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MAGNET: Improving the Multilingual Fairness of Language Models with Adaptive Gradient-Based Tokenization

Paper · 2024 · Orevaoghene Ahia, Sachin Kumar, Hila Gonen et al.

Summary

Byte-level and subword language models usually split non-Latin-script text into many more pieces than English. This raises compute cost and hurts model quality for many languages. Earlier gradient-based tokenizers inside hourglass transformers learn segment boundaries end-to-end. However, they use a single boundary predictor with one target compression rate, so scripts that need more UTF-8 bytes for the same content remain over-fragmented.

The authors propose MAGNET. It keeps the hourglass design (a byte encoder, a pooled middle transformer and an upsampling block) but routes each byte sequence to a boundary predictor dedicated to its script, such as Latin, Cyrillic or Indic. Each predictor is trained with hard Gumbel-sigmoid reparameterization and has its own compression setting.

Experiments on nine typologically diverse languages compare MAGNET with BPE, uncompressed byte-level models and the single-predictor DTP approach. MAGNET produces segments of similar granularity across scripts, speeds up language modelling and keeps downstream performance competitive, with some trade-offs from strong compression of non-Latin languages. For Cyrillic-script work, including Ukrainian, this points toward cheaper and fairer tokenizer-free models.

Key points

  • The motivating disparity is large. An English sentence takes 43 UTF-8 bytes while its Telugu translation takes 148, and non-Latin scripts can need up to about 4× more bytes for the same information.
  • Each boundary predictor is an MLP with a sigmoid, applied over byte hidden states. A Binomial-prior regularizer with hyperparameter β keeps compression near 1/β, and MAGNET assigns a separate predictor and β to each script.
  • The baselines are BPE, byte-level models without compression and DTP (the gradient-based method of Nawrot et al.). Downstream evaluation includes the SIB dataset.
  • Fine-tuning on downstream tasks barely changes the learned boundaries. The few small shifts showed no clear effect on task performance.
  • The paper appeared at NeurIPS 2024. Code and data are released at github.com/orevaahia/magnet-tokenization, and the qualitative examples include Russian, Ukrainian, Hindi and Telugu.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Fields, topics and concepts

Cite

Cite as Orevaoghene Ahia, Sachin Kumar, Hila Gonen, Valentin Hofmann, Tomasz Limisiewicz, Yulia Tsvetkov and Noah A. Smith. 2024. MAGNET: Improving the Multilingual Fairness of Language Models with Adaptive Gradient-Based Tokenization. arXiv:2407.08818.

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.48550/arxiv.2407.08818 · arXiv 2407.08818

@misc{ahia2024magnet,
  title = {{MAGNET: Improving the Multilingual Fairness of Language Models with Adaptive Gradient-Based Tokenization}},
  author = {Orevaoghene Ahia, Sachin Kumar, Hila Gonen, Valentin Hofmann, Tomasz Limisiewicz, Yulia Tsvetkov and Noah A. Smith},
  year = {2024},
  doi = {10.48550/arxiv.2407.08818},
  eprint = {2407.08818},
  archivePrefix = {arXiv},
  url = {https://doi.org/10.48550/arxiv.2407.08818}
}

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