arXiv AI
Oct 21

The Router Already Knows

The paper investigates whether a sparse dictionary can reuse the routing decisions already made by a mixture‑of‑experts (MoE) model. Using the NR‑SAE approach, each routed expert is given a small dictionary that is opened only when the frozen router selects that expert. Experiments on Gemma 4 26B‑A4B show that the expert‑aligned autoencoder explains 51.8 % of the variance in router‑weighted expert outputs, outperforming several control variants and suggesting that the router already encodes useful information that a dictionary would otherwise need to learn.

By Andrew Bistras, Marty Johnson
arXiv Machine Learning
Sep 21

IntBMoE: Integrating Block-Level Conditioning into Expert Composition for Full-Participation Mixture-of-Experts

IntBMoE introduces a block‑conditioned mixture‑of‑experts that decouples participation, execution, and materialization by combining dense expert composition with sparse block execution. Each internal layer uses a lightweight hypernetwork to merge all expert bases into a single composed expert, while a router selects only a few blocks per token, keeping compute and memory costs low. Experiments on image classification, language modeling, and sequential recommendation demonstrate consistent performance gains, and the model is deployed in AMap’s generative recommendation system, improving UVCTR by 2.4% in online A/B tests.

By Ran Cheng, Longfei Xu, Zheng Liu, Kaikui Liu, Xiangxiang Chu
arXiv AI
Oct 31

Interpretability Is Not Just a Tax: Sparsity and Diversity Yield Legible and Composable Reward Experts for Personalization

The paper investigates how to make Mixture-of-Experts (MoE) reward models more interpretable and useful for personalization by focusing on sparsity and diversity regularizers. By keeping the architecture and training data constant, the authors show that conventional MoE reward models learn entangled components that hinder both interpretability and personalization. Introducing a sparse MoE objective reduces entanglement, yielding experts that align with semantic categories and functional strengths, and enables composable, few‑shot personalization with a 25.81‑point improvement over entangled models.

By Yifan Wang, Jinyi Mu, Mayank Jobanputra, Yu Wang, Ji-Ung Lee, Soyoung Oh, Isabel Valera, Vera Demberg