def test_modified_precision_empty():
for k in range(1, 5):
n, d = modified_precision([[]], [], k)
assert n == 0 and d == 0
n, d = modified_precision([[]], [0], k)
assert n == 0 and d == (k == 1)
n, d = modified_precision([[0]], [], k)
assert n == 0 and d == 0
n, d = modified_precision([[]], list(range(k)), k)
assert n == 0 and d == 1
n, d = modified_precision([list(range(k))], [], k)
assert n == 0 and d == 0
def _n_gram_counter(
self,
references: Sequence[Sequence[Sequence[Any]]],
candidates: Sequence[Sequence[Any]],
p_numerators: torch.Tensor,
p_denominators: torch.Tensor,
) -> Tuple[int, int]:
if len(references) != len(candidates):
raise ValueError(
f"nb of candidates should be equal to nb of reference lists ({len(candidates)} != "
f"{len(references)})")
hyp_lengths = 0
ref_lengths = 0
# Iterate through each hypothesis and their corresponding references.
for refs, hyp in zip(references, candidates):
# For each order of ngram, calculate the numerator and
# denominator for the corpus-level modified precision.
for i in range(1, self.ngrams_order + 1):
numerator, denominator = modified_precision(refs, hyp, i)
p_numerators[i] += numerator
p_denominators[i] += denominator
# Calculate the hypothesis lengths
hyp_lengths += len(hyp)
# Calculate the closest reference lengths.
ref_lengths += _closest_ref_length(refs, len(hyp))
return hyp_lengths, ref_lengths
def _corpus_bleu(
self,
references: Sequence[Sequence[Any]],
candidates: Sequence[Sequence[Any]],
) -> float:
p_numerators: Counter = Counter()
p_denominators: Counter = Counter()
if len(references) != len(candidates):
raise ValueError(
f"nb of candidates should be equal to nb of reference lists ({len(candidates)} != "
f"{len(references)})")
# Iterate through each hypothesis and their corresponding references.
for refs, hyp in zip(references, candidates):
# For each order of ngram, calculate the numerator and
# denominator for the corpus-level modified precision.
for i in range(1, self.ngrams_order + 1):
numerator, denominator = modified_precision(refs, hyp, i)
p_numerators[i] += numerator
p_denominators[i] += denominator
# Returns 0 if there's no matching n-grams
# We only need to check for p_numerators[1] == 0, since if there's
# no unigrams, there won't be any higher order ngrams.
if p_numerators[1] == 0:
return 0
# If no smoother, returns 0 if there's at least one a not matching n-grams
if self.smoother.smooth == "no_smooth" and min(
p_numerators.values()) == 0:
return 0
# Calculate the hypothesis lengths
hyp_lengths = [len(hyp) for hyp in candidates]
# Calculate the closest reference lengths.
ref_lengths = [
_closest_ref_length(refs, hyp_len)
for refs, hyp_len in zip(references, hyp_lengths)
]
# Sum of hypothesis and references lengths
hyp_len = sum(hyp_lengths)
ref_len = sum(ref_lengths)
# Calculate corpus-level brevity penalty.
if hyp_len < ref_len:
bp = math.exp(1 - ref_len / hyp_len) if hyp_len > 0 else 0.0
else:
bp = 1.0
# Smoothing
p_n = self.smoother(p_numerators, p_denominators)
# Compute the geometric mean
s = [w_i * math.log(p_i) for w_i, p_i in zip(self.weights, p_n)]
gm = bp * math.exp(math.fsum(s))
return gm
def test_modified_precision(references, candidate, expected):
for n, (e_n, e_d) in enumerate(expected, start=1):
n, d = modified_precision(references, candidate, n)
assert n == e_n and d == e_d
