Revisiting Prefix-tuning: Statistical Benefits of Reparameterization among Prompts

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Main Authors: Le, Minh, Nguyen, Chau, Nguyen, Huy, Tran, Quyen, Le, Trung, Ho, Nhat
Format: Preprint
Published: 2024
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author Le, Minh
Nguyen, Chau
Nguyen, Huy
Tran, Quyen
Le, Trung
Ho, Nhat
author_facet Le, Minh
Nguyen, Chau
Nguyen, Huy
Tran, Quyen
Le, Trung
Ho, Nhat
contents Prompt-based techniques, such as prompt-tuning and prefix-tuning, have gained prominence for their efficiency in fine-tuning large pre-trained models. Despite their widespread adoption, the theoretical foundations of these methods remain limited. For instance, in prefix-tuning, we observe that a key factor in achieving performance parity with full fine-tuning lies in the reparameterization strategy. However, the theoretical principles underpinning the effectiveness of this approach have yet to be thoroughly examined. Our study demonstrates that reparameterization is not merely an engineering trick but is grounded in deep theoretical foundations. Specifically, we show that the reparameterization strategy implicitly encodes a shared structure between prefix key and value vectors. Building on recent insights into the connection between prefix-tuning and mixture of experts models, we further illustrate that this shared structure significantly improves sample efficiency in parameter estimation compared to non-shared alternatives. The effectiveness of prefix-tuning across diverse tasks is empirically confirmed to be enhanced by the shared structure, through extensive experiments in both visual and language domains. Additionally, we uncover similar structural benefits in prompt-tuning, offering new perspectives on its success. Our findings provide theoretical and empirical contributions, advancing the understanding of prompt-based methods and their underlying mechanisms.
format Preprint
id arxiv_https___arxiv_org_abs_2410_02200
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Revisiting Prefix-tuning: Statistical Benefits of Reparameterization among Prompts
Le, Minh
Nguyen, Chau
Nguyen, Huy
Tran, Quyen
Le, Trung
Ho, Nhat
Machine Learning
Prompt-based techniques, such as prompt-tuning and prefix-tuning, have gained prominence for their efficiency in fine-tuning large pre-trained models. Despite their widespread adoption, the theoretical foundations of these methods remain limited. For instance, in prefix-tuning, we observe that a key factor in achieving performance parity with full fine-tuning lies in the reparameterization strategy. However, the theoretical principles underpinning the effectiveness of this approach have yet to be thoroughly examined. Our study demonstrates that reparameterization is not merely an engineering trick but is grounded in deep theoretical foundations. Specifically, we show that the reparameterization strategy implicitly encodes a shared structure between prefix key and value vectors. Building on recent insights into the connection between prefix-tuning and mixture of experts models, we further illustrate that this shared structure significantly improves sample efficiency in parameter estimation compared to non-shared alternatives. The effectiveness of prefix-tuning across diverse tasks is empirically confirmed to be enhanced by the shared structure, through extensive experiments in both visual and language domains. Additionally, we uncover similar structural benefits in prompt-tuning, offering new perspectives on its success. Our findings provide theoretical and empirical contributions, advancing the understanding of prompt-based methods and their underlying mechanisms.
title Revisiting Prefix-tuning: Statistical Benefits of Reparameterization among Prompts
topic Machine Learning
url https://arxiv.org/abs/2410.02200