SmartRAG: Jointly Learn RAG-Related Tasks From the Environment Feedback

RAG systems consist of multiple modules to work together. However, these modules are usually separately trained. We argue that a system like RAG that incorporates multiple modules should be jointly optimized to achieve optimal performance. To demonstrate this, we design a specific pipeline called SmartRAG that includes a policy network and a retriever. The policy network can serve as 1) a decision maker that decides when to retrieve, 2) a query rewriter to generate a query most suited to the retriever, and 3) an answer generator that produces the final response with/without the observations. We then propose to jointly optimize the whole system using a reinforcement learning algorithm, with the reward designed to encourage the system to achieve the best performance with minimal retrieval cost. When jointly optimized, all the modules can be aware of how other modules are working and thus find the best way to work together as a complete system. Empirical results demonstrate that the jointly optimized SmartRAG can achieve better performance than separately optimized counterparts. Although large language models(LLMs) (Chowdhery et al., 2023; Touvron et al., 2023; Chung et al., 2024) have demonstrated exceptional capabilities across various domains, addressing knowledgerelated issues beyond model parameters remains a challenging task (Mallen et al., 2023b; Min et al., 2023). Retrieval-augmentation generation(RAG) effectively enhances model performance in these scenarios by retrieving additional information from external tools (Ram et al., 2023). RAG systems usually consist of multiple modules including at least a retriever and a generator. Some systems may have other modules like a reranker (Glass et al., 2022), a decision maker deciding when to retrieve (Jeong et al., 2024; Wang et al., 2023a), a query rewriter (Ma et al., 2023; Tan et al., 2024) or a verifier (Lewis et al., 2020; Izacard et al., 2023). These modules are often hand-designed and separately optimized. One of the issues is that the golden answer of the intermediate modules are usually not accessible. What is worse, sometimes the golden answer is model-dependent or retriever-dependent. For example, Asai et al. (2024) uses the result of GPT4 (Achiam et al., 2023) as the ground truth for the decision maker, which can be suboptimal.