Paul Harrison on Logarithmic.net has decided to share his approach to winning the $1 milion Netflix Prize, How to get an RMSE of 0.8937 in the NetFlix Challenge.
The current NetFlix leader has an RMSE of 0.8847, which my approach won't be able to beat no matter how much computing power I throw at it. There is therefore no longer a reason for me to keep my approach secret.
I did my calculations using Python and a small amount of inline C++, using the Numpy and Weave libraries.
My approach is based on simonfunk's SVD method. That is, we predict a user's rating of a movie by taking the dot product of two vectors, one corresponding to the movie and one corresponding to the user.
Are you working on the Netflix Prize? I'd love to hear your story.