Reinforced Self-Training (ReST) for Language Modeling
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "CC BY-NC-ND 4.0 (arXiv)" does not allow redistributing the text itself. Original — arxiv.org/pdf/2308.08998
Summary
Aligning large language models with human preferences through RLHF usually relies on online algorithms such as PPO. These are costly because the model must keep producing fresh samples and having them scored throughout training, and they are vulnerable to reward hacking. Gulcehre et al. (Google DeepMind / Google Research) introduce Reinforced Self-Training (ReST), which treats alignment as a growing-batch RL problem split into two decoupled loops. In the outer Grow loop, the current policy samples many candidate outputs per source context, and a learned reward model scores them. In the inner Improve loop, the policy is fine-tuned on progressively stricter reward-filtered subsets of that data, using either an NLL (BC) loss or an offline RL loss. The method is tested on machine translation (IWSLT 2014, WMT 2020 and internal Web Domain benchmarks). ReST raises reward-model scores and is preferred by human raters over a supervised baseline, while using compute and samples efficiently. It is a simple and inspectable recipe that transfers to any setting with a reliable reward model and scalable sampling.
Key points
- How ReST works: Grow generates and scores a dataset from the current policy, and Improve fine-tunes on filtered data with thresholds τ₁ < τ₂ < … < τₙ. Each new policy starts from the previous one at a lower learning rate. The original dataset stays in the training mix to prevent divergence.
- Efficiency: Each Grow step is reused across several Improve steps, which amortises the cost of sampling compared with online RLHF.
- Loss comparison: The tested losses were BC/NLL, V-MPO, offline actor-critic and BVE. Plain BC improved reward-model scores the most, although it can overfit to the reward model.
- Human vs. automatic evaluation: Reward scores kept rising with additional Grow steps, but human evaluation favoured stopping after a single Grow step. This reflects the reward model being only a proxy for human preferences.
- Relation to RAFT: The concurrent method RAFT corresponds to ReST with one Improve step per Grow step. The authors found that several Improve steps with rising thresholds give further gains.
Cited by
- Many-Shot In-Context Learning
- Quiet-STaR: Language models can teach themselves to think before speaking
- Towards Reasoning Era: A Survey of Long Chain-of-Thought for Reasoning Large Language Models
- xCOMET: Transparent Machine Translation Evaluation through Fine-grained Error Detection
- V-STaR: Training Verifiers for Self-Taught Reasoners
- Camels in a Changing Climate: Enhancing LM Adaptation with Tulu 2
- Kimi k1.5: Scaling Reinforcement Learning with LLMs
- Iterative Reasoning Preference Optimization
- Beyond Correlation: Interpretable Evaluation of Machine Translation Metrics
- Beyond Human Data: Scaling Self-Training for Problem-Solving with Language Models
- ReFT: Reasoning with Reinforced Fine-Tuning
- Interpretable Preferences via Multi-Objective Reward Modeling and Mixture-of-Experts
- Demystifying Long Chain-of-Thought Reasoning in LLMs
- Does Reinforcement Learning Really Incentivize Reasoning Capacity in LLMs Beyond the Base Model?
- ReST-MCTS*: LLM Self-Training via Process Reward Guided Tree Search
Cite
@misc{gulcehre2023reinforced,
title = {{Reinforced Self-Training (ReST) for Language Modeling}},
author = {Gulcehre, Caglar and Paine, Tom Le and Srinivasan, Srivatsan and Konyushkova, Ksenia and Weerts, Lotte and Sharma, Abhishek and Siddhant, Aditya and Ahern, Alex and Wang, Miaosen and Gu, Chenjie and Macherey, Wolfgang and Doucet, Arnaud and Firat, Orhan and Freitas, Nando de},
year = {2023},
doi = {10.48550/arxiv.2308.08998},
eprint = {2308.08998},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2308.08998}
}References
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