Vicomtech@WMT 2026: Mask-based Pruning for Model Compression

David Ponce, Thierry Etchegoyhen


Abstract
We describe Vicomtech’s participation in the constrained track of the WMT 2026 Shared Task on Model Compression. We addressed all three translation directions of the task, namely Czech to German, English to Simplified Chinese, and English to Egyptian Arabic, using Gemma 3 12B IT as our base model. Our approach performs task-aware structured post-training pruning, which learns differentiable masks to prune model components using machine translation calibration data and an objective combining next-token cross-entropy, knowledge distillation, and intermediate representation matching. We systematically evaluated pruning at two target compression ratios (0.25 and 0.50) and explored different structured pruning configurations, combined with supervised fine-tuning to recover performance after pruning. Additionally, we explored language-specific vocabulary pruning and 4-bit AWQ quantization to achieve further reductions in model size and memory requirements. Our experimental results demonstrate that the combination of structured pruning, targeted post-training, vocabulary reduction, and quantization can achieve substantial model compression while maintaining competitive translation quality across all language directions.
Anthology ID:
2026.wmt-main.142
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:
2038–2050
Language:
URL:
https://aclanthology.org/2026.wmt-main.142/
DOI:
Bibkey:
Cite (ACL):
David Ponce and Thierry Etchegoyhen. 2026. Vicomtech@WMT 2026: Mask-based Pruning for Model Compression. In Proceedings of the Eleventh Conference on Machine Translation, pages 2038–2050, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Vicomtech@WMT 2026: Mask-based Pruning for Model Compression (Ponce & Etchegoyhen, WMT 2026)
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PDF:
https://aclanthology.org/2026.wmt-main.142.pdf