UltraBERT mixed 5 percent and 50 percent masking with separate LM heads, and the 380M encoder hit 91.0 on GLUE and 47.7 on BEIR with a native 32K context
AspireAI community · Hugging Face
dmis-lab released UltraBERT, a family of Apache 2.0 English encoders in 150M and 380M sizes, plus a ready-to-use UltraBERT-Embed-150M embedding model. The team trained encoders across more than 70 trillion tokens, with the longest single run at 8.8 trillion, and reported three findings: encoders plateau on GLUE, SQuAD and BEIR at roughly 1 to 2 trillion tokens while loss keeps falling, classification and retrieval favour opposite masking ratios, and distillation only helps at the low ratio. The fix is to mix 5 percent and 50 percent masked sequences in every batch and give each regime its own LM head. The 380M model scores 91.0 on GLUE and 47.7 on BEIR with 99 percent passkey accuracy out to 32K tokens, and UltraBERT-Embed-150M reaches 67.24 on MTEB English v2, the best dense embedding under 200M parameters. The honest caveat: these are the authors' own numbers on their own recipe, and the saturation finding rests on their data mixture rather than a sweep across mixtures.
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