Training Matryoshka Mixture-of-Experts for Elastic Inference-Time Expert Utilization

Yaoxiang Wang, Qingguo Hu, Yucheng Ding, Ruizhe Wang, Yeyun Gong, Jian Jiao, Yelong Shen, Peng Cheng, Jinsong Su


Abstract
Mixture-of-Experts (MoE) has emerged as a promising paradigm for efficiently scaling large language models without a proportional increase in computational cost. However, the standard training strategy of Top-K router prevents MoE models from realizing their full potential for elastic inference. When the number of activated experts is altered at inference time, these models exhibit precipitous performance degradation. In this work, we introduce Matryoshka MoE (M-MoE), a training framework that instills a coarse-to-fine structure directly into the expert ensemble. By systematically varying the number of activated experts during training, M-MoE compels the model to learn a meaningful ranking: top-ranked experts collaborate to provide essential, coarse-grained capabilities, while subsequent experts add progressively finer-grained detail. We explore this principle at multiple granularities, identifying a layer-wise randomization strategy as the most effective. Our experiments demonstrate that a single M-MoE model achieves remarkable elasticity, with its performance at various expert counts closely matching that of an entire suite of specialist models, but at only a fraction of the total training cost. This flexibility not only unlocks elastic inference but also enables optimizing performance by allocating different computational budgets to different model layers. Our work paves the way for more practical and adaptable deployments of large-scale MoE models.
Anthology ID:
2026.emnlp-main.1449
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
33093–33111
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1449/
DOI:
Bibkey:
Cite (ACL):
Yaoxiang Wang, Qingguo Hu, Yucheng Ding, Ruizhe Wang, Yeyun Gong, Jian Jiao, Yelong Shen, Peng Cheng, and Jinsong Su. 2026. Training Matryoshka Mixture-of-Experts for Elastic Inference-Time Expert Utilization. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 33093–33111, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Training Matryoshka Mixture-of-Experts for Elastic Inference-Time Expert Utilization (Wang et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1449.pdf