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squad.py
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squad.py
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# Copyright The Lightning team.
#
# 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.
# Adapted from:
# Link: https://worksheets.codalab.org/rest/bundles/0x6b567e1cf2e041ec80d7098f031c5c9e/contents/blob/
# Link: https://github.com/huggingface/datasets/blob/master/metrics/squad/squad.py
import re
import string
from collections import Counter
from typing import Any, Callable, Dict, List, Tuple, Union
from torch import Tensor, tensor
from torchmetrics.utilities import rank_zero_warn
SINGLE_PRED_TYPE = Dict[str, str]
PREDS_TYPE = Union[SINGLE_PRED_TYPE, List[SINGLE_PRED_TYPE]]
SINGLE_TARGET_TYPE = Dict[str, Union[str, Dict[str, Union[List[str], List[int]]]]]
TARGETS_TYPE = Union[SINGLE_TARGET_TYPE, List[SINGLE_TARGET_TYPE]]
UPDATE_METHOD_SINGLE_PRED_TYPE = Union[List[Dict[str, Union[str, int]]], str, Dict[str, Union[List[str], List[int]]]]
SQuAD_FORMAT = {
"answers": {"answer_start": [1], "text": ["This is a test text"]},
"context": "This is a test context.",
"id": "1",
"question": "Is this a test?",
"title": "train test",
}
def _normalize_text(s: str) -> str:
"""Lower text and remove punctuation, articles and extra whitespace."""
def remove_articles(text: str) -> str:
return re.sub(r"\b(a|an|the)\b", " ", text)
def white_space_fix(text: str) -> str:
return " ".join(text.split())
def remove_punc(text: str) -> str:
exclude = set(string.punctuation)
return "".join(ch for ch in text if ch not in exclude)
def lower(text: str) -> str:
return text.lower()
return white_space_fix(remove_articles(remove_punc(lower(s))))
def _get_tokens(s: str) -> List[str]:
"""Split a sentence into separate tokens."""
return [] if not s else _normalize_text(s).split()
def _compute_f1_score(predicted_answer: str, target_answer: str) -> Tensor:
"""Compute F1 Score for two sentences."""
target_tokens = _get_tokens(target_answer)
predicted_tokens = _get_tokens(predicted_answer)
common = Counter(target_tokens) & Counter(predicted_tokens)
num_same = tensor(sum(common.values()))
if len(target_tokens) == 0 or len(predicted_tokens) == 0:
# If either is no-answer, then F1 is 1 if they agree, 0 otherwise
return tensor(int(target_tokens == predicted_tokens))
if num_same == 0:
return tensor(0.0)
precision = 1.0 * num_same / tensor(len(predicted_tokens))
recall = 1.0 * num_same / tensor(len(target_tokens))
return (2 * precision * recall) / (precision + recall)
def _compute_exact_match_score(prediction: str, ground_truth: str) -> Tensor:
"""Compute Exact Match for two sentences."""
return tensor(int(_normalize_text(prediction) == _normalize_text(ground_truth)))
def _metric_max_over_ground_truths(
metric_fn: Callable[[str, str], Tensor], prediction: str, ground_truths: List[str]
) -> Tensor:
"""Calculate maximum score for a predicted answer with all reference answers."""
return max(metric_fn(prediction, truth) for truth in ground_truths) # type: ignore[type-var]
def _squad_input_check(
preds: PREDS_TYPE, targets: TARGETS_TYPE
) -> Tuple[Dict[str, str], List[Dict[str, List[Dict[str, List[Dict[str, Any]]]]]]]:
"""Check for types and convert the input to necessary format to compute the input."""
if isinstance(preds, Dict):
preds = [preds]
if isinstance(targets, Dict):
targets = [targets]
for pred in preds:
pred_keys = pred.keys()
if "prediction_text" not in pred_keys or "id" not in pred_keys:
raise KeyError(
"Expected keys in a single prediction are 'prediction_text' and 'id'."
"Please make sure that 'prediction_text' maps to the answer string and 'id' maps to the key string."
)
for target in targets:
target_keys = target.keys()
if "answers" not in target_keys or "id" not in target_keys:
raise KeyError(
"Expected keys in a single target are 'answers' and 'id'."
"Please make sure that 'answers' maps to a `SQuAD` format dictionary and 'id' maps to the key string.\n"
"SQuAD Format: "
f"{SQuAD_FORMAT}"
)
answers: Dict[str, Union[List[str], List[int]]] = target["answers"] # type: ignore[assignment]
if "text" not in answers:
raise KeyError(
"Expected keys in a 'answers' are 'text'."
"Please make sure that 'answer' maps to a `SQuAD` format dictionary.\n"
"SQuAD Format: "
f"{SQuAD_FORMAT}"
)
preds_dict = {prediction["id"]: prediction["prediction_text"] for prediction in preds}
_fn_answer = lambda tgt: {"answers": [{"text": txt} for txt in tgt["answers"]["text"]], "id": tgt["id"]}
targets_dict = [{"paragraphs": [{"qas": [_fn_answer(target) for target in targets]}]}]
return preds_dict, targets_dict
def _squad_update(
preds: Dict[str, str],
target: List[Dict[str, List[Dict[str, List[Dict[str, Any]]]]]],
) -> Tuple[Tensor, Tensor, Tensor]:
"""Compute F1 Score and Exact Match for a collection of predictions and references.
Args:
preds: A dictionary mapping an `id` to the predicted `answer`.
target:
A list of dictionary mapping `paragraphs` to list of dictionary mapping `qas` to a list of dictionary
containing `id` and list of all possible `answers`.
Return:
Tuple containing F1 score, Exact match score and total number of examples.
Example:
>>> from torchmetrics.functional.text.squad import _squad_update
>>> preds = [{"prediction_text": "1976", "id": "56e10a3be3433e1400422b22"}]
>>> target = [{"answers": {"answer_start": [97], "text": ["1976"]}, "id": "56e10a3be3433e1400422b22"}]
>>> preds_dict = {pred["id"]: pred["prediction_text"] for pred in preds}
>>> targets_dict = [
... dict(paragraphs=[dict(qas=[dict(answers=[
... {"text": txt} for txt in tgt["answers"]["text"]], id=tgt["id"]) for tgt in target
... ])])
... ]
>>> _squad_update(preds_dict, targets_dict)
(tensor(1.), tensor(1.), tensor(1))
"""
f1 = tensor(0.0)
exact_match = tensor(0.0)
total = tensor(0)
for article in target:
for paragraph in article["paragraphs"]:
for qa in paragraph["qas"]:
total += 1
if qa["id"] not in preds:
rank_zero_warn(f"Unanswered question {qa['id']} will receive score 0.")
continue
ground_truths = [x["text"] for x in qa["answers"]]
pred = preds[qa["id"]]
exact_match += _metric_max_over_ground_truths(_compute_exact_match_score, pred, ground_truths)
f1 += _metric_max_over_ground_truths(_compute_f1_score, pred, ground_truths)
return f1, exact_match, total
def _squad_compute(f1: Tensor, exact_match: Tensor, total: Tensor) -> Dict[str, Tensor]:
"""Aggregate the F1 Score and Exact match for the batch.
Return:
Dictionary containing the F1 score, Exact match score for the batch.
"""
exact_match = 100.0 * exact_match / total
f1 = 100.0 * f1 / total
return {"exact_match": exact_match, "f1": f1}
def squad(preds: PREDS_TYPE, target: TARGETS_TYPE) -> Dict[str, Tensor]:
"""Calculate `SQuAD Metric`_ .
Args:
preds: A Dictionary or List of Dictionary-s that map `id` and `prediction_text` to the respective values.
Example prediction:
.. code-block:: python
{"prediction_text": "TorchMetrics is awesome", "id": "123"}
target: A Dictionary or List of Dictionary-s that contain the `answers` and `id` in the SQuAD Format.
Example target:
.. code-block:: python
{
'answers': [{'answer_start': [1], 'text': ['This is a test answer']}],
'id': '1',
}
Reference SQuAD Format:
.. code-block:: python
{
'answers': {'answer_start': [1], 'text': ['This is a test text']},
'context': 'This is a test context.',
'id': '1',
'question': 'Is this a test?',
'title': 'train test'
}
Return:
Dictionary containing the F1 score, Exact match score for the batch.
Example:
>>> from torchmetrics.functional.text.squad import squad
>>> preds = [{"prediction_text": "1976", "id": "56e10a3be3433e1400422b22"}]
>>> target = [{"answers": {"answer_start": [97], "text": ["1976"]},"id": "56e10a3be3433e1400422b22"}]
>>> squad(preds, target)
{'exact_match': tensor(100.), 'f1': tensor(100.)}
Raises:
KeyError:
If the required keys are missing in either predictions or targets.
References:
[1] SQuAD: 100,000+ Questions for Machine Comprehension of Text by Pranav Rajpurkar, Jian Zhang, Konstantin
Lopyrev, Percy Liang `SQuAD Metric`_ .
"""
preds_dict, target_dict = _squad_input_check(preds, target)
f1, exact_match, total = _squad_update(preds_dict, target_dict)
return _squad_compute(f1, exact_match, total)