RLMA: Reinforcement Learning with PolyMetric Alignment

Jia Xu


Abstract
RLHF, RLAIF, and RLVR align LLMs with human instructions but rely on costly human labels, potentially biased LLM judges, or task-specific verifiers. We propose PolyMetric Alignment (RLMA), a reference-based reward framework for supervised-answer tasks that fuses heterogeneous evaluation metrics against a given reference answer using a Residual Set Transformer (RST) trained with a Bradley-Terry objective. Empirically, RLMA is stronger than all three paradigms, achieving 98.0% of the Pass@K oracle on a 9-pool benchmark, with gains of +17.6 pp over the RLA single-metric baseline and +7.4 to +15.4 pp over RLHF, RLAIF, and RLVR. RLMA also generalizes broadly, reaching 97.2% of oracle on unseen GSM8K and, when used as a DPO reward, improving TriviaQA Pass@1 by +4.80 pp on Qwen-2.5-7B-Instruct. Finally, RLMA is efficient to deploy. Its 113K-parameter gate requires only 0.33 ms per candidate, roughly 300x faster than a single 8B reward-model forward.
Anthology ID:
2026.emnlp-industry.126
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Pepa Atanasova, Gholamreza Haffari, Minghan Wang
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
2165–2182
Language:
URL:
https://aclanthology.org/2026.emnlp-industry.126/
DOI:
Bibkey:
Cite (ACL):
Jia Xu. 2026. RLMA: Reinforcement Learning with PolyMetric Alignment. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track, pages 2165–2182, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RLMA: Reinforcement Learning with PolyMetric Alignment (Xu, EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-industry.126.pdf