Efficient and Effective Prompt Tuning via Prompt Decomposition and Compressed Outer Product

TL;DR

This paper introduces LAMP, a prompt tuning method that decomposes prompts and uses compressed outer products to improve semantic interactions and efficiency in large language models.

Contribution

LAMP combines prompt decomposition with compressed outer products to enhance semantic interactions and reduce computational costs in prompt tuning.

Findings

LAMP outperforms state-of-the-art methods in accuracy.

LAMP reduces memory and training time significantly.

LAMP is effective across multiple architectures and datasets.

Abstract

Prompt tuning (PT) offers a cost-effective alternative to fine-tuning large-scale pre-trained language models (PLMs), requiring only a few parameters in soft prompt tokens added before the input text. However, existing PT approaches face two significant issues: (i) They overlook intrinsic semantic associations between soft prompt tokens, leading to high discreteness and limited interactions, thus reducing the model's comprehension and effectiveness in complex tasks. (ii) Due to the complexity of downstream tasks, long soft prompt is necessitated to improve performance, but prompt length correlates positively with memory usage and computational costs. Achieving high efficiency and performance remains an ongoing challenge. To address these issues, we propose a novel Low-parameters prompt tuning (LAMP) method, which leverages prompt decomposition and compressed outer product. Specifically, the prompt decomposition module employs Truncated SVD to reduce training parameters and significantly lower the dimensionality of the soft prompt parameter space. It then utilizes a compressed outer product module to facilitate multiple interactions among prompt tokens, exploring their intrinsic associations to enhance knowledge representation. Finally, LAMP uses average pooling to reduce memory usage and training/inference time. Extensive experiments across six architectures and eight datasets demonstrate that LAMP outperforms state-of-the-art PT-based and LoRA-based methods in performance and efficiency.