A Hierarchical Network with User Memory Matrix for Long Sequence Recommendation

Table 1

Notations.

Symbol	Size	Description
		The set of all users
		The set of sessions for user
		The sequence of items that generate interactions in a session
		The number of memory vectors of memory matrix
		The length of memory vector in matrix
		The memory matrix of user
		The -th memory vector of user
		Preference vector of user
		The score of positive samples
		The score of negative samples