initialize(network);
93 // Read network header
94 bool ReadHeader(std::istream& stream, std::uint32_t* hash_value, std::string* architecture)
96 std::uint32_t version, size;
98 version = read_little_endian<std::uint32_t>(stream);
99 *hash_value = read_little_endian<std::uint32_t>(stream);
100 size = read_little_endian<std::uint32_t>(stream);
101 if (!stream || version != kVersion) return false;
102 architecture->resize(size);
103 stream.read(&(*architecture)[0], size);
104 return !stream.fail();
107 // Read network parameters
108 bool ReadParameters(std::istream& stream) {
110 std::uint32_t hash_value;
111 std::string architecture;
112 if (!ReadHeader(stream, &hash_value, &architecture)) return false;
113 if (hash_value != kHashValue) return false;
114 if (!Detail::ReadParameters(stream, feature_transformer)) return false;
115 if (!Detail::ReadParameters(stream, network)) return false;
116 return stream && stream.peek() == std::ios::traits_type::eof();
119 // Proceed with the difference calculation if possible
120 static void UpdateAccumulatorIfPossible(const Position& pos) {
122 feature_transformer->UpdateAccumulatorIfPossible(pos);
125 // Calculate the evaluation value
126 static Value ComputeScore(const Position& pos, bool refresh) {
128 auto& accumulator = pos.state()->accumulator;
129 if (!refresh && accumulator.computed_score) {
130 return accumulator.score;
133 alignas(kCacheLineSize) TransformedFeatureType
134 transformed_features[FeatureTransformer::kBufferSize];
135 feature_transformer->Transform(pos, transformed_features, refresh);
136 alignas(kCacheLineSize) char buffer[Network::kBufferSize];
137 const auto output = network->Propagate(transformed_features, buffer);
139 auto score = static_cast<Value>(output[0] / FV_SCALE);
141 accumulator.score = score;
142 accumulator.computed_score = true;
143 return accumulator.score;
146 // Load the evaluation function file
147 bool load_eval_file(const std::string& evalFile) {
152 std::ifstream stream(evalFile, std::ios::binary);
154 const bool result = ReadParameters(stream);
159 // Evaluation function. Perform differential calculation.
160 Value evaluate(const Position& pos) {
161 return ComputeScore(pos, false);
164 // Evaluation function. Perform full calculation.
165 Value compute_eval(const Position& pos) {
166 return ComputeScore(pos, true);
169 // Proceed with the difference calculation if possible
170 void update_eval(const Position& pos) {
171 UpdateAccumulatorIfPossible(pos);
174 } // namespace Eval::NNUE