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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 <sstream>
#include <iomanip>
#include <fstream>
#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> featureTransformer;
// Evaluation function
AlignedPtr<Network> network[LayerStacks];
// Evaluation function file name
std::string fileName;
std::string netDescription;
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 read_parameters(std::istream& stream, T& reference) {
std::uint32_t header;
header = read_little_endian<std::uint32_t>(stream);
if (!stream || header != T::get_hash_value()) return false;
return reference.read_parameters(stream);
}
// Write evaluation function parameters
template <typename T>
bool write_parameters(std::ostream& stream, const T& reference) {
write_little_endian<std::uint32_t>(stream, T::get_hash_value());
return reference.write_parameters(stream);
}
} // namespace Detail
// Initialize the evaluation function parameters
void initialize() {
Detail::initialize(featureTransformer);
for (std::size_t i = 0; i < LayerStacks; ++i)
Detail::initialize(network[i]);
}
// Read network header
bool read_header(std::istream& stream, std::uint32_t* hashValue, std::string* desc)
{
std::uint32_t version, size;
version = read_little_endian<std::uint32_t>(stream);
*hashValue = read_little_endian<std::uint32_t>(stream);
size = read_little_endian<std::uint32_t>(stream);
if (!stream || version != Version) return false;
desc->resize(size);
stream.read(&(*desc)[0], size);
return !stream.fail();
}
// Write network header
bool write_header(std::ostream& stream, std::uint32_t hashValue, const std::string& desc)
{
write_little_endian<std::uint32_t>(stream, Version);
write_little_endian<std::uint32_t>(stream, hashValue);
write_little_endian<std::uint32_t>(stream, desc.size());
stream.write(&desc[0], desc.size());
return !stream.fail();
}
// Read network parameters
bool read_parameters(std::istream& stream) {
std::uint32_t hashValue;
if (!read_header(stream, &hashValue, &netDescription)) return false;
if (hashValue != HashValue) return false;
if (!Detail::read_parameters(stream, *featureTransformer)) return false;
for (std::size_t i = 0; i < LayerStacks; ++i)
if (!Detail::read_parameters(stream, *(network[i]))) return false;
return stream && stream.peek() == std::ios::traits_type::eof();
}
// Write network parameters
bool write_parameters(std::ostream& stream) {
if (!write_header(stream, HashValue, netDescription)) return false;
if (!Detail::write_parameters(stream, *featureTransformer)) return false;
for (std::size_t i = 0; i < LayerStacks; ++i)
if (!Detail::write_parameters(stream, *(network[i]))) return false;
return (bool)stream;
}
// Evaluation function. Perform differential calculation.
Value evaluate(const Position& pos, bool adjusted) {
// 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 = CacheLineSize;
int delta = 7;
#if defined(ALIGNAS_ON_STACK_VARIABLES_BROKEN)
TransformedFeatureType transformedFeaturesUnaligned[
FeatureTransformer::BufferSize + alignment / sizeof(TransformedFeatureType)];
char bufferUnaligned[Network::BufferSize + alignment];
auto* transformedFeatures = align_ptr_up<alignment>(&transformedFeaturesUnaligned[0]);
auto* buffer = align_ptr_up<alignment>(&bufferUnaligned[0]);
#else
alignas(alignment)
TransformedFeatureType transformedFeatures[FeatureTransformer::BufferSize];
alignas(alignment) char buffer[Network::BufferSize];
#endif
ASSERT_ALIGNED(transformedFeatures, alignment);
ASSERT_ALIGNED(buffer, alignment);
const std::size_t bucket = (pos.count<ALL_PIECES>() - 1) / 4;
const auto psqt = featureTransformer->transform(pos, transformedFeatures, bucket);
const auto positional = network[bucket]->propagate(transformedFeatures, buffer)[0];
// Give more value to positional evaluation when material is balanced
if ( adjusted
&& abs(pos.non_pawn_material(WHITE) - pos.non_pawn_material(BLACK)) <= RookValueMg - BishopValueMg)
return static_cast<Value>(((128 - delta) * psqt + (128 + delta) * positional) / 128 / OutputScale);
else
return static_cast<Value>((psqt + positional) / OutputScale);
}
struct NnueEvalTrace {
static_assert(LayerStacks == PSQTBuckets);
Value psqt[LayerStacks];
Value positional[LayerStacks];
std::size_t correctBucket;
};
static NnueEvalTrace trace_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 = CacheLineSize;
#if defined(ALIGNAS_ON_STACK_VARIABLES_BROKEN)
TransformedFeatureType transformedFeaturesUnaligned[
FeatureTransformer::BufferSize + alignment / sizeof(TransformedFeatureType)];
char bufferUnaligned[Network::BufferSize + alignment];
auto* transformedFeatures = align_ptr_up<alignment>(&transformedFeaturesUnaligned[0]);
auto* buffer = align_ptr_up<alignment>(&bufferUnaligned[0]);
#else
alignas(alignment)
TransformedFeatureType transformedFeatures[FeatureTransformer::BufferSize];
alignas(alignment) char buffer[Network::BufferSize];
#endif
ASSERT_ALIGNED(transformedFeatures, alignment);
ASSERT_ALIGNED(buffer, alignment);
NnueEvalTrace t{};
t.correctBucket = (pos.count<ALL_PIECES>() - 1) / 4;
for (std::size_t bucket = 0; bucket < LayerStacks; ++bucket) {
const auto psqt = featureTransformer->transform(pos, transformedFeatures, bucket);
const auto output = network[bucket]->propagate(transformedFeatures, buffer);
int materialist = psqt;
int positional = output[0];
t.psqt[bucket] = static_cast<Value>( materialist / OutputScale );
t.positional[bucket] = static_cast<Value>( positional / OutputScale );
}
return t;
}
static const std::string PieceToChar(" PNBRQK pnbrqk");
// format_cp_compact() converts a Value into (centi)pawns and writes it in a buffer.
// The buffer must have capacity for at least 5 chars.
static void format_cp_compact(Value v, char* buffer) {
buffer[0] = (v < 0 ? '-' : v > 0 ? '+' : ' ');
int cp = std::abs(100 * v / PawnValueEg);
if (cp >= 10000)
{
buffer[1] = '0' + cp / 10000; cp %= 10000;
buffer[2] = '0' + cp / 1000; cp %= 1000;
buffer[3] = '0' + cp / 100; cp %= 100;
buffer[4] = ' ';
}
else if (cp >= 1000)
{
buffer[1] = '0' + cp / 1000; cp %= 1000;
buffer[2] = '0' + cp / 100; cp %= 100;
buffer[3] = '.';
buffer[4] = '0' + cp / 10;
}
else
{
buffer[1] = '0' + cp / 100; cp %= 100;
buffer[2] = '.';
buffer[3] = '0' + cp / 10; cp %= 10;
buffer[4] = '0' + cp / 1;
}
}
// format_cp_aligned_dot() converts a Value into (centi)pawns and writes it in a buffer,
// always keeping two decimals. The buffer must have capacity for at least 7 chars.
static void format_cp_aligned_dot(Value v, char* buffer) {
buffer[0] = (v < 0 ? '-' : v > 0 ? '+' : ' ');
double cp = 1.0 * std::abs(int(v)) / PawnValueEg;
sprintf(&buffer[1], "%6.2f", cp);
}
// trace() returns a string with the value of each piece on a board,
// and a table for (PSQT, Layers) values bucket by bucket.
std::string trace(Position& pos) {
std::stringstream ss;
char board[3*8+1][8*8+2];
std::memset(board, ' ', sizeof(board));
for (int row = 0; row < 3*8+1; ++row)
board[row][8*8+1] = '\0';
// A lambda to output one box of the board
auto writeSquare = [&board](File file, Rank rank, Piece pc, Value value) {
const int x = ((int)file) * 8;
const int y = (7 - (int)rank) * 3;
for (int i = 1; i < 8; ++i)
board[y][x+i] = board[y+3][x+i] = '-';
for (int i = 1; i < 3; ++i)
board[y+i][x] = board[y+i][x+8] = '|';
board[y][x] = board[y][x+8] = board[y+3][x+8] = board[y+3][x] = '+';
if (pc != NO_PIECE)
board[y+1][x+4] = PieceToChar[pc];
if (value != VALUE_NONE)
format_cp_compact(value, &board[y+2][x+2]);
};
// We estimate the value of each piece by doing a differential evaluation from
// the current base eval, simulating the removal of the piece from its square.
Value base = evaluate(pos);
base = pos.side_to_move() == WHITE ? base : -base;
for (File f = FILE_A; f <= FILE_H; ++f)
for (Rank r = RANK_1; r <= RANK_8; ++r)
{
Square sq = make_square(f, r);
Piece pc = pos.piece_on(sq);
Value v = VALUE_NONE;
if (pc != NO_PIECE && type_of(pc) != KING)
{
auto st = pos.state();
pos.remove_piece(sq);
st->accumulator.computed[WHITE] = false;
st->accumulator.computed[BLACK] = false;
Value eval = evaluate(pos);
eval = pos.side_to_move() == WHITE ? eval : -eval;
v = base - eval;
pos.put_piece(pc, sq);
st->accumulator.computed[WHITE] = false;
st->accumulator.computed[BLACK] = false;
}
writeSquare(f, r, pc, v);
}
ss << " NNUE derived piece values:\n";
for (int row = 0; row < 3*8+1; ++row)
ss << board[row] << '\n';
ss << '\n';
auto t = trace_evaluate(pos);
ss << " NNUE network contributions "
<< (pos.side_to_move() == WHITE ? "(White to move)" : "(Black to move)") << std::endl
<< "+------------+------------+------------+------------+\n"
<< "| Bucket | Material | Positional | Total |\n"
<< "| | (PSQT) | (Layers) | |\n"
<< "+------------+------------+------------+------------+\n";
for (std::size_t bucket = 0; bucket < LayerStacks; ++bucket)
{
char buffer[3][8];
std::memset(buffer, '\0', sizeof(buffer));
format_cp_aligned_dot(t.psqt[bucket], buffer[0]);
format_cp_aligned_dot(t.positional[bucket], buffer[1]);
format_cp_aligned_dot(t.psqt[bucket] + t.positional[bucket], buffer[2]);
ss << "| " << bucket << " "
<< " | " << buffer[0] << " "
<< " | " << buffer[1] << " "
<< " | " << buffer[2] << " "
<< " |";
if (bucket == t.correctBucket)
ss << " <-- this bucket is used";
ss << '\n';
}
ss << "+------------+------------+------------+------------+\n";
return ss.str();
}
// Load eval, from a file stream or a memory stream
bool load_eval(std::string name, std::istream& stream) {
initialize();
fileName = name;
return read_parameters(stream);
}
// Save eval, to a file stream or a memory stream
bool save_eval(std::ostream& stream) {
if (fileName.empty())
return false;
return write_parameters(stream);
}
/// Save eval, to a file given by its name
bool save_eval(const std::optional<std::string>& filename) {
std::string actualFilename;
std::string msg;
if (filename.has_value())
actualFilename = filename.value();
else
{
if (currentEvalFileName != EvalFileDefaultName)
{
msg = "Failed to export a net. A non-embedded net can only be saved if the filename is specified";
sync_cout << msg << sync_endl;
return false;
}
actualFilename = EvalFileDefaultName;
}
std::ofstream stream(actualFilename, std::ios_base::binary);
bool saved = save_eval(stream);
msg = saved ? "Network saved successfully to " + actualFilename
: "Failed to export a net";
sync_cout << msg << sync_endl;
return saved;
}
} // namespace Stockfish::Eval::NNUE
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