arXiv Machine Learning By Sangyoon Bae, Sk Miraj Ahmed, Shinjae Yoo, Jiook Cha

Pretraining Shapes Spectral Structure: Architecture- and Strategy-Conditional Prediction of OOD Robustness in Foundation Models

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arXiv Computer Vision
Oct 2

Dataset Identity, Not Novelty: The Source of an Inflated OOD Detection Gain

The paper investigates why post‑hoc out‑of‑distribution (OOD) detectors often report inflated gains. It shows that many detectors learn to recognize the specific dataset they were trained on rather than true novelty, a phenomenon called the inflation gap. By holding out entire OOD datasets during evaluation, the authors demonstrate that most reported gains vanish, and they provide a closed‑form method to predict which fits will inflate.

By Donghoon Lee, Shinjin Kang
arXiv AI
1d ago

Don't Replace, Complement: A Detector-Agnostic Subspace Signal for Near-OOD Detection

The paper introduces PLUS, a detector‑agnostic subspace signal that enhances near‑out‑of‑distribution (near‑OOD) detection. PLUS selects the most class‑active neurons via a sparse autoencoder, orthonormalizes their decoder directions to form a low‑dimensional subspace, and scores inputs using a per‑class whitened squared Mahalanobis distance within that subspace. The resulting signal is fused additively with any calibrated base score using a single global weight, improving near‑OOD AUROC across 126 detector–backbone combinations while largely preserving far‑OOD performance.

By Wonseok Shin, Songkuk Kim