Acknowledgements
Table 4.1: “Baseline” is a model trained from random initialization with own specific vocabulary. “Direct Transfer” is using the parent vocabulary. Models in the top part of the table use the English→Czech parent model, models in the bottom part use Czech→English. The scores and difference are in BLEU. The ‡ represents significantly better results based on significance test described in Section 2.4.3.
['Translation direction', 'Baseline', 'Direct Transfer', 'Difference']
The second criterion behind the selection of languages is to include language pairs reaching various levels of translation quality. This is indicated by automatic scores of the baseline setups ranging from 3.54 BLEU (English→Odia) to 36.72 BLEU (English→German) We start with the results of Direct Transfer method, which uses parent vocabulary without any change. The baseline uses child-specific vocabulary. The statistical significance ‡ is measured between Direct Transfer and Transformed Vocabulary. We added a column with results of Transformed Vocabulary. We see “Transformed Vocabulary” delivering the best performance for all language pairs except English→Estonian, significantly improving over “Direct Transfer” in most cases. The only exceptions are Estonian→English, English→French and French→Spanish, where neither of the systems is significantly better than the other, however, both of them are significantly better than the baseline. BiRNN Bidirectional Recurrent Neural Network BP Brevity Penalty BPE Byte Pair Encoding CNN Convolutional Neural Network IWSLT International Workshop on Spoken Language Translation LanideNN Language Identification by Neural Networks LM Language Model LSTM Long Short-Term Memory cells MT Machine Translation NLP Natural Language Processing NMT Neural Machine Translation NN Neural Network PBMT Phrase-Based Machine Translation POS Part-of-Speech OOV Out-of-Vocabulary RNN Recurrent Neural Network SMT Statistical Machine Translation T2T Tensor2tensor WAT Workshop on Asian Translation WMT Workshop on Statistical Machine Translation