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Learning Dynamics of LLM Finetuning

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arxiv 2407.10490 v4 pith:IH7UWDP3 submitted 2024-07-15 cs.LG cs.AIcs.CL

classification cs.LGcs.AIcs.CL
keywords learningfinetuningdynamicsframeworkmodeldifferentexamplesmight
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Learning dynamics, which describes how the learning of specific training examples influences the model's predictions on other examples, gives us a powerful tool for understanding the behavior of deep learning systems. We study the learning dynamics of large language models during different types of finetuning, by analyzing the step-wise decomposition of how influence accumulates among different potential responses. Our framework allows a uniform interpretation of many interesting observations about the training of popular algorithms for both instruction tuning and preference tuning. In particular, we propose a hypothetical explanation of why specific types of hallucination are strengthened after finetuning, e.g., the model might use phrases or facts in the response for question B to answer question A, or the model might keep repeating similar simple phrases when generating responses. We also extend our framework and highlight a unique "squeezing effect" to explain a previously observed phenomenon in off-policy direct preference optimization (DPO), where running DPO for too long makes even the desired outputs less likely. This framework also provides insights into where the benefits of on-policy DPO and other variants come from. The analysis not only provides a novel perspective of understanding LLM's finetuning but also inspires a simple, effective method to improve alignment performance.

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Cited by 9 Pith papers

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

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  2. Supervised Fine-Tuning vs. In-Context Learning: An Equilibrium Analysis of LLM Personalization under Congestion

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    In a linear model of LLM personalization with shared compute, SFT beats ICL above a coverage-dependent signal-to-noise threshold, congestion can reverse that ranking, and adding SFT never reduces platform profit.

  3. Towards Revealing the Effectiveness of Small-Scale Fine-tuning in R1-style Reinforcement Learning

    cs.LG 2025-05 conditional novelty 6.0 of 10

    Re-distilling a model's own RL-trained policy into 1K SFT samples reproduces RL accuracy at a fraction of the compute.

  4. An Emergent Mirage: Is Emergent Misalignment and Realignment Indeed a Robust Phenomenon?

    cs.CL 2026-07 conditional novelty 5.5 of 10

    Emergent misalignment and realignment are brittle surface effects driven by dataset artifacts like response length rather than stable representational changes.

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  6. Decoupling Task-Solving and Output Formatting in LLM Generation

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    A decoding-time method that keeps the format in a separate module improves LLM accuracy by 1–6% with guaranteed format compliance on math, judging, and extraction.

  7. RL Is Neither a Panacea Nor a Mirage: Understanding Supervised vs. Reinforcement Learning Fine-Tuning for LLMs

    cs.LG 2025-08 reject novelty 5.0 of 10

    Reinforcement fine-tuning largely recovers out-of-distribution performance lost during supervised fine-tuning by counteracting rotations of singular vector directions, with low-rank or shallow-layer restoration recove...

  8. Implicit Reward as the Bridge: A Unified View of SFT and DPO Connections

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    SFT is cast as a special case of implicit reward learning, and a slower SFT learning rate improves downstream DPO/SimPO results by up to 25% relative win rate.

  9. On the Effect of Negative Gradient in Group Relative Deep Reinforcement Optimization

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    GRPO can suffer from Lazy Likelihood Displacement, where correct responses gain little or lose likelihood, and selectively downweighting penalties on harmful tokens (NTHR) mitigates this and boosts math reasoning performance.

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