<p>Despite continuous critics and debates starting with <a href="http://homepages.inf.ed.ac.uk/miles/papers/eacl06.pdf" rel="nofollow noreferrer">this 2006 article</a>, <strong>BLEU</strong> (<strong><em>B</strong>i<strong>L</strong>ingual <strong>E</strong>valuation <strong>U</strong>nderstudy</em>) score is still the most commonly used metric for machine translation. According to the <a href="https://en.wikipedia.org/wiki/BLEU" rel="nofollow noreferrer">Wikipedia page</a>, </p>

<blockquote>
  <p>BLEU is an algorithm for evaluating the quality of text which has been machine-translated from one natural language to another. Quality is considered to be the correspondence between a machine's output and that of a human: "the closer a machine translation is to a professional human translation, the better it is" – this is the central idea behind BLEU. BLEU was one of the first metrics to achieve a high correlation with human judgements of quality, and remains one of the most popular automated and inexpensive metrics.</p>
</blockquote>

<p>More specifically, if you want to look at Japanese-English translation, there was a <a href="https://cs224d.stanford.edu/reports/GreensteinEric.pdf" rel="nofollow noreferrer">class project from Stanford CS 224d</a> that translates simple Japanese sentences like 「彼女は敵だった」 into English with neural network techniques, and uses BLEU as the evaluation metric. </p>

<p>If you want more readings on machine translation, I suggest a good start with one of the most influential one recently, namely <a href="https://arxiv.org/pdf/1409.0473" rel="nofollow noreferrer">Neural machine translation by jointly learning to align and translate</a> by Yoshua Bengio et al. You can also look at the <a href="https://scholar.google.com/scholar?cites=8900239586727494087" rel="nofollow noreferrer">top papers that cited the BLEU critics</a> to get a sense of other commonly used metrics.</p>
Metrics or evaluation about machine learning translation
<p>Could you guys recommend some evaluation or metrics about machine learning for translation: for example Japanese to English et al. If possible, could you tell me some papers about metrics. I am a new one to translation. Thanks! </p>