Repository Analysis

simdjson/simdjson

Parsing gigabytes of JSON per second : used by Facebook/Meta Velox, the Node.js runtime, ClickHouse, WatermelonDB, Apache Doris, Milvus, StarRocks

3.7 Likely human-written View on GitHub

Analysis Overview

This report presents the forensic synthetic code analysis of simdjson/simdjson, a C++ project with 23,952 GitHub stars. SynthScan v2.0 examined 145,087 lines of code across 701 source files, recording 526 pattern matches distributed across 12 syntactic categories. The overall adjusted score of 3.7 places this repository in the Likely human-written 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).

3.7
Adjusted Score
3.7
Raw Score
100%
Time Factor
2026-07-13
Last Push
24.0K
Stars
C++
Language
145.1K
Lines of Code
701
Files
526
Pattern Hits
2026-07-14
Scan Date
0.00
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 1MEDIUM 2LOW 523

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 526 distinct pattern matches across 12 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 Block475 hits · 463 pts
SeverityFileLineSnippetContext
LOW.travis.yml141 key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'COMMENT
LOWbenchmark/benchmarker.h1#ifndef __BENCHMARKER_HCOMMENT
LOWbenchmark/benchmarker.h21#include <chrono>COMMENT
LOWbenchmark/benchmarker.h261 event_collector& collector;COMMENT
LOWbenchmark/benchfeatures.cpp1#include <counters/event_counter.h>COMMENT
LOWbenchmark/benchfeatures.cpp21#include <iomanip>COMMENT
LOWbenchmark/bench_ondemand.cpp1#include "simdjson.h"COMMENT
LOWbenchmark/bench_ondemand.cpp21#include <nlohmann/json.hpp>COMMENT
LOWbenchmark/bench_ondemand.cpp41COMMENT
LOWbenchmark/bench_ondemand.cpp61#include "distinct_user_id/simdjson_ondemand_json_pointer.h"COMMENT
LOWbenchmark/bench_ondemand.cpp81#if SIMDJSON_COMPETITION_ONDEMAND_SAJSONCOMMENT
LOWbenchmark/bench_ondemand.cpp101#if SIMDJSON_COMPETITION_SAXCOMMENT
LOWbenchmark/bench_ondemand.cpp121#include "kostya/nlohmann_json.h"COMMENT
LOWbenchmark/bench_ondemand.cpp141#include "large_random/nlohmann_json.h"COMMENT
LOWbenchmark/distinct_user_id/rapidjson_sax.h61#endif // SIMDJSON_COMPETITION_RAPIDJSONCOMMENT
LOW…eflect/twitter_benchmark/benchmark_parsing_twitter.cpp1#include <cassert>COMMENT
LOW…/twitter_benchmark/benchmark_serialization_twitter.cpp1#include <cassert>COMMENT
LOWbenchmark/static_reflect/serde-benchmark/lib.rs241// FFI Overhead Measurement FunctionsCOMMENT
LOW…log_benchmark/benchmark_serialization_citm_catalog.cpp1#include <cassert>COMMENT
LOW…lect/citm_catalog_benchmark/benchmark_parsing_citm.cpp1#include <cassert>COMMENT
LOWbenchmark/partial_tweets/tweet.h1#pragma onceCOMMENT
LOWbenchmark/dom/perfdiff.cpp1#include <cstdio>COMMENT
LOWbenchmark/dom/parse.cpp1#include <counters/event_counter.h>COMMENT
LOWbenchmark/dom/parse.cpp21#include <iostream>COMMENT
LOWtools/minify.cpp1#include <chrono>COMMENT
LOWtools/json2json.cpp1#include <iostream>COMMENT
LOWinclude/simdjson.h41#include "simdjson/simdjson_version.h"COMMENT
LOWinclude/simdjson.h61#include "simdjson/compile_time_json.h"COMMENT
LOWinclude/simdjson/builtin.h1#ifndef SIMDJSON_BUILTIN_HCOMMENT
LOWinclude/simdjson/builtin.h21#elif SIMDJSON_BUILTIN_IMPLEMENTATION_IS(westmere)COMMENT
LOWinclude/simdjson/fallback.h1#ifndef SIMDJSON_FALLBACK_HCOMMENT
LOWinclude/simdjson/dom.h1#ifndef SIMDJSON_DOM_HCOMMENT
LOWinclude/simdjson/dom.h21#include "simdjson/internal/tape_ref-inl.h"COMMENT
LOWinclude/simdjson/ppc64.h1#ifndef SIMDJSON_PPC64_HCOMMENT
LOWinclude/simdjson/rvv-vls.h1#ifndef SIMDJSON_RVV_VLS_HCOMMENT
LOWinclude/simdjson/haswell.h1#ifndef SIMDJSON_HASWELL_HCOMMENT
LOWinclude/simdjson/convert-inl.h121#endif // SIMDJSON_SUPPORTS_CONCEPTSCOMMENT
LOWinclude/simdjson/icelake.h1#ifndef SIMDJSON_ICELAKE_HCOMMENT
LOWinclude/simdjson/portability.h1#ifndef SIMDJSON_PORTABILITY_HCOMMENT
LOWinclude/simdjson/portability.h41COMMENT
LOWinclude/simdjson/portability.h61COMMENT
LOWinclude/simdjson/portability.h81 // We are not using GCC, so we assume that we can support runtime dispatch for LASX.COMMENT
LOWinclude/simdjson/portability.h101#elif defined(__PPC__) || defined(_M_PPC)COMMENT
LOWinclude/simdjson/portability.h121#define SIMDJSON_STRINGIFY(a,...) SIMDJSON_CAT_IMPLEMENTATION_(a, __VA_ARGS__)COMMENT
LOWinclude/simdjson/portability.h141//COMMENT
LOWinclude/simdjson/portability.h161#endif // defined(SIMDJSON_IS_X86_64) || defined(SIMDJSON_IS_LSX)COMMENT
LOWinclude/simdjson/portability.h181// Lack of compiler optimization may generate high stack usage.COMMENT
LOWinclude/simdjson/portability.h201#define simdjson_pureCOMMENT
LOWinclude/simdjson/portability.h221#define simdjson_strncasecmp _strnicmpCOMMENT
LOWinclude/simdjson/portability.h241#endifCOMMENT
LOWinclude/simdjson/portability.h261#elif defined(__MVS__)COMMENT
LOWinclude/simdjson/portability.h281#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__COMMENT
LOWinclude/simdjson/portability.h301// On Windows the class is disabled by default and must be explicitlyCOMMENT
LOWinclude/simdjson/portability.h321// simply does not exist — any attempt to use it fails at compile timeCOMMENT
LOWinclude/simdjson/common_defs.h21double from_chars(const char *first) noexcept;COMMENT
LOWinclude/simdjson/common_defs.h41 #define SIMDJSON_BEGIN_DEBUG_BLOCK(name) __asm volatile("# LLVM-MCA-BEGIN " #name);COMMENT
LOWinclude/simdjson/common_defs.h61 #define simdjson_unusedCOMMENT
LOWinclude/simdjson/common_defs.h81 #endifCOMMENT
LOWinclude/simdjson/common_defs.h101COMMENT
LOWinclude/simdjson/common_defs.h141 SIMDJSON_DISABLE_GCC_WARNING(-Wunused-variable) \COMMENT
415 more matches not shown…
Fake / Example Data19 hits · 19 pts
SeverityFileLineSnippetContext
LOWbenchmark/benchmark_reflection_usage_compilation.sh322 "name": "John Doe",CODE
LOWbenchmark/benchmark_reflection_usage_compilation.sh327 "street": "123 Main St",CODE
LOWbenchmark/benchmark_reflection_usage_compilation.sh393 "name": "John Doe",CODE
LOWbenchmark/benchmark_reflection_usage_compilation.sh398 "street": "123 Main St",CODE
LOWbenchmark/accessor_performance/accessor_benchmark.h16 "street": "123 Main St",CODE
LOWtests/ondemand/compile_time_json_path_tests.cpp47 "name": "John Doe",CODE
LOWtests/ondemand/compile_time_json_path_tests.cpp58 "street": "123 Main St",CODE
LOWtests/ondemand/compile_time_json_path_tests.cpp133 ASSERT_EQUAL(name, "John Doe");CODE
LOWtests/ondemand/compile_time_json_path_tests.cpp178 ASSERT_EQUAL(street, "123 Main St");CODE
LOWtests/ondemand/compile_time_json_pointer_tests.cpp47 "name": "John Doe",CODE
LOWtests/ondemand/compile_time_json_pointer_tests.cpp96 "street": "123 Main St",CODE
LOWtests/ondemand/compile_time_json_pointer_tests.cpp120 ASSERT_EQUAL(name, "John Doe");CODE
LOWtests/ondemand/compile_time_json_pointer_tests.cpp432 ASSERT_EQUAL(street, "123 Main St");CODE
LOWtests/ondemand/compile_time_json_pointer_tests.cpp527 ASSERT_EQUAL(name, "John Doe");CODE
LOWtests/builder/static_reflection_comprehensive_tests.cpp577 Person person{"John Doe", 30, "john@example.com", std::nullopt};CODE
LOWtests/builder/static_reflection_comprehensive_tests.cpp592 ASSERT_EQUAL(name, "John Doe");CODE
LOWtests/builder/static_reflection_comprehensive_tests.cpp598 Person person{"Jane Smith", 25, "jane@example.com", "555-1234"};CODE
LOWtests/builder/static_reflection_comprehensive_tests.cpp617 ASSERT_EQUAL(phone, "555-1234");CODE
LOWtests/builder/static_reflection_comprehensive_tests.cpp672 Company company{"TechCorp", {"123 Main St", "San Francisco", "94105"}, 500};CODE
Verbosity Indicators7 hits · 15 pts
SeverityFileLineSnippetContext
LOW…lude/simdjson/generic/builder/fractured_json_builder.h42 // Step 1: Serialize to minified JSONCOMMENT
LOW…lude/simdjson/generic/builder/fractured_json_builder.h49 // Step 2: Reformat with FracturedJsonCOMMENT
LOW…lude/simdjson/generic/builder/fractured_json_builder.h73 // Step 1: Extract fields to minified JSONCOMMENT
LOW…lude/simdjson/generic/builder/fractured_json_builder.h80 // Step 2: Reformat with FracturedJsonCOMMENT
LOWsrc/to_chars.cpp919 // Step 1: Schubfach multiplier calculation.COMMENT
LOWsrc/to_chars.cpp928 // Step 2: Try larger divisor; remove trailing zeros if necessary.COMMENT
LOWsrc/to_chars.cpp958 // Step 3: Find the significand with the smaller divisor.COMMENT
Structural Annotation Overuse7 hits · 15 pts
SeverityFileLineSnippetContext
LOW…lude/simdjson/generic/builder/fractured_json_builder.h42 // Step 1: Serialize to minified JSONCOMMENT
LOW…lude/simdjson/generic/builder/fractured_json_builder.h49 // Step 2: Reformat with FracturedJsonCOMMENT
LOW…lude/simdjson/generic/builder/fractured_json_builder.h73 // Step 1: Extract fields to minified JSONCOMMENT
LOW…lude/simdjson/generic/builder/fractured_json_builder.h80 // Step 2: Reformat with FracturedJsonCOMMENT
LOWsrc/to_chars.cpp919 // Step 1: Schubfach multiplier calculation.COMMENT
LOWsrc/to_chars.cpp928 // Step 2: Try larger divisor; remove trailing zeros if necessary.COMMENT
LOWsrc/to_chars.cpp958 // Step 3: Find the significand with the smaller divisor.COMMENT
Deep Nesting6 hits · 6 pts
SeverityFileLineSnippetContext
LOWstyle/run-clang-format.py36CODE
LOWstyle/run-clang-format.py163CODE
LOWscripts/detect_nonascii_sourcefiles.py5CODE
LOWsingleheader/amalgamate.py717CODE
LOWsingleheader/amalgamate.py375CODE
LOWsingleheader/amalgamate.py540CODE
Cross-Language Confusion1 hit · 5 pts
SeverityFileLineSnippetContext
HIGHtools/release.py188print("to issue release, enter \n git commit -a && git push && git tag -a v"+toversionstring(*newversion)+" -m \"versiCODE
Decorative Section Separators1 hit · 3 pts
SeverityFileLineSnippetContext
MEDIUMbenchmark/benchmark_reflection_usage_compilation.sh57# ───────────────────────────── BOX-PRINT HELPER ────────────────────────────COMMENT
Unused Imports3 hits · 3 pts
SeverityFileLineSnippetContext
LOWtools/release.py8CODE
LOWstyle/run-clang-format.py11CODE
LOWstyle/run-clang-format.py11CODE
Excessive Try-Catch Wrapping2 hits · 3 pts
SeverityFileLineSnippetContext
LOWstyle/run-clang-format.py97 except Exception as e:CODE
MEDIUMstyle/run-clang-format.py91def run_clang_format_diff_wrapper(args, file):CODE
Hyper-Verbose Identifiers3 hits · 2 pts
SeverityFileLineSnippetContext
LOWstyle/run-clang-format.py91def run_clang_format_diff_wrapper(args, file):CODE
LOWsingleheader/amalgamate.py375 def validate_free_dependency_file(self):STRING
LOWsingleheader/amalgamate.py423 def validate_free_dependency_files(self):STRING
Redundant / Tautological Comments1 hit · 2 pts
SeverityFileLineSnippetContext
LOWbenchmark/benchmark_reflection_usage_compilation.sh167# Check if we found a working compilerCOMMENT
Slop Phrases1 hit · 2 pts
SeverityFileLineSnippetContext
LOWfuzz/ossfuzz.sh9# make sure to exit on problemsCOMMENT