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A General Theoretical Paradigm to Understand Learning from Human Preferences

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arxiv 2310.12036 v2 pith:RQZSILRI submitted 2023-10-18 cs.AI cs.LGstat.ML

classification cs.AIcs.LGstat.ML
keywords preferenceslearningdatageneralhumanapproximationapproximationsassumes
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abstract

The prevalent deployment of learning from human preferences through reinforcement learning (RLHF) relies on two important approximations: the first assumes that pairwise preferences can be substituted with pointwise rewards. The second assumes that a reward model trained on these pointwise rewards can generalize from collected data to out-of-distribution data sampled by the policy. Recently, Direct Preference Optimisation (DPO) has been proposed as an approach that bypasses the second approximation and learn directly a policy from collected data without the reward modelling stage. However, this method still heavily relies on the first approximation. In this paper we try to gain a deeper theoretical understanding of these practical algorithms. In particular we derive a new general objective called $\Psi$PO for learning from human preferences that is expressed in terms of pairwise preferences and therefore bypasses both approximations. This new general objective allows us to perform an in-depth analysis of the behavior of RLHF and DPO (as special cases of $\Psi$PO) and to identify their potential pitfalls. We then consider another special case for $\Psi$PO by setting $\Psi$ simply to Identity, for which we can derive an efficient optimisation procedure, prove performance guarantees and demonstrate its empirical superiority to DPO on some illustrative examples.

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Cited by 29 Pith papers

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

  1. ORPO: Monolithic Preference Optimization without Reference Model

    cs.CL 2024-03 conditional novelty 8.0 of 10

    ORPO performs preference alignment during supervised fine-tuning via a monolithic odds ratio penalty, allowing 7B models to outperform larger state-of-the-art models on alignment benchmarks.

  2. CrossVLA: Cross-Paradigm Post-Training and Inference Optimization for Vision-Language-Action Models

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

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    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.

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

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    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.

  6. Block-R1: Rethinking the Role of Block Size in Multi-domain Reinforcement Learning for Diffusion Large Language Models

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    Block-R1 formulates domain block size conflicts in multi-domain RL for dLLMs, releases a 41K-sample dataset with per-sample best block sizes and a conflict score, and provides a benchmark plus simple cross-domain trai...

  8. Safety Alignment of LMs via Non-cooperative Games

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    Jointly training an Attacker and Defender LLM in a non-zero-sum game with pairwise preference judges produces a defender with much lower jailbreak success while preserving general utility.

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

    cs.LG 2026-07 conditional novelty 6.0 of 10

    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.

  10. ACPO: Adaptive Credit Policy Optimization via Fine-Grained Surrogate Entropy

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    Mode-local surrogate entropy asymmetrically reweights token advantages in RLVR, improving LLM math and code reasoning over SAPO, DAPO, and GTPO.

  11. Towards Spec Learning: Inference-Time Alignment from Preference Pairs

    cs.CL 2026-06 unverdicted novelty 6.0 of 10

    Proposes compiling preference pairs into readable natural-language specifications for inference-time LLM alignment, claiming outperformance over DPO on dense-preference domains.

  12. Weight-Space Geometry of Offline Reasoning Training

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    Comparative weight-space analysis finds SFT/RFT/RIFT colinear with similar accuracy, DFT more divergent, GRPO partially orthogonal, and DPO near-orthogonal with highest GSM8K/AIME accuracy but using 10x smaller learning rate.

  13. FlowPRO: Reward-Free Reinforced Fine-Tuning of Flow-Matching VLAs via Proximalized Preference Optimization

    cs.RO 2026-06 unverdicted novelty 6.0 of 10

    FlowPRO applies proximalized preference optimization to flow-matching VLAs with intervention-rollback data to reach higher success rates on long-horizon bimanual tasks without rewards or critics.

  14. AdaDPO: Self-Adaptive Direct Preference Optimization with Balanced Gradient Updates

    cs.CL 2026-05 unverdicted novelty 6.0 of 10

    AdaDPO uses self-adaptive stop-gradient coefficients to balance preferred and dispreferred gradients in DPO, achieving higher AlpacaEval 2 win rates than standard DPO on Llama-3-8B-Instruct.

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

    cs.CL 2026-05 unverdicted novelty 6.0 of 10

    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.

  16. Response Time Enhances Alignment with Heterogeneous Preferences

    cs.LG 2026-05 unverdicted novelty 6.0 of 10

    Response times modeled as drift-diffusion processes enable consistent estimation of population-average preferences from heterogeneous anonymous binary choices.

  17. Gradient-Gated DPO: Stabilizing Preference Optimization in Language Models

    cs.LG 2026-05 conditional novelty 6.0 of 10

    Gate-DPO attenuates gradients on low-probability rejected responses to reduce probability collapse and improve chosen-response likelihood during preference optimization.

  18. Adaptive Margin RLHF via Preference over Preferences

    cs.LG 2025-09 conditional novelty 6.0 of 10

    Adaptive margins for DPO inferred from preference-over-preference comparisons improve alignment quality, with random sampling of comparisons working best overall.

  19. Process Reinforcement through Implicit Rewards

    cs.LG 2025-02 conditional novelty 6.0 of 10

    PRIME enables online process reward model updates in LLM RL using implicit rewards from rollouts and outcome labels, yielding 15.1% average gains on reasoning benchmarks and surpassing a stronger instruct model with 1...

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

    cs.LG 2026-07 conditional novelty 5.0 of 10

    By replaying teacher prefixes with a step-decay schedule, multi-turn on-policy distillation can run without live environment interaction, matching or slightly beating online OPD accuracy.

  21. Towards Spec Learning: Inference-Time Alignment from Preference Pairs

    cs.CL 2026-06 unverdicted novelty 5.0 of 10

    Spec learning compiles brief instructions and preference pairs into readable natural-language specifications that condition LLMs at inference time and can outperform DPO on domains with dense preference signals.

  22. Constitutional On-Policy Safe Distillation

    cs.LG 2026-06 unverdicted novelty 5.0 of 10

    COPSD uses a Cross-SFT cold-start followed by constitution-conditioned distillation to achieve stronger safety-helpfulness balance and lower safety tax on reasoning than prior on-policy self-distillation methods.

  23. YFPO: A Preliminary Study of Yoked Feature Preference Optimization with Neuron-Guided Rewards for Mathematical Reasoning

    cs.CL 2026-05 unverdicted novelty 5.0 of 10

    YFPO augments standard preference optimization with neuron-level activation margins from math-related features to improve LLM reasoning on math tasks.

  24. Failure Modes of Maximum Entropy RLHF

    cs.LG 2025-09 unverdicted novelty 5.0 of 10

    Derives SimPO from MaxEnt RL and reports that MaxEnt RL in online RLHF exhibits frequent overoptimization and unstable KL dynamics across scales, unlike stable KL-constrained baselines.

  25. Enhancing Small LLM Alignment through Margin-Based Objective Modifications under Resource Constraints

    cs.CL 2025-08 unverdicted novelty 5.0 of 10

    A modified DPO loss with a hinge margin improves small LLM alignment on AlpacaEval by about 2 points over the APO-zero baseline.

  26. Difficulty-Based Preference Data Selection by DPO Implicit Reward Gap

    cs.CL 2025-08 unverdicted novelty 5.0 of 10

    Selecting preference pairs whose DPO implicit reward gap is small yields better LLM alignment than random or baseline selection while using only 10% of the data.

  27. (Towards) Scalable Reliable Automated Evaluation with Large Language Models

    cs.CL 2026-07 conditional novelty 4.0 of 10

    Multi-LLM pairwise Elo ranking with adjustable consensus thresholds produces rankings of competency profiles that average Spearman ρ≈0.83 with expert judgments.

  28. The Hitchhiker's Guide to Agentic AI: From Foundations to Systems

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