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Revisiting the Weaknesses of Reinforcement Learning for Neural Machine Translation

Samuel Kiegeland
Julia Kreutzer
NAACL (2021)

Abstract

Policy gradient algorithms have found wide adoption in NLP, but have recently become subject to criticism, doubting their suitability for NMT. Choshen et al. (2020) identify multiple weaknesses and suspect that their success is determined by the shape of output distributions rather than the reward. In this paper, we revisit these claims and study them under a wider range of configurations. Our experiments on in-domain and cross-domain adaptation reveal the importance of exploration and reward scaling, and provide empirical counterevidence to these claims.