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arXiv 2603.20100cs.CLcs.AI
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小语言模型中SFT-DPO交互与参数化的实证研究

An Empirical Study of SFT-DPO Interaction and Parameterization in Small Language Models

Department of Computer Science(计算机科学系);Stanford University(斯坦福大学)

Yuming Feng, Christy Yang

AI总结:

本文通过对比SFT、DPO及分阶段训练方法,发现全参数微调在小模型中表现更优,而偏好优化和低秩适应带来的边际收益有限。

摘要:

直接偏好优化(DPO)在监督微调(SFT)后广泛用于对齐语言模型,但其在小模型和少量数据下的行为尚不明确。本文系统比较了仅SFT、仅DPO、分阶段SFT到DPO训练以及全微调(FFT)与LoRA在GPT-2规模解码器上的表现,评估了同义词检测和莎士比亚十四行诗续写任务。DPO在任务相关性方面对强SFT有小幅度提升,当偏好构建与监督目标相似时可达到与竞争性SFT相同的准确性,无需预热。相比之下,参数化起主导作用:FFT在匹配训练深度时始终优于LoRA,且LoRA在我们的硬件上不减少运行时间。这些发现表明,在小规模范围内,监督全参数适应仍是主要性能杠杆,而偏好优化和低秩适应提供的边际收益有限。

英文摘要:

Direct Preference Optimization (DPO) is widely used after supervised fine-tuning (SFT) to align language models, yet empirical behavior under small backbones and modest data is under-specified. We systematically compare SFT-only, DPO-only, and staged SFT-to-DPO training alongside full fine-tuning (FFT) versus LoRA on a GPT-2-scale decoder, evaluating paraphrase detection and Shakespearean sonnet continuation. DPO yields small, task-dependent gains over strong SFT and can match competitive SFT accuracy without a warm start when the preference construction closely parallels the supervised objective. In contrast, parameterization dominates: FFT consistently outperforms LoRA at matched training depth, and LoRA does not reduce wall-clock time on our hardware. These findings indicate that, in this small-scale regime, supervised full-parameter adaptation remains the primary performance lever, while preference optimization and low-rank adaptation provide limited marginal returns.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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