We define a distance matrix D, between the mapped source embeddings and target embeddings, where "dist" is some distance metric.
for the ith source word, Nearest Neighbor (NN) criterion determines (the index of) its translation in the Y set, by arg min several works (Radovanovic et al., 2010;Dinu et al., 2014) have observed that the accuracy of NN is often significantly degraded by a phenomenon called hubness.