35.4. Sizing and knobs🔗

D6 and D7 are the rubrics that a deployment document is most tempted to skip, because the numbers involved are easy to type and hard to justify.

• D6 — Sizing from measured records. A run is sized from measured records rather than from constants typed by hand. A hand-typed size does not report the machine; it reports how far from saturation the author's memory happened to be.

• D7 — Operating points from a sweep. Operating points come from a sweep whose own turnover or plateau names them, reported with the dispersion any threshold has to beat. A threshold below the resolution of the measurement that produced it decides nothing, and — the part worth watching for — it fails silently, printing an optimum chosen by scatter. Reporting the dispersion beside the decision is what makes the failure visible, and refusing a comparison the data cannot support is a better answer than making one.

• D8 — The environment knobs. Every environment knob a job may set is enumerated with what it decides. A knob that is settable and undocumented is a way for a run to differ from the run that was accepted.