# coding=utf-8
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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import copy
from collections import OrderedDict
from nltk.translate.bleu_score import corpus_bleu
from libai.utils import distributed as dist
from .evaluator import DatasetEvaluator
[docs]class BLEUEvaluator(DatasetEvaluator):
"""
Evaluate BLEU(Bilingual Evaluation Understudy) score.
BLEU is a score for comparing a candidate translation
of text to one or more reference translations.
"""
def __init__(self):
super().__init__()
self._predictions = []
[docs] def reset(self):
self._predictions = []
[docs] def process(self, inputs, outputs):
candidate = outputs["candidate"]
reference = inputs["reference"]
self._predictions.append({"candidate": candidate, "reference": reference})
[docs] def evaluate(self):
if not dist.is_main_process():
return {}
else:
predictions = self._predictions
candidates = []
references = []
for pred in predictions:
candidates.append(pred["candidate"])
references.append(pred["reference"])
bleu_score = corpus_bleu(references, candidates)
self._results = OrderedDict()
self._results["bleu_score"] = bleu_score
return copy.deepcopy(self._results)