Optimizing LLMs for Italian: Reducing Token Fertility and Enhancing Efficiency Through Vocabulary Adaptation

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Main Authors: Moroni, Luca, Puccetti, Giovanni, Cabot, Pere-Lluis Huguet, Bejgu, Andrei Stefan, Barba, Edoardo, Miaschi, Alessio, Dell'Orletta, Felice, Esuli, Andrea, Navigli, Roberto
Format: Preprint
Published: 2025
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author Moroni, Luca
Puccetti, Giovanni
Cabot, Pere-Lluis Huguet
Bejgu, Andrei Stefan
Barba, Edoardo
Miaschi, Alessio
Dell'Orletta, Felice
Esuli, Andrea
Navigli, Roberto
author_facet Moroni, Luca
Puccetti, Giovanni
Cabot, Pere-Lluis Huguet
Bejgu, Andrei Stefan
Barba, Edoardo
Miaschi, Alessio
Dell'Orletta, Felice
Esuli, Andrea
Navigli, Roberto
contents The number of pretrained Large Language Models (LLMs) is increasing steadily, though the majority are designed predominantly for the English language. While state-of-the-art LLMs can handle other languages, due to language contamination or some degree of multilingual pretraining data, they are not optimized for non-English languages, leading to inefficient encoding (high token "fertility") and slower inference speed. In this work, we thoroughly compare a variety of vocabulary adaptation techniques for optimizing English LLMs for the Italian language, and put forward Semantic Alignment Vocabulary Adaptation (SAVA), a novel method that leverages neural mapping for vocabulary substitution. SAVA achieves competitive performance across multiple downstream tasks, enhancing grounded alignment strategies. We adapt two LLMs: Mistral-7b-v0.1, reducing token fertility by 25\%, and Llama-3.1-8B, optimizing the vocabulary and reducing the number of parameters by 1 billion. We show that, following the adaptation of the vocabulary, these models can recover their performance with a relatively limited stage of continual training on the target language. Finally, we test the capabilities of the adapted models on various multi-choice and generative tasks.
format Preprint
id arxiv_https___arxiv_org_abs_2504_17025
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Optimizing LLMs for Italian: Reducing Token Fertility and Enhancing Efficiency Through Vocabulary Adaptation
Moroni, Luca
Puccetti, Giovanni
Cabot, Pere-Lluis Huguet
Bejgu, Andrei Stefan
Barba, Edoardo
Miaschi, Alessio
Dell'Orletta, Felice
Esuli, Andrea
Navigli, Roberto
Computation and Language
The number of pretrained Large Language Models (LLMs) is increasing steadily, though the majority are designed predominantly for the English language. While state-of-the-art LLMs can handle other languages, due to language contamination or some degree of multilingual pretraining data, they are not optimized for non-English languages, leading to inefficient encoding (high token "fertility") and slower inference speed. In this work, we thoroughly compare a variety of vocabulary adaptation techniques for optimizing English LLMs for the Italian language, and put forward Semantic Alignment Vocabulary Adaptation (SAVA), a novel method that leverages neural mapping for vocabulary substitution. SAVA achieves competitive performance across multiple downstream tasks, enhancing grounded alignment strategies. We adapt two LLMs: Mistral-7b-v0.1, reducing token fertility by 25\%, and Llama-3.1-8B, optimizing the vocabulary and reducing the number of parameters by 1 billion. We show that, following the adaptation of the vocabulary, these models can recover their performance with a relatively limited stage of continual training on the target language. Finally, we test the capabilities of the adapted models on various multi-choice and generative tasks.
title Optimizing LLMs for Italian: Reducing Token Fertility and Enhancing Efficiency Through Vocabulary Adaptation
topic Computation and Language
url https://arxiv.org/abs/2504.17025