In preliminary experiments, we find in adversarial training that the single-direction criterion S(F, X, Y ) by<cite> Conneau et al. (2018)</cite> does not always work well. To address this, we make a simple extension by calculating the weighted average of forward and backward scores: Where λ is a hyperparameter to control the importance of the two objectives. 1 Here S first generates bilingual lexicons by learned mappings, and then computes the average cosine similarity of these translations.