Bug 2024208: Add a column to denote a magnitude of change based on the modality analysis

[kala-moz]

The Median Diff (%) column has been replaced with a Mode Δ (%) column that reports the largest matched-pair peak shift between the Base and New distributions, derived from the same KDE + mode-detection + modality-matching pipeline that powers the chart and the expanded-row blurb.

Like bootstrapCi, the value is precomputed once in the four data loaders (loader.ts, overTimeLoader.ts, subtestsLoader.ts, subtestsOverTimeLoader.tsx) via precomputeLargestPeakShift and attached to result.modeDeltaPct. KDE + mode matching is expensive enough that running it on every sort comparison or render would tank interactions.

Speedometer 3 preview link

I had some trouble with netlify thus all the open / reopen commands. :/

Update: The Mode Δ (%) column and the Distribution Interpretation row in MannWhitneyCompareMetrics were reading mode counts from two independent sources: the client-side ISJ/SJ KDE pipeline vs. the backend's wider Silverman KDE. Therefore, could could disagree in jarring ways (e.g. "Mode Δ = 4.16%" sitting directly above "No modes or data, possible oversmoothing"). Now, both views are piped through a single precomputed analysis so they can't drift.

Update 2: I precompute modality on replicates when available

Update 3: Flip the sortFunction to ASC semantics so the framework's swap produces the intuitive direction: DESC → biggest improvements first, ASC → biggest regressions first. Comment updated to spell this out (same convention the Sig column already uses).

Update 4: Lazy-precompute Mode Δ analysis to restore load speed. All four loaders no longer call precomputeModalityAnalysis

[netlify]

✅ Deploy Preview for mozilla-perfcompare ready!

Name	Link
🔨 Latest commit	cc4d261
🔍 Latest deploy log	https://app.netlify.com/projects/mozilla-perfcompare/deploys/6a3c98e0b8714300084c808a
😎 Deploy Preview	https://deploy-preview-1059--mozilla-perfcompare.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[padenot]

Similarly to #1056 (comment) I only see - ?

[kala-moz]

Similarly to #1056 (comment) I only see - ?

I've decided to also remove the dash since it doesn't give enough information. I've switched to NM which mean No Modes. I've updated the tooltip with more information.

Ahhh, I didn't use replicates. That's were the bug was. Updated subtests preview

Mozilla central preview