SPARSEUP paper: training recipe for learned sparse retrievers hits 56.4 nDCG@10 on BEIR-13 under 150M params

antoine_chaffin · x · 2026-11-09

Linkup's research team released SPARSEUP on arXiv, a recipe for training Splade-like sparse encoders on modern backbones. Key contributions: analyzing logit distribution's impact on training stability and sparsity, a per-position fan-out hard cap on vocabulary dimensions, and a vocabulary merging strategy that removes redundant case/word-boundary variants from cased BPE backbones. Applied to LightOn's LateOn backbone, SPARSEUP reaches 56.4 average nDCG@10 on BEIR-13 — the highest known among public vocabulary-based sparse encoders below 150M parameters, with extended comparisons against DenseOn, LateOn and SlideOn.

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