FA-13772 / Numerical aggregation / Member archive

Adjusted partition pair agreement: Chance agreement uses a sum of marginal pair totals. · case 02

The reduction disagrees with its explicit aggregation oracle.

Member previewVariant 2 · 3 implementations · 9 checks per implementation

Case contract

Two equal-length integer cluster label arrays describe the same observations. Return exact adjusted Rand index from pair-count contingency reduction. Label names have no numerical meaning. Matching degenerate partitions with zero normalization return "1"; length mismatch 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 5	`"3/28"`	`"-2/23"`	Failed

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

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