Distribution-Consistent Inference for Dynamic Sparse Mixture-of-Experts

Dohyeon Kim, Bedionita Soro, Sung Ju Hwang


Abstract
Mixture-of-Experts (MoE) architectures have emerged as a powerful paradigm for scaling model capacity while preserving efficient inference in large foundation models. However, most MoE models use a fixed top-k expert selection policy, assigning the same expert budget to every token even when fewer experts may be sufficient. Inference-time dynamic top-k routing can reduce computation without retraining, but existing methods often overlook the distributional shift caused by deviating from the training-time routing configuration. We show that reducing the number of activated experts consistently increases the RMS scale and variance of SMoE outputs, inducing a representation mismatch that contributes to downstream performance degradation in addition to the loss of expert capacity. To address this correctable component, we propose Layer-wise Distribution Alignment (LDA), a lightweight inference-time correction that uses layer-wise calibration statistics to align reduced-routing representations with the default configuration. Across multiple SMoE LLMs, benchmarks, and routing strategies, LDA recovers much of the performance lost induced by the distributional shift under reduced routing while preserving sparse-inference efficiency with negligible overhead.
Anthology ID:
2026.findings-emnlp.2320
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
49812–49836
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2320/
DOI:
10.18653/2026.findings-emnlp.2320
Bibkey:
Cite (ACL):
Dohyeon Kim, Bedionita Soro, and Sung Ju Hwang. 2026. Distribution-Consistent Inference for Dynamic Sparse Mixture-of-Experts. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 49812–49836, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Distribution-Consistent Inference for Dynamic Sparse Mixture-of-Experts (Kim et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2320.pdf