GRRM: Group Relative Reward Modeling for Machine Translation

Sen Yang, Shanbo Cheng, Lu Xu, Jianbing Zhang, Shujian Huang


Abstract
While Group Relative Policy Optimization (GRPO) offers a powerful framework for LLM post-training, its effectiveness in open-ended domains like Machine Translation hinges on accurate intra-group ranking. We identify that standard Pointwise Quality Metrics (PQM) fall short in this context: candidates are evaluated in isolation, so the comparative context is missing for distinguishing fine-grained linguistic nuances. To address this, we introduce the Group Quality Metric (GQM) paradigm and its instantiation, the Group Relative Reward Model (GRRM). Unlike traditional independent scorers, GRRM jointly processes the entire candidate group, leveraging comparative analysis to rigorously resolve relative quality and adaptive granularity. Empirical evaluations confirm that GRRM achieves competitive ranking accuracy among all baselines; integrating GRRM into the GRPO training not only improves general translation quality but also unlocks reasoning capabilities comparable to state-of-the-art reasoning models.
Anthology ID:
2026.emnlp-main.2283
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
51934–51956
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2283/
DOI:
Bibkey:
Cite (ACL):
Sen Yang, Shanbo Cheng, Lu Xu, Jianbing Zhang, and Shujian Huang. 2026. GRRM: Group Relative Reward Modeling for Machine Translation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 51934–51956, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
GRRM: Group Relative Reward Modeling for Machine Translation (Yang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2283.pdf