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from math import exp,log |
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class BleuScoreException(Exception): |
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pass |
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class BleuScorer: |
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def __init__(self): |
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"""References should be a list. If each element is a string, assume |
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they are filenames, if a list, assume tokenised strings""" |
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self.smooth = 1.0 |
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self.order = 4 |
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def score(self,scores): |
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if len(scores) != self.order*2+1: |
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raise BleuScoreException("Wrong number of scores. Expected %d, but found %d" % |
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(self.order*2+1, len(scores))) |
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logbleu = 0.0 |
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for j in range(self.order): |
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logbleu += log(scores[2*j] + self.smooth) - log(scores[2*j+1] + self.smooth) |
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logbleu /= self.order |
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brevity = 1.0 - float(scores[-1]) / scores[1] |
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if brevity < 0: |
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logbleu += brevity |
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return exp(logbleu) |
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