ESSA: Evolutionary Strategies for Scalable Alignment

Daria Korotyshova, Boris Shaposhnikov, Alexey Malakhov, Alexey Khokhulin, Nikita Surnachev, Kirill Ovcharenko, George Bredis, Alexey Gorbatovski, Viacheslav Sinii, Daniil Gavrilov


Abstract
Online alignment of large language models (LLMs) is dominated by reinforcement learning from human feedback (RLHF) with gradient-based optimizers such as PPO or GRPO. While effective, these pipelines require backpropagation through long rollouts, gradient synchronization across devices, and careful hyperparameter tuning, all of which become increasingly costly at scale. We present **ESSA** (Evolutionary Strategies for Scalable Alignment), a gradient-free online alignment stage that follows supervised fine-tuning (SFT) and replaces the gradient loop with inference-only black-box search. ESSA optimizes only the singular values of low-rank adaptation (LoRA) factors after a short SFT warm-start, restricting the search to a compact, task-aligned subspace where evolutionary search is practical even for 72B-parameter models. Because the loop is inference-only, ESSA is compatible with INT4/INT8 weight quantization and reduces inter-GPU communication to a few bytes per iteration. Across instruction following (IFEval), preference-based assistant tuning (HelpSteer2, HH-RLHF), and mathematical reasoning (GSM8K, MATH500), ESSA matches or exceeds LoRA-GRPO in the reported LoRA comparisons; on GSM8K it also outperforms Online DPO and PPO, while remaining competitive with both methods on IFEval. At scale, ESSA reaches a fixed MATH500 accuracy on Qwen2.5-32B/PRM800K up to 7.8× faster than LoRA-GRPO on 128 GPUs.
Anthology ID:
2026.emnlp-main.2204
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
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Pages:
50104–50142
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URL:
https://aclanthology.org/2026.emnlp-main.2204/
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Bibkey:
Cite (ACL):
Daria Korotyshova, Boris Shaposhnikov, Alexey Malakhov, Alexey Khokhulin, Nikita Surnachev, Kirill Ovcharenko, George Bredis, Alexey Gorbatovski, Viacheslav Sinii, and Daniil Gavrilov. 2026. ESSA: Evolutionary Strategies for Scalable Alignment. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 50104–50142, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ESSA: Evolutionary Strategies for Scalable Alignment (Korotyshova et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.2204.pdf