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Scatter returns only explicitly updated lanes · case 02

Scatter returns only explicitly updated lanes.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Apply an ordered scatter update to a column using [target-index,value,is-valid,is-selected] records. Unselected writes do nothing; selected null writes clear validity. Repeated targets use the final selected write, and untouched lanes retain both payload visibility and validity.

Why this case matters

A bounded deterministic data engine model makes representation and changelog faults reproducible.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
nonzero target	`[5]`	`[2, 3, 5]`	Failed

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