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Character-level Convolutional Networks for Text Classification

Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive licence to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/1509.01626

Summary

Most text classifiers of the time worked on words or word n-grams. This paper asks whether a deep convolutional network can classify documents when it sees only raw characters, with no tokenization and no knowledge of words, syntax or semantics. Each character is one-hot encoded over a fixed 70-symbol alphabet, and documents are cut to 1014 characters. A 9-layer temporal ConvNet then processes the input: 6 convolutional layers followed by 3 fully-connected layers, in a large and a small version. ConvNets need a lot of training data, so the authors built several large datasets covering news topics, ontology categories, Q&A topics and review sentiment. They compared the model with bag-of-words, n-gram and TFIDF baselines, with word-based ConvNets and with an LSTM. The character-level model was competitive or best on the million-sample datasets. Classic n-gram TFIDF still won on smaller ones. The work matters because it showed that text can be treated as a raw signal. That could make one system usable across languages and robust to noisy user-generated text.

Key points

  • New benchmark datasets: AG News, Sogou News, DBPedia, Yelp Review (Polarity/Full), Yahoo! Answers and Amazon Review (Full/Polarity). Amazon Polarity has 1.8M training samples per class.
  • Architecture: 70-character alphabet, input length 1014, 6 conv layers (1024 features in the large model, 256 in the small) and 3 FC layers with dropout 0.5. Temporal max-pooling made networks deeper than 6 layers trainable.
  • Data augmentation replaces words with synonyms from a WordNet-derived thesaurus (LibreOffice mytheas). The number of replacements and the synonym chosen are both drawn from geometric distributions with p = q = 0.5.
  • Dataset size decides the winner. n-gram TFIDF stays strong up to a few hundred thousand samples, and the character-level ConvNet pulls ahead at millions of samples. It also does relatively well on less-curated texts such as Amazon reviews.
  • Treating upper- and lower-case letters as the same often helped on large datasets. Bag-of-means over word2vec clusters was the weakest model in every comparison.

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: Computing & GPUs

Cited by

1547 papers of our library cite it (of the 140673 whose bibliographies we read); 60 of them have a page here, 1487 not yet.

Cite

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.48550/arxiv.1509.01626 · arXiv 1509.01626

@misc{zhang2015character,
  title = {{Character-level Convolutional Networks for Text Classification}},
  author = {Zhang, Xiang and Zhao, Junbo and LeCun, Yann},
  year = {2015},
  doi = {10.48550/arxiv.1509.01626},
  eprint = {1509.01626},
  archivePrefix = {arXiv},
  url = {https://doi.org/10.48550/arxiv.1509.01626}
}

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