Upload utils_qa.py

utils_qa.py

@@ -0,0 +1,443 @@
+# Copyright 2020 The HuggingFace Team All rights reserved.
+#
+# 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.
+"""
+Post-processing utilities for question answering.
+"""
+
+import collections
+import json
+import logging
+import os
+from typing import Optional
+
+import numpy as np
+from tqdm.auto import tqdm
+
+
+logger = logging.getLogger(__name__)
+
+
+def postprocess_qa_predictions(
+    examples,
+    features,
+    predictions: tuple[np.ndarray, np.ndarray],
+    version_2_with_negative: bool = False,
+    n_best_size: int = 20,
+    max_answer_length: int = 30,
+    null_score_diff_threshold: float = 0.0,
+    output_dir: Optional[str] = None,
+    prefix: Optional[str] = None,
+    log_level: Optional[int] = logging.WARNING,
+):
+    """
+    Post-processes the predictions of a question-answering model to convert them to answers that are substrings of the
+    original contexts. This is the base postprocessing functions for models that only return start and end logits.
+
+    Args:
+        examples: The non-preprocessed dataset (see the main script for more information).
+        features: The processed dataset (see the main script for more information).
+        predictions (:obj:`Tuple[np.ndarray, np.ndarray]`):
+            The predictions of the model: two arrays containing the start logits and the end logits respectively. Its
+            first dimension must match the number of elements of :obj:`features`.
+        version_2_with_negative (:obj:`bool`, `optional`, defaults to :obj:`False`):
+            Whether or not the underlying dataset contains examples with no answers.
+        n_best_size (:obj:`int`, `optional`, defaults to 20):
+            The total number of n-best predictions to generate when looking for an answer.
+        max_answer_length (:obj:`int`, `optional`, defaults to 30):
+            The maximum length of an answer that can be generated. This is needed because the start and end predictions
+            are not conditioned on one another.
+        null_score_diff_threshold (:obj:`float`, `optional`, defaults to 0):
+            The threshold used to select the null answer: if the best answer has a score that is less than the score of
+            the null answer minus this threshold, the null answer is selected for this example (note that the score of
+            the null answer for an example giving several features is the minimum of the scores for the null answer on
+            each feature: all features must be aligned on the fact they `want` to predict a null answer).
+
+            Only useful when :obj:`version_2_with_negative` is :obj:`True`.
+        output_dir (:obj:`str`, `optional`):
+            If provided, the dictionaries of predictions, n_best predictions (with their scores and logits) and, if
+            :obj:`version_2_with_negative=True`, the dictionary of the scores differences between best and null
+            answers, are saved in `output_dir`.
+        prefix (:obj:`str`, `optional`):
+            If provided, the dictionaries mentioned above are saved with `prefix` added to their names.
+        log_level (:obj:`int`, `optional`, defaults to ``logging.WARNING``):
+            ``logging`` log level (e.g., ``logging.WARNING``)
+    """
+    if len(predictions) != 2:
+        raise ValueError("`predictions` should be a tuple with two elements (start_logits, end_logits).")
+    all_start_logits, all_end_logits = predictions
+
+    if len(predictions[0]) != len(features):
+        raise ValueError(f"Got {len(predictions[0])} predictions and {len(features)} features.")
+
+    # Build a map example to its corresponding features.
+    example_id_to_index = {k: i for i, k in enumerate(examples["id"])}
+    features_per_example = collections.defaultdict(list)
+    for i, feature in enumerate(features):
+        features_per_example[example_id_to_index[feature["example_id"]]].append(i)
+
+    # The dictionaries we have to fill.
+    all_predictions = collections.OrderedDict()
+    all_nbest_json = collections.OrderedDict()
+    if version_2_with_negative:
+        scores_diff_json = collections.OrderedDict()
+
+    # Logging.
+    logger.setLevel(log_level)
+    logger.info(f"Post-processing {len(examples)} example predictions split into {len(features)} features.")
+
+    # Let's loop over all the examples!
+    for example_index, example in enumerate(tqdm(examples)):
+        # Those are the indices of the features associated to the current example.
+        feature_indices = features_per_example[example_index]
+
+        min_null_prediction = None
+        prelim_predictions = []
+
+        # Looping through all the features associated to the current example.
+        for feature_index in feature_indices:
+            # We grab the predictions of the model for this feature.
+            start_logits = all_start_logits[feature_index]
+            end_logits = all_end_logits[feature_index]
+            # This is what will allow us to map some the positions in our logits to span of texts in the original
+            # context.
+            offset_mapping = features[feature_index]["offset_mapping"]
+            # Optional `token_is_max_context`, if provided we will remove answers that do not have the maximum context
+            # available in the current feature.
+            token_is_max_context = features[feature_index].get("token_is_max_context", None)
+
+            # Update minimum null prediction.
+            feature_null_score = start_logits[0] + end_logits[0]
+            if min_null_prediction is None or min_null_prediction["score"] > feature_null_score:
+                min_null_prediction = {
+                    "offsets": (0, 0),
+                    "score": feature_null_score,
+                    "start_logit": start_logits[0],
+                    "end_logit": end_logits[0],
+                }
+
+            # Go through all possibilities for the `n_best_size` greater start and end logits.
+            start_indexes = np.argsort(start_logits)[-1 : -n_best_size - 1 : -1].tolist()
+            end_indexes = np.argsort(end_logits)[-1 : -n_best_size - 1 : -1].tolist()
+            for start_index in start_indexes:
+                for end_index in end_indexes:
+                    # Don't consider out-of-scope answers, either because the indices are out of bounds or correspond
+                    # to part of the input_ids that are not in the context.
+                    if (
+                        start_index >= len(offset_mapping)
+                        or end_index >= len(offset_mapping)
+                        or offset_mapping[start_index] is None
+                        or len(offset_mapping[start_index]) < 2
+                        or offset_mapping[end_index] is None
+                        or len(offset_mapping[end_index]) < 2
+                    ):
+                        continue
+                    # Don't consider answers with a length that is either < 0 or > max_answer_length.
+                    if end_index < start_index or end_index - start_index + 1 > max_answer_length:
+                        continue
+                    # Don't consider answer that don't have the maximum context available (if such information is
+                    # provided).
+                    if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
+                        continue
+
+                    prelim_predictions.append(
+                        {
+                            "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),
+                            "score": start_logits[start_index] + end_logits[end_index],
+                            "start_logit": start_logits[start_index],
+                            "end_logit": end_logits[end_index],
+                        }
+                    )
+        if version_2_with_negative and min_null_prediction is not None:
+            # Add the minimum null prediction
+            prelim_predictions.append(min_null_prediction)
+            null_score = min_null_prediction["score"]
+
+        # Only keep the best `n_best_size` predictions.
+        predictions = sorted(prelim_predictions, key=lambda x: x["score"], reverse=True)[:n_best_size]
+
+        # Add back the minimum null prediction if it was removed because of its low score.
+        if (
+            version_2_with_negative
+            and min_null_prediction is not None
+            and not any(p["offsets"] == (0, 0) for p in predictions)
+        ):
+            predictions.append(min_null_prediction)
+
+        # Use the offsets to gather the answer text in the original context.
+        context = example["context"]
+        for pred in predictions:
+            offsets = pred.pop("offsets")
+            pred["text"] = context[offsets[0] : offsets[1]]
+
+        # In the very rare edge case we have not a single non-null prediction, we create a fake prediction to avoid
+        # failure.
+        if len(predictions) == 0 or (len(predictions) == 1 and predictions[0]["text"] == ""):
+            predictions.insert(0, {"text": "empty", "start_logit": 0.0, "end_logit": 0.0, "score": 0.0})
+
+        # Compute the softmax of all scores (we do it with numpy to stay independent from torch/tf in this file, using
+        # the LogSumExp trick).
+        scores = np.array([pred.pop("score") for pred in predictions])
+        exp_scores = np.exp(scores - np.max(scores))
+        probs = exp_scores / exp_scores.sum()
+
+        # Include the probabilities in our predictions.
+        for prob, pred in zip(probs, predictions):
+            pred["probability"] = prob
+
+        # Pick the best prediction. If the null answer is not possible, this is easy.
+        if not version_2_with_negative:
+            all_predictions[example["id"]] = predictions[0]["text"]
+        else:
+            # Otherwise we first need to find the best non-empty prediction.
+            i = 0
+            while predictions[i]["text"] == "":
+                i += 1
+            best_non_null_pred = predictions[i]
+
+            # Then we compare to the null prediction using the threshold.
+            score_diff = null_score - best_non_null_pred["start_logit"] - best_non_null_pred["end_logit"]
+            scores_diff_json[example["id"]] = float(score_diff)  # To be JSON-serializable.
+            if score_diff > null_score_diff_threshold:
+                all_predictions[example["id"]] = ""
+            else:
+                all_predictions[example["id"]] = best_non_null_pred["text"]
+
+        # Make `predictions` JSON-serializable by casting np.float back to float.
+        all_nbest_json[example["id"]] = [
+            {k: (float(v) if isinstance(v, (np.float16, np.float32, np.float64)) else v) for k, v in pred.items()}
+            for pred in predictions
+        ]
+
+    # If we have an output_dir, let's save all those dicts.
+    if output_dir is not None:
+        if not os.path.isdir(output_dir):
+            raise OSError(f"{output_dir} is not a directory.")
+
+        prediction_file = os.path.join(
+            output_dir, "predictions.json" if prefix is None else f"{prefix}_predictions.json"
+        )
+        nbest_file = os.path.join(
+            output_dir, "nbest_predictions.json" if prefix is None else f"{prefix}_nbest_predictions.json"
+        )
+        if version_2_with_negative:
+            null_odds_file = os.path.join(
+                output_dir, "null_odds.json" if prefix is None else f"{prefix}_null_odds.json"
+            )
+
+        logger.info(f"Saving predictions to {prediction_file}.")
+        with open(prediction_file, "w") as writer:
+            writer.write(json.dumps(all_predictions, indent=4) + "\n")
+        logger.info(f"Saving nbest_preds to {nbest_file}.")
+        with open(nbest_file, "w") as writer:
+            writer.write(json.dumps(all_nbest_json, indent=4) + "\n")
+        if version_2_with_negative:
+            logger.info(f"Saving null_odds to {null_odds_file}.")
+            with open(null_odds_file, "w") as writer:
+                writer.write(json.dumps(scores_diff_json, indent=4) + "\n")
+
+    return all_predictions
+
+
+def postprocess_qa_predictions_with_beam_search(
+    examples,
+    features,
+    predictions: tuple[np.ndarray, np.ndarray],
+    version_2_with_negative: bool = False,
+    n_best_size: int = 20,
+    max_answer_length: int = 30,
+    start_n_top: int = 5,
+    end_n_top: int = 5,
+    output_dir: Optional[str] = None,
+    prefix: Optional[str] = None,
+    log_level: Optional[int] = logging.WARNING,
+):
+    """
+    Post-processes the predictions of a question-answering model with beam search to convert them to answers that are substrings of the
+    original contexts. This is the postprocessing functions for models that return start and end logits, indices, as well as
+    cls token predictions.
+
+    Args:
+        examples: The non-preprocessed dataset (see the main script for more information).
+        features: The processed dataset (see the main script for more information).
+        predictions (:obj:`Tuple[np.ndarray, np.ndarray]`):
+            The predictions of the model: two arrays containing the start logits and the end logits respectively. Its
+            first dimension must match the number of elements of :obj:`features`.
+        version_2_with_negative (:obj:`bool`, `optional`, defaults to :obj:`False`):
+            Whether or not the underlying dataset contains examples with no answers.
+        n_best_size (:obj:`int`, `optional`, defaults to 20):
+            The total number of n-best predictions to generate when looking for an answer.
+        max_answer_length (:obj:`int`, `optional`, defaults to 30):
+            The maximum length of an answer that can be generated. This is needed because the start and end predictions
+            are not conditioned on one another.
+        start_n_top (:obj:`int`, `optional`, defaults to 5):
+            The number of top start logits too keep when searching for the :obj:`n_best_size` predictions.
+        end_n_top (:obj:`int`, `optional`, defaults to 5):
+            The number of top end logits too keep when searching for the :obj:`n_best_size` predictions.
+        output_dir (:obj:`str`, `optional`):
+            If provided, the dictionaries of predictions, n_best predictions (with their scores and logits) and, if
+            :obj:`version_2_with_negative=True`, the dictionary of the scores differences between best and null
+            answers, are saved in `output_dir`.
+        prefix (:obj:`str`, `optional`):
+            If provided, the dictionaries mentioned above are saved with `prefix` added to their names.
+        log_level (:obj:`int`, `optional`, defaults to ``logging.WARNING``):
+            ``logging`` log level (e.g., ``logging.WARNING``)
+    """
+    if len(predictions) != 5:
+        raise ValueError("`predictions` should be a tuple with five elements.")
+    start_top_log_probs, start_top_index, end_top_log_probs, end_top_index, cls_logits = predictions
+
+    if len(predictions[0]) != len(features):
+        raise ValueError(f"Got {len(predictions[0])} predictions and {len(features)} features.")
+
+    # Build a map example to its corresponding features.
+    example_id_to_index = {k: i for i, k in enumerate(examples["id"])}
+    features_per_example = collections.defaultdict(list)
+    for i, feature in enumerate(features):
+        features_per_example[example_id_to_index[feature["example_id"]]].append(i)
+
+    # The dictionaries we have to fill.
+    all_predictions = collections.OrderedDict()
+    all_nbest_json = collections.OrderedDict()
+    scores_diff_json = collections.OrderedDict() if version_2_with_negative else None
+
+    # Logging.
+    logger.setLevel(log_level)
+    logger.info(f"Post-processing {len(examples)} example predictions split into {len(features)} features.")
+
+    # Let's loop over all the examples!
+    for example_index, example in enumerate(tqdm(examples)):
+        # Those are the indices of the features associated to the current example.
+        feature_indices = features_per_example[example_index]
+
+        min_null_score = None
+        prelim_predictions = []
+
+        # Looping through all the features associated to the current example.
+        for feature_index in feature_indices:
+            # We grab the predictions of the model for this feature.
+            start_log_prob = start_top_log_probs[feature_index]
+            start_indexes = start_top_index[feature_index]
+            end_log_prob = end_top_log_probs[feature_index]
+            end_indexes = end_top_index[feature_index]
+            feature_null_score = cls_logits[feature_index]
+            # This is what will allow us to map some the positions in our logits to span of texts in the original
+            # context.
+            offset_mapping = features[feature_index]["offset_mapping"]
+            # Optional `token_is_max_context`, if provided we will remove answers that do not have the maximum context
+            # available in the current feature.
+            token_is_max_context = features[feature_index].get("token_is_max_context", None)
+
+            # Update minimum null prediction
+            if min_null_score is None or feature_null_score < min_null_score:
+                min_null_score = feature_null_score
+
+            # Go through all possibilities for the `n_start_top`/`n_end_top` greater start and end logits.
+            for i in range(start_n_top):
+                for j in range(end_n_top):
+                    start_index = int(start_indexes[i])
+                    j_index = i * end_n_top + j
+                    end_index = int(end_indexes[j_index])
+                    # Don't consider out-of-scope answers (last part of the test should be unnecessary because of the
+                    # p_mask but let's not take any risk)
+                    if (
+                        start_index >= len(offset_mapping)
+                        or end_index >= len(offset_mapping)
+                        or offset_mapping[start_index] is None
+                        or len(offset_mapping[start_index]) < 2
+                        or offset_mapping[end_index] is None
+                        or len(offset_mapping[end_index]) < 2
+                    ):
+                        continue
+
+                    # Don't consider answers with a length negative or > max_answer_length.
+                    if end_index < start_index or end_index - start_index + 1 > max_answer_length:
+                        continue
+                    # Don't consider answer that don't have the maximum context available (if such information is
+                    # provided).
+                    if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
+                        continue
+                    prelim_predictions.append(
+                        {
+                            "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),
+                            "score": start_log_prob[i] + end_log_prob[j_index],
+                            "start_log_prob": start_log_prob[i],
+                            "end_log_prob": end_log_prob[j_index],
+                        }
+                    )
+
+        # Only keep the best `n_best_size` predictions.
+        predictions = sorted(prelim_predictions, key=lambda x: x["score"], reverse=True)[:n_best_size]
+
+        # Use the offsets to gather the answer text in the original context.
+        context = example["context"]
+        for pred in predictions:
+            offsets = pred.pop("offsets")
+            pred["text"] = context[offsets[0] : offsets[1]]
+
+        # In the very rare edge case we have not a single non-null prediction, we create a fake prediction to avoid
+        # failure.
+        if len(predictions) == 0:
+            # Without predictions min_null_score is going to be None and None will cause an exception later
+            min_null_score = -2e-6
+            predictions.insert(0, {"text": "", "start_logit": -1e-6, "end_logit": -1e-6, "score": min_null_score})
+
+        # Compute the softmax of all scores (we do it with numpy to stay independent from torch/tf in this file, using
+        # the LogSumExp trick).
+        scores = np.array([pred.pop("score") for pred in predictions])
+        exp_scores = np.exp(scores - np.max(scores))
+        probs = exp_scores / exp_scores.sum()
+
+        # Include the probabilities in our predictions.
+        for prob, pred in zip(probs, predictions):
+            pred["probability"] = prob
+
+        # Pick the best prediction and set the probability for the null answer.
+        all_predictions[example["id"]] = predictions[0]["text"]
+        if version_2_with_negative:
+            scores_diff_json[example["id"]] = float(min_null_score)
+
+        # Make `predictions` JSON-serializable by casting np.float back to float.
+        all_nbest_json[example["id"]] = [
+            {k: (float(v) if isinstance(v, (np.float16, np.float32, np.float64)) else v) for k, v in pred.items()}
+            for pred in predictions
+        ]
+
+    # If we have an output_dir, let's save all those dicts.
+    if output_dir is not None:
+        if not os.path.isdir(output_dir):
+            raise OSError(f"{output_dir} is not a directory.")
+
+        prediction_file = os.path.join(
+            output_dir, "predictions.json" if prefix is None else f"{prefix}_predictions.json"
+        )
+        nbest_file = os.path.join(
+            output_dir, "nbest_predictions.json" if prefix is None else f"{prefix}_nbest_predictions.json"
+        )
+        if version_2_with_negative:
+            null_odds_file = os.path.join(
+                output_dir, "null_odds.json" if prefix is None else f"{prefix}_null_odds.json"
+            )
+
+        logger.info(f"Saving predictions to {prediction_file}.")
+        with open(prediction_file, "w") as writer:
+            writer.write(json.dumps(all_predictions, indent=4) + "\n")
+        logger.info(f"Saving nbest_preds to {nbest_file}.")
+        with open(nbest_file, "w") as writer:
+            writer.write(json.dumps(all_nbest_json, indent=4) + "\n")
+        if version_2_with_negative:
+            logger.info(f"Saving null_odds to {null_odds_file}.")
+            with open(null_odds_file, "w") as writer:
+                writer.write(json.dumps(scores_diff_json, indent=4) + "\n")
+
+    return all_predictions, scores_diff_json