Computing BLEU Score for Machine Translation

In this tutorial, I am going to explain how I compute the BLEU score for the Machine Translation output using Python.

BLEU is simply a measure for evaluating the quality of your Machine Translation system. It does not really matter whether your MT target is from a high-level framework like OpenNMT or Marian, or from a lower-level one like TensorFlow or PyTorch. It does not also matter whether it is a Neural Machine Translation system or a Statistical Machine Translation tool like Moses.

So let’s see the steps I follow to calculate the BLEU score.

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Domain Adaptation Techniques for Low-Resource Domains, Institutions and Languages

Domain Adaptation

So what is Domain Adaptation? Let’s imagine this scenario. You have a new Machine Translation project, and you feel excited; however, you have realized that your training corpus is too small. Now, you see that if you use such limited corpus, your machine translation model will be very poor, with many out-of-vocabulary words and maybe unidiomatic translations.

So, what is the solution? Should you just give up? Fortunately, Domain Adaptation can be a good solution to this issue.

Do you have another corpus that is big enough? Does this big corpus share some characteristics with the small corpus, like language pair and/or the major subject?

In this case, you can use one of Domain Adaptation techniques to make use of both the big generic corpus and the small specialized corpus. While the big generic corpus will help avoid out-of-vocabulary words and unidiomatic translations, the small specialized corpus will help force terminology and vocabulary required for your current Machine Translation project.

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Domain Adaptation in Neural Machine Translation

Domain Adaptation is useful for specializing current generic Machine Translation models, mainly when the specialized corpus is too limited to train a separate model. Furthermore, Domain Adaptation techniques can be handy for low-resource languages that share vocabulary and structure with other rich-resource family languages.

As part of my Machine Translation research, I managed to achieve successful results in retraining Neural Machine Translation models for the purpose of Domain Adaptation using OpenNMT-py (the PyTorch version of OpenNMT). In this article, I am elaborating on the path I took and the achieved outcomes; hopefully, this will be useful for others.

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GPU Options for Neural Machine Translation

GPU

In this article, I am exploring several GPU options I have either used myself or considered, for training my Neural Machine Translation models. As GPU machines are known for being expensive, the main factor I am concentrating on here is “cost”, which can be determined not only by machine rates, but also in light of other considerations such as technical specifications, and long-term vs. short-term commitments.

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Stand-alone Executable Translator for OpenNMT

The question was: if I want to have a stand-alone version of OpenNMT that does not require any manual preparations or installations on the target machine, and does not connect to the Internet for Machine Translation, what are my options to achieve this?

Note that my current implementation depends on an OpenNMT Localhost REST API which is perfect for most cases, but not for the case when a client wants to be able to move the whole thing as one package without any prior (manual) preparation or installation of dependencies.

After some research, I finally managed to achieve progress using Python Tkinter, PyInstaller, NSIS and the PyTorch version of OpenNMT.

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