sacrebleu / sacrebleu.py
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# Copyright 2020 The HuggingFace Evaluate Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" SACREBLEU metric. """
import datasets
import sacrebleu as scb
from packaging import version
import evaluate
_CITATION = """\
@inproceedings{post-2018-call,
title = "A Call for Clarity in Reporting {BLEU} Scores",
author = "Post, Matt",
booktitle = "Proceedings of the Third Conference on Machine Translation: Research Papers",
month = oct,
year = "2018",
address = "Belgium, Brussels",
publisher = "Association for Computational Linguistics",
url = "https://www.aclweb.org/anthology/W18-6319",
pages = "186--191",
}
"""
_DESCRIPTION = """\
SacreBLEU provides hassle-free computation of shareable, comparable, and reproducible BLEU scores.
Inspired by Rico Sennrich's `multi-bleu-detok.perl`, it produces the official WMT scores but works with plain text.
It also knows all the standard test sets and handles downloading, processing, and tokenization for you.
See the [README.md] file at https://github.com/mjpost/sacreBLEU for more information.
"""
_KWARGS_DESCRIPTION = """
Produces BLEU scores along with its sufficient statistics
from a source against one or more references.
Args:
predictions (`list` of `str`): list of translations to score. Each translation should be tokenized into a list of tokens.
references (`list` of `list` of `str`): A list of lists of references. The contents of the first sub-list are the references for the first prediction, the contents of the second sub-list are for the second prediction, etc. Note that there must be the same number of references for each prediction (i.e. all sub-lists must be of the same length).
smooth_method (`str`): The smoothing method to use, defaults to `'exp'`. Possible values are:
- `'none'`: no smoothing
- `'floor'`: increment zero counts
- `'add-k'`: increment num/denom by k for n>1
- `'exp'`: exponential decay
smooth_value (`float`): The smoothing value. Only valid when `smooth_method='floor'` (in which case `smooth_value` defaults to `0.1`) or `smooth_method='add-k'` (in which case `smooth_value` defaults to `1`).
tokenize (`str`): Tokenization method to use for BLEU. If not provided, defaults to `'zh'` for Chinese, `'ja-mecab'` for Japanese and `'13a'` (mteval) otherwise. Possible values are:
- `'none'`: No tokenization.
- `'zh'`: Chinese tokenization.
- `'13a'`: mimics the `mteval-v13a` script from Moses.
- `'intl'`: International tokenization, mimics the `mteval-v14` script from Moses
- `'char'`: Language-agnostic character-level tokenization.
- `'ja-mecab'`: Japanese tokenization. Uses the [MeCab tokenizer](https://pypi.org/project/mecab-python3).
lowercase (`bool`): If `True`, lowercases the input, enabling case-insensitivity. Defaults to `False`.
force (`bool`): If `True`, insists that your tokenized input is actually detokenized. Defaults to `False`.
use_effective_order (`bool`): If `True`, stops including n-gram orders for which precision is 0. This should be `True`, if sentence-level BLEU will be computed. Defaults to `False`.
Returns:
'score': BLEU score,
'counts': Counts,
'totals': Totals,
'precisions': Precisions,
'bp': Brevity penalty,
'sys_len': predictions length,
'ref_len': reference length,
Examples:
Example 1:
>>> predictions = ["hello there general kenobi", "foo bar foobar"]
>>> references = [["hello there general kenobi", "hello there !"], ["foo bar foobar", "foo bar foobar"]]
>>> sacrebleu = evaluate.load("sacrebleu")
>>> results = sacrebleu.compute(predictions=predictions, references=references)
>>> print(list(results.keys()))
['score', 'counts', 'totals', 'precisions', 'bp', 'sys_len', 'ref_len']
>>> print(round(results["score"], 1))
100.0
Example 2:
>>> predictions = ["hello there general kenobi",
... "on our way to ankh morpork"]
>>> references = [["hello there general kenobi", "hello there !"],
... ["goodbye ankh morpork", "ankh morpork"]]
>>> sacrebleu = evaluate.load("sacrebleu")
>>> results = sacrebleu.compute(predictions=predictions,
... references=references)
>>> print(list(results.keys()))
['score', 'counts', 'totals', 'precisions', 'bp', 'sys_len', 'ref_len']
>>> print(round(results["score"], 1))
39.8
"""
@evaluate.utils.file_utils.add_start_docstrings(_DESCRIPTION, _KWARGS_DESCRIPTION)
class Sacrebleu(evaluate.Metric):
def _info(self):
if version.parse(scb.__version__) < version.parse("1.4.12"):
raise ImportWarning(
"To use `sacrebleu`, the module `sacrebleu>=1.4.12` is required, and the current version of `sacrebleu` doesn't match this condition.\n"
'You can install it with `pip install "sacrebleu>=1.4.12"`.'
)
return evaluate.MetricInfo(
description=_DESCRIPTION,
citation=_CITATION,
homepage="https://github.com/mjpost/sacreBLEU",
inputs_description=_KWARGS_DESCRIPTION,
features=[
datasets.Features(
{
"predictions": datasets.Value("string", id="sequence"),
"references": datasets.Sequence(datasets.Value("string", id="sequence"), id="references"),
}
),
datasets.Features(
{
"predictions": datasets.Value("string", id="sequence"),
"references": datasets.Value("string", id="sequence"),
}
),
],
codebase_urls=["https://github.com/mjpost/sacreBLEU"],
reference_urls=[
"https://github.com/mjpost/sacreBLEU",
"https://en.wikipedia.org/wiki/BLEU",
"https://towardsdatascience.com/evaluating-text-output-in-nlp-bleu-at-your-own-risk-e8609665a213",
],
)
def _compute(
self,
predictions,
references,
smooth_method="exp",
smooth_value=None,
force=False,
lowercase=False,
tokenize=None,
use_effective_order=False,
):
# if only one reference is provided make sure we still use list of lists
if isinstance(references[0], str):
references = [[ref] for ref in references]
references_per_prediction = len(references[0])
if any(len(refs) != references_per_prediction for refs in references):
raise ValueError("Sacrebleu requires the same number of references for each prediction")
transformed_references = [[refs[i] for refs in references] for i in range(references_per_prediction)]
output = scb.corpus_bleu(
predictions,
transformed_references,
smooth_method=smooth_method,
smooth_value=smooth_value,
force=force,
lowercase=lowercase,
use_effective_order=use_effective_order,
**(dict(tokenize=tokenize) if tokenize else {}),
)
output_dict = {
"score": output.score,
"counts": output.counts,
"totals": output.totals,
"precisions": output.precisions,
"bp": output.bp,
"sys_len": output.sys_len,
"ref_len": output.ref_len,
}
return output_dict