Rethinking LLM Ensembling from the Perspective of Mixture Models

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Hauptverfasser: Fu, Jiale, Jiang, Yuchu, Wu, Peijun, Liu, Chonghan, Zhou, Joey Tianyi, Yang, Xu
Format: Preprint
Veröffentlicht: 2026
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author Fu, Jiale
Jiang, Yuchu
Wu, Peijun
Liu, Chonghan
Zhou, Joey Tianyi
Yang, Xu
author_facet Fu, Jiale
Jiang, Yuchu
Wu, Peijun
Liu, Chonghan
Zhou, Joey Tianyi
Yang, Xu
contents Model ensembling is a well-established technique for improving the performance of machine learning models. Conventionally, this involves averaging the output distributions of multiple models and selecting the most probable label. This idea has been naturally extended to large language models (LLMs), yielding improved performance but incurring substantial computational cost. This inefficiency stems from directly applying conventional ensemble implementation to LLMs, which require a separate forward pass for each model to explicitly compute the ensemble distribution. In this paper, we propose the Mixture-model-like Ensemble (ME). By reinterpreting the ensemble as a mixture model, ME stochastically selects a single model at each step to generate the next token, thereby avoiding the need to explicitly compute the full ensemble distribution. ME is mathematically equivalent to sampling from the ensemble distribution, but requires invoking only one model, making it 1.78x-2.68x faster than conventional ensembling. Furthermore, this perspective connects LLM ensembling and token-level routing methods, suggesting that LLM ensembling is a special case of routing methods. Our findings open new avenues for efficient LLM ensembling and motivate further exploration of token-level routing strategies for LLMs. Our code is available at https://github.com/Kamichanw/Mixture-model-like-Ensemble.
format Preprint
id arxiv_https___arxiv_org_abs_2605_00419
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Rethinking LLM Ensembling from the Perspective of Mixture Models
Fu, Jiale
Jiang, Yuchu
Wu, Peijun
Liu, Chonghan
Zhou, Joey Tianyi
Yang, Xu
Machine Learning
Computation and Language
Model ensembling is a well-established technique for improving the performance of machine learning models. Conventionally, this involves averaging the output distributions of multiple models and selecting the most probable label. This idea has been naturally extended to large language models (LLMs), yielding improved performance but incurring substantial computational cost. This inefficiency stems from directly applying conventional ensemble implementation to LLMs, which require a separate forward pass for each model to explicitly compute the ensemble distribution. In this paper, we propose the Mixture-model-like Ensemble (ME). By reinterpreting the ensemble as a mixture model, ME stochastically selects a single model at each step to generate the next token, thereby avoiding the need to explicitly compute the full ensemble distribution. ME is mathematically equivalent to sampling from the ensemble distribution, but requires invoking only one model, making it 1.78x-2.68x faster than conventional ensembling. Furthermore, this perspective connects LLM ensembling and token-level routing methods, suggesting that LLM ensembling is a special case of routing methods. Our findings open new avenues for efficient LLM ensembling and motivate further exploration of token-level routing strategies for LLMs. Our code is available at https://github.com/Kamichanw/Mixture-model-like-Ensemble.
title Rethinking LLM Ensembling from the Perspective of Mixture Models
topic Machine Learning
Computation and Language
url https://arxiv.org/abs/2605.00419