One-Layer Transformer Provably Learns Multiclass One-Nearest Neighbor in Context

Abstract:We extend recent work establishing an equivalence between one-layer transformers and nearest-neighbor classifiers in the binary setting to the multiclass case. By leveraging the simplex encoding, we show that one-layer transformers with an argmax classification head behave identically to a one-nearest-neighbor classifier in the multiclass setting. This closes a gap left by prior work, whose multiclass result relied on a non-standard rounding-based approach rather than the typical argmax head used in practice.

Machine Learning (cs.LG); Machine Learning (stat.ML)

arXiv:2609.01311 [cs.LG]

(or arXiv:2609.01311v1 [cs.LG] for this version)

https://doi.org/10.48550/arXiv.2609.01311 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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