Repository Analysis

official-stockfish/Stockfish

A free and strong UCI chess engine

6.1 Low AI signal View on GitHub

Analysis Overview

This report presents the forensic synthetic code analysis of official-stockfish/Stockfish, a C++ project with 16,431 GitHub stars. SynthScan v2.0 examined 30,973 lines of code across 107 source files, recording 134 pattern matches distributed across 8 syntactic categories. The overall adjusted score of 6.1 places this repository in the Low AI signal band.

The scanner applied 160+ deterministic lexical heuristics, multi-line block detectors, abstract syntax tree depth profilers, and a cross-file Jaccard similarity matrix to construct a statistically normalised synthetic code estimate. All matches are individually weighted by severity coefficient and contextual multiplier before summation, and the resulting headline score is temporally discounted to account for the repository's development history relative to the commercial emergence of large language model coding tooling (November 2022 onward).

6.1
Adjusted Score
6.1
Raw Score
100%
Time Factor
2026-08-25
Last Push
16.4K
Stars
C++
Language
31.0K
Lines of Code
107
Files
134
Pattern Hits
2026-08-29
Scan Date
0.06
HC Hit Rate

What These Metrics Mean

Adjusted Score
Primary synthetic code indicator. Raw score normalised per 1,000 lines of code and multiplied by the temporal discount factor. This is the definitive comparative metric — use it to rank repositories by AI authorship density.
Raw Score
The unmodified sum of all severity-weighted, context-multiplied pattern match scores before temporal discounting. Reflects the absolute signal strength independent of when the repository was last active.
Time Factor
The temporal discount multiplier (0–100%) applied to the raw score. Repositories last updated before ChatGPT's launch (Nov 2022) receive a 5% factor. Full signal is only assigned to repositories active in the post-adoption era (Jan 2024+).
Pattern Hits
Total count of individual pattern matches across all files and categories. A high hit count with a low score may indicate a very large codebase with isolated AI snippets; a low count with a high score indicates dense, concentrated AI signatures.
HC Hit Rate
High+Critical pattern hits per file, averaged across the repository. This orthogonal signal catches repositories where a few files are densely packed with high-severity AI tells — a strong indicator even when the normalised score appears moderate due to codebase size.
Lines of Code / Files
Total lines and files analysed. The scanner examines 94 file extensions. These denominators are used to normalise the score, enabling fair comparison between repositories of vastly different sizes.

Score History

This chart maps the temporal evolution of the adjusted synthetic code score across successive scan runs. An upward trajectory indicates ongoing incorporation of AI-generated code or expanding LLM-assisted scaffolding; a stable or declining trajectory may reflect active human refactoring, code removal, or the adoption of stricter authorship policies. The dashed secondary line (right axis) independently tracks total raw pattern hit count, which can diverge from the normalised score when codebase size changes significantly between scans.

Severity Breakdown

Classifies detected patterns by their diagnostic confidence and structural impact. CRITICAL patterns (coefficient 10) represent definitive synthetic signatures — hallucinated imports, explicit LLM attribution metadata — virtually never produced by human authors. HIGH (5) indicates strong structural tells such as cross-file repetition or cross-linguistic idioms. MEDIUM (2) covers recognisable conversational padding and AI-specific vocabulary. LOW (1) captures subtle indicators like tautological comments and generic boilerplate that require density to carry independent signal.

CRITICAL 0HIGH 6MEDIUM 8LOW 120

Directory Score Breakdown

This horizontal bar chart decomposes the repository's raw synthetic code score by top-level directory, allowing you to pinpoint precisely which modules or components carry the highest AI authorship density. Directories with disproportionately high scores relative to their size warrant targeted manual review: concentrated AI signatures often trace back to mass-generated configuration layers, auto-ported test suites, LLM-scaffolded boilerplate classes, or entire subsystems authored under heavy copilot assistance. Use this view to prioritise your human code-review effort.

Pattern Findings

The scanner identified 134 distinct pattern matches across 8 syntactic categories. Each entry below represents a discrete location in the source code where the engine recorded a statistically significant AI authorship indicator. Expand any category row to inspect the individual file paths, line numbers, code snippets, and the lexical context (CODE, COMMENT, or STRING) in which each match was detected.

Reading the findings table: The Severity column indicates the diagnostic confidence level (CRITICAL / HIGH / MEDIUM / LOW). The Context column identifies whether the match occurred inside executable code, an inline comment, or a string literal — comment-context matches receive a ×1.5 weight because LLMs systematically over-annotate. The ⚡ bolt icon marks clustered matches: three or more patterns within a 10-line window, each receiving an additional ×1.5 density multiplier as dense clusters constitute far stronger evidence of synthetic authorship than isolated hits.

Over-Commented Block101 hits · 101 pts
SeverityFileLineSnippetContext
LOWscripts/get_native_properties.sh1#!/bin/shCOMMENT
LOWsrc/memory.cpp21#include <cstdlib>COMMENT
LOWsrc/memory.cpp41 #include <stdlib.h>COMMENT
LOWsrc/thread.cpp21#include <algorithm>COMMENT
LOWsrc/engine.h21COMMENT
LOWsrc/numa.h21COMMENT
LOWsrc/numa.h41#include "shm.h"COMMENT
LOWsrc/numa.h501// Use system NUMA nodesCOMMENT
LOWsrc/numa.h521// be removed, or the user may create custom nodes.COMMENT
LOWsrc/numa.h601 #if defined(_WIN64)COMMENT
LOWsrc/numa.h901 // This is defensive, allowed because this code is not performance critical.COMMENT
LOWsrc/types.h21COMMENT
LOWsrc/types.h41 #include <cstdint>COMMENT
LOWsrc/types.h61 #if defined(__GNUC__) && !defined(__clang__) \COMMENT
LOWsrc/types.h81COMMENT
LOWsrc/types.h221constexpr Value PieceValue[PIECE_NB] = {COMMENT
LOWsrc/misc.cpp21#include <array>COMMENT
LOWsrc/misc.cpp121 std::cin.rdbuf(&l.in);COMMENT
LOWsrc/misc.cpp181COMMENT
LOWsrc/misc.cpp261#if defined(USE_VNNI)COMMENT
LOWsrc/tune.h61// If you have a my_post_update() function to run after values have been updated,COMMENT
LOWsrc/misc.h21COMMENT
LOWsrc/misc.h421 inner = val;COMMENT
LOWsrc/misc.h561#endifCOMMENT
LOWsrc/misc.h581#endifCOMMENT
LOWsrc/thread_native.h21COMMENT
LOWsrc/benchmark.cpp381COMMENT
LOWsrc/evaluate.cpp21#include <algorithm>COMMENT
LOWsrc/thread.h21COMMENT
LOWsrc/history.h21COMMENT
LOWsrc/search.cpp21#include <algorithm>COMMENT
LOWsrc/search.cpp41#include "movepick.h"COMMENT
LOWsrc/search.cpp401 // first and eventually the new best one is set to -VALUE_INFINITECOMMENT
LOWsrc/search.cpp2241 // during engine game play, since we have a winning score, and play correctlyCOMMENT
LOWsrc/shm.h21COMMENT
LOWsrc/shm.h41 #define USE_UNIX_SHMCOMMENT
LOWsrc/shm.h61 #include <cstring>COMMENT
LOWsrc/shm.h81 #include <unistd.h>COMMENT
LOWsrc/memory.h21COMMENT
LOWsrc/memory.h41 #endifCOMMENT
LOWsrc/shm_unix.h21COMMENT
LOWsrc/shm_unix.h41#include <sys/file.h>COMMENT
LOWsrc/engine.cpp21#include <algorithm>COMMENT
LOWsrc/attacks.h21COMMENT
LOWsrc/attacks.h101 // We always compute [bishop, rook] attacks at once, then rely onCOMMENT
LOWsrc/movegen.cpp21#include <cassert>COMMENT
LOWsrc/tt.cpp21#include <algorithm>COMMENT
LOWsrc/tt.cpp41// pv node 1 bitCOMMENT
LOWsrc/search.h21COMMENT
LOWsrc/position.h21COMMENT
LOWsrc/position.cpp21#include <algorithm>COMMENT
LOWsrc/uci.cpp21#include <algorithm>COMMENT
LOWsrc/universal/patch_x86_slice.sh1#!/bin/shCOMMENT
LOWsrc/universal/nnue_embed.cpp21#include "../evaluate.h"COMMENT
LOWsrc/nnue/network.cpp21#include <algorithm>COMMENT
LOWsrc/nnue/network.cpp41COMMENT
LOWsrc/nnue/nnue_accumulator.cpp21#include <algorithm>COMMENT
LOWsrc/nnue/nnue_common.h21#ifndef NNUE_COMMON_H_INCLUDEDCOMMENT
LOWsrc/nnue/nnue_feature_transformer.h21#ifndef NNUE_FEATURE_TRANSFORMER_H_INCLUDEDCOMMENT
LOWsrc/nnue/nnue_feature_transformer.h281COMMENT
41 more matches not shown…
Cross-Language Confusion6 hits · 40 pts
SeverityFileLineSnippetContext
HIGHtests/instrumented.py226 self.stockfish.equals("uciok")CODE
HIGHtests/instrumented.py330 self.stockfish.equals("bestmove d5e6")CODE
HIGHtests/instrumented.py645 self.stockfish.equals("readyok")CODE
HIGHtests/instrumented.py650 self.stockfish.equals("readyok")CODE
HIGHtests/instrumented.py655 self.stockfish.equals("readyok")CODE
HIGHtests/instrumented.py672 self.stockfish.equals("readyok")CODE
Decorative Section Separators6 hits · 18 pts
SeverityFileLineSnippetContext
MEDIUMscripts/get_native_properties.sh10# ---------------------------COMMENT
MEDIUMscripts/get_native_properties.sh12# ---------------------------COMMENT
MEDIUMscripts/get_native_properties.sh202# ---------------------------COMMENT
MEDIUMscripts/get_native_properties.sh204# ---------------------------COMMENT
MEDIUMscripts/get_native_properties.sh285# ---------------------------COMMENT
MEDIUMscripts/get_native_properties.sh287# ---------------------------COMMENT
Hyper-Verbose Identifiers13 hits · 17 pts
SeverityFileLineSnippetContext
LOWtests/instrumented.py172 def test_export_net_verify_nnue(self):CODE
LOWtests/instrumented.py237 def test_ucinewgame_and_startpos_moves(self):CODE
LOWtests/instrumented.py341 def test_fen_position_fixed_node(self):CODE
LOWtests/instrumented.py349 def test_fen_position_with_mate_go_depth(self):CODE
LOWtests/instrumented.py359 def test_fen_position_with_mate_go_mate(self):CODE
LOWtests/instrumented.py369 def test_fen_position_with_mate_go_nodes(self):CODE
LOWtests/instrumented.py389 def test_fen_position_with_mate_go_depth_and_promotion(self):CODE
LOWtests/instrumented.py398 def test_fen_position_with_mate_go_depth_and_searchmoves(self):CODE
LOWtests/instrumented.py408 def test_fen_position_with_moves_with_mate_go_depth_and_searchmoves(self):CODE
LOWtests/instrumented.py434 def test_fen_position_with_skill_level(self):CODE
LOWtests/instrumented.py619 def test_invalid_side_to_move(self):CODE
LOWtests/instrumented.py662 def test_numa_malformed_range(self):CODE
LOWtests/testing.py49 def get_valgrind_thread_command():CODE
AI Slop Vocabulary2 hits · 6 pts
SeverityFileLineSnippetContext
MEDIUMsrc/numa.h1079 // node. On Windows we utilize GetNumaProcessorNodeEx, which has its quirks, seeCOMMENT
MEDIUMsrc/search.cpp1369 // std::clamp has been replaced by a more robust implementation.COMMENT
Deep Nesting3 hits · 3 pts
SeverityFileLineSnippetContext
LOWtests/instrumented.py41CODE
LOWtests/testing.py77CODE
LOWtests/testing.py134CODE
Excessive Try-Catch Wrapping2 hits · 2 pts
SeverityFileLineSnippetContext
LOWtests/testing.py147 except Exception as e:CODE
LOWtests/testing.py201 except Exception as e:CODE
TODO Padding1 hit · 2 pts
SeverityFileLineSnippetContext
LOWsrc/thread_native.h56 // TODO: implement fallible thread creation for MSVCCOMMENT