Eliciting In-context Retrieval and Reasoning for Long-context Large Language Models

Recent advancements in long-context language models (LCLMs) promise to transform Retrieval-Augmented Generation (RAG) by simplifying pipelines.With their expanded context windows, LCLMs can process entire knowledge bases and perform retrieval and reasoning directly -a capability we define as In-Context Retrieval and Reasoning (ICR 2 ).However, existing benchmarks like LOFT often overestimate LCLM performance by providing overly simplified contexts.To address this, we introduce ICR 2 , a benchmark that evaluates LCLMs in more realistic scenarios by including confounding passages retrieved with strong retrievers.We then propose three methods to enhance LCLM performance: (1) retrieve-then-generate fine-tuning, (2) retrievalattention-probing, which uses attention heads to filter and de-noise long contexts during decoding, and (3) joint retrieval head training alongside the generation head.Our evaluation of five well-known LCLMs on LOFT and ICR 2 demonstrates significant gains with our best approach applied to Mistral-7B: +17 and +15 points by Exact Match on LOFT, and +13 and +2 points on ICR 2 , compared to vanilla RAG and supervised fine-tuning, respectively.It even outperforms GPT-4-Turbo on most tasks despite being a much smaller model.