Look Within or Look Beyond? A Theoretical Comparison Between Parameter-Efficient and Full Fine-Tuning

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Hauptverfasser: Liu, Yongkang, Xu, Xingle, Nie, Ercong, Wang, Zijing, Feng, Shi, Wang, Daling, Li, Qian, Schütze, Hinrich
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Veröffentlicht: 2025
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author Liu, Yongkang
Xu, Xingle
Nie, Ercong
Wang, Zijing
Feng, Shi
Wang, Daling
Li, Qian
Schütze, Hinrich
author_facet Liu, Yongkang
Xu, Xingle
Nie, Ercong
Wang, Zijing
Feng, Shi
Wang, Daling
Li, Qian
Schütze, Hinrich
contents Parameter-Efficient Fine-Tuning (PEFT) methods achieve performance comparable to Full Fine-Tuning (FFT) while requiring significantly fewer computing resources, making it the go-to choice for researchers. We find that although PEFT can achieve competitive results on some benchmarks, its performance falls short of FFT in complex tasks, such as reasoning and instruction-based fine-tuning. In this paper, we compare the characteristics of PEFT and FFT in terms of representational capacity and robustness based on optimization theory. We theoretically demonstrate that PEFT is a strict subset of FFT. By providing theoretical upper bounds for PEFT, we show that the limited parameter space constrains the model's representational ability, making it more susceptible to perturbations. Experiments on 15 datasets encompassing classification, generation, reasoning, instruction fine-tuning tasks and 11 adversarial test sets validate our theories. We hope that these results spark further research beyond the realms of well established PEFT. The source code is in the anonymous Github repository\footnote{https://github.com/misonsky/PEFTEval}.
format Preprint
id arxiv_https___arxiv_org_abs_2505_22355
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Look Within or Look Beyond? A Theoretical Comparison Between Parameter-Efficient and Full Fine-Tuning
Liu, Yongkang
Xu, Xingle
Nie, Ercong
Wang, Zijing
Feng, Shi
Wang, Daling
Li, Qian
Schütze, Hinrich
Machine Learning
Parameter-Efficient Fine-Tuning (PEFT) methods achieve performance comparable to Full Fine-Tuning (FFT) while requiring significantly fewer computing resources, making it the go-to choice for researchers. We find that although PEFT can achieve competitive results on some benchmarks, its performance falls short of FFT in complex tasks, such as reasoning and instruction-based fine-tuning. In this paper, we compare the characteristics of PEFT and FFT in terms of representational capacity and robustness based on optimization theory. We theoretically demonstrate that PEFT is a strict subset of FFT. By providing theoretical upper bounds for PEFT, we show that the limited parameter space constrains the model's representational ability, making it more susceptible to perturbations. Experiments on 15 datasets encompassing classification, generation, reasoning, instruction fine-tuning tasks and 11 adversarial test sets validate our theories. We hope that these results spark further research beyond the realms of well established PEFT. The source code is in the anonymous Github repository\footnote{https://github.com/misonsky/PEFTEval}.
title Look Within or Look Beyond? A Theoretical Comparison Between Parameter-Efficient and Full Fine-Tuning
topic Machine Learning
url https://arxiv.org/abs/2505.22355