Doc2FRC: Length-Consistent Document-Level Machine Translation via Fixed-Range Chunking

Xiaotian Wang, Youyuan Lin, Zhan Shen, Hitomi Yanaka


Abstract
Advanced large language models (LLMs) with long context windows can substantially reduce input truncation in document-level machine translation (DocMT). However, direct Doc2Doc translation remains prone to n-gram repetition and progressive quality degradation. A common remedy is to segment the document into finer-grained chunks. Nonetheless, conventional rule-based chunking approaches fail to handle the length distribution mismatch between training and inference. To address this, we introduce Fixed-Range Chunking (FRC), utilizing dynamic programming to partition documents into chunks within a predefined length interval. By consistently applying FRC during training and inference, the input documents of any length are mapped to the same length distribution, substantially reducing train-test length mismatch. Centered on FRC, we propose a lightweight dual-boundary matching algorithm for chunk alignment, alongside four distinct training strategies. Experimental results show that FRC-based fine-tuning substantially improves 7B LLMs over direct Doc2Doc fine-tuning and outperforms existing DocMT methods on IWSLT2017. We further construct GlobVDoc, a 10-language test set independent of mainstream DocMT training sources, and show that FRC improves out-of-distribution document translation.
Anthology ID:
2026.wmt-main.44
Volume:
Proceedings of the Eleventh Conference on Machine Translation
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Barry Haddow, Tom Kocmi, Philipp Koehn, Christof Monz
Venues:
WMT | WS
SIG:
SIGMT
Publisher:
Association for Computational Linguistics
Note:
Pages:
782–817
Language:
URL:
https://aclanthology.org/2026.wmt-main.44/
DOI:
Bibkey:
Cite (ACL):
Xiaotian Wang, Youyuan Lin, Zhan Shen, and Hitomi Yanaka. 2026. Doc2FRC: Length-Consistent Document-Level Machine Translation via Fixed-Range Chunking. In Proceedings of the Eleventh Conference on Machine Translation, pages 782–817, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Doc2FRC: Length-Consistent Document-Level Machine Translation via Fixed-Range Chunking (Wang et al., WMT 2026)
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PDF:
https://aclanthology.org/2026.wmt-main.44.pdf