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Auteurs principaux: Wicks, Rachel, Ravisankar, Kartik, Yang, Xinchen, Koehn, Philipp, Post, Matt
Format: Preprint
Publié: 2025
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Accès en ligne:https://arxiv.org/abs/2502.21265
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author Wicks, Rachel
Ravisankar, Kartik
Yang, Xinchen
Koehn, Philipp
Post, Matt
author_facet Wicks, Rachel
Ravisankar, Kartik
Yang, Xinchen
Koehn, Philipp
Post, Matt
contents Model ensembling is a technique to combine the predicted distributions of two or more models, often leading to improved robustness and performance. For ensembling in text generation, the next token's probability distribution is derived from a weighted sum of the distributions of each individual model. This requires the underlying models to share the same subword vocabulary, limiting the applicability of ensembling, since many open-sourced models have distinct vocabularies. In research settings, experimentation or upgrades to vocabularies may introduce multiple vocabulary sizes. This paper proposes an inference-time only algorithm that allows for ensembling models with different vocabularies, without the need to learn additional parameters or alter the underlying models. Instead, the algorithm ensures that tokens generated by the ensembled models \textit{agree} in their surface form. We apply this technique to combinations of traditional encoder-decoder models and decoder-only LLMs and evaluate on machine translation. In addition to expanding to model pairs that were previously incapable of token-level ensembling, our algorithm frequently improves translation performance over either model individually.
format Preprint
id arxiv_https___arxiv_org_abs_2502_21265
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Token-level Ensembling of Models with Different Vocabularies
Wicks, Rachel
Ravisankar, Kartik
Yang, Xinchen
Koehn, Philipp
Post, Matt
Computation and Language
Model ensembling is a technique to combine the predicted distributions of two or more models, often leading to improved robustness and performance. For ensembling in text generation, the next token's probability distribution is derived from a weighted sum of the distributions of each individual model. This requires the underlying models to share the same subword vocabulary, limiting the applicability of ensembling, since many open-sourced models have distinct vocabularies. In research settings, experimentation or upgrades to vocabularies may introduce multiple vocabulary sizes. This paper proposes an inference-time only algorithm that allows for ensembling models with different vocabularies, without the need to learn additional parameters or alter the underlying models. Instead, the algorithm ensures that tokens generated by the ensembled models \textit{agree} in their surface form. We apply this technique to combinations of traditional encoder-decoder models and decoder-only LLMs and evaluate on machine translation. In addition to expanding to model pairs that were previously incapable of token-level ensembling, our algorithm frequently improves translation performance over either model individually.
title Token-level Ensembling of Models with Different Vocabularies
topic Computation and Language
url https://arxiv.org/abs/2502.21265