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- # Copyright 2020 The HuggingFace Team All rights reserved.
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- #
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- # Licensed under the Apache License, Version 2.0 (the "License");
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- # you may not use this file except in compliance with the License.
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- # You may obtain a copy of the License at
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- #
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- # http://www.apache.org/licenses/LICENSE-2.0
8
- #
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- # Unless required by applicable law or agreed to in writing, software
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- # distributed under the License is distributed on an "AS IS" BASIS,
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- # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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- # See the License for the specific language governing permissions and
13
- # limitations under the License.
14
- """
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- Post-processing utilities for question answering.
16
- """
17
-
18
- import collections
19
- import json
20
- import logging
21
- import os
22
- from typing import Optional
23
-
24
- import numpy as np
25
- from tqdm.auto import tqdm
26
-
27
-
28
- logger = logging.getLogger(__name__)
29
-
30
-
31
- def postprocess_qa_predictions(
32
- examples,
33
- features,
34
- predictions: tuple[np.ndarray, np.ndarray],
35
- version_2_with_negative: bool = False,
36
- n_best_size: int = 20,
37
- max_answer_length: int = 30,
38
- null_score_diff_threshold: float = 0.0,
39
- output_dir: Optional[str] = None,
40
- prefix: Optional[str] = None,
41
- log_level: Optional[int] = logging.WARNING,
42
- ):
43
- """
44
- Post-processes the predictions of a question-answering model to convert them to answers that are substrings of the
45
- original contexts. This is the base postprocessing functions for models that only return start and end logits.
46
-
47
- Args:
48
- examples: The non-preprocessed dataset (see the main script for more information).
49
- features: The processed dataset (see the main script for more information).
50
- predictions (:obj:`Tuple[np.ndarray, np.ndarray]`):
51
- The predictions of the model: two arrays containing the start logits and the end logits respectively. Its
52
- first dimension must match the number of elements of :obj:`features`.
53
- version_2_with_negative (:obj:`bool`, `optional`, defaults to :obj:`False`):
54
- Whether or not the underlying dataset contains examples with no answers.
55
- n_best_size (:obj:`int`, `optional`, defaults to 20):
56
- The total number of n-best predictions to generate when looking for an answer.
57
- max_answer_length (:obj:`int`, `optional`, defaults to 30):
58
- The maximum length of an answer that can be generated. This is needed because the start and end predictions
59
- are not conditioned on one another.
60
- null_score_diff_threshold (:obj:`float`, `optional`, defaults to 0):
61
- The threshold used to select the null answer: if the best answer has a score that is less than the score of
62
- the null answer minus this threshold, the null answer is selected for this example (note that the score of
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- the null answer for an example giving several features is the minimum of the scores for the null answer on
64
- each feature: all features must be aligned on the fact they `want` to predict a null answer).
65
-
66
- Only useful when :obj:`version_2_with_negative` is :obj:`True`.
67
- output_dir (:obj:`str`, `optional`):
68
- If provided, the dictionaries of predictions, n_best predictions (with their scores and logits) and, if
69
- :obj:`version_2_with_negative=True`, the dictionary of the scores differences between best and null
70
- answers, are saved in `output_dir`.
71
- prefix (:obj:`str`, `optional`):
72
- If provided, the dictionaries mentioned above are saved with `prefix` added to their names.
73
- log_level (:obj:`int`, `optional`, defaults to ``logging.WARNING``):
74
- ``logging`` log level (e.g., ``logging.WARNING``)
75
- """
76
- if len(predictions) != 2:
77
- raise ValueError("`predictions` should be a tuple with two elements (start_logits, end_logits).")
78
- all_start_logits, all_end_logits = predictions
79
-
80
- if len(predictions[0]) != len(features):
81
- raise ValueError(f"Got {len(predictions[0])} predictions and {len(features)} features.")
82
-
83
- # Build a map example to its corresponding features.
84
- example_id_to_index = {k: i for i, k in enumerate(examples["id"])}
85
- features_per_example = collections.defaultdict(list)
86
- for i, feature in enumerate(features):
87
- features_per_example[example_id_to_index[feature["example_id"]]].append(i)
88
-
89
- # The dictionaries we have to fill.
90
- all_predictions = collections.OrderedDict()
91
- all_nbest_json = collections.OrderedDict()
92
- if version_2_with_negative:
93
- scores_diff_json = collections.OrderedDict()
94
-
95
- # Logging.
96
- logger.setLevel(log_level)
97
- logger.info(f"Post-processing {len(examples)} example predictions split into {len(features)} features.")
98
-
99
- # Let's loop over all the examples!
100
- for example_index, example in enumerate(tqdm(examples)):
101
- # Those are the indices of the features associated to the current example.
102
- feature_indices = features_per_example[example_index]
103
-
104
- min_null_prediction = None
105
- prelim_predictions = []
106
-
107
- # Looping through all the features associated to the current example.
108
- for feature_index in feature_indices:
109
- # We grab the predictions of the model for this feature.
110
- start_logits = all_start_logits[feature_index]
111
- end_logits = all_end_logits[feature_index]
112
- # This is what will allow us to map some the positions in our logits to span of texts in the original
113
- # context.
114
- offset_mapping = features[feature_index]["offset_mapping"]
115
- # Optional `token_is_max_context`, if provided we will remove answers that do not have the maximum context
116
- # available in the current feature.
117
- token_is_max_context = features[feature_index].get("token_is_max_context", None)
118
-
119
- # Update minimum null prediction.
120
- feature_null_score = start_logits[0] + end_logits[0]
121
- if min_null_prediction is None or min_null_prediction["score"] > feature_null_score:
122
- min_null_prediction = {
123
- "offsets": (0, 0),
124
- "score": feature_null_score,
125
- "start_logit": start_logits[0],
126
- "end_logit": end_logits[0],
127
- }
128
-
129
- # Go through all possibilities for the `n_best_size` greater start and end logits.
130
- start_indexes = np.argsort(start_logits)[-1 : -n_best_size - 1 : -1].tolist()
131
- end_indexes = np.argsort(end_logits)[-1 : -n_best_size - 1 : -1].tolist()
132
- for start_index in start_indexes:
133
- for end_index in end_indexes:
134
- # Don't consider out-of-scope answers, either because the indices are out of bounds or correspond
135
- # to part of the input_ids that are not in the context.
136
- if (
137
- start_index >= len(offset_mapping)
138
- or end_index >= len(offset_mapping)
139
- or offset_mapping[start_index] is None
140
- or len(offset_mapping[start_index]) < 2
141
- or offset_mapping[end_index] is None
142
- or len(offset_mapping[end_index]) < 2
143
- ):
144
- continue
145
- # Don't consider answers with a length that is either < 0 or > max_answer_length.
146
- if end_index < start_index or end_index - start_index + 1 > max_answer_length:
147
- continue
148
- # Don't consider answer that don't have the maximum context available (if such information is
149
- # provided).
150
- if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
151
- continue
152
-
153
- prelim_predictions.append(
154
- {
155
- "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),
156
- "score": start_logits[start_index] + end_logits[end_index],
157
- "start_logit": start_logits[start_index],
158
- "end_logit": end_logits[end_index],
159
- }
160
- )
161
- if version_2_with_negative and min_null_prediction is not None:
162
- # Add the minimum null prediction
163
- prelim_predictions.append(min_null_prediction)
164
- null_score = min_null_prediction["score"]
165
-
166
- # Only keep the best `n_best_size` predictions.
167
- predictions = sorted(prelim_predictions, key=lambda x: x["score"], reverse=True)[:n_best_size]
168
-
169
- # Add back the minimum null prediction if it was removed because of its low score.
170
- if (
171
- version_2_with_negative
172
- and min_null_prediction is not None
173
- and not any(p["offsets"] == (0, 0) for p in predictions)
174
- ):
175
- predictions.append(min_null_prediction)
176
-
177
- # Use the offsets to gather the answer text in the original context.
178
- context = example["context"]
179
- for pred in predictions:
180
- offsets = pred.pop("offsets")
181
- pred["text"] = context[offsets[0] : offsets[1]]
182
-
183
- # In the very rare edge case we have not a single non-null prediction, we create a fake prediction to avoid
184
- # failure.
185
- if len(predictions) == 0 or (len(predictions) == 1 and predictions[0]["text"] == ""):
186
- predictions.insert(0, {"text": "empty", "start_logit": 0.0, "end_logit": 0.0, "score": 0.0})
187
-
188
- # Compute the softmax of all scores (we do it with numpy to stay independent from torch/tf in this file, using
189
- # the LogSumExp trick).
190
- scores = np.array([pred.pop("score") for pred in predictions])
191
- exp_scores = np.exp(scores - np.max(scores))
192
- probs = exp_scores / exp_scores.sum()
193
-
194
- # Include the probabilities in our predictions.
195
- for prob, pred in zip(probs, predictions):
196
- pred["probability"] = prob
197
-
198
- # Pick the best prediction. If the null answer is not possible, this is easy.
199
- if not version_2_with_negative:
200
- all_predictions[example["id"]] = predictions[0]["text"]
201
- else:
202
- # Otherwise we first need to find the best non-empty prediction.
203
- i = 0
204
- while predictions[i]["text"] == "":
205
- i += 1
206
- best_non_null_pred = predictions[i]
207
-
208
- # Then we compare to the null prediction using the threshold.
209
- score_diff = null_score - best_non_null_pred["start_logit"] - best_non_null_pred["end_logit"]
210
- scores_diff_json[example["id"]] = float(score_diff) # To be JSON-serializable.
211
- if score_diff > null_score_diff_threshold:
212
- all_predictions[example["id"]] = ""
213
- else:
214
- all_predictions[example["id"]] = best_non_null_pred["text"]
215
-
216
- # Make `predictions` JSON-serializable by casting np.float back to float.
217
- all_nbest_json[example["id"]] = [
218
- {k: (float(v) if isinstance(v, (np.float16, np.float32, np.float64)) else v) for k, v in pred.items()}
219
- for pred in predictions
220
- ]
221
-
222
- # If we have an output_dir, let's save all those dicts.
223
- if output_dir is not None:
224
- if not os.path.isdir(output_dir):
225
- raise OSError(f"{output_dir} is not a directory.")
226
-
227
- prediction_file = os.path.join(
228
- output_dir, "predictions.json" if prefix is None else f"{prefix}_predictions.json"
229
- )
230
- nbest_file = os.path.join(
231
- output_dir, "nbest_predictions.json" if prefix is None else f"{prefix}_nbest_predictions.json"
232
- )
233
- if version_2_with_negative:
234
- null_odds_file = os.path.join(
235
- output_dir, "null_odds.json" if prefix is None else f"{prefix}_null_odds.json"
236
- )
237
-
238
- logger.info(f"Saving predictions to {prediction_file}.")
239
- with open(prediction_file, "w") as writer:
240
- writer.write(json.dumps(all_predictions, indent=4) + "\n")
241
- logger.info(f"Saving nbest_preds to {nbest_file}.")
242
- with open(nbest_file, "w") as writer:
243
- writer.write(json.dumps(all_nbest_json, indent=4) + "\n")
244
- if version_2_with_negative:
245
- logger.info(f"Saving null_odds to {null_odds_file}.")
246
- with open(null_odds_file, "w") as writer:
247
- writer.write(json.dumps(scores_diff_json, indent=4) + "\n")
248
-
249
- return all_predictions
250
-
251
-
252
- def postprocess_qa_predictions_with_beam_search(
253
- examples,
254
- features,
255
- predictions: tuple[np.ndarray, np.ndarray],
256
- version_2_with_negative: bool = False,
257
- n_best_size: int = 20,
258
- max_answer_length: int = 30,
259
- start_n_top: int = 5,
260
- end_n_top: int = 5,
261
- output_dir: Optional[str] = None,
262
- prefix: Optional[str] = None,
263
- log_level: Optional[int] = logging.WARNING,
264
- ):
265
- """
266
- Post-processes the predictions of a question-answering model with beam search to convert them to answers that are substrings of the
267
- original contexts. This is the postprocessing functions for models that return start and end logits, indices, as well as
268
- cls token predictions.
269
-
270
- Args:
271
- examples: The non-preprocessed dataset (see the main script for more information).
272
- features: The processed dataset (see the main script for more information).
273
- predictions (:obj:`Tuple[np.ndarray, np.ndarray]`):
274
- The predictions of the model: two arrays containing the start logits and the end logits respectively. Its
275
- first dimension must match the number of elements of :obj:`features`.
276
- version_2_with_negative (:obj:`bool`, `optional`, defaults to :obj:`False`):
277
- Whether or not the underlying dataset contains examples with no answers.
278
- n_best_size (:obj:`int`, `optional`, defaults to 20):
279
- The total number of n-best predictions to generate when looking for an answer.
280
- max_answer_length (:obj:`int`, `optional`, defaults to 30):
281
- The maximum length of an answer that can be generated. This is needed because the start and end predictions
282
- are not conditioned on one another.
283
- start_n_top (:obj:`int`, `optional`, defaults to 5):
284
- The number of top start logits too keep when searching for the :obj:`n_best_size` predictions.
285
- end_n_top (:obj:`int`, `optional`, defaults to 5):
286
- The number of top end logits too keep when searching for the :obj:`n_best_size` predictions.
287
- output_dir (:obj:`str`, `optional`):
288
- If provided, the dictionaries of predictions, n_best predictions (with their scores and logits) and, if
289
- :obj:`version_2_with_negative=True`, the dictionary of the scores differences between best and null
290
- answers, are saved in `output_dir`.
291
- prefix (:obj:`str`, `optional`):
292
- If provided, the dictionaries mentioned above are saved with `prefix` added to their names.
293
- log_level (:obj:`int`, `optional`, defaults to ``logging.WARNING``):
294
- ``logging`` log level (e.g., ``logging.WARNING``)
295
- """
296
- if len(predictions) != 5:
297
- raise ValueError("`predictions` should be a tuple with five elements.")
298
- start_top_log_probs, start_top_index, end_top_log_probs, end_top_index, cls_logits = predictions
299
-
300
- if len(predictions[0]) != len(features):
301
- raise ValueError(f"Got {len(predictions[0])} predictions and {len(features)} features.")
302
-
303
- # Build a map example to its corresponding features.
304
- example_id_to_index = {k: i for i, k in enumerate(examples["id"])}
305
- features_per_example = collections.defaultdict(list)
306
- for i, feature in enumerate(features):
307
- features_per_example[example_id_to_index[feature["example_id"]]].append(i)
308
-
309
- # The dictionaries we have to fill.
310
- all_predictions = collections.OrderedDict()
311
- all_nbest_json = collections.OrderedDict()
312
- scores_diff_json = collections.OrderedDict() if version_2_with_negative else None
313
-
314
- # Logging.
315
- logger.setLevel(log_level)
316
- logger.info(f"Post-processing {len(examples)} example predictions split into {len(features)} features.")
317
-
318
- # Let's loop over all the examples!
319
- for example_index, example in enumerate(tqdm(examples)):
320
- # Those are the indices of the features associated to the current example.
321
- feature_indices = features_per_example[example_index]
322
-
323
- min_null_score = None
324
- prelim_predictions = []
325
-
326
- # Looping through all the features associated to the current example.
327
- for feature_index in feature_indices:
328
- # We grab the predictions of the model for this feature.
329
- start_log_prob = start_top_log_probs[feature_index]
330
- start_indexes = start_top_index[feature_index]
331
- end_log_prob = end_top_log_probs[feature_index]
332
- end_indexes = end_top_index[feature_index]
333
- feature_null_score = cls_logits[feature_index]
334
- # This is what will allow us to map some the positions in our logits to span of texts in the original
335
- # context.
336
- offset_mapping = features[feature_index]["offset_mapping"]
337
- # Optional `token_is_max_context`, if provided we will remove answers that do not have the maximum context
338
- # available in the current feature.
339
- token_is_max_context = features[feature_index].get("token_is_max_context", None)
340
-
341
- # Update minimum null prediction
342
- if min_null_score is None or feature_null_score < min_null_score:
343
- min_null_score = feature_null_score
344
-
345
- # Go through all possibilities for the `n_start_top`/`n_end_top` greater start and end logits.
346
- for i in range(start_n_top):
347
- for j in range(end_n_top):
348
- start_index = int(start_indexes[i])
349
- j_index = i * end_n_top + j
350
- end_index = int(end_indexes[j_index])
351
- # Don't consider out-of-scope answers (last part of the test should be unnecessary because of the
352
- # p_mask but let's not take any risk)
353
- if (
354
- start_index >= len(offset_mapping)
355
- or end_index >= len(offset_mapping)
356
- or offset_mapping[start_index] is None
357
- or len(offset_mapping[start_index]) < 2
358
- or offset_mapping[end_index] is None
359
- or len(offset_mapping[end_index]) < 2
360
- ):
361
- continue
362
-
363
- # Don't consider answers with a length negative or > max_answer_length.
364
- if end_index < start_index or end_index - start_index + 1 > max_answer_length:
365
- continue
366
- # Don't consider answer that don't have the maximum context available (if such information is
367
- # provided).
368
- if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
369
- continue
370
- prelim_predictions.append(
371
- {
372
- "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),
373
- "score": start_log_prob[i] + end_log_prob[j_index],
374
- "start_log_prob": start_log_prob[i],
375
- "end_log_prob": end_log_prob[j_index],
376
- }
377
- )
378
-
379
- # Only keep the best `n_best_size` predictions.
380
- predictions = sorted(prelim_predictions, key=lambda x: x["score"], reverse=True)[:n_best_size]
381
-
382
- # Use the offsets to gather the answer text in the original context.
383
- context = example["context"]
384
- for pred in predictions:
385
- offsets = pred.pop("offsets")
386
- pred["text"] = context[offsets[0] : offsets[1]]
387
-
388
- # In the very rare edge case we have not a single non-null prediction, we create a fake prediction to avoid
389
- # failure.
390
- if len(predictions) == 0:
391
- # Without predictions min_null_score is going to be None and None will cause an exception later
392
- min_null_score = -2e-6
393
- predictions.insert(0, {"text": "", "start_logit": -1e-6, "end_logit": -1e-6, "score": min_null_score})
394
-
395
- # Compute the softmax of all scores (we do it with numpy to stay independent from torch/tf in this file, using
396
- # the LogSumExp trick).
397
- scores = np.array([pred.pop("score") for pred in predictions])
398
- exp_scores = np.exp(scores - np.max(scores))
399
- probs = exp_scores / exp_scores.sum()
400
-
401
- # Include the probabilities in our predictions.
402
- for prob, pred in zip(probs, predictions):
403
- pred["probability"] = prob
404
-
405
- # Pick the best prediction and set the probability for the null answer.
406
- all_predictions[example["id"]] = predictions[0]["text"]
407
- if version_2_with_negative:
408
- scores_diff_json[example["id"]] = float(min_null_score)
409
-
410
- # Make `predictions` JSON-serializable by casting np.float back to float.
411
- all_nbest_json[example["id"]] = [
412
- {k: (float(v) if isinstance(v, (np.float16, np.float32, np.float64)) else v) for k, v in pred.items()}
413
- for pred in predictions
414
- ]
415
-
416
- # If we have an output_dir, let's save all those dicts.
417
- if output_dir is not None:
418
- if not os.path.isdir(output_dir):
419
- raise OSError(f"{output_dir} is not a directory.")
420
-
421
- prediction_file = os.path.join(
422
- output_dir, "predictions.json" if prefix is None else f"{prefix}_predictions.json"
423
- )
424
- nbest_file = os.path.join(
425
- output_dir, "nbest_predictions.json" if prefix is None else f"{prefix}_nbest_predictions.json"
426
- )
427
- if version_2_with_negative:
428
- null_odds_file = os.path.join(
429
- output_dir, "null_odds.json" if prefix is None else f"{prefix}_null_odds.json"
430
- )
431
-
432
- logger.info(f"Saving predictions to {prediction_file}.")
433
- with open(prediction_file, "w") as writer:
434
- writer.write(json.dumps(all_predictions, indent=4) + "\n")
435
- logger.info(f"Saving nbest_preds to {nbest_file}.")
436
- with open(nbest_file, "w") as writer:
437
- writer.write(json.dumps(all_nbest_json, indent=4) + "\n")
438
- if version_2_with_negative:
439
- logger.info(f"Saving null_odds to {null_odds_file}.")
440
- with open(null_odds_file, "w") as writer:
441
- writer.write(json.dumps(scores_diff_json, indent=4) + "\n")
442
-
443
- return all_predictions, scores_diff_json