Larger tokenizers suffer more multi-epoch regret, small vocabs survive repeats

SonglinYang4 · x · 2026-11-04

Wenhao Chai's new experiment blog finds that while n-gram models dominate recent pre-training speedruns, they fall apart in multi-epoch setups. Training a fixed amount of text for 8 epochs, larger tokenizers incur more multi-epoch regret — the extra loss from repeating data instead of training on unique tokens. Small vocabularies survive better.

The post walks through byte-level BPE mechanics (merging frequent pairs from 256 bytes, embedding and softmax rows per token), demos encoding with Llama 3's Marin 128K tokenizer, and publishes code, training curves, and the full experiment log.

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