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Byte Pair Encoding (BPE) is a widely used tokenization algorithm, whose tokens cannot extend across pre-tokenization boundaries, functionally limiting it to representing at most full words. The BoundlessBPE and SuperBPE algorithms extend…

Computation and Language · Computer Science 2026-04-08 Craig W. Schmidt , Chris Tanner , Yuval Pinter

Tokenization significantly influences language models(LMs)' performance. This paper traces the evolution of tokenizers from word-level to subword-level, analyzing how they balance tokens and types to enhance model adaptability while…

Computation and Language · Computer Science 2024-03-04 Jinbiao Yang

Modern language models represent probability distributions over character strings as distributions over (shorter) token strings derived via a deterministic tokenizer, such as byte-pair encoding. While this approach is highly effective at…

Many natural language processing systems operate over tokenizations of text to address the open-vocabulary problem. In this paper, we give and analyze an algorithm for the efficient construction of deterministic finite automata (DFA)…

Formal Languages and Automata Theory · Computer Science 2025-05-27 Martin Berglund , Willeke Martens , Brink van der Merwe

The Byte Pair Encoding algorithm can be safely batched to merge hundreds of pairs of tokens at a time when building up a tokenizer's vocabulary. This technique combined with reducing the memory footprint of text used in vocabulary training…

Computation and Language · Computer Science 2024-08-12 Alexander P. Morgan

Tokenization is the act of breaking down text into smaller parts, or tokens, that are easier for machines to process. This is a key phase in machine translation (MT) models. Subword tokenization enhances this process by breaking down words…

Computation and Language · Computer Science 2025-05-23 Sudhansu Bala Das , Samujjal Choudhury , Tapas Kumar Mishra , Bidyut Kr. Patra

As a cornerstone in language modeling, tokenization involves segmenting text inputs into pre-defined atomic units. Conventional statistical tokenizers often disrupt constituent boundaries within words, thereby corrupting semantic…

Computation and Language · Computer Science 2025-07-11 Qingyang Zhu , Xiang Hu , Pengyu Ji , Wei Wu , Kewei Tu

The prevalent use of Byte Pair Encoding (BPE) in Large Language Models (LLMs) facilitates robust handling of subword units and avoids issues of out-of-vocabulary words. Despite its success, a critical challenge persists: long tokens, rich…

Computation and Language · Computer Science 2024-11-11 Haoran Lian , Yizhe Xiong , Zijia Lin , Jianwei Niu , Shasha Mo , Hui Chen , Peng Liu , Guiguang Ding

Subword tokenization has become the prevailing standard in the field of natural language processing (NLP) over recent years, primarily due to the widespread utilization of pre-trained language models. This shift began with Byte-Pair…

Computation and Language · Computer Science 2024-06-11 Yanis Labrak , Adrien Bazoge , Beatrice Daille , Mickael Rouvier , Richard Dufour

We explore threshold vocabulary trimming in Byte-Pair Encoding subword tokenization, a postprocessing step that replaces rare subwords with their component subwords. The technique is available in popular tokenization libraries but has not…

Computation and Language · Computer Science 2024-04-02 Marco Cognetta , Tatsuya Hiraoka , Naoaki Okazaki , Rico Sennrich , Yuval Pinter

Language models typically tokenize text into subwords, using a deterministic, hand-engineered heuristic of combining characters into longer surface-level strings such as 'ing' or whole words. Recent literature has repeatedly shown the…

Computation and Language · Computer Science 2023-10-19 Avijit Thawani , Saurabh Ghanekar , Xiaoyuan Zhu , Jay Pujara

We propose a generalization of neural network sequence models. Instead of predicting one symbol at a time, our multi-scale model makes predictions over multiple, potentially overlapping multi-symbol tokens. A variation of the byte-pair…

Machine Learning · Statistics 2017-07-06 Bart van Merriënboer , Amartya Sanyal , Hugo Larochelle , Yoshua Bengio

Tokenization is an important text preprocessing step to prepare input tokens for deep language models. WordPiece and BPE are de facto methods employed by important models, such as BERT and GPT. However, the impact of tokenization can be…

Computation and Language · Computer Science 2023-03-28 Cagri Toraman , Eyup Halit Yilmaz , Furkan Şahinuç , Oguzhan Ozcelik

In recent years, language models have become increasingly larger and more complex. However, the input representations for these models continue to rely on simple and greedy subword tokenization methods. In this paper, we propose a novel…

Computation and Language · Computer Science 2023-06-14 David Samuel , Lilja Øvrelid

Subword regularization, used widely in NLP, improves model performance by reducing the dependency on exact tokenizations, augmenting the training corpus, and exposing the model to more unique contexts during training. BPE and MaxMatch, two…

Computation and Language · Computer Science 2024-08-22 Marco Cognetta , Vilém Zouhar , Naoaki Okazaki

Byte Pair Encoding (BPE) tokenizers, widely used in Large Language Models, face challenges in multilingual settings, including penalization of non-Western scripts and the creation of tokens with partial UTF-8 sequences. Pretokenization,…

Computation and Language · Computer Science 2025-06-02 Sander Land , Catherine Arnett

Subword tokenization is a commonly used input pre-processing step in most recent NLP models. However, it limits the models' ability to leverage end-to-end task learning. Its frequency-based vocabulary creation compromises tokenization in…

Computation and Language · Computer Science 2022-04-25 Md Mofijul Islam , Gustavo Aguilar , Pragaash Ponnusamy , Clint Solomon Mathialagan , Chengyuan Ma , Chenlei Guo

Byte Pair Encoding (BPE) serves as a foundation method for text tokenization in the Natural Language Processing (NLP) field. Despite its wide adoption, the original BPE algorithm harbors an inherent flaw: it inadvertently introduces a…

Computation and Language · Computer Science 2024-11-14 Haoran Lian , Yizhe Xiong , Jianwei Niu , Shasha Mo , Zhenpeng Su , Zijia Lin , Hui Chen , Peng Liu , Jungong Han , Guiguang Ding

The success of pretrained transformer language models (LMs) in natural language processing has led to a wide range of pretraining setups. In particular, these models employ a variety of subword tokenization methods, most notably byte-pair…

Computation and Language · Computer Science 2020-10-06 Kaj Bostrom , Greg Durrett

The assumption across nearly all language model (LM) tokenization schemes is that tokens should be subwords, i.e., contained within word boundaries. While providing a seemingly reasonable inductive bias, is this common practice limiting the…

Computation and Language · Computer Science 2025-08-28 Alisa Liu , Jonathan Hayase , Valentin Hofmann , Sewoong Oh , Noah A. Smith , Yejin Choi