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;
58 std::string currentEvalFileName = "None";
60 /// NNUE::init() tries to load a NNUE network at startup time, or when the engine
61 /// receives a UCI command "setoption name EvalFile value nn-[a-z0-9]{12}.nnue"
62 /// The name of the NNUE network is always retrieved from the EvalFile option.
63 /// We search the given network in three locations: internally (the default
64 /// network may be embedded in the binary), in the active working directory and
65 /// in the engine directory. Distro packagers may define the DEFAULT_NNUE_DIRECTORY
66 /// variable to have the engine search in a special directory in their distro.
70 std::string eval_file = std::string(Options["EvalFile"]);
71 if (eval_file.empty())
72 eval_file = EvalFileDefaultName;
74 #if defined(DEFAULT_NNUE_DIRECTORY)
75 std::vector<std::string> dirs = { "<internal>" , "" , CommandLine::binaryDirectory , stringify(DEFAULT_NNUE_DIRECTORY) };
77 std::vector<std::string> dirs = { "<internal>" , "" , CommandLine::binaryDirectory };
80 for (const std::string& directory : dirs)
81 if (currentEvalFileName != eval_file)
83 if (directory != "<internal>")
85 std::ifstream stream(directory + eval_file, std::ios::binary);
86 if (NNUE::load_eval(eval_file, stream))
87 currentEvalFileName = eval_file;
90 if (directory == "<internal>" && eval_file == EvalFileDefaultName)
92 // C++ way to prepare a buffer for a memory stream
93 class MemoryBuffer : public std::basic_streambuf<char> {
94 public: MemoryBuffer(char* p, size_t n) { setg(p, p, p + n); setp(p, p + n); }
97 MemoryBuffer buffer(const_cast<char*>(reinterpret_cast<const char*>(gEmbeddedNNUEData)),
98 size_t(gEmbeddedNNUESize));
99 (void) gEmbeddedNNUEEnd; // Silence warning on unused variable
101 std::istream stream(&buffer);
102 if (NNUE::load_eval(eval_file, stream))
103 currentEvalFileName = eval_file;
108 /// NNUE::verify() verifies that the last net used was loaded successfully
109 void NNUE::verify() {
111 std::string eval_file = std::string(Options["EvalFile"]);
112 if (eval_file.empty())
113 eval_file = EvalFileDefaultName;
115 if (currentEvalFileName != eval_file)
118 std::string msg1 = "Network evaluation parameters compatible with the engine must be available.";
119 std::string msg2 = "The network file " + eval_file + " was not loaded successfully.";
120 std::string msg3 = "The UCI option EvalFile might need to specify the full path, including the directory name, to the network file.";
121 std::string msg4 = "The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/" + std::string(EvalFileDefaultName);
122 std::string msg5 = "The engine will be terminated now.";
124 sync_cout << "info string ERROR: " << msg1 << sync_endl;
125 sync_cout << "info string ERROR: " << msg2 << sync_endl;
126 sync_cout << "info string ERROR: " << msg3 << sync_endl;
127 sync_cout << "info string ERROR: " << msg4 << sync_endl;
128 sync_cout << "info string ERROR: " << msg5 << sync_endl;
133 sync_cout << "info string NNUE evaluation using " << eval_file << sync_endl;
138 /// simple_eval() returns a static, purely materialistic evaluation of the position
139 /// from the point of view of the given color. It can be divided by PawnValue to get
140 /// an approximation of the material advantage on the board in terms of pawns.
142 Value Eval::simple_eval(const Position& pos, Color c) {
143 return PawnValue * (pos.count<PAWN>(c) - pos.count<PAWN>(~c))
144 + (pos.non_pawn_material(c) - pos.non_pawn_material(~c));
148 /// evaluate() is the evaluator for the outer world. It returns a static evaluation
149 /// of the position from the point of view of the side to move.
151 Value Eval::evaluate(const Position& pos) {
153 assert(!pos.checkers());
156 Color stm = pos.side_to_move();
157 int shuffling = pos.rule50_count();
158 int simpleEval = simple_eval(pos, stm) + (int(pos.key() & 7) - 3);
160 bool lazy = abs(simpleEval) >= RookValue + KnightValue
161 + 16 * shuffling * shuffling
162 + abs(pos.this_thread()->bestValue)
163 + abs(pos.this_thread()->rootSimpleEval);
166 v = Value(simpleEval);
170 Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);
172 Value optimism = pos.this_thread()->optimism[stm];
174 // Blend optimism and eval with nnue complexity and material imbalance
175 optimism += optimism * (nnueComplexity + abs(simpleEval - nnue)) / 512;
176 nnue -= nnue * (nnueComplexity + abs(simpleEval - nnue)) / 32768;
178 int npm = pos.non_pawn_material() / 64;
179 v = ( nnue * (915 + npm + 9 * pos.count<PAWN>())
180 + optimism * (154 + npm )) / 1024;
183 // Damp down the evaluation linearly when shuffling
184 v = v * (200 - shuffling) / 214;
186 // Guarantee evaluation does not hit the tablebase range
187 v = std::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
192 /// trace() is like evaluate(), but instead of returning a value, it returns
193 /// a string (suitable for outputting to stdout) that contains the detailed
194 /// descriptions and values of each evaluation term. Useful for debugging.
195 /// Trace scores are from white's point of view
197 std::string Eval::trace(Position& pos) {
200 return "Final evaluation: none (in check)";
202 // Reset any global variable used in eval
203 pos.this_thread()->bestValue = VALUE_ZERO;
204 pos.this_thread()->rootSimpleEval = VALUE_ZERO;
205 pos.this_thread()->optimism[WHITE] = VALUE_ZERO;
206 pos.this_thread()->optimism[BLACK] = VALUE_ZERO;
208 std::stringstream ss;
209 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2);
210 ss << '\n' << NNUE::trace(pos) << '\n';
212 ss << std::showpoint << std::showpos << std::fixed << std::setprecision(2) << std::setw(15);
215 v = NNUE::evaluate(pos, false);
216 v = pos.side_to_move() == WHITE ? v : -v;
217 ss << "NNUE evaluation " << 0.01 * UCI::to_cp(v) << " (white side)\n";
220 v = pos.side_to_move() == WHITE ? v : -v;
221 ss << "Final evaluation " << 0.01 * UCI::to_cp(v) << " (white side)";
222 ss << " [with scaled NNUE, ...]";
228 } // namespace Stockfish