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# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import ctypes
import math
import sys
from dataclasses import dataclass, field
import torch
from fairseq.dataclass import FairseqDataclass
from fairseq.scoring import BaseScorer, register_scorer
from fairseq.scoring.tokenizer import EvaluationTokenizer
class BleuStat(ctypes.Structure):
_fields_ = [
("reflen", ctypes.c_size_t),
("predlen", ctypes.c_size_t),
("match1", ctypes.c_size_t),
("count1", ctypes.c_size_t),
("match2", ctypes.c_size_t),
("count2", ctypes.c_size_t),
("match3", ctypes.c_size_t),
("count3", ctypes.c_size_t),
("match4", ctypes.c_size_t),
("count4", ctypes.c_size_t),
]
@dataclass
class SacrebleuConfig(FairseqDataclass):
sacrebleu_tokenizer: EvaluationTokenizer.ALL_TOKENIZER_TYPES = field(
default="13a", metadata={"help": "tokenizer"}
)
sacrebleu_lowercase: bool = field(
default=False, metadata={"help": "apply lowercasing"}
)
sacrebleu_char_level: bool = field(
default=False, metadata={"help": "evaluate at character level"}
)
@register_scorer("sacrebleu", dataclass=SacrebleuConfig)
class SacrebleuScorer(BaseScorer):
def __init__(self, cfg):
super(SacrebleuScorer, self).__init__(cfg)
import sacrebleu
self.sacrebleu = sacrebleu
self.tokenizer = EvaluationTokenizer(
tokenizer_type=cfg.sacrebleu_tokenizer,
lowercase=cfg.sacrebleu_lowercase,
character_tokenization=cfg.sacrebleu_char_level,
)
def add_string(self, ref, pred):
self.ref.append(self.tokenizer.tokenize(ref))
self.pred.append(self.tokenizer.tokenize(pred))
def score(self, order=4):
return self.result_string(order).score
def result_string(self, order=4):
if order != 4:
raise NotImplementedError
# tokenization and lowercasing are performed by self.tokenizer instead.
return self.sacrebleu.corpus_bleu(
self.pred, [self.ref], tokenize="none"
).format()
@dataclass
class BleuConfig(FairseqDataclass):
pad: int = field(default=1, metadata={"help": "padding index"})
eos: int = field(default=2, metadata={"help": "eos index"})
unk: int = field(default=3, metadata={"help": "unk index"})
@register_scorer("bleu", dataclass=BleuConfig)
class Scorer(object):
def __init__(self, cfg):
self.stat = BleuStat()
self.pad = cfg.pad
self.eos = cfg.eos
self.unk = cfg.unk
try:
from fairseq import libbleu
except ImportError as e:
sys.stderr.write(
"ERROR: missing libbleu.so. run `pip install --editable .`\n"
)
raise e
self.C = ctypes.cdll.LoadLibrary(libbleu.__file__)
self.reset()
def reset(self, one_init=False):
if one_init:
self.C.bleu_one_init(ctypes.byref(self.stat))
else:
self.C.bleu_zero_init(ctypes.byref(self.stat))
def add(self, ref, pred):
if not isinstance(ref, torch.IntTensor):
raise TypeError("ref must be a torch.IntTensor (got {})".format(type(ref)))
if not isinstance(pred, torch.IntTensor):
raise TypeError("pred must be a torch.IntTensor(got {})".format(type(pred)))
# don't match unknown words
rref = ref.clone()
assert not rref.lt(0).any()
rref[rref.eq(self.unk)] = -999
rref = rref.contiguous().view(-1)
pred = pred.contiguous().view(-1)
self.C.bleu_add(
ctypes.byref(self.stat),
ctypes.c_size_t(rref.size(0)),
ctypes.c_void_p(rref.data_ptr()),
ctypes.c_size_t(pred.size(0)),
ctypes.c_void_p(pred.data_ptr()),
ctypes.c_int(self.pad),
ctypes.c_int(self.eos),
)
def score(self, order=4):
psum = sum(
math.log(p) if p > 0 else float("-Inf") for p in self.precision()[:order]
)
return self.brevity() * math.exp(psum / order) * 100
def precision(self):
def ratio(a, b):
return a / b if b > 0 else 0
return [
ratio(self.stat.match1, self.stat.count1),
ratio(self.stat.match2, self.stat.count2),
ratio(self.stat.match3, self.stat.count3),
ratio(self.stat.match4, self.stat.count4),
]
def brevity(self):
r = self.stat.reflen / self.stat.predlen
return min(1, math.exp(1 - r))
def result_string(self, order=4):
assert order <= 4, "BLEU scores for order > 4 aren't supported"
fmt = "BLEU{} = {:2.2f}, {:2.1f}"
for _ in range(1, order):
fmt += "/{:2.1f}"
fmt += " (BP={:.3f}, ratio={:.3f}, syslen={}, reflen={})"
bleup = [p * 100 for p in self.precision()[:order]]
return fmt.format(
order,
self.score(order=order),
*bleup,
self.brevity(),
self.stat.predlen / self.stat.reflen,
self.stat.predlen,
self.stat.reflen
)
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