dialog_qa.py

import logging
from typing import Any, Dict, List, Optional
import numpy as np

import torch
import torch.nn.functional as F
from torch.nn.functional import nll_loss

from allennlp.common.checks import check_dimensions_match
from allennlp.data import Vocabulary
from allennlp.models.model import Model
from allennlp.modules import Seq2SeqEncoder, TimeDistributed, TextFieldEmbedder
from allennlp.modules.input_variational_dropout import InputVariationalDropout
from allennlp.modules.matrix_attention.linear_matrix_attention import LinearMatrixAttention
from allennlp.nn import InitializerApplicator, util
from allennlp.training.metrics import Average, BooleanAccuracy, CategoricalAccuracy

from allennlp_models.rc.tools import squad
from allennlp_models.rc.models.utils import replace_masked_values_with_big_negative_number

logger = logging.getLogger(__name__)


@Model.register("dialog_qa")
class DialogQA(Model):
    """
    This class implements modified version of BiDAF
    (with self attention and residual layer, from Clark and Gardner ACL 17 paper) model as used in
    Question Answering in Context (EMNLP 2018) paper [https://arxiv.org/pdf/1808.07036.pdf].

    In this set-up, a single instance is a dialog, list of question answer pairs.

    Parameters
    ----------
    vocab : ``Vocabulary``
    text_field_embedder : ``TextFieldEmbedder``
        Used to embed the ``question`` and ``passage`` ``TextFields`` we get as input to the model.
    phrase_layer : ``Seq2SeqEncoder``
        The encoder (with its own internal stacking) that we will use in between embedding tokens
        and doing the bidirectional attention.
    span_start_encoder : ``Seq2SeqEncoder``
        The encoder that we will use to incorporate span start predictions into the passage state
        before predicting span end.
    span_end_encoder : ``Seq2SeqEncoder``
        The encoder that we will use to incorporate span end predictions into the passage state.
    dropout : ``float``, optional (default=0.2)
        If greater than 0, we will apply dropout with this probability after all encoders (pytorch
        LSTMs do not apply dropout to their last layer).
    num_context_answers : ``int``, optional (default=0)
        If greater than 0, the model will consider previous question answering context.
    max_span_length: ``int``, optional (default=0)
        Maximum token length of the output span.
    max_turn_length: ``int``, optional (default=12)
        Maximum length of an interaction.
    """

    def __init__(
        self,
        vocab: Vocabulary,
        text_field_embedder: TextFieldEmbedder,
        phrase_layer: Seq2SeqEncoder,
        residual_encoder: Seq2SeqEncoder,
        span_start_encoder: Seq2SeqEncoder,
        span_end_encoder: Seq2SeqEncoder,
        initializer: Optional[InitializerApplicator] = None,
        dropout: float = 0.2,
        num_context_answers: int = 0,
        marker_embedding_dim: int = 10,
        max_span_length: int = 30,
        max_turn_length: int = 12,
    ) -> None:
        super().__init__(vocab)
        self._num_context_answers = num_context_answers
        self._max_span_length = max_span_length
        self._text_field_embedder = text_field_embedder
        self._phrase_layer = phrase_layer
        self._marker_embedding_dim = marker_embedding_dim
        self._encoding_dim = phrase_layer.get_output_dim()

        self._matrix_attention = LinearMatrixAttention(
            self._encoding_dim, self._encoding_dim, "x,y,x*y"
        )
        self._merge_atten = TimeDistributed(
            torch.nn.Linear(self._encoding_dim * 4, self._encoding_dim)
        )

        self._residual_encoder = residual_encoder

        if num_context_answers > 0:
            self._question_num_marker = torch.nn.Embedding(
                max_turn_length, marker_embedding_dim * num_context_answers
            )
            self._prev_ans_marker = torch.nn.Embedding(
                (num_context_answers * 4) + 1, marker_embedding_dim
            )

        self._self_attention = LinearMatrixAttention(
            self._encoding_dim, self._encoding_dim, "x,y,x*y"
        )

        self._followup_lin = torch.nn.Linear(self._encoding_dim, 3)
        self._merge_self_attention = TimeDistributed(
            torch.nn.Linear(self._encoding_dim * 3, self._encoding_dim)
        )

        self._span_start_encoder = span_start_encoder
        self._span_end_encoder = span_end_encoder

        self._span_start_predictor = TimeDistributed(torch.nn.Linear(self._encoding_dim, 1))
        self._span_end_predictor = TimeDistributed(torch.nn.Linear(self._encoding_dim, 1))
        self._span_yesno_predictor = TimeDistributed(torch.nn.Linear(self._encoding_dim, 3))
        self._span_followup_predictor = TimeDistributed(self._followup_lin)

        check_dimensions_match(
            phrase_layer.get_input_dim(),
            text_field_embedder.get_output_dim() + marker_embedding_dim * num_context_answers,
            "phrase layer input dim",
            "embedding dim + marker dim * num context answers",
        )

        if initializer is not None:
            initializer(self)

        self._span_start_accuracy = CategoricalAccuracy()
        self._span_end_accuracy = CategoricalAccuracy()
        self._span_yesno_accuracy = CategoricalAccuracy()
        self._span_followup_accuracy = CategoricalAccuracy()

        self._span_gt_yesno_accuracy = CategoricalAccuracy()
        self._span_gt_followup_accuracy = CategoricalAccuracy()

        self._span_accuracy = BooleanAccuracy()
        self._official_f1 = Average()
        self._variational_dropout = InputVariationalDropout(dropout)

    def forward(  # type: ignore
        self,
        question: Dict[str, torch.LongTensor],
        passage: Dict[str, torch.LongTensor],
        span_start: torch.IntTensor = None,
        span_end: torch.IntTensor = None,
        p1_answer_marker: torch.IntTensor = None,
        p2_answer_marker: torch.IntTensor = None,
        p3_answer_marker: torch.IntTensor = None,
        yesno_list: torch.IntTensor = None,
        followup_list: torch.IntTensor = None,
        metadata: List[Dict[str, Any]] = None,
    ) -> Dict[str, torch.Tensor]:

        """
        Parameters
        ----------
        question : Dict[str, torch.LongTensor]
            From a ``TextField``.
        passage : Dict[str, torch.LongTensor]
            From a ``TextField``.  The model assumes that this passage contains the answer to the
            question, and predicts the beginning and ending positions of the answer within the
            passage.
        span_start : ``torch.IntTensor``, optional
            From an ``IndexField``.  This is one of the things we are trying to predict - the
            beginning position of the answer with the passage.  This is an `inclusive` token index.
            If this is given, we will compute a loss that gets included in the output dictionary.
        span_end : ``torch.IntTensor``, optional
            From an ``IndexField``.  This is one of the things we are trying to predict - the
            ending position of the answer with the passage.  This is an `inclusive` token index.
            If this is given, we will compute a loss that gets included in the output dictionary.
        p1_answer_marker : ``torch.IntTensor``, optional
            This is one of the inputs, but only when num_context_answers > 0.
            This is a tensor that has a shape [batch_size, max_qa_count, max_passage_length].
            Most passage token will have assigned 'O', except the passage tokens belongs to the previous answer
            in the dialog, which will be assigned labels such as <1_start>, <1_in>, <1_end>.
            For more details, look into dataset_readers/util/make_reading_comprehension_instance_quac
        p2_answer_marker :  ``torch.IntTensor``, optional
            This is one of the inputs, but only when num_context_answers > 1.
            It is similar to p1_answer_marker, but marking previous previous answer in passage.
        p3_answer_marker :  ``torch.IntTensor``, optional
            This is one of the inputs, but only when num_context_answers > 2.
            It is similar to p1_answer_marker, but marking previous previous previous answer in passage.
        yesno_list :  ``torch.IntTensor``, optional
            This is one of the outputs that we are trying to predict.
            Three way classification (the yes/no/not a yes no question).
        followup_list :  ``torch.IntTensor``, optional
            This is one of the outputs that we are trying to predict.
            Three way classification (followup / maybe followup / don't followup).
        metadata : ``List[Dict[str, Any]]``, optional
            If present, this should contain the question ID, original passage text, and token
            offsets into the passage for each instance in the batch.  We use this for computing
            official metrics using the official SQuAD evaluation script.  The length of this list
            should be the batch size, and each dictionary should have the keys ``id``,
            ``original_passage``, and ``token_offsets``.  If you only want the best span string and
            don't care about official metrics, you can omit the ``id`` key.

        Returns
        -------
        An output dictionary consisting of the followings.
        Each of the followings is a nested list because first iterates over dialog, then questions in dialog.

        qid : List[List[str]]
            A list of list, consisting of question ids.
        followup : List[List[int]]
            A list of list, consisting of continuation marker prediction index.
            (y :yes, m: maybe follow up, n: don't follow up)
        yesno : List[List[int]]
            A list of list, consisting of affirmation marker prediction index.
            (y :yes, x: not a yes/no question, n: np)
        best_span_str : List[List[str]]
            If sufficient metadata was provided for the instances in the batch, we also return the
            string from the original passage that the model thinks is the best answer to the
            question.
        loss : torch.FloatTensor, optional
            A scalar loss to be optimised.
        """
        token_character_ids = question["token_characters"]["token_characters"]
        batch_size, max_qa_count, max_q_len, _ = token_character_ids.size()
        total_qa_count = batch_size * max_qa_count
        qa_mask = torch.ge(followup_list, 0).view(total_qa_count)
        embedded_question = self._text_field_embedder(question, num_wrapping_dims=1)
        embedded_question = embedded_question.reshape(
            total_qa_count, max_q_len, self._text_field_embedder.get_output_dim()
        )
        embedded_question = self._variational_dropout(embedded_question)
        embedded_passage = self._variational_dropout(self._text_field_embedder(passage))
        passage_length = embedded_passage.size(1)

        question_mask = util.get_text_field_mask(question, num_wrapping_dims=1)
        question_mask = question_mask.reshape(total_qa_count, max_q_len)
        passage_mask = util.get_text_field_mask(passage)

        repeated_passage_mask = passage_mask.unsqueeze(1).repeat(1, max_qa_count, 1)
        repeated_passage_mask = repeated_passage_mask.view(total_qa_count, passage_length)

        if self._num_context_answers > 0:
            # Encode question turn number inside the dialog into question embedding.
            question_num_ind = util.get_range_vector(
                max_qa_count, util.get_device_of(embedded_question)
            )
            question_num_ind = question_num_ind.unsqueeze(-1).repeat(1, max_q_len)
            question_num_ind = question_num_ind.unsqueeze(0).repeat(batch_size, 1, 1)
            question_num_ind = question_num_ind.reshape(total_qa_count, max_q_len)
            question_num_marker_emb = self._question_num_marker(question_num_ind)
            embedded_question = torch.cat([embedded_question, question_num_marker_emb], dim=-1)

            # Encode the previous answers in passage embedding.
            repeated_embedded_passage = (
                embedded_passage.unsqueeze(1)
                .repeat(1, max_qa_count, 1, 1)
                .view(total_qa_count, passage_length, self._text_field_embedder.get_output_dim())
            )
            # batch_size * max_qa_count, passage_length, word_embed_dim
            p1_answer_marker = p1_answer_marker.view(total_qa_count, passage_length)
            p1_answer_marker_emb = self._prev_ans_marker(p1_answer_marker)
            repeated_embedded_passage = torch.cat(
                [repeated_embedded_passage, p1_answer_marker_emb], dim=-1
            )
            if self._num_context_answers > 1:
                p2_answer_marker = p2_answer_marker.view(total_qa_count, passage_length)
                p2_answer_marker_emb = self._prev_ans_marker(p2_answer_marker)
                repeated_embedded_passage = torch.cat(
                    [repeated_embedded_passage, p2_answer_marker_emb], dim=-1
                )
                if self._num_context_answers > 2:
                    p3_answer_marker = p3_answer_marker.view(total_qa_count, passage_length)
                    p3_answer_marker_emb = self._prev_ans_marker(p3_answer_marker)
                    repeated_embedded_passage = torch.cat(
                        [repeated_embedded_passage, p3_answer_marker_emb], dim=-1
                    )

            repeated_encoded_passage = self._variational_dropout(
                self._phrase_layer(repeated_embedded_passage, repeated_passage_mask)
            )
        else:
            encoded_passage = self._variational_dropout(
                self._phrase_layer(embedded_passage, passage_mask)
            )
            repeated_encoded_passage = encoded_passage.unsqueeze(1).repeat(1, max_qa_count, 1, 1)
            repeated_encoded_passage = repeated_encoded_passage.view(
                total_qa_count, passage_length, self._encoding_dim
            )

        encoded_question = self._variational_dropout(
            self._phrase_layer(embedded_question, question_mask)
        )

        # Shape: (batch_size * max_qa_count, passage_length, question_length)
        passage_question_similarity = self._matrix_attention(
            repeated_encoded_passage, encoded_question
        )
        # Shape: (batch_size * max_qa_count, passage_length, question_length)
        passage_question_attention = util.masked_softmax(passage_question_similarity, question_mask)
        # Shape: (batch_size * max_qa_count, passage_length, encoding_dim)
        passage_question_vectors = util.weighted_sum(encoded_question, passage_question_attention)

        # We replace masked values with something really negative here, so they don't affect the
        # max below.
        masked_similarity = replace_masked_values_with_big_negative_number(
            passage_question_similarity, question_mask.unsqueeze(1)
        )

        question_passage_similarity = masked_similarity.max(dim=-1)[0].squeeze(-1)
        question_passage_attention = util.masked_softmax(
            question_passage_similarity, repeated_passage_mask
        )
        # Shape: (batch_size * max_qa_count, encoding_dim)
        question_passage_vector = util.weighted_sum(
            repeated_encoded_passage, question_passage_attention
        )
        tiled_question_passage_vector = question_passage_vector.unsqueeze(1).expand(
            total_qa_count, passage_length, self._encoding_dim
        )

        # Shape: (batch_size * max_qa_count, passage_length, encoding_dim * 4)
        final_merged_passage = torch.cat(
            [
                repeated_encoded_passage,
                passage_question_vectors,
                repeated_encoded_passage * passage_question_vectors,
                repeated_encoded_passage * tiled_question_passage_vector,
            ],
            dim=-1,
        )

        final_merged_passage = F.relu(self._merge_atten(final_merged_passage))

        residual_layer = self._variational_dropout(
            self._residual_encoder(final_merged_passage, repeated_passage_mask)
        )
        self_attention_matrix = self._self_attention(residual_layer, residual_layer)

        mask = repeated_passage_mask.reshape(
            total_qa_count, passage_length, 1
        ) * repeated_passage_mask.reshape(total_qa_count, 1, passage_length)
        self_mask = torch.eye(
            passage_length, passage_length, dtype=torch.bool, device=self_attention_matrix.device
        )
        self_mask = self_mask.reshape(1, passage_length, passage_length)
        mask = mask & ~self_mask

        self_attention_probs = util.masked_softmax(self_attention_matrix, mask)

        # (batch, passage_len, passage_len) * (batch, passage_len, dim) -> (batch, passage_len, dim)
        self_attention_vecs = torch.matmul(self_attention_probs, residual_layer)
        self_attention_vecs = torch.cat(
            [self_attention_vecs, residual_layer, residual_layer * self_attention_vecs], dim=-1
        )
        residual_layer = F.relu(self._merge_self_attention(self_attention_vecs))

        final_merged_passage = final_merged_passage + residual_layer
        # batch_size * maxqa_pair_len * max_passage_len * 200
        final_merged_passage = self._variational_dropout(final_merged_passage)
        start_rep = self._span_start_encoder(final_merged_passage, repeated_passage_mask)
        span_start_logits = self._span_start_predictor(start_rep).squeeze(-1)

        end_rep = self._span_end_encoder(
            torch.cat([final_merged_passage, start_rep], dim=-1), repeated_passage_mask
        )
        span_end_logits = self._span_end_predictor(end_rep).squeeze(-1)

        span_yesno_logits = self._span_yesno_predictor(end_rep).squeeze(-1)
        span_followup_logits = self._span_followup_predictor(end_rep).squeeze(-1)

        span_start_logits = replace_masked_values_with_big_negative_number(
            span_start_logits, repeated_passage_mask
        )
        # batch_size * maxqa_len_pair, max_document_len
        span_end_logits = replace_masked_values_with_big_negative_number(
            span_end_logits, repeated_passage_mask
        )

        best_span = self._get_best_span_yesno_followup(
            span_start_logits,
            span_end_logits,
            span_yesno_logits,
            span_followup_logits,
            self._max_span_length,
        )

        output_dict: Dict[str, Any] = {}

        # Compute the loss.
        if span_start is not None:
            loss = nll_loss(
                util.masked_log_softmax(span_start_logits, repeated_passage_mask),
                span_start.view(-1),
                ignore_index=-1,
            )
            self._span_start_accuracy(span_start_logits, span_start.view(-1), mask=qa_mask)
            loss += nll_loss(
                util.masked_log_softmax(span_end_logits, repeated_passage_mask),
                span_end.view(-1),
                ignore_index=-1,
            )
            self._span_end_accuracy(span_end_logits, span_end.view(-1), mask=qa_mask)
            self._span_accuracy(
                best_span[:, 0:2],
                torch.stack([span_start, span_end], -1).view(total_qa_count, 2),
                mask=qa_mask.unsqueeze(1).expand(-1, 2),
            )
            # add a select for the right span to compute loss
            gold_span_end_loc = []
            span_end = span_end.view(total_qa_count).squeeze().data.cpu().numpy()
            for i in range(0, total_qa_count):
                gold_span_end_loc.append(max(span_end[i] * 3 + i * passage_length * 3, 0))
                gold_span_end_loc.append(max(span_end[i] * 3 + i * passage_length * 3 + 1, 0))
                gold_span_end_loc.append(max(span_end[i] * 3 + i * passage_length * 3 + 2, 0))
            gold_span_end_loc = span_start.new(gold_span_end_loc)

            pred_span_end_loc = []
            for i in range(0, total_qa_count):
                pred_span_end_loc.append(max(best_span[i][1] * 3 + i * passage_length * 3, 0))
                pred_span_end_loc.append(max(best_span[i][1] * 3 + i * passage_length * 3 + 1, 0))
                pred_span_end_loc.append(max(best_span[i][1] * 3 + i * passage_length * 3 + 2, 0))
            predicted_end = span_start.new(pred_span_end_loc)

            _yesno = span_yesno_logits.view(-1).index_select(0, gold_span_end_loc).view(-1, 3)
            _followup = span_followup_logits.view(-1).index_select(0, gold_span_end_loc).view(-1, 3)
            loss += nll_loss(F.log_softmax(_yesno, dim=-1), yesno_list.view(-1), ignore_index=-1)
            loss += nll_loss(
                F.log_softmax(_followup, dim=-1), followup_list.view(-1), ignore_index=-1
            )

            _yesno = span_yesno_logits.view(-1).index_select(0, predicted_end).view(-1, 3)
            _followup = span_followup_logits.view(-1).index_select(0, predicted_end).view(-1, 3)
            self._span_yesno_accuracy(_yesno, yesno_list.view(-1), mask=qa_mask)
            self._span_followup_accuracy(_followup, followup_list.view(-1), mask=qa_mask)
            output_dict["loss"] = loss

        # Compute F1 and preparing the output dictionary.
        output_dict["best_span_str"] = []
        output_dict["qid"] = []
        output_dict["followup"] = []
        output_dict["yesno"] = []
        best_span_cpu = best_span.detach().cpu().numpy()
        for i in range(batch_size):
            passage_str = metadata[i]["original_passage"]
            offsets = metadata[i]["token_offsets"]
            f1_score = 0.0
            per_dialog_best_span_list = []
            per_dialog_yesno_list = []
            per_dialog_followup_list = []
            per_dialog_query_id_list = []
            for per_dialog_query_index, (iid, answer_texts) in enumerate(
                zip(metadata[i]["instance_id"], metadata[i]["answer_texts_list"])
            ):
                predicted_span = tuple(best_span_cpu[i * max_qa_count + per_dialog_query_index])

                start_offset = offsets[predicted_span[0]][0]
                end_offset = offsets[predicted_span[1]][1]

                yesno_pred = predicted_span[2]
                followup_pred = predicted_span[3]
                per_dialog_yesno_list.append(yesno_pred)
                per_dialog_followup_list.append(followup_pred)
                per_dialog_query_id_list.append(iid)

                best_span_string = passage_str[start_offset:end_offset]
                per_dialog_best_span_list.append(best_span_string)
                if answer_texts:
                    if len(answer_texts) > 1:
                        t_f1 = []
                        # Compute F1 over N-1 human references and averages the scores.
                        for answer_index in range(len(answer_texts)):
                            idxes = list(range(len(answer_texts)))
                            idxes.pop(answer_index)
                            refs = [answer_texts[z] for z in idxes]
                            t_f1.append(
                                squad.metric_max_over_ground_truths(
                                    squad.compute_f1, best_span_string, refs
                                )
                            )
                        f1_score = 1.0 * sum(t_f1) / len(t_f1)
                    else:
                        f1_score = squad.metric_max_over_ground_truths(
                            squad.compute_f1, best_span_string, answer_texts
                        )
                self._official_f1(100 * f1_score)
            output_dict["qid"].append(per_dialog_query_id_list)
            output_dict["best_span_str"].append(per_dialog_best_span_list)
            output_dict["yesno"].append(per_dialog_yesno_list)
            output_dict["followup"].append(per_dialog_followup_list)
        return output_dict

    def make_output_human_readable(
        self, output_dict: Dict[str, torch.Tensor]
    ) -> Dict[str, torch.Tensor]:
        yesno_tags = [
            [self.vocab.get_token_from_index(x, namespace="yesno_labels") for x in yn_list]
            for yn_list in output_dict.pop("yesno")
        ]
        followup_tags = [
            [self.vocab.get_token_from_index(x, namespace="followup_labels") for x in followup_list]
            for followup_list in output_dict.pop("followup")
        ]
        output_dict["yesno"] = yesno_tags
        output_dict["followup"] = followup_tags
        return output_dict

    def get_metrics(self, reset: bool = False) -> Dict[str, float]:
        return {
            "start_acc": self._span_start_accuracy.get_metric(reset),
            "end_acc": self._span_end_accuracy.get_metric(reset),
            "span_acc": self._span_accuracy.get_metric(reset),
            "yesno": self._span_yesno_accuracy.get_metric(reset),
            "followup": self._span_followup_accuracy.get_metric(reset),
            "f1": self._official_f1.get_metric(reset),
        }

    @staticmethod
    def _get_best_span_yesno_followup(
        span_start_logits: torch.Tensor,
        span_end_logits: torch.Tensor,
        span_yesno_logits: torch.Tensor,
        span_followup_logits: torch.Tensor,
        max_span_length: int,
    ) -> torch.Tensor:
        # Returns the index of highest-scoring span that is not longer than 30 tokens, as well as
        # yesno prediction bit and followup prediction bit from the predicted span end token.
        if span_start_logits.dim() != 2 or span_end_logits.dim() != 2:
            raise ValueError("Input shapes must be (batch_size, passage_length)")
        batch_size, passage_length = span_start_logits.size()
        max_span_log_prob = [util.min_value_of_dtype(span_start_logits.dtype)] * batch_size
        span_start_argmax = [0] * batch_size

        best_word_span = span_start_logits.new_zeros((batch_size, 4), dtype=torch.long)

        span_start_logits = span_start_logits.data.cpu().numpy()
        span_end_logits = span_end_logits.data.cpu().numpy()
        span_yesno_logits = span_yesno_logits.data.cpu().numpy()
        span_followup_logits = span_followup_logits.data.cpu().numpy()
        for b_i in range(batch_size):
            for j in range(passage_length):
                val1 = span_start_logits[b_i, span_start_argmax[b_i]]
                if val1 < span_start_logits[b_i, j]:
                    span_start_argmax[b_i] = j
                    val1 = span_start_logits[b_i, j]
                val2 = span_end_logits[b_i, j]
                if val1 + val2 > max_span_log_prob[b_i]:
                    if j - span_start_argmax[b_i] > max_span_length:
                        continue
                    best_word_span[b_i, 0] = span_start_argmax[b_i]
                    best_word_span[b_i, 1] = j
                    max_span_log_prob[b_i] = val1 + val2
        for b_i in range(batch_size):
            j = best_word_span[b_i, 1]
            yesno_pred = np.argmax(span_yesno_logits[b_i, j])
            followup_pred = np.argmax(span_followup_logits[b_i, j])
            best_word_span[b_i, 2] = int(yesno_pred)
            best_word_span[b_i, 3] = int(followup_pred)
        return best_word_span

    default_predictor = "dialog_qa"