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Abstract
LightGBM's source-macro ROC AUC decreased from 0.764 to 0.585 when tested with source holdout.
- Random-row validation may overestimate model performance for unseen data sources.
- A paired mean loss of 0.179 (P = 2.5 × 10⁻¹⁹) indicates significant performance decline under source holdout.
- Continuous-rank correlation dropped from 0.463 to 0.160, suggesting reduced predictive accuracy.
- Top-10% candidate enrichment decreased from 2.61-fold to 1.39-fold, highlighting challenges in identifying high-performing candidates.
- Intermediate results from exact-lipid and descriptor-cluster holdouts suggest that chemical novelty does not equate to complete source novelty.
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