src/transformers/data/metrics/squad_metrics.py/compute_predictions_log_probs
def compute_predictions_log_probs(
    all_examples,
    all_features,
    all_results,
    n_best_size,
    max_answer_length,
    output_prediction_file,
    output_nbest_file,
    output_null_log_odds_file,
    start_n_top,
    end_n_top,
    version_2_with_negative,
    tokenizer,
    verbose_logging,
):
    """
    XLNet write prediction logic (more complex than Bert's). Write final predictions to the json file and log-odds of
    null if needed.

    Requires utils_squad_evaluate.py
    """
    _PrelimPrediction = collections.namedtuple(  # pylint: disable=invalid-name
        "PrelimPrediction", ["feature_index", "start_index", "end_index", "start_log_prob", "end_log_prob"]
    )

    _NbestPrediction = collections.namedtuple(  # pylint: disable=invalid-name
        "NbestPrediction", ["text", "start_log_prob", "end_log_prob"]
    )

    logger.info(f"Writing predictions to: {output_prediction_file}")

    example_index_to_features = collections.defaultdict(list)
    for feature in all_features:
        example_index_to_features[feature.example_index].append(feature)

    unique_id_to_result = {}
    for result in all_results:
        unique_id_to_result[result.unique_id] = result

    all_predictions = collections.OrderedDict()
    all_nbest_json = collections.OrderedDict()
    scores_diff_json = collections.OrderedDict()

    for (example_index, example) in enumerate(all_examples):
        features = example_index_to_features[example_index]

        prelim_predictions = []
        # keep track of the minimum score of null start+end of position 0
        score_null = 1000000  # large and positive

        for (feature_index, feature) in enumerate(features):
            result = unique_id_to_result[feature.unique_id]

            cur_null_score = result.cls_logits

            # if we could have irrelevant answers, get the min score of irrelevant
            score_null = min(score_null, cur_null_score)

            for i in range(start_n_top):
                for j in range(end_n_top):
                    start_log_prob = result.start_logits[i]
                    start_index = result.start_top_index[i]

                    j_index = i * end_n_top + j

                    end_log_prob = result.end_logits[j_index]
                    end_index = result.end_top_index[j_index]

                    # We could hypothetically create invalid predictions, e.g., predict
                    # that the start of the span is in the question. We throw out all
                    # invalid predictions.
                    if start_index >= feature.paragraph_len - 1:
                        continue
                    if end_index >= feature.paragraph_len - 1:
                        continue

                    if not feature.token_is_max_context.get(start_index, False):
                        continue
                    if end_index < start_index:
                        continue
                    length = end_index - start_index + 1
                    if length > max_answer_length:
                        continue

                    prelim_predictions.append(
                        _PrelimPrediction(
                            feature_index=feature_index,
                            start_index=start_index,
                            end_index=end_index,
                            start_log_prob=start_log_prob,
                            end_log_prob=end_log_prob,
                        )
                    )

        prelim_predictions = sorted(
            prelim_predictions, key=lambda x: (x.start_log_prob + x.end_log_prob), reverse=True
        )

        seen_predictions = {}
        nbest = []
        for pred in prelim_predictions:
            if len(nbest) >= n_best_size:
                break
            feature = features[pred.feature_index]

            # XLNet un-tokenizer
            # Let's keep it simple for now and see if we need all this later.
            #
            # tok_start_to_orig_index = feature.tok_start_to_orig_index
            # tok_end_to_orig_index = feature.tok_end_to_orig_index
            # start_orig_pos = tok_start_to_orig_index[pred.start_index]
            # end_orig_pos = tok_end_to_orig_index[pred.end_index]
            # paragraph_text = example.paragraph_text
            # final_text = paragraph_text[start_orig_pos: end_orig_pos + 1].strip()

            # Previously used Bert untokenizer
            tok_tokens = feature.tokens[pred.start_index : (pred.end_index + 1)]
            orig_doc_start = feature.token_to_orig_map[pred.start_index]
            orig_doc_end = feature.token_to_orig_map[pred.end_index]
            orig_tokens = example.doc_tokens[orig_doc_start : (orig_doc_end + 1)]
            tok_text = tokenizer.convert_tokens_to_string(tok_tokens)

            # Clean whitespace
            tok_text = tok_text.strip()
            tok_text = " ".join(tok_text.split())
            orig_text = " ".join(orig_tokens)

            if hasattr(tokenizer, "do_lower_case"):
                do_lower_case = tokenizer.do_lower_case
            else:
                do_lower_case = tokenizer.do_lowercase_and_remove_accent

            final_text = get_final_text(tok_text, orig_text, do_lower_case, verbose_logging)

            if final_text in seen_predictions:
                continue

            seen_predictions[final_text] = True

            nbest.append(
                _NbestPrediction(text=final_text, start_log_prob=pred.start_log_prob, end_log_prob=pred.end_log_prob)
            )

        # In very rare edge cases we could have no valid predictions. So we
        # just create a nonce prediction in this case to avoid failure.
        if not nbest:
            nbest.append(_NbestPrediction(text="", start_log_prob=-1e6, end_log_prob=-1e6))

        total_scores = []
        best_non_null_entry = None
        for entry in nbest:
            total_scores.append(entry.start_log_prob + entry.end_log_prob)
            if not best_non_null_entry:
                best_non_null_entry = entry

        probs = _compute_softmax(total_scores)

        nbest_json = []
        for (i, entry) in enumerate(nbest):
            output = collections.OrderedDict()
            output["text"] = entry.text
            output["probability"] = probs[i]
            output["start_log_prob"] = entry.start_log_prob
            output["end_log_prob"] = entry.end_log_prob
            nbest_json.append(output)

        assert len(nbest_json) >= 1, "No valid predictions"
        assert best_non_null_entry is not None, "No valid predictions"

        score_diff = score_null
        scores_diff_json[example.qas_id] = score_diff
        # note(zhiliny): always predict best_non_null_entry
        # and the evaluation script will search for the best threshold
        all_predictions[example.qas_id] = best_non_null_entry.text

        all_nbest_json[example.qas_id] = nbest_json

    with open(output_prediction_file, "w") as writer:
        writer.write(json.dumps(all_predictions, indent=4) + "\n")

    with open(output_nbest_file, "w") as writer:
        writer.write(json.dumps(all_nbest_json, indent=4) + "\n")

    if version_2_with_negative:
        with open(output_null_log_odds_file, "w") as writer:
            writer.write(json.dumps(scores_diff_json, indent=4) + "\n")

    return all_predictions