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New MO-GRPO algorithm tackles reward hacking in multi-objective RL

Researchers have introduced MO-GRPO, a novel algorithm designed to address reward hacking in multi-objective reinforcement learning. This new method extends the Group Relative Policy Optimization (GRPO) by incorporating a simple normalization technique to automatically reweight reward functions based on their value variances. MO-GRPO ensures that all objectives contribute equitably to the loss function, eliminating the need for manual scaling and preserving preference order. Experimental evaluations across various domains, including multi-armed bandits, simulated control tasks, machine translation, and instruction following, demonstrate MO-GRPO's ability to achieve stable learning and outperform standard GRPO. AI

IMPACT Introduces a method to improve stability and performance in multi-objective reinforcement learning tasks.

RANK_REASON This is a research paper detailing a new algorithm for reinforcement learning. [lever_c_demoted from research: ic=1 ai=1.0]

Read on arXiv cs.LG →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

New MO-GRPO algorithm tackles reward hacking in multi-objective RL

COVERAGE [1]

  1. arXiv cs.LG TIER_1 English(EN) · Yuki Ichihara, Yuu Jinnai, Tetsuro Morimura, Mitsuki Sakamoto, Ryota Mitsuhashi, Eiji Uchibe ·

    MO-GRPO: Mitigating Reward Hacking of Group Relative Policy Optimization on Multi-Objective Problems

    arXiv:2509.22047v3 Announce Type: replace Abstract: Group Relative Policy Optimization (GRPO) has been shown to be an effective algorithm when an accurate reward model is available. However, such a highly reliable reward model is not available in many real-world tasks. In this pa…