Follow-up A: Fix profile_accuracy::accuracy_single_threaded flake (6σ envelope) - #27
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- Replace the hard 5% bound on sum(weight) with the derived 6-sigma envelope of the Poisson unbiased-sum estimator (Var ~ N*SIZE*RATE). At the chosen constants (N=100_000, SIZE=64, RATE=4096) the old 5% bound was only ~1.97 sigma, giving a ~5% per-run flake rate under sibling cargo-test CPU contention. The new window is [5_428_293, 7_371_707] bytes around the 6_400_000 expected. - Verified by running the test 50x in a tight loop: 0 failures. - Ticket: 86aj0h83a.
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Summary
Replaces the 5% bound on
sum(weights)with a derived 6σ statistical envelope.Analysis — for Poisson sampling at rate R, the unbiased sum estimator has variance
~ N*SIZE*R. At N=100_000, SIZE=64, RATE=4096: σ ≈ 161,951 bytes ≈ 2.53% of expected. The pre-existing 5% bound was ~1.97σ → two-tailed P(fail) ≈ 4.8% — matches the observed ~1/10 flake rate.Fix — 6σ envelope
[5_428_293, 7_371_707](matches the rigor of the adjacent sample-count assertion).Closes ClickUp ticket 86aj0h83a.
Test plan
cargo test --features profiling --test profile_accuracy accuracy_single_threadedin tight loop — 0 failures