Controlling the Output Length of Neural Machine Translation
Table 5: Results for En-It with Tok+Enc Rel by scaling the target length with different constant factors.
['[BOLD] Token', '[BOLD] Scale', 'BLEU', 'BLEU∗', 'LR [ITALIC] src', 'LR [ITALIC] ref']
Controlling output length. In order to achieve LRsrc as close as possible to 1.0, we set the target length during generation equal to the source length when using the length encoding methods. However, one advantage of length encoding is the possibility to set the target length to modify the average output length. We illustrate this option by using the Tok+Enc Rel system for En-It, and translating with the tokens normal or short and different scaling factors for the target length.