Analyzing Retrieval Scaling in RAG Systems for Complex QA Benchmarks
摘要
Large Language Models (LLMs) have shown strong performance on a wide range of natural language processing tasks, yet they still struggle with multi-hop question answering, which demands complex reasoning over multiple evidence sources. While extending context windows has been proposed as a solution, this approach remains cost-prohibitive and suffers from attention degradation over long contexts. Retrieval-Augmented Generation (RAG) offers a more efficient alternative by selectively incorporating external information. In this paper, we present a systematic evaluation of multiple RAG configurations using lexical (BM25) and semantic retrievers (msmarco-bert-base-dot-v, ColBERTv2), as well as graph-based approaches (HippoRAG). We assess performance across four QA datasets (HotpotQA, 2Wiki, MuSiQue, and LoCoMo) employing accessible LLMs such as GPT-4o-mini, Qwen2.5-14B-Instruct, and o3-mini. Our experiments analyze the trade-offs between retrieval depth, cost, and model performance, showing that medium-scale LLMs can achieve competitive results through retrieval scaling. However, for highly compositional tasks like MuSiQue, larger reasoning models remain advantageous. Our results offer practical insights into optimizing RAG pipelines in budget-constrained environments, and we provide a publicly available framework to facilitate further research.