Large language models (LLMs) exhibit exceptional performance across a wide range of natural language processing tasks, often relying on lengthy prompts to harness their full capabilities. However, extended prompts can lead to substantial computational overhead and increased hardware demands, limiting the scalability and efficiency of such models. In this paper, we propose DisComp, a two-stage prompt compression framework based on knowledge distillation that combines task-agnostic and task-aware strategies, designed to efficiently compress prompt length without compromising performance.In the first stage, task-agnostic compression is achieved through knowledge distillation, transferring the summarization capabilities of a LLM to a smaller, more efficient model. The distillation process combines cross-entropy loss and keyword matching loss to ensure the smaller model generates concise and informative summaries. In the second stage, sentence-level pruning is applied, where sentences are ranked by relevance to the query, and irrelevant sentences are pruned to retain only task-critical information. We evaluate our method on three benchmark datasets, LongBench , ZeroSCROLLS and NaturalQuestions. The results show that DisComp significantly outperforms previous task-agnostic and task-specific compression approaches, and it is up to 6.56× faster at inference compared to the best token-level compression method.

Although large-scale pretrained language models, such as BERT and RoBERTa, have achieved superhuman performance on in-distribution test sets, their performance suffers on out-of-distribution test sets (e.g., on contrast sets). Building contrast sets often requires human-expert annotation, which is expensive and hard to create on a large scale. In this work, we propose a Linguistically-Informed Transformation (LIT) method to automatically generate contrast sets, which enables practitioners to explore linguistic phenomena of interests as well as compose different phenomena. Experimenting with our method on SNLI and MNLI shows that current pretrained language models, although being claimed to contain sufficient linguistic knowledge, struggle on our automatically generated contrast sets. Furthermore, we improve models’ performance on the contrast sets by applying LIT to augment the training data, without affecting performance on the original data.