Fˆ2-Softmax: Diversifying Neural Text Generation via Frequency Factorized Softmax

Byung-Ju Choi, Jimin Hong, David Park, Sang Wan Lee


Abstract
Despite recent advances in neural text generation, encoding the rich diversity in human language remains elusive. We argue that the sub-optimal text generation is mainly attributable to the imbalanced token distribution, which particularly misdirects the learning model when trained with the maximum-likelihood objective. As a simple yet effective remedy, we propose two novel methods, Fˆ2-Softmax and MefMax, for a balanced training even with the skewed frequency distribution. MefMax assigns tokens uniquely to frequency classes, trying to group tokens with similar frequencies and equalize frequency mass between the classes. Fˆ2-Softmax then decomposes a probability distribution of the target token into a product of two conditional probabilities of (1) frequency class, and (2) token from the target frequency class. Models learn more uniform probability distributions because they are confined to subsets of vocabularies. Significant performance gains on seven relevant metrics suggest the supremacy of our approach in improving not only the diversity but also the quality of generated texts.
Anthology ID:
2020.emnlp-main.737
Volume:
Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP)
Month:
November
Year:
2020
Address:
Online
Editors:
Bonnie Webber, Trevor Cohn, Yulan He, Yang Liu
Venue:
EMNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
9167–9182
Language:
URL:
https://aclanthology.org/2020.emnlp-main.737
DOI:
10.18653/v1/2020.emnlp-main.737
Bibkey:
Cite (ACL):
Byung-Ju Choi, Jimin Hong, David Park, and Sang Wan Lee. 2020. Fˆ2-Softmax: Diversifying Neural Text Generation via Frequency Factorized Softmax. In Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP), pages 9167–9182, Online. Association for Computational Linguistics.
Cite (Informal):
Fˆ2-Softmax: Diversifying Neural Text Generation via Frequency Factorized Softmax (Choi et al., EMNLP 2020)
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PDF:
https://aclanthology.org/2020.emnlp-main.737.pdf
Optional supplementary material:
 2020.emnlp-main.737.OptionalSupplementaryMaterial.zip
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