Recommendation systems are an important application in Machine Learning used by an increasing number of websites given its immediate impact on people's choices. For example, Amazon recommends its customers products they should buy, Netflix recommends its subscribers movies to watch.

The Netflix Prize Competition was one of the first and largest machine learning contests, with a grand prize of $1 million. The problem was that of predicting what rating a user would give to a movie that they have not watched yet. Recommendation systems via matrix factorization was one of the premier algorithms that came out of the extensive research that followed.