FA-45109 / Data systems / Member archive

Scatter updates validity at the first lane instead of the target · case 04

Scatter updates validity at the first lane instead of the target.

Member previewVariant 4 · 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
selected null	`[null, 6]`	`[4, null]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.