ReDit: Reward Dithering for Improved LLM Policy Optimization
Authors: name: Chenxing Wei; name: Jiarui Yu; name: Ying Tiffany He; name: Hande Dong; name: Yao Shu; name: Fei Yu
Published: 2025-06-23 13:36:24

Abstract: DeepSeek-R1 has successfully enhanced Large Language Model (LLM) reasoning
capabilities through its rule-based reward system. While it's a ''perfect''
reward system that effectively mitigates reward hacking, such reward functions
are often discrete. Our experimental observations suggest that discrete rewards
can lead to gradient anomaly, unstable optimization, and slow convergence. To
address this issue, we propose ReDit (Reward Dithering), a method that dithers
the discrete reward signal by adding simple random noise. With this perturbed
reward, exploratory gradients are continuously provided throughout the learning
process, enabling smoother gradient updates and accelerating convergence. The
injected noise also introduces stochasticity into flat reward regions,
encouraging the model to explore novel policies and escape local optima.
Experiments across diverse tasks demonstrate the effectiveness and efficiency
of ReDit. On average, ReDit achieves performance comparable to vanilla GRPO
with only approximately 10% the training steps, and furthermore, still exhibits
a 4% performance improvement over vanilla GRPO when trained for a similar
duration. Visualizations confirm significant mitigation of gradient issues with
ReDit. Moreover, theoretical analyses are provided to further validate these
advantages.