Elsevier

Neurocomputing

Volume 342, 21 May 2019, Pages 60-65
Neurocomputing

Neural networks for personalized item rankings

https://doi.org/10.1016/j.neucom.2018.10.083Get rights and content

Abstract

Most users typically interact with products only through implicit feedback such as clicks or purchases rather than explicit user-provided information like product ratings. Learning to rank products according to individual preferences using only implicit feedback can be helpful to make useful recommendations. In this paper, a neural network architecture to solve collaborative filtering problems for personalized rankings on implicit feedback datasets is presented. It is shown how a layer of constant weights forces the network to learn pairwise item rankings. Additionally, similarities between the proposed neural network and a matrix factorization model trained with the Bayesian Personalized Ranking optimization criterion are proven. The experiments indicate state-of-the-art performance for the task of personalized ranking.

Section snippets

Introduction and related work

Users can be overwhelmed by the number of available items to choose from in today’s ecommerce sites. Helping the user by limiting this selection with personalized item recommendations can therefore substantially increase the probability of a purchase. However, selecting the most appropriate items is a difficult task. Especially, if there is no individual explicit feedback, like ratings, available.

Implicit feedback is one of the most available sources of information about user preferences. With

Preliminaries

Let U={1,,N} be a set of users and I={1,,M} a set of items with N,MN. We have a dataset of observed interactions S ⊆ U × I, where (u, i) ∈ S means that user u interacted with item i in some way. Each observation (u, i) ∈ S is regarded as positive feedback and (u, i) ∈ (U × I)∖S as negative feedback. We are calling an item positive or negative if it is associated with positive or negative feedback, respectively, and define Iu+ as the set of all positive items of user u ∈ U and Iu as the set

Overview and notation

Our proposed model is a modified feedforward neural net with four specific layers L: an user layer L1 with N units, a hidden layer L2 with K units, an item layer L3 with M units and a ranking layer L4 with one unit (see Fig. 1). Therefore, the user layer L1 has as many units as there are users and the item layer L3 has as many units as there are items. The parameter K determines the size of the user and item representations [5].

The following short notations are used in this paper: let Wl be the

Connections to Bayesian personalized ranking

The optimization criterion BPR was proposed by Rendle et al. in [3]. It was designed to directly optimize AUC and the authors also applied it to a matrix factorization model. In this section, we will now show that a simplified version of our proposed network is equivalent to a matrix factorization model trained with the BPR criterion. This simplified version uses only identity activations functions and no bias layer.

First of all, the network proposed in this paper is similar to a matrix

Setting

The MovieLens 1M dataset [11], the Netflix Prize dataset [12] and the Jester dataset (version 2) [13] are used to evaluate our model. Since all datasets contain explicit ratings, they are converted to implicit ones by only keeping samples with a rating above 3 for the Netflix Prize and Movielens 1M dataset and a score above 0 for the Jester dataset. A random sample of 10,000 users is used for the Netflix Prize dataset to speed up the evaluation. Each dataset is split randomly into two sets of

Summary

In this paper, we have designed a neural network architecture to achieve a matrix factorization which directly optimizes the AUC metric to learn personalized item rankings. It was shown how to train this network with the BPR optimization criterion using a layer of constant weights and the common cross entropy cost function. We have proven that a simplified version of our network is similar to a matrix factorization model trained with BPR. Due to the transition to neural networks we were able to

Josef Feigl received a diploma in business mathematics from the University of Leipzig in 2011. Since 2014, he is pursuing his Ph.D. at the Department of Computer Engineering at the same university. His main areas of interest and research are the use of neural networks for recommender systems.

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    Josef Feigl received a diploma in business mathematics from the University of Leipzig in 2011. Since 2014, he is pursuing his Ph.D. at the Department of Computer Engineering at the same university. His main areas of interest and research are the use of neural networks for recommender systems.

    Martin Bogdan In 1987 Martin Bogdan started his education in communication engineering at the Fachhochschule Offenburg. From 1991 to 1993 he studied Informatique Industrielle et Instrumentation in parallel with his studies at Offenburg resulting in a double diploma in 1993. Within his thesis he proved the feasibility of controlling a commercial limb prosthesis using recorded nerve signals obtaining his doctorate in 1999. From 2000 until 2015 he heads the research group for Neural Networks and Machine Learning at the University of Tübingen redirecting the main focus of the group towards biomedical applications, especially towards the communication with the nervous system and bio inspired information processing. Herein non-invasive and invasive Brain-Computer-Interfaces are playing a main role. In 2008 he received a full professorship for Computer Engineering at the Leipzig University. His department still deals with biomedical signal processing focused on neuroinformatics regarding neuro-inspired information processing and cognitive science (cognitive computing) as well as machine learning. In addition, his department works on Mainframe Computer and cyber security, respectively, cyber forensics.

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