  Autoencoder recommenders have recently shown state-of-the-art performance in
the recommendation task due to their ability to model non-linear item
relationships effectively. However, existing autoencoder recommenders use
fully-connected neural network layers and do not employ structure learning.
This can lead to inefficient training, especially when the data is sparse as
commonly found in collaborative filtering. The aforementioned results in lower
generalization ability and reduced performance. In this paper, we introduce
structure learning for autoencoder recommenders by taking advantage of the
inherent item groups present in the collaborative filtering domain. Due to the
nature of items in general, we know that certain items are more related to each
other than to other items. Based on this, we propose a method that first learns
groups of related items and then uses this information to determine the
connectivity structure of an auto-encoding neural network. This results in a
network that is sparsely connected. This sparse structure can be viewed as a
prior that guides the network training. Empirically we demonstrate that the
proposed structure learning enables the autoencoder to converge to a local
optimum with a much smaller spectral norm and generalization error bound than
the fully-connected network. The resultant sparse network considerably
outperforms the state-of-the-art methods like \textsc{Mult-vae/Mult-dae} on
multiple benchmarked datasets even when the same number of parameters and flops
are used. It also has a better cold-start performance.
