Computational Complexity Reduction for Factorization-Based Collaborative Filtering Algorithms

  • Authors:
  • István Pilászy;Domonkos Tikk

  • Affiliations:
  • Budapest University of Technology and Economics Email:info@gravitrd.com, Budapest, Hungary;Budapest University of Technology and Economics Email:info@gravitrd.com, Budapest, Hungary

  • Venue:
  • EC-Web 2009 Proceedings of the 10th International Conference on E-Commerce and Web Technologies
  • Year:
  • 2009

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Abstract

Alternating least squares (ALS) is a powerful matrix factorization (MF) algorithm for both implicit and explicit feedback based recommender systems. We show that by using the Sherman-Morrison formula (SMF), we can reduce the computational complexity of several ALS based algorithms. It also reduces the complexity of greedy forward and backward feature selection algorithms by an order of magnitude. We propose linear kernel ridge regression (KRR) for users with few ratings. We show that both SMF and KRR can efficiently handle new ratings.