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Main Authors: Huang, Sterling, Brown, Abigayle, Noh, Jiyoo, Xu, Jiakang, Huo, Wantong, Kyaw, Kaung Myat, Chan, Jonathan
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2605.17932
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author Huang, Sterling
Brown, Abigayle
Noh, Jiyoo
Xu, Jiakang
Huo, Wantong
Kyaw, Kaung Myat
Chan, Jonathan
author_facet Huang, Sterling
Brown, Abigayle
Noh, Jiyoo
Xu, Jiakang
Huo, Wantong
Kyaw, Kaung Myat
Chan, Jonathan
contents Prompt compression reduces inference cost and context length in large language models, but prior evaluations focus primarily on autoregressive architectures. This study investigates whether prompt compression transfers effectively to diffusion large language models (DLLMs) using LLMLingua-2, specifically the 8B-parameter DLLM LLaDA. We evaluate compression performance on GSM8K, DUC2004, and ShareGPT using 250 prompts per dataset at an approximate 2$\times$ compression ratio, across mathematical reasoning, prompt reconstruction, and summarization tasks. Outputs generated from original prompts, compressed prompts, reconstructed prompts, and reconstructed-prompt reasoning were compared using exact-match accuracy, BLEU, ROUGE, and BERTScore. Results show that semantic preservation does not necessarily imply stable downstream behavior in diffusion models. Summarization tasks remained comparatively robust under compression, while mathematical reasoning degraded substantially despite high semantic similarity scores. Reconstruction experiments further showed that semantically similar prompts may still omit reasoning-critical information required for stable denoising. Across tasks, BERTScore recall was consistently lower than precision, suggesting that compression failures are primarily driven by information omission rather than semantic drift. These findings indicate that prompt compression methods designed for autoregressive models do not transfer uniformly to diffusion large language models and motivate the development of diffusion-aware compression strategies.
format Preprint
id arxiv_https___arxiv_org_abs_2605_17932
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Prompt Compression in Diffusion Large Language Models: Evaluating LLMLingua-2 on LLaDA
Huang, Sterling
Brown, Abigayle
Noh, Jiyoo
Xu, Jiakang
Huo, Wantong
Kyaw, Kaung Myat
Chan, Jonathan
Computation and Language
Artificial Intelligence
Prompt compression reduces inference cost and context length in large language models, but prior evaluations focus primarily on autoregressive architectures. This study investigates whether prompt compression transfers effectively to diffusion large language models (DLLMs) using LLMLingua-2, specifically the 8B-parameter DLLM LLaDA. We evaluate compression performance on GSM8K, DUC2004, and ShareGPT using 250 prompts per dataset at an approximate 2$\times$ compression ratio, across mathematical reasoning, prompt reconstruction, and summarization tasks. Outputs generated from original prompts, compressed prompts, reconstructed prompts, and reconstructed-prompt reasoning were compared using exact-match accuracy, BLEU, ROUGE, and BERTScore. Results show that semantic preservation does not necessarily imply stable downstream behavior in diffusion models. Summarization tasks remained comparatively robust under compression, while mathematical reasoning degraded substantially despite high semantic similarity scores. Reconstruction experiments further showed that semantically similar prompts may still omit reasoning-critical information required for stable denoising. Across tasks, BERTScore recall was consistently lower than precision, suggesting that compression failures are primarily driven by information omission rather than semantic drift. These findings indicate that prompt compression methods designed for autoregressive models do not transfer uniformly to diffusion large language models and motivate the development of diffusion-aware compression strategies.
title Prompt Compression in Diffusion Large Language Models: Evaluating LLMLingua-2 on LLaDA
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2605.17932