Context Gates for Neural Machine Translation
Table 4: Evaluation of alignment quality. The lower the score, the better the alignment quality.
['[BOLD] System', 'SAER', 'AER']
Following \newciteTu:2016:ACL, we used the alignment error rate (AER) S and P are the sets of sure and possible links in the reference alignment respectively (S⊆P). M denotes the alignment matrix, and for both MS and MP we assign the elements that correspond to the existing links in S and P probability 1 and the other elements probability 0. In this way, we are able to better evaluate the quality of the soft alignments produced by attention-based NMT.