Resolve the cause of the C. elegans implementation-control discrepancy

Identify the cause of the unresolved disagreement between the asynchronous implementation control and reference UMAP for the excluded C. elegans global-QC annotated dataset.

Background

The mechanism study excludes the C. elegans global-QC annotated dataset because its asynchronous implementation control failed to match reference UMAP bitwise at seed 2026. Repeated checks on the original CPU reproduced each implementation’s saved output but confirmed that the two outputs disagreed.

The unresolved implementation discrepancy prevented the dataset from being included in the mechanism-quality evaluation. Determining its cause would clarify whether the issue arises from the reference implementation, the asynchronous control, numerical behavior, or another execution detail, and would improve confidence in the validity of the comparison protocol.

References

We exclude the C.~elegans global-QC annotated dataset ($n=54{,}649$) from all variants and seeds because its asynchronous implementation control fails the bitwise comparison with reference UMAP at seed 2026. Two repeated checks on the original CPU reproduce each implementation's saved output but confirm the disagreement between them; its cause remains unresolved.

— ibUMAP: Coherent and Scalable Field Evaluation for UMAP Optimization  (2610.01445 - Chen et al., 1 Oct 2026) in Appendix, Section “Mechanism Study: Protocol and Robustness,” paragraph “Coverage and weighting”