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Claude
328aafae77
Commit the spec and scaffold the system it describes:
- SPEC.md: the full v0.1 engineering spec
- crates/: trust-layer Rust workspace, unit-tested
- bench-runner: interleaved ABAB scheduling with discarded warm-ups,
deterministic bootstrap CIs over the ratio of medians,
CI-lower-bound accept rule, env fingerprinting, and a CLI with
compare + A/A self-test modes (A/A verified passing end-to-end)
- diff-test: gate outcome model, sha256 corpus pin verifier that
refuses on mismatch, per-target equivalence policy parser
(byte-identical default, explicit fp-tolerance opt-in)
- ledger: append-only SQLite attempt schema with UPDATE/DELETE
refused by triggers, anti-double-attempt query
- report: cores-saved and dollars/yr ROI math over speedup CIs,
pricing.toml inputs
- playbook/: classes 1-7 with preconditions, procedure, verification
notes, and known failure modes per class
- agent/: Python package skeleton — six-tool contract and prompting
spine, harness IPC deferred to Phase 1
- config/: accept.toml (2% threshold, 30 runs/side), pricing.toml
- targets/, corpora/, results/calibration/: layout and policy docs
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2
37 lines
1.7 KiB
Markdown
37 lines
1.7 KiB
Markdown
# Class 3 — Allocation churn
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First source-touching class: reduce the *number* of allocations, not the
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allocator servicing them.
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## Preconditions
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- Class 2 helped but allocator symbols still hot, or allocation shows up
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as cache misses from pointer-chasing freshly allocated objects.
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- Profile signature: allocation inside hot loops; `Vec`/`String`
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reallocation churn; many short-lived objects of the same type.
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## Procedure (cheapest first)
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1. Hoist allocations out of loops; reuse buffers via `clear()` instead
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of re-creation.
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2. `Vec::with_capacity` / `reserve` where the size is known or bounded.
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3. Small-vector types (`smallvec`, fixed inline buffers) for collections
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that are almost always tiny — confirm the size distribution from the
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profile or a counting instrument first.
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4. Arena allocation (`bumpalo`, typed arenas) for phase-scoped object
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graphs with a clear reset point.
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## Verification notes
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- Buffer reuse is where stale-data bugs come from: golden replay must
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cover inputs of *decreasing* size across a session so a dirty buffer
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would surface. Add such a sequence to the corpus if missing.
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- Arenas change drop order; targets with observable `Drop` side effects
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(logging, flushing) can diverge on golden replay — that divergence is
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a real reject, not noise.
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## Known failure modes
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- `with_capacity` guesses that overshoot: RSS regression the wall-clock
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number won't show — check the captured max RSS.
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- smallvec inline sizes chosen by vibes: an inline buffer bigger than
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the cache line it saves. Measure, don't guess.
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- Reuse introducing borrow-checker contortions that force `unsafe` —
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`unsafe` introduction routes to `needs-human-review` (SPEC §8).
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