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DPO Meets PPO: Reinforced Token Optimization for RLHF

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arxiv 2404.18922 v4 pith:JCXXAV75 submitted 2024-04-29 cs.LG cs.AIcs.CLstat.ML

DPO Meets PPO: Reinforced Token Optimization for RLHF

classification cs.LG cs.AIcs.CLstat.ML
keywords optimizationtexttttoken-wiseframeworklearningmodelspolicypreference
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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In the classical Reinforcement Learning from Human Feedback (RLHF) framework, Proximal Policy Optimization (PPO) is employed to learn from sparse, sentence-level rewards -- a challenging scenario in traditional deep reinforcement learning. Despite the great successes of PPO in the alignment of large language models, its open-source implementation is still largely sub-optimal. To address these issues, we introduce a framework that models RLHF problems as a Markov decision process (MDP), enabling the capture of fine-grained token-wise information. Under this framework, we introduce an algorithm Reinforced Token Optimization (\texttt{RTO}), which learns the token-wise reward function from preference data and performs policy optimization based on this learned token-wise reward signal. Theoretically, \texttt{RTO} is proven to have the capability of finding the near-optimal policy sample-efficiently. For its practical implementation, \texttt{RTO} innovatively integrates Direct Preference Optimization (DPO) and PPO. DPO, originally derived from sparse sentence rewards, surprisingly provides us with a token-wise characterization of response quality, which is seamlessly incorporated into our subsequent PPO training stage. Extensive experiments demonstrate that \texttt{RTO} performs better than PPO and other direct preference learning algorithms. In particular, RTO outperforms PPO by 7.5 points on the AlpacaEval 2 benchmark and by 4.1 points on Arena-Hard. Our code and models are available at \href{https://github.com/zkshan2002/RTO}{https://github.com/zkshan2002/RTO}.

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Cited by 10 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. TokenRatio: Principled Token-Level Preference Optimization via Ratio Matching

    cs.CL 2026-05 unverdicted novelty 7.0

    TBPO posits a token-level Bradley-Terry model and derives a Bregman-divergence density-ratio matching loss that generalizes DPO while preserving token-level optimality.

  2. TokenRatio: Principled Token-Level Preference Optimization via Ratio Matching

    cs.CL 2026-05 unverdicted novelty 7.0

    Introduces TBPO, which derives a Bregman-divergence density-ratio matching objective for token-level preference optimization that generalizes DPO while preserving the induced optimal policy.

  3. LASER: A Data-Centric Method for Low-Cost and Efficient SQL Rewriting based on SQL-GRPO

    cs.DB 2026-04 unverdicted novelty 7.0

    LASER generates complex slow-query training data with MCTS and aligns small models via SQL-GRPO to deliver efficient, low-cost SQL rewriting that outperforms rules and large models.

  4. Multi-Turn On-Policy Distillation with Prefix Replay

    cs.LG 2026-07 conditional novelty 6.0

    ReOPD offline-distills multi-turn agentic LLMs via teacher-prefix replay plus step-decay sampling, matching online OPD accuracy at ≥4× speed with zero tool calls.

  5. Entropy Is Not Enough: Unlocking Effective Reinforcement Learning for Visual Reasoning via Vision-Anchored Token Selection

    cs.AI 2026-06 unverdicted novelty 6.0

    VEPO improves RL for visual reasoning by multiplicatively coupling visual sensitivity with token entropy, outperforming entropy-only baselines by 2.28 points at 7B and 3.15 points at 3B scale.

  6. LC-ERD: Mining Latent Logic for Self-Evolving Reasoning via Consistency-Regulated Reward Decomposition

    cs.AI 2026-05 unverdicted novelty 6.0

    LC-ERD frames LLM self-alignment as latent structure mining via a Variational Logic Potential and Multi-Agent Value Decomposition to provide granular, logic-consistent supervision.

  7. TokenRatio: Principled Token-Level Preference Optimization via Ratio Matching

    cs.CL 2026-05 unverdicted novelty 6.0

    TBPO derives a token-level preference optimization objective from sequence-level pairwise data via Bregman divergence ratio matching that generalizes DPO and improves alignment quality.

  8. Leveraging RAG for Training-Free Alignment of LLMs

    cs.LG 2026-05 unverdicted novelty 6.0

    RAG-Pref is a training-free RAG-based alignment technique that conditions LLMs on contrastive preference samples during inference, yielding over 3.7x average improvement in agentic attack refusals when combined with o...

  9. Data Agent: Learning to Select Data via End-to-End Dynamic Optimization

    cs.LG 2026-03 unverdicted novelty 6.0

    Data Agent learns a co-evolving sample selection policy end-to-end that accelerates training by over 50% on ImageNet-1k and MMLU with no performance loss.

  10. SCOPE-RL: Stable and Quantitative Control of Policy Entropy in RL Post-Training

    cs.LG 2025-10 unverdicted novelty 6.0

    SCOPE-RL adds a regularization term built from high-temperature positive samples to quantitatively control entropy dynamics and maintain exploration in RL post-training of reasoning LLMs.