CMU’s Machine Translation System for IWSLT 2019

20686

Authors

nan

Abstract

AbstractIn Neural Machine Translation (NMT) the usage of sub-words and characters as source and target units offers a simple and flexible solution for translation of rare and unseen words. However, selecting the optimal subword segmentation involves a trade-off between expressiveness and flexibility, and is language and dataset-dependent. We present Block Multitask Learning (BMTL), a novel NMT architecture that predicts multiple targets of different granularities simulta- neously, removing the need to search for the optimal seg- mentation strategy. Our multi-task model exhibits improvements of up to 1.7 BLEU points on each decoder over single-task baseline models with the same number of parameters on datasets from two language pairs of IWSLT15 and one from IWSLT19. The multiple hypotheses generated at different granularities can also be combined as a post-processing step to give better translations.

Keywords

nan

Full Content

CMU’s Machine Translation System for IWSLT 2019 Tejas Srinivasan, Ramon Sanabria, Florian Metze Language Technologies Institute Carnegie Mellon University, USA tsriniva@cs.cmu.edu Abstract In Neural Machine Translation (NMT) the usage of sub- words and characters as source and target units offers a sim- ple and flexible solution for translation of rare and unseen words. However, selecting the optimal subword segmenta- tion involves a trade-off between expressiveness and flexibil- ity, and is language and dataset-dependent. We present Block Multitask Learning (BMTL), a novel NMT architecture that predicts multiple targets of different granularities simulta- neously, removing the need to search for the optimal seg- mentation strategy. Our multi-task model exhibits improve- ments of up to 1.7 BLEU points on each decoder over single- task baseline models with the same number of parameters on datasets from two language pairs of IWSLT15 and one from IWSLT19. The multiple hypotheses generated at different granularities can also be combined as a post-processing step to give better translations. 1. Introduction Neural Machine Translation (NMT) [1, 2, 3] provides a sim- ple, end-to-end framework for translating text from one lan- guage to another. NMT approaches have largely outper- formed and replaced previous statistical translation methods. Traditionally, NMT systems used words as source and tar- get units, which have three main disadvantages. First, word- based models are unable to translate rare and out of vocab- ulary (OOV) words in the source language. Second, they can not produce unseen target words, such as morphologi- cal variants of observed words (e.g., deriving realistic from real). Third, they have to handle large source and target language vocabularies (i.e., large look-up matrices), which makes them less scalable in term of computation and mem- ory. A large vocabulary also implies data sparsity where the number of tokens is not balanced. A common solution for the problems mentioned above is to perform word segmentation. The Byte-Pair Encod- ing (BPE) algorithm [4] groups units together according to their frequency. By presetting the desired vocabulary size, the BPE algorithm generates a segmentation of the data by representing words as a collection of subword units. More recently, [5] proposed a forward probabilistic subword seg- mentation algorithm which is based on a unigram language model, in contrast to the deterministic BPE algorithm. Un- �I �flew �on �Air �Force �Tw o �for �eight �years �. 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decoder PROJ Subword10k PROJ Unit-specific CE Loss Unit-specific CE Loss Unit-specific CE Loss …

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Labeled Text

AbstractIn Neural Machine Translation (NMT) the usage of sub-words and characters as source and target units offers a simple and flexible solution for translation of rare and unseen words. However, selecting the optimal subword segmentation involves a trade-off between expressiveness and flexibility, and is language and dataset-dependent. We present Block Multitask Learning (BMTL), a novel NMT architecture that predicts multiple targets of different granularities simulta- neously, removing the need to search for the optimal seg- mentation strategy. Our multi-task model exhibits improvements of up to 1.7 BLEU points on each decoder over single-task baseline models with the same number of parameters on datasets from two language pairs of IWSLT15 and one from IWSLT19. The multiple hypotheses generated at different granularities can also be combined as a post-processing step to give better translations.

Publication Details

Paper ID:
20686
Year:
2019
Publication:
TIPSTER
Publication Type:
conf
DOI:
nan