IndicMT at WMT 2026: Full Fine-Tuning of NLLB-200-600M with Round-Trip Filtering and Forward Self-Training for Arabic-Asian Translation

Pramit Jana, Arindam Adhikari, Priyobroto Acharya, Dipankar Das


Abstract
We describe the IndicMT submission to the WMT 2026 Shared Task on Low-Resource Arabic-Asian Language Translation. Our system covers all ten translation directions between Arabic and Bangla, English, Hindi, Indonesian, and Urdu. For each direction, we fully fine-tune a separate NLLB-200-distilled-600M model using two NVIDIA T4 graphics processing units. The training pipeline combines Unicode normalization and length filtering with direction-specific round-trip consistency filtering of the available parallel data. We additionally augment each direction with 500 source-side sentences whose target translations are generated by the pretrained NLLB model, a procedure corresponding to forward self-training rather than conventional back-translation. On the official test set, our strongest relative results are obtained for Arabic$\rightarrow$Indonesian and Indonesian$\rightarrow$Arabic. Across all five language pairs, translation from Arabic obtains higher BLEU scores than translation into Arabic. Our results demonstrate that full adaptation of a compact multilingual translation model, combined with model-based data selection and synthetic-target augmentation, provides a practical baseline under limited computational resources.
Anthology ID:
2026.wmt-main.172
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:
2311–2317
Language:
URL:
https://aclanthology.org/2026.wmt-main.172/
DOI:
Bibkey:
Cite (ACL):
Pramit Jana, Arindam Adhikari, Priyobroto Acharya, and Dipankar Das. 2026. IndicMT at WMT 2026: Full Fine-Tuning of NLLB-200-600M with Round-Trip Filtering and Forward Self-Training for Arabic-Asian Translation. In Proceedings of the Eleventh Conference on Machine Translation, pages 2311–2317, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
IndicMT at WMT 2026: Full Fine-Tuning of NLLB-200-600M with Round-Trip Filtering and Forward Self-Training for Arabic-Asian Translation (Jana et al., WMT 2026)
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PDF:
https://aclanthology.org/2026.wmt-main.172.pdf