- The reach parse cache lives in the shared parity folder, keyed by content,
so a new worktree starts warm (written atomically, other worktrees'
entries kept within bounds).
- A harness's reach search stops as soon as it reaches a changed file that
differs in more than its `mod` declarations; partial searches are not
memoized. Declaration diffs are memoized (one git show per file).
- A harness whose changed dependency is outside crates/ is picked without a
search (narrowing always keeps those).
- After PARITY_REACH_BUDGET seconds (default 180) the remaining harnesses
count every source their probes link.
- crate_of is cached; no pathlib in the hot paths.
Same 79 harnesses on the 19-file diff from contrib-gate-16; CPU 19.9 s cold /
16.6 s warm before, 13.1 s cold / 9.9 s warm after (Mac mini under load).
parity.yml: skip the prepare_output check for heads made before #1947 (no
OUTPUT_VERSION, no tool): the job runs main's workflow on the head's files.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
`--changed` / `--changed-files` now narrow each harness's recorded Rust
sources to those its probes can reach (tools/parity_reach.py): an item-level
reachability walk from the probe modules a harness ran (or the binary it
built) over free items, inherent methods, trait impls and macros, matched by
name so it only over-approximates. Parent modules count through their `mod`
declarations, compared with the merge base. A harness whose probe can't be
placed keeps every source; `--by-crate` turns the narrowing off.
On the last 20 PRs merged on 2026-10-25: 2255 -> 1061 harnesses picked,
2384 -> 1592 harness-minutes. Replaying the week's 61 failed CI parity runs,
every failed harness the old selection picked is still picked; LLVM coverage of
six harnesses' probes executes only kept files.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Ludovic Marie