representations.py 文件源码

def user_representation(self, item_sequences):
        """
        Compute user representation from a given sequence.

        Returns
        -------

        tuple (all_representations, final_representation)
            The first element contains all representations from step
            -1 (no items seen) to t - 1 (all but the last items seen).
            The second element contains the final representation
            at step t (all items seen). This final state can be used
            for prediction or evaluation.
        """

        # Make the embedding dimension the channel dimension
        sequence_embeddings = (self.item_embeddings(item_sequences)
                               .permute(0, 2, 1))

        # Add a trailing dimension of 1
        sequence_embeddings = (sequence_embeddings
                               .unsqueeze(3))

        # Pad it with zeros from left
        sequence_embeddings = F.pad(sequence_embeddings,
                                    (0, 0, 1, 0))

        # Average representations, ignoring padding.
        sequence_embedding_sum = torch.cumsum(sequence_embeddings, 2)
        non_padding_entries = (
            torch.cumsum((sequence_embeddings != 0.0).float(), 2)
            .expand_as(sequence_embedding_sum)
        )

        user_representations = (
            sequence_embedding_sum / (non_padding_entries + 1)
        ).squeeze(3)

        return user_representations[:, :, :-1], user_representations[:, :, -1]