from abc import ABCMeta, abstractmethod
from collections import namedtuple
from typing import Any, Callable, List, Mapping, Optional, Sequence, Tuple, Union
import torch
from ignite.exceptions import NotComputableError
from ignite.metrics import Metric
# These decorators helps with distributed settings
from ignite.metrics.metric import reinit__is_reduced, sync_all_reduce
from ignite.metrics.nlp.utils import lcs, ngrams
__all__ = ["Rouge", "RougeN", "RougeL"]
class Score(namedtuple("Score", ["match", "candidate", "reference"])):
r"""
Computes precision and recall for given matches, candidate and reference lengths.
"""
def precision(self) -> float:
"""
Calculates precision.
"""
return self.match / self.candidate if self.candidate > 0 else 0
def recall(self) -> float:
"""
Calculates recall.
"""
return self.match / self.reference if self.reference > 0 else 0
def compute_ngram_scores(candidate: Sequence[Any], reference: Sequence[Any], n: int = 4) -> Score:
"""
Compute the score based on ngram co-occurence of sequences of items
Args:
candidate: candidate sequence of items
reference: reference sequence of items
n: ngram order
Returns:
The score containing the number of ngram co-occurences
.. versionadded:: 0.4.5
"""
# ngrams of the candidate
candidate_counter = ngrams(candidate, n)
# ngrams of the references
reference_counter = ngrams(reference, n)
# ngram co-occurences in the candidate and the references
match_counters = candidate_counter & reference_counter
# the score is defined using Fraction
return Score(
match=sum(match_counters.values()),
candidate=sum(candidate_counter.values()),
reference=sum(reference_counter.values()),
)
def compute_lcs_scores(candidate: Sequence[Any], reference: Sequence[Any]) -> Score:
"""
Compute the score based on longest common subsequence of sequences of items
Args:
candidate: candidate sequence of items
reference: reference sequence of items
Returns:
The score containing the length of longest common subsequence
.. versionadded:: 0.4.5
"""
# lcs of candidate and reference
match = lcs(candidate, reference)
# the score is defined using Fraction
return Score(match=match, candidate=len(candidate), reference=len(reference))
class MultiRefReducer(metaclass=ABCMeta):
r"""
Reducer interface for multi-reference
"""
@abstractmethod
def __call__(self, scores: Sequence[Score]) -> Score:
pass
class MultiRefAverageReducer(MultiRefReducer):
r"""
Reducer for averaging the scores
"""
def __call__(self, scores: Sequence[Score]) -> Score:
match = sum([score.match for score in scores])
candidate = sum([score.candidate for score in scores])
reference = sum([score.reference for score in scores])
return Score(match=match, candidate=candidate, reference=reference)
class MultiRefBestReducer(MultiRefReducer):
r"""
Reducer for selecting the best score
"""
def __call__(self, scores: Sequence[Score]) -> Score:
return max(scores, key=lambda x: x.recall())
class _BaseRouge(Metric):
r"""
Rouge interface for Rouge-L and Rouge-N
"""
def __init__(
self,
multiref: str = "average",
alpha: float = 0,
output_transform: Callable = lambda x: x,
device: Union[str, torch.device] = torch.device("cpu"),
) -> None:
super(_BaseRouge, self).__init__(output_transform=output_transform, device=device)
self._alpha = alpha
if not 0 <= self._alpha <= 1:
raise ValueError(f"alpha must be in interval [0, 1] (got : {self._alpha})")
self._multiref = multiref
valid_multiref = ["best", "average"]
if self._multiref not in valid_multiref:
raise ValueError(f"multiref : valid values are {valid_multiref} (got : {self._multiref})")
self._mutliref_reducer = self._get_multiref_reducer()
def _get_multiref_reducer(self) -> MultiRefReducer:
if self._multiref == "average":
return MultiRefAverageReducer()
return MultiRefBestReducer()
@reinit__is_reduced
def reset(self) -> None:
self._recall = 0.0
self._precision = 0.0
self._fmeasure = 0.0
self._num_examples = 0
@reinit__is_reduced
def update(self, output: Tuple[Sequence[Sequence[Any]], Sequence[Sequence[Sequence[Any]]]]) -> None:
candidates, references = output
for _candidate, _reference in zip(candidates, references):
multiref_scores = [self._compute_score(candidate=_candidate, reference=_ref) for _ref in _reference]
score = self._mutliref_reducer(multiref_scores)
precision = score.precision()
recall = score.recall()
self._precision += precision
self._recall += recall
precision_recall = precision * recall
if precision_recall > 0: # avoid zero division
self._fmeasure += precision_recall / ((1 - self._alpha) * precision + self._alpha * recall)
self._num_examples += 1
@sync_all_reduce("_precision", "_recall", "_fmeasure", "_num_examples")
def compute(self) -> Mapping:
if self._num_examples == 0:
raise NotComputableError("Rouge metric must have at least one example before be computed")
return {
f"{self._metric_name()}-P": float(self._precision / self._num_examples),
f"{self._metric_name()}-R": float(self._recall / self._num_examples),
f"{self._metric_name()}-F": float(self._fmeasure / self._num_examples),
}
@abstractmethod
def _compute_score(self, candidate: Sequence[Any], reference: Sequence[Any]) -> Score:
pass
@abstractmethod
def _metric_name(self) -> str:
pass
[docs]class RougeN(_BaseRouge):
r"""Calculates the Rouge-N score.
The Rouge-N is based on the ngram co-occurences of candidates and references.
More details can be found in `Lin 2004`__.
__ https://www.aclweb.org/anthology/W04-1013.pdf
- ``update`` must receive output of the form ``(y_pred, y)`` or ``{'y_pred': y_pred, 'y': y}``.
- `y_pred` (list(list(str))) must be a sequence of tokens.
- `y` (list(list(list(str))) must be a list of sequence of tokens.
Args:
ngram: ngram order (default: 4).
multiref: reduces scores for multi references. Valid values are "best" and "average"
(default: "average").
alpha: controls the importance between recall and precision (alpha -> 0: recall is more important, alpha -> 1:
precision is more important)
output_transform: a callable that is used to transform the
:class:`~ignite.engine.engine.Engine`'s ``process_function``'s output into the
form expected by the metric. This can be useful if, for example, you have a multi-output model and
you want to compute the metric with respect to one of the outputs.
device: specifies which device updates are accumulated on. Setting the metric's
device to be the same as your ``update`` arguments ensures the ``update`` method is non-blocking. By
default, CPU.
Examples:
For more information on how metric works with :class:`~ignite.engine.engine.Engine`, visit :ref:`attach-engine`.
.. testcode::
from ignite.metrics import RougeN
m = RougeN(ngram=2, multiref="best")
candidate = "the cat is not there".split()
references = [
"the cat is on the mat".split(),
"there is a cat on the mat".split()
]
m.update(([candidate], [references]))
print(m.compute())
.. testoutput::
{'Rouge-2-P': 0.5, 'Rouge-2-R': 0.4, 'Rouge-2-F': 0.4}
.. versionadded:: 0.4.5
"""
def __init__(
self,
ngram: int = 4,
multiref: str = "average",
alpha: float = 0,
output_transform: Callable = lambda x: x,
device: Union[str, torch.device] = torch.device("cpu"),
):
super(RougeN, self).__init__(multiref=multiref, alpha=alpha, output_transform=output_transform, device=device)
self._ngram = ngram
if self._ngram < 1:
raise ValueError(f"ngram order must be greater than zero (got : {self._ngram})")
def _compute_score(self, candidate: Sequence[Any], reference: Sequence[Any]) -> Score:
return compute_ngram_scores(candidate=candidate, reference=reference, n=self._ngram)
def _metric_name(self) -> str:
return f"Rouge-{self._ngram}"
[docs]class RougeL(_BaseRouge):
r"""Calculates the Rouge-L score.
The Rouge-L is based on the length of the longest common subsequence of candidates and references.
More details can be found in `Lin 2004`__.
__ https://www.aclweb.org/anthology/W04-1013.pdf
- ``update`` must receive output of the form ``(y_pred, y)`` or ``{'y_pred': y_pred, 'y': y}``.
- `y_pred` (list(list(str))) must be a sequence of tokens.
- `y` (list(list(list(str))) must be a list of sequence of tokens.
Args:
multiref: reduces scores for multi references. Valid values are "best" and "average" (default: "average").
alpha: controls the importance between recall and precision (alpha -> 0: recall is more important, alpha -> 1:
precision is more important)
output_transform: a callable that is used to transform the
:class:`~ignite.engine.engine.Engine`'s ``process_function``'s output into the
form expected by the metric. This can be useful if, for example, you have a multi-output model and
you want to compute the metric with respect to one of the outputs.
device: specifies which device updates are accumulated on. Setting the metric's
device to be the same as your ``update`` arguments ensures the ``update`` method is non-blocking. By
default, CPU.
Examples:
For more information on how metric works with :class:`~ignite.engine.engine.Engine`, visit :ref:`attach-engine`.
.. testcode::
from ignite.metrics import RougeL
m = RougeL(multiref="best")
candidate = "the cat is not there".split()
references = [
"the cat is on the mat".split(),
"there is a cat on the mat".split()
]
m.update(([candidate], [references]))
print(m.compute())
.. testoutput::
{'Rouge-L-P': 0.6, 'Rouge-L-R': 0.5, 'Rouge-L-F': 0.5}
.. versionadded:: 0.4.5
"""
def __init__(
self,
multiref: str = "average",
alpha: float = 0,
output_transform: Callable = lambda x: x,
device: Union[str, torch.device] = torch.device("cpu"),
):
super(RougeL, self).__init__(multiref=multiref, alpha=alpha, output_transform=output_transform, device=device)
def _compute_score(self, candidate: Sequence[Any], reference: Sequence[Any]) -> Score:
return compute_lcs_scores(candidate=candidate, reference=reference)
def _metric_name(self) -> str:
return "Rouge-L"
[docs]class Rouge(Metric):
r"""Calculates the Rouge score for multiples Rouge-N and Rouge-L metrics.
More details can be found in `Lin 2004`__.
__ https://www.aclweb.org/anthology/W04-1013.pdf
- ``update`` must receive output of the form ``(y_pred, y)`` or ``{'y_pred': y_pred, 'y': y}``.
- `y_pred` (list(list(str))) must be a sequence of tokens.
- `y` (list(list(list(str))) must be a list of sequence of tokens.
Args:
variants: set of metrics computed. Valid inputs are "L" and integer 1 <= n <= 9.
multiref: reduces scores for multi references. Valid values are "best" and "average" (default: "average").
alpha: controls the importance between recall and precision (alpha -> 0: recall is more important, alpha -> 1:
precision is more important)
output_transform: a callable that is used to transform the
:class:`~ignite.engine.engine.Engine`'s ``process_function``'s output into the
form expected by the metric. This can be useful if, for example, you have a multi-output model and
you want to compute the metric with respect to one of the outputs.
device: specifies which device updates are accumulated on. Setting the metric's
device to be the same as your ``update`` arguments ensures the ``update`` method is non-blocking. By
default, CPU.
Examples:
For more information on how metric works with :class:`~ignite.engine.engine.Engine`, visit :ref:`attach-engine`.
.. testcode::
from ignite.metrics import Rouge
m = Rouge(variants=["L", 2], multiref="best")
candidate = "the cat is not there".split()
references = [
"the cat is on the mat".split(),
"there is a cat on the mat".split()
]
m.update(([candidate], [references]))
print(m.compute())
.. testoutput::
{'Rouge-L-P': 0.6, 'Rouge-L-R': 0.5, 'Rouge-L-F': 0.5, 'Rouge-2-P': 0.5, 'Rouge-2-R': 0.4, 'Rouge-2-F': 0.4}
.. versionadded:: 0.4.5
.. versionchanged:: 0.4.7
``update`` method has changed and now works on batch of inputs.
"""
def __init__(
self,
variants: Optional[Sequence[Union[str, int]]] = None,
multiref: str = "average",
alpha: float = 0,
output_transform: Callable = lambda x: x,
device: Union[str, torch.device] = torch.device("cpu"),
):
if variants is None or len(variants) == 0:
variants = [1, 2, 4, "L"]
self.internal_metrics: List[_BaseRouge] = []
for m in variants:
variant: Optional[_BaseRouge] = None
if isinstance(m, str) and m == "L":
variant = RougeL(multiref=multiref, alpha=alpha, output_transform=output_transform, device=device)
elif isinstance(m, int):
variant = RougeN(
ngram=m, multiref=multiref, alpha=alpha, output_transform=output_transform, device=device
)
else:
raise ValueError("variant must be 'L' or integer greater to zero")
self.internal_metrics.append(variant)
super(Rouge, self).__init__(output_transform=output_transform, device=device)
[docs] @reinit__is_reduced
def reset(self) -> None:
for m in self.internal_metrics:
m.reset()
[docs] @reinit__is_reduced
def update(self, output: Tuple[Sequence[Sequence[Any]], Sequence[Sequence[Sequence[Any]]]]) -> None:
for m in self.internal_metrics:
m.update(output)
[docs] def compute(self) -> Mapping:
results = {}
for m in self.internal_metrics:
results.update(m.compute())
return results