Yuxuan Chen


2022

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Why only Micro-F1? Class Weighting of Measures for Relation Classification
David Harbecke | Yuxuan Chen | Leonhard Hennig | Christoph Alt
Proceedings of NLP Power! The First Workshop on Efficient Benchmarking in NLP

Relation classification models are conventionally evaluated using only a single measure, e.g., micro-F1, macro-F1 or AUC. In this work, we analyze weighting schemes, such as micro and macro, for imbalanced datasets. We introduce a framework for weighting schemes, where existing schemes are extremes, and two new intermediate schemes. We show that reporting results of different weighting schemes better highlights strengths and weaknesses of a model.

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A Comparative Study of Pre-trained Encoders for Low-Resource Named Entity Recognition
Yuxuan Chen | Jonas Mikkelsen | Arne Binder | Christoph Alt | Leonhard Hennig
Proceedings of the 7th Workshop on Representation Learning for NLP

Pre-trained language models (PLM) are effective components of few-shot named entity recognition (NER) approaches when augmented with continued pre-training on task-specific out-of-domain data or fine-tuning on in-domain data. However, their performance in low-resource scenarios, where such data is not available, remains an open question. We introduce an encoder evaluation framework, and use it to systematically compare the performance of state-of-the-art pre-trained representations on the task of low-resource NER. We analyze a wide range of encoders pre-trained with different strategies, model architectures, intermediate-task fine-tuning, and contrastive learning. Our experimental results across ten benchmark NER datasets in English and German show that encoder performance varies significantly, suggesting that the choice of encoder for a specific low-resource scenario needs to be carefully evaluated.

2020

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Query-Key Normalization for Transformers
Alex Henry | Prudhvi Raj Dachapally | Shubham Shantaram Pawar | Yuxuan Chen
Findings of the Association for Computational Linguistics: EMNLP 2020

Low-resource language translation is a challenging but socially valuable NLP task. Building on recent work adapting the Transformer’s normalization to this setting, we propose QKNorm, a normalization technique that modifies the attention mechanism to make the softmax function less prone to arbitrary saturation without sacrificing expressivity. Specifically, we apply l2-normalization along the head dimension of each query and key matrix prior to multiplying them and then scale up by a learnable parameter instead of dividing by the square root of the embedding dimension. We show improvements averaging 0.928 BLEU over state-of-the-art bilingual benchmarks for 5 low-resource translation pairs from the TED Talks corpus and IWSLT’15.