Fundamental Limits of Prompt Compression: A Rate-Distortion Framework for Black-Box Language Models

Fuente: arXiv
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Autores principales: Nagle, Alliot, Girish, Adway, Bondaschi, Marco, Gastpar, Michael, Makkuva, Ashok Vardhan, Kim, Hyeji
Formato: Preprint
Publicado: 2024
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author Nagle, Alliot
Girish, Adway
Bondaschi, Marco
Gastpar, Michael
Makkuva, Ashok Vardhan
Kim, Hyeji
author_facet Nagle, Alliot
Girish, Adway
Bondaschi, Marco
Gastpar, Michael
Makkuva, Ashok Vardhan
Kim, Hyeji
contents We formalize the problem of prompt compression for large language models (LLMs) and present a framework to unify token-level prompt compression methods which create hard prompts for black-box models. We derive the distortion-rate function for this setup as a linear program, and provide an efficient algorithm to compute this fundamental limit via the dual of the linear program. Using the distortion-rate function as the baseline, we study the performance of existing compression schemes on a synthetic dataset consisting of prompts generated from a Markov chain, natural language queries, and their respective answers. Our empirical analysis demonstrates the criticality of query-aware prompt compression, where the compressor has knowledge of the downstream task/query for the black-box LLM. We show that there is a large gap between the performance of current prompt compression methods and the optimal strategy, and propose Adaptive QuerySelect, a query-aware, variable-rate adaptation of a prior work to close the gap. We extend our experiments to a small natural language dataset to further confirm our findings on our synthetic dataset.
format Preprint
id arxiv_https___arxiv_org_abs_2407_15504
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Fundamental Limits of Prompt Compression: A Rate-Distortion Framework for Black-Box Language Models
Nagle, Alliot
Girish, Adway
Bondaschi, Marco
Gastpar, Michael
Makkuva, Ashok Vardhan
Kim, Hyeji
Machine Learning
Computation and Language
Information Theory
We formalize the problem of prompt compression for large language models (LLMs) and present a framework to unify token-level prompt compression methods which create hard prompts for black-box models. We derive the distortion-rate function for this setup as a linear program, and provide an efficient algorithm to compute this fundamental limit via the dual of the linear program. Using the distortion-rate function as the baseline, we study the performance of existing compression schemes on a synthetic dataset consisting of prompts generated from a Markov chain, natural language queries, and their respective answers. Our empirical analysis demonstrates the criticality of query-aware prompt compression, where the compressor has knowledge of the downstream task/query for the black-box LLM. We show that there is a large gap between the performance of current prompt compression methods and the optimal strategy, and propose Adaptive QuerySelect, a query-aware, variable-rate adaptation of a prior work to close the gap. We extend our experiments to a small natural language dataset to further confirm our findings on our synthetic dataset.
title Fundamental Limits of Prompt Compression: A Rate-Distortion Framework for Black-Box Language Models
topic Machine Learning
Computation and Language
Information Theory
url https://arxiv.org/abs/2407.15504