Tokenizers act as a bridge between human language and the latent space of language models, influencing how language is represented in these models. Despite the dominance of English-Centric (EC) Large Language Models (LLMs), tokenization methods often fail to fairly represent complex scripts like Tamil, Sinhala, and Hindi, primarily due to pre-tokenization choices. This study demonstrates that pre-tokenization has a more significant impact than tokenization algorithms on achieving egalitarian representation. To address this, we introduce an improvement to the Byte Pair Encoding (BPE) algorithm by incorporating graphemes, which we term Grapheme Pair Encoding (GPE). Our experiments show that grapheme-based character extraction outperforms byte-level tokenizers for complex scripts. We validate this approach through experiments on Tamil, Sinhala, and Hindi. The codebase and resources used in this work are publicly available at https://github.com/vmenan/tokenizers-coling2025.

Domain adaptation in Neural Machine Translation (NMT) is commonly achieved through fine-tuning, but this approach becomes inefficient as the number of domains increases. Knowledge distillation (KD) provides a scalable alternative by training a compact model on distilled data from a larger model. However, we hypothesize that vanilla sequence-level KD primarily distills the decoder while neglecting encoder knowledge, leading to suboptimal knowledge transfer and limiting its effectiveness in low-resource settings, where both data and computational resources are constrained. To address this, we propose an improved sequence-level KD method that enhances encoder knowledge transfer through a cosine-based alignment loss. Our approach first trains a large model on a mixed-domain dataset and generates a Distilled Mixed Dataset (DMD). A small model is then trained on this dataset via sequence-level KD with encoder alignment. Experiments in a low-resource setting validate our hypothesis, demonstrating that our approach outperforms vanilla sequence-level KD, improves generalization to out-of-domain data, and facilitates efficient domain adaptation while reducing model size and computational cost.

This paper describes our submission to the WMT24 shared task for Low-Resource Languages of Spain in the Constrained task category. Due to the lack of deep learning-based data filtration methods for these languages, we propose a purely statistical-based, two-stage pipeline for data filtration. In the primary stage, we begin by removing spaces and punctuation from the source sentences (Spanish) and deduplicating them. We then filter out sentence pairs with inconsistent language predictions by the language identification model, followed by the removal of pairs with anomalous sentence length and word count ratios, using the development set statistics as the threshold. In the secondary stage, for corpora of significant size, we employ a Jensen Shannon divergence-based method to curate training data of the desired size. Our filtered data allowed us to complete a two-step training process in under 3 hours, with GPU power consumption kept below 1 kWh, making our system both economical and eco-friendly. The source code, training data, and best models are available on the project’s GitHub page.