---
title: Expert-Choice Routing
type: vocabulary
url: "https://www.envisioning.com/vocab/expert-choice-routing"
summary: Routing scheme in mixture-of-experts and mixture-of-recursions where each expert selects its top-k tokens, rather than each token selecting its top-k experts.
year: 2021
generality: 0.55
---

# Expert-Choice Routing

Routing scheme in mixture-of-experts and mixture-of-recursions where each expert selects its top-k tokens, rather than each token selecting its top-k experts.
Expert-choice routing is an assignment scheme for mixture-of-experts and related architectures in which each expert independently selects the top-k tokens it will process. It is the inverse of token-choice routing, where each token picks its own top-k experts. Because every expert picks a fixed number of tokens, the load is automatically balanced and no auxiliary load-balancing loss is needed.

The scheme was formalized by Zhou et al. in their 2021 paper, 'Mixture-of-Experts with Expert Choice Routing.' It generalizes to variable recursion depth: in Mixture-of-Recursions, each depth level picks the tokens that should be processed at that depth, producing a separation between tokens that loop once, twice, or three times.

Expert-choice routing trades some flexibility (some tokens may be chosen by multiple depths, others by none) for predictable compute. The scheme is useful in inference scenarios where the cost of uneven routing outweighs the benefit of fully token-adaptive assignment.

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Source: Envisioning — Technology Research Institute (https://www.envisioning.com/vocab/expert-choice-routing)