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Giving BERT a Calculator: Finding Operations and Arguments with Reading Comprehension

Paper · 2019 · Daniel Andor, Luheng He, Kenton Lee et al.

Summary

Neural reading comprehension systems are good at extracting answer spans but weak at arithmetic. On DROP, many answers must be computed instead of copied from the passage. The authors address this by letting a BERT-based reader choose a small executable program rather than generate the number itself. The program space includes:

  • literals (yes/no/unknown, digits 0–9);
  • text spans;
  • arithmetic over numbers found in the passage (Sum, Diff, Diff100, and later Mul and Div);
  • shallow two-step compositions (Sum3, Merge).

Each candidate is scored from BERT token representations, and an external calculator executes the best one. Training marginalizes over all oracle derivations that yield the gold answer, and pruning keeps the composed operations tractable. The approach gains over 33 absolute points over the previous best DROP system, NAQANet. It also learns new operations from few examples on the Illinois math word problems. The work matters because it moves computation out of the network and makes predictions partly interpretable. The operation inventory can also grow without redesigning the architecture.

Key points

  • DROP results: NAQANet reaches 47.77 test F1. The model pre-trained on CoQA and fine-tuned on DROP reaches 80.47 test F1, and a 6-model ensemble reaches 81.78. The oracle ceiling with all operations is 93.01 dev F1.
  • Ablations: Diff100 adds about 9 points and Sum3 about 1.1. Merge helps multi-span answers, but they stay under-predicted because single spans outnumber them about 11:1.
  • CoQA and forgetting: Fine-tuning on DROP alone drops CoQA dev F1 to 52.2. Joint training keeps both: 82.2 F1 on CoQA and 81.1 F1 on DROP.
  • Illinois math word problems: Accuracy is 48.6 for the basic model, 74.0 after adding Mul/Div, and 83.2 when DROP data is also used. This exceeds prior systems at 73.3–80.1.
  • Training details: 36% of answerable examples have several valid derivations, and the model learns to resolve this ambiguity during training. Pruning keeps the top 128 Span and Sum candidates before composing Merge and Sum3.

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

 Institutions

 Fields, topics and concepts

Cite

Cite as Daniel Andor, Luheng He, Kenton Lee and Emily Pitler. 2019. Giving BERT a Calculator: Finding Operations and Arguments with Reading Comprehension. Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP).

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/d19-1609 · arXiv 1909.00109

@inproceedings{andor2019giving,
  title = {{Giving BERT a Calculator: Finding Operations and Arguments with Reading Comprehension}},
  author = {Daniel Andor, Luheng He, Kenton Lee and Emily Pitler},
  booktitle = {Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP)},
  year = {2019},
  doi = {10.18653/v1/d19-1609},
  eprint = {1909.00109},
  archivePrefix = {arXiv},
  url = {https://doi.org/10.18653/v1/d19-1609}
}

References

13 references, 8 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet.

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  3. Kenton Lee, Tom Kwiatkowski, Ankur P. Parikh, and Dipanjan Das. 2017. Learning recurrent span representations for extractive question answering. CoRR, abs/1611.01436. — [arXiv:1611.01436](https://arxiv.org/abs/1611.01436) find
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