Dictionary-Based Speculative Decoding for Non-Latin-Script Languages

Oleksiy Syvokon


Abstract
Large language models tokenize non-Latin-script languagesinefficiently: a single word in Ukrainian or Crimean Tatar is split intotwo to three times as many tokens as its English equivalent. We propose_dictionary-based speculative decoding_ (DictSpec), which acceleratesinference by proposing draft continuations from a static n-gram lookuptable built offline from an unlabeled corpus. The lookup table requiresno trainable parameters or GPU resources, is inexpensive to construct,adds under 5 MB of memory overhead, and can be reused across modelsthat share a tokenizer. We evaluate DictSpec on Ukrainian and Crimean Tatar(Cyrillic and Latin scripts), implementing a vLLM plugin to benchmarkfive models ranging from 3B to 70B parameters on consumer- andserver-grade GPUs. In controlled emulation, DictSpec reduces verificationsteps by up to 1.65×, with gains correlating substantially with tokenizerfertility. In live vLLM serving, pure DictSpec gives modest speedups,while a hybrid with prompt-local n-gram speculation reaches up to 1.76×.We release our code and vLLM plugin as opensource.
Anthology ID:
2026.unlp-1.15
Volume:
Proceedings of the Fifth Ukrainian Natural Language Processing Conference (UNLP 2026)
Month:
May
Year:
2026
Address:
Lviv, Ukraine
Editor:
Mariana Romanyshyn
Venue:
UNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
169–183
Language:
URL:
https://aclanthology.org/2026.unlp-1.15/
DOI:
Bibkey:
Cite (ACL):
Oleksiy Syvokon. 2026. Dictionary-Based Speculative Decoding for Non-Latin-Script Languages. In Proceedings of the Fifth Ukrainian Natural Language Processing Conference (UNLP 2026), pages 169–183, Lviv, Ukraine. Association for Computational Linguistics.
Cite (Informal):
Dictionary-Based Speculative Decoding for Non-Latin-Script Languages (Syvokon, UNLP 2026)
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PDF:
https://aclanthology.org/2026.unlp-1.15.pdf