FA-14139 / Numerical aggregation / Member archive

Frequency cosine squared: Norms discard coordinates absent from the other sample. · case 04

The reduction disagrees with its explicit aggregation oracle.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Treat samples as frequency vectors over nominal integer labels. Return squared cosine dot**2/(sum count_a**2 * sum count_b**2) as exact Fraction string. A zero norm on either side returns None.

Why this case matters

Exact bounded examples isolate a reduction defect without floating-point or external-service effects.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression 4	`null`	`"0"`	Failed

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