Although large language models (LLMs) store vast amount of knowledge in their parameters, they still have limitations in the memorization and utilization of certain knowledge, leading to undesired behaviors such as generating untruthful and inaccurate responses. This highlights the critical need to understand the knowledge boundary of LLMs, a concept that remains inadequately defined in existing research. In this survey, we propose a comprehensive definition of the LLM knowledge boundary and introduce a formalized taxonomy categorizing knowledge into four distinct types. Using this foundation, we systematically review the field through three key lenses: the motivation for studying LLM knowledge boundaries, methods for identifying these boundaries, and strategies for mitigating the challenges they present. Finally, we discuss open challenges and potential research directions in this area. We aim for this survey to offer the community a comprehensive overview, facilitate access to key issues, and inspire further advancements in LLM knowledge research.

Self-supervised pre-training and instruction fine-tuning demonstrate the potential of large language models (LLMs) for domain adaptation (DA). In pursuit of superhuman performance, LLMs have demonstrated significant potential in math and coding through self-improvement algorithms that rely on iterative training with self-generated data. This success stems from the clear reward signals in these environments, which provide a solid foundation for self-improvement. However, when it comes to general DA scenarios, two main challenges emerge: 1) ambiguous self-improvement reward signals and 2) lack of high-quality instruction fine-tuning datasets. This motivates this paper addresses how LLMs can adapt autonomously to new domains using only a large amount of unlabeled target corpora. Inspired by the human practice of self-reflection through open- and closed-book exercises to achieve domain generalization, we propose autonomous learning, which creates a self-improvement learning environment for DA. Here, the model generates questions from documents and conducts two explorations—one with the original document and one with a masked version. By comparing these explorations, the LLMs can independently identify and enhance its policy for reducing knowledge gaps. Experiments across various DA tasks demonstrate that autonomous learning enhances the DA performance of existing models, outperforming traditional fine-tuning and self-improvement methods. Our code is publicly available at https://github.com/FreedomIntelligence/AL.

Multimodal large language models (MLLMs) have broadened the scope of AI applications. Existing automatic evaluation methodologies for MLLMs are mainly limited in evaluating objective queries without considering real-world user experiences, inadequately addressing the nuances of creative and associative multimodal tasks. However, the open-ended and subjective nature of such tasks poses a significant challenge to the evaluation methodology, where it is difficult to define the ground-truth answers for them. To this end, in our paper, we propose a new evaluation paradigm for MLLMs, which is evaluating MLLMs with per-sample criteria using potent MLLM as the judge. To validate the feasibility and effectiveness of this paradigm, we design a benchmark, dubbed MLLM-Bench, by curating the evaluation samples across six comprehensive cognitive levels. We benchmark 26 popular MLLMs in a pairwise-comparison fashion, showing diverse performance across models. Moreover, the validity of our benchmark manifests itself in reaching 88.02% agreement with human evaluation. We contend that the proposed paradigm explores the potential of MLLMs as effective evaluation tools with the help of per-sample criteria.