Do all Roads Lead to Rome?Understanding the Role of Initialization in Iterative Back-Translation
Table 1: Test results using different initial systems for warmup (BLEU), before (init column) and after iterative back-translation (final column).
['[EMPTY]', 'DE-EN init', 'DE-EN final', 'EN-DE init', 'EN-DE final']
As it can be seen, the standard deviation across final systems is substantially lower than across initial systems (1.7 vs 5.6 in German-to-English and 1.4 vs 4.9 in English-to-German), which shows that iterative back-translation tends to converge to solutions of a similar quality. This way, while the initial system does have certain influence in final performance, differences greatly diminish after applying iterative back-translation. For instance, the full NMT system is 13.4 points better than the RBMT system in German-to-English, but this difference goes down to 2.3 points after iterative back-translation.