perf: better string building

pypa/packaging#997 · merged 2026-01-06 · base 1c4e8056b1 → head 65092ce350 · ran on Docker

PASS

No behaviour divergence found by any probe.

Performance · Version

No realistic input family measured slower.

Measured in backtest packaging-v2 (same commits, run bt-997-27f243, image bw-pair:d358a5c896312bf0). The semantic results above are from a later run; perf doesn't use the semantic planner, so it was not re-measured.

Head/base cachegrind instructions per call, by input size (log-log). Each line is one input family Nemotron proposed; points above 1× are where the "faster" code does more work.

Family	Inputs	Ratio range	Slope base → head	Verdict
`F3`	Plain versions that have only a release segment (any length) and no epoch, pre, post, dev or local parts. The change was motivated by avoiding the `self.base_version` property access; the new code builds the release string directly with a single `join` and returns it.claimed speedup · plan	1.00× – 1.00×	0.74 → 0.74	neutral

Receipt

Target	Backend	Image	Run	Audit	Adjudication
`packaging.version:Version`	local Docker	`bw-pair:b6408f6a83d7d09d`	`bt-997-7f3e77`	$0.033	$0.000

Nemotron cost on Nebius Token Factory. Backend: where the untrusted code ran. local Docker (an image cited by its content-addressed tag). Every image is content-addressed (repo at each commit + harness), so every card re-runs from the image and seed 0. Raw data: audit.