Regularizing Matrix Factorization with User and Item
Embeddings for Recommendation
Thanh Tran, Kyumin Lee
Worcester Polytechnic Institute, USA
{tdtran,kmlee}@wpi.edu
Yiming Liao, Dongwon Lee
Penn State University, USA
{yiming,dongwon}@psu.edu
ABSTRACT
Following recent successes in exploiting both latent factor and word
embedding models in recommendation, we propose a novel Regu-
larized Multi-Embedding (RME) based recommendation model that
simultaneously encapsulates the following ideas via decomposition:
(1) which items a user likes, (2) which two users co-like the same
items, (3) which two items users often co-liked, and (4) which two
items users often co-disliked. In experimental validation, the RME
outperforms competing state-of-the-art models in both explicit and
implicit feedback datasets, signicantly improving Recall@5 by
5.9
∼
7.0%, NDCG@20 by 4.3
∼
5.6%, and MAP@10 by 7.9
∼
8.9%. In
addition, under the cold-start scenario for users with the lowest
number of interactions, against the competing models, the RME
outperforms NDCG@5 by 20.2% and 29.4% in MovieLens-10M and
MovieLens-20M datasets, respectively. Our datasets and source
code are available at: https://github.com/thanhdtran/RME.git.
KEYWORDS
Recommendation; item embeddings; user embeddings; negative
sampling; collaborative ltering.
ACM Reference Format:
Thanh Tran, Kyumin Lee and Yiming Liao, Dongwon Lee. 2018. Regularizing
Matrix Factorization with User and Item Embeddings for Recommendation.
In The 27th ACM International Conference on Information and Knowledge
Management (CIKM ’18), October 22–26, 2018, Torino, Italy. ACM, New York,
NY, USA, 10 pages. https://doi.org/10.1145/3269206.3271730
1 INTRODUCTION
Among popular Collaborative Filtering (CF) methods in recommen-
dation [
14
,
17
,
29
,
33
], in recent years, latent factor models (LFM)
using matrix factorization have been widely used. LFM are known to
yield relatively high prediction accuracy, are language independent,
and allow additional side information to be easily incorporated and
decomposed together [
1
,
35
]. However, most of conventional LFM
only exploited positive feedback while neglected negative feedback
and treated them as missing data [8, 14, 27, 34].
In movie recommender systems, it was observed that many users
who enjoyed watching Thor: The Dark World, also enjoyed Thor:
Ragnarok. In this case, Thor: The Dark World and Thor: Ragnarok
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https://doi.org/10.1145/3269206.3271730
2
2
1
1
Users
Users
Liked)items
items
Co-liked)it ems
Co-liked+item+ co-occurrence+ matrix
2
2
User+co-occurrence+ matrix
1
1
2
2
items
Co-disliked) items
Co-dis lik ed+ item+ co-occurrence+ m atrix
p1
p2 p3
p4
p1
p2
p3
p4
p1
p2 p3
p4
p1
p2
p3
p4
p1
p2 p3
p4
p1
p2 p3
p4
Figure 1: An overview of our RME Model, which jointly
decomposes user-item interaction matrix, co-liked item co-
occurrence matrix, co-disliked item co-occurrence matrix,
and user co-occurrence matrix. (V : liked, X : disliked, and
?
:
unknown)
can be seen as a pair of co-liked movies. So, if a user preferred Thor:
The Dark World but never watch Thor: Ragnarok, the system can
precisely recommend Thor: Ragnarok to her (
rst observation
).
Similarly, if two users A and B liked the same movies, we can
assume A and B have the same movie interests. If user A likes a
movie that B has never watched, the system can recommend the
movie to B (
second observation
). In the same manner, we ask if co-
occurred disliked movies can provide any meaningful information.
We observed that most users, who rated Pledge This! poorly (0.8/5.0
on average), also gave a low rating to Run for Your Wife (1.3/5.0 on
average). If the disliked co-occurrence pattern was exploited, Run
for Your Wife would not be recommended to other users who did not
enjoy Pledge This! (
third observation
). This will help reduce the
false positive rate for recommender systems. The same phenomena
would have also occurred in other recommendation domains.
The rst two observations are similar to the basic assumptions of
item CF and user CF where similar scores between items/users are
used to infer the next recommended items for users. Unfortunately,
only the rst two observations have been exploited in conventional
CF. While treating the negative-feedback items dierently from
missing data led to better results [
13
], to the best of our knowledge,
no previous works exploited the
third observation
to enhance
the recommender systems’ performance.
Therefore, in this paper, we attempt to exploit all three observa-
tions in one model to achieve better recommendation results. With
the recent success of word embedding techniques in natural lan-
guage processing, if we consider pairs of co-occurred liked/disliked
items or pairs of co-occurred users as pairs of co-occurred words,
we can apply word embedding to learn latent representations of
items (e.g., item embeddings) and users (e.g. user embeddings).
Based on this, we propose a Regularized Multi-Embedding based
Session 4E: Recommendation 1
CIKM’18, October 22-26, 2018, Torino, Italy