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ml-debug/references/sweeps.md
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wassname2andPi 76d93f2297 Clarify expensive-run exploration and sweep uncertainty
Preserve the full anti-skimming form and distinguish it from the brief end message. Describe batched changes with distinct predicted effects and conditional Bayesian updates. Replace normalized-score reliability verdicts with raw paired comparisons and explicit uncertainty.

Validation: diff --check; fresh-agent design scenarios exercised batching, normalization and full-form requirements. No actual training run or measured uplift test. Scenario agent placed the full form in the linked run log, leaving chat-display interpretation unresolved.

Co-Authored-By: Pi <288921227+claudypoo@users.noreply.github.com>
2026-09-07 11:37:12 +08:00

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Sweeps: learning what to try, and comparing results

Appendix to the ML Debugging skill. Choose the experiment for the question and iteration cost. Learning which direction to try next needs less certainty than claiming one method reliably beats another.

Expensive exploratory runs

For cheap runs, changing one thing at a time often makes diagnosis easier. For hours-long runs, batch changes when they have distinguishable predicted effects. Record what each should change in the logs before running, including possible interactions. Update the Bayesian mental model from trajectories and demos as well as final metrics; keep unresolved explanations rather than forcing attribution.

For example, a loader change may predict less time waiting for data, while a regularisation change predicts a different train–validation gap. Seeing both supports those explanations, but does not prove the changes acted independently. If both predict only a better final score, the log may not separate them. A later isolated comparison is useful when that uncertainty changes what to do next.

Comparing configurations or methods

Keep the evaluation data, metric definition and relevant budget comparable. Pair runs where meaningful: reuse seeds and inputs, but check that the changed implementation has not changed what those seeds control. Pairing can reduce noise; it does not guarantee its cancellation.

Inspect paired differences in the original metric units, their spread, and failed runs. A comparison of two bundles estimates the bundle difference, not each component's contribution. Distinguish exploratory selection from confirmation on seeds or data not used to select the winner.

Within-seed z-scores can describe response shapes, but erase effect magnitude. With just two settings, they can give the winner the same normalized value on every seed despite very different raw gains. Do not use that artificial lack of variance as evidence of reliability.

Describe uncertainty in the raw differences, with a method suited to the sample size and dependence. There is no universal “t > 2 with four seeds” guarantee. A noisy estimate leaves the effect uncertain; it does not establish either “no effect” or “a lucky seed.” One run can inform the next experiment without establishing reliability across seeds.

Keep crashed or divergent runs visible and investigate them. Do not silently exclude them from the comparison.