Repository Analysis

google/tcmalloc

8.2 Low AI signal View on GitHub

Analysis Overview

This report presents the forensic synthetic code analysis of google/tcmalloc, a C++ project with 5,333 GitHub stars. SynthScan v2.0 examined 42,695 lines of code across 156 source files, recording 355 pattern matches distributed across 2 syntactic categories. The overall adjusted score of 8.2 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).

8.2
Adjusted Score
8.2
Raw Score
100%
Time Factor
2026-08-29
Last Push
5.3K
Stars
C++
Language
42.7K
Lines of Code
156
Files
355
Pattern Hits
2026-08-29
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 0MEDIUM 0LOW 355

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 355 distinct pattern matches across 2 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 Block354 hits · 350 pts
SeverityFileLineSnippetContext
LOWCMakeLists.txt1# Copyright 2026 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/page_allocator_test_util.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/tcmalloc.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/tcmalloc.h21COMMENT
LOWtcmalloc/transfer_cache.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/transfer_cache.h21#include <algorithm>COMMENT
LOWtcmalloc/huge_address_map.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/huge_address_map.h21#include "tcmalloc/huge_pages.h"COMMENT
LOWtcmalloc/new_extension.h1// Copyright 2020 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/experiment.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/experiment.h21#include <optional>COMMENT
LOWtcmalloc/profile_marshaler.h1// Copyright 2021 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/malloc_hook.h1// Copyright 2025 The TCMalloc Authors.COMMENT
LOWtcmalloc/malloc_hook.h81 //COMMENT
LOWtcmalloc/global_stats.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/static_vars.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/static_vars.h21#include <stdint.h>COMMENT
LOWtcmalloc/static_vars.h41#include "tcmalloc/internal/numa.h"COMMENT
LOWtcmalloc/huge_cache.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/huge_cache.h21COMMENT
LOWtcmalloc/huge_cache.h121 .freq = absl::base_internal::CycleClock::Frequency}) {}COMMENT
LOWtcmalloc/huge_page_tracker.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/huge_page_tracker.h21#include <algorithm>COMMENT
LOWtcmalloc/huge_page_tracker.h41#include "tcmalloc/common.h"COMMENT
LOWtcmalloc/huge_page_tracker.h81 unbroken_(true),COMMENT
LOWtcmalloc/huge_page_tracker.h261 hugepage_residency_state_ = state;COMMENT
LOWtcmalloc/huge_page_tracker.h361COMMENT
LOWtcmalloc/pages.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/pages.h21#include <limits>COMMENT
LOWtcmalloc/CMakeLists.txt1# Copyright 2026 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/huge_page_filler.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/huge_page_filler.h21#include <algorithm>COMMENT
LOWtcmalloc/huge_page_filler.h41#include "tcmalloc/common.h"COMMENT
LOWtcmalloc/huge_page_filler.h61#include "tcmalloc/pages.h"COMMENT
LOWtcmalloc/huge_page_filler.h721 struct TryGetResult {COMMENT
LOWtcmalloc/huge_page_filler.h861 // attempts.COMMENT
LOWtcmalloc/huge_page_filler.h941 // allocated, partially free, and partially returned to the OS.COMMENT
LOWtcmalloc/huge_page_filler.h1101inline typename HugePageFiller<TrackerType>::TryGetResultCOMMENT
LOWtcmalloc/huge_page_filler.h1121 // Our primary measure of fragmentation of a hugepage by a proxy measure: theCOMMENT
LOWtcmalloc/huge_page_filler.h1141 // way, they can be reassembled as a single large hugepage range if theCOMMENT
LOWtcmalloc/huge_page_filler.h1541 } else {COMMENT
LOWtcmalloc/huge_page_filler.h1581 // enabled, we increase the desired number of pages below to the total numberCOMMENT
LOWtcmalloc/huge_page_filler.h2381template <class TrackerType>COMMENT
LOWtcmalloc/pagemap.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/pagemap.h21//COMMENT
LOWtcmalloc/page_allocator.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/page_allocator.h21#include <cstdint>COMMENT
LOWtcmalloc/page_allocator.h221COMMENT
LOWtcmalloc/sizemap.h1// Copyright 2022 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/sizemap.h21#include <limits>COMMENT
LOWtcmalloc/sizemap.h61COMMENT
LOWtcmalloc/sizemap.h81 // 1024 (1024 + 7) / 8 128COMMENT
LOWtcmalloc/sizemap.h101 // * If the heap partitioning feature is not active, then the lookups forCOMMENT
LOWtcmalloc/sizemap.h121 // aligned, this member is also aligned to the width of a cache line.COMMENT
LOWtcmalloc/sizemap.h181 // constexpr constructor to guarantee zero-initialization at compile-time. WeCOMMENT
LOWtcmalloc/central_freelist.h1// Copyright 2019 The TCMalloc AuthorsCOMMENT
LOWtcmalloc/central_freelist.h21#include <array>COMMENT
LOWtcmalloc/central_freelist.h41#include "tcmalloc/internal/central_freelist_hooks.h"COMMENT
LOWtcmalloc/central_freelist.h241 // list with the lowest possible index. Returns the span if one exists in theCOMMENT
LOWtcmalloc/central_freelist.h341 // so writes are performed using LossyAdd for speed, the lock stillCOMMENT
294 more matches not shown…
Example Usage Blocks1 hit · 2 pts
SeverityFileLineSnippetContext
LOWtcmalloc/internal/prefetch.h49// Example usage:COMMENT