2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2023 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/>.
30 #include "incbin/incbin.h"
32 #include "nnue/evaluate_nnue.h"
38 // Macro to embed the default efficiently updatable neural network (NNUE) file
39 // data in the engine binary (using incbin.h, by Dale Weiler).
40 // This macro invocation will declare the following three variables
41 // const unsigned char gEmbeddedNNUEData[]; // a pointer to the embedded data
42 // const unsigned char *const gEmbeddedNNUEEnd; // a marker to the end
43 // const unsigned int gEmbeddedNNUESize; // the size of the embedded file
44 // Note that this does not work in Microsoft Visual Studio.
45 #if !defined(_MSC_VER) && !defined(NNUE_EMBEDDING_OFF)
46 INCBIN(EmbeddedNNUE, EvalFileDefaultName);
48 const unsigned char gEmbeddedNNUEData[1] = {0x0};
49 const unsigned char *const gEmbeddedNNUEEnd = &gEmbeddedNNUEData[1];
50 const unsigned int gEmbeddedNNUESize = 1;
60 string currentEvalFileName = "None";
62 /// NNUE::init() tries to load a NNUE network at startup time, or when the engine
63 /// receives a UCI command "setoption name EvalFile value nn-[a-z0-9]{12}.nnue"
64 /// The name of the NNUE network is always retrieved from the EvalFile option.
65 /// We search the given network in three locations: internally (the default
66 /// network may be embedded in the binary), in the active working directory and
67 /// in the engine directory. Distro packagers may define the DEFAULT_NNUE_DIRECTORY
68 /// variable to have the engine search in a special directory in their distro.
72 string eval_file = string(Options["EvalFile"]);
73 if (eval_file.empty())
74 eval_file = EvalFileDefaultName;
76 #if defined(DEFAULT_NNUE_DIRECTORY)
77 vector<string> dirs = { "<internal>" , "" , CommandLine::binaryDirectory , stringify(DEFAULT_NNUE_DIRECTORY) };
79 vector<string> dirs = { "<internal>" , "" , CommandLine::binaryDirectory };
82 for (const string& directory : dirs)
83 if (currentEvalFileName != eval_file)
85 if (directory != "<internal>")
87 ifstream stream(directory + eval_file, ios::binary);
88 if (NNUE::load_eval(eval_file, stream))
89 currentEvalFileName = eval_file;
92 if (directory == "<internal>" && eval_file == EvalFileDefaultName)
94 // C++ way to prepare a buffer for a memory stream
95 class MemoryBuffer : public basic_streambuf<char> {
96 public: MemoryBuffer(char* p, size_t n) { setg(p, p, p + n); setp(p, p + n); }
99 MemoryBuffer buffer(const_cast<char*>(reinterpret_cast<const char*>(gEmbeddedNNUEData)),
100 size_t(gEmbeddedNNUESize));
101 (void) gEmbeddedNNUEEnd; // Silence warning on unused variable
103 istream stream(&buffer);
104 if (NNUE::load_eval(eval_file, stream))
105 currentEvalFileName = eval_file;
110 /// NNUE::verify() verifies that the last net used was loaded successfully
111 void NNUE::verify() {
113 string eval_file = string(Options["EvalFile"]);
114 if (eval_file.empty())
115 eval_file = EvalFileDefaultName;
117 if (currentEvalFileName != eval_file)
120 string msg1 = "Network evaluation parameters compatible with the engine must be available.";
121 string msg2 = "The network file " + eval_file + " was not loaded successfully.";
122 string msg3 = "The UCI option EvalFile might need to specify the full path, including the directory name, to the network file.";
123 string msg4 = "The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/" + std::string(EvalFileDefaultName);
124 string msg5 = "The engine will be terminated now.";
126 sync_cout << "info string ERROR: " << msg1 << sync_endl;
127 sync_cout << "info string ERROR: " << msg2 << sync_endl;
128 sync_cout << "info string ERROR: " << msg3 << sync_endl;
129 sync_cout << "info string ERROR: " << msg4 << sync_endl;
130 sync_cout << "info string ERROR: " << msg5 << sync_endl;
135 sync_cout << "info string NNUE evaluation using " << eval_file << sync_endl;
140 /// simple_eval() returns a static, purely materialistic evaluation of the position
141 /// from the point of view of the given color. It can be divided by PawnValue to get
142 /// an approximation of the material advantage on the board in terms of pawns.
144 Value Eval::simple_eval(const Position& pos, Color c) {
145 return PawnValue * (pos.count<PAWN>(c) - pos.count<PAWN>(~c))
146 + (pos.non_pawn_material(c) - pos.non_pawn_material(~c));
150 /// evaluate() is the evaluator for the outer world. It returns a static evaluation
151 /// of the position from the point of view of the side to move.
153 Value Eval::evaluate(const Position& pos) {
155 assert(!pos.checkers());
158 Color stm = pos.side_to_move();
159 int shuffling = pos.rule50_count();
160 int simpleEval = simple_eval(pos, stm) + (int(pos.key() & 7) - 3);
162 bool lazy = abs(simpleEval) >= RookValue + KnightValue
163 + 16 * shuffling * shuffling
164 + abs(pos.this_thread()->bestValue)
165 + abs(pos.this_thread()->rootSimpleEval);
168 v = Value(simpleEval);
172 Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);
174 Value optimism = pos.this_thread()->optimism[stm];
176 // Blend optimism and eval with nnue complexity and material imbalance
177 optimism += optimism * (nnueComplexity + abs(simpleEval - nnue)) / 512;
178 nnue -= nnue * (nnueComplexity + abs(simpleEval - nnue)) / 32768;
180 int npm = pos.non_pawn_material() / 64;
181 v = ( nnue * (915 + npm + 9 * pos.count<PAWN>())
182 + optimism * (154 + npm + pos.count<PAWN>())) / 1024;
185 // Damp down the evaluation linearly when shuffling
186 v = v * (200 - shuffling) / 214;
188 // Guarantee evaluation does not hit the tablebase range
189 v = std::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
194 /// trace() is like evaluate(), but instead of returning a value, it returns
195 /// a string (suitable for outputting to stdout) that contains the detailed
196 /// descriptions and values of each evaluation term. Useful for debugging.
197 /// Trace scores are from white's point of view
199 std::string Eval::trace(Position& pos) {
202 return "Final evaluation: none (in check)";
204 // Reset any global variable used in eval
205 pos.this_thread()->bestValue = VALUE_ZERO;
206 pos.this_thread()->rootSimpleEval = VALUE_ZERO;
207 pos.this_thread()->optimism[WHITE] = VALUE_ZERO;
208 pos.this_thread()->optimism[BLACK] = VALUE_ZERO;
210 std::stringstream ss;
211 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2);
212 ss << '\n' << NNUE::trace(pos) << '\n';
214 ss << std::showpoint << std::showpos << std::fixed << std::setprecision(2) << std::setw(15);
217 v = NNUE::evaluate(pos, false);
218 v = pos.side_to_move() == WHITE ? v : -v;
219 ss << "NNUE evaluation " << 0.01 * UCI::to_cp(v) << " (white side)\n";
222 v = pos.side_to_move() == WHITE ? v : -v;
223 ss << "Final evaluation " << 0.01 * UCI::to_cp(v) << " (white side)";
224 ss << " [with scaled NNUE, ...]";
230 } // namespace Stockfish