@inproceedings{zhang-etal-2025-advancing-smoe,
    title = "Advancing {SM}o{E} for Continuous Domain Adaptation of {MLLM}s: Adaptive Router and Domain-Specific Loss",
    author = "Zhang, Liang  and
      Lu, Ziyao  and
      Meng, Fandong  and
      Li, Hui  and
      Zhou, Jie  and
      Su, Jinsong",
    editor = "Che, Wanxiang  and
      Nabende, Joyce  and
      Shutova, Ekaterina  and
      Pilehvar, Mohammad Taher",
    booktitle = "Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)",
    month = jul,
    year = "2025",
    address = "Vienna, Austria",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/ingestion-acl-25/2025.acl-long.1290/",
    pages = "26584--26602",
    ISBN = "979-8-89176-251-0",
    abstract = "Recent studies have explored Continual Instruction Tuning (CIT) in Multimodal Large Language Models (MLLMs), with a primary focus on Task-incremental CIT, where MLLMs are required to continuously acquire new tasks. However, the more practical and challenging Domain-incremental CIT, focused on the continual adaptation of MLLMs to new domains, remains underexplored. In this paper, we propose a new Sparse Mixture of Expert (SMoE) based method for domain-incremental CIT in MLLMs. During training, we learn a domain-specific SMoE module for each new domain in every FFN sub-layer of MLLMs, preventing catastrophic forgetting caused by inter-domain conflicts. Moreover, we equip the SMoE module with a domain-specific autoregressive loss (DSAL), which is used to identify the most suitable SMoE module for processing each test instruction during inference. To further enhance the SMoE module{'}s ability to learn domain knowledge, we design an adaptive threshold-based router (AT-Router) that allocates computing resources (experts) to instruction tokens based on their importance. Finally, we establish a new benchmark to evaluate the efficacy of our method and advance future research. Extensive experiments show that our method consistently outperforms all competitive baselines."
}