Winsteps
Tuesday, October 24, 2006
The Netflix Prize - more
The Facets bug on the customer x movie analysis turned out to be rather silly. It was in computing the location of the progress bar across the screen. After fixing that, the analysis worked and I submitted its predictions to Netflix. The result was an RMSE of .98. This was better than merely submitting the mean rating. This gives an RMSE of 1.05. Netflix themselves have 0.95, and the best so far is .90.
So now I am trying a movie x customer-style model. Each customer is modeled to have his/her own rating scale. This produces 480,189 Rasch-Masters partial credit scales. First time out, this blew up Facets. Facets had a maximum of 16,000 partial credit scales. But now that is fixed and various other optimizations made. Facets is running again, about one iteration per hour, and 20 iterations to converge. Perhaps I will be able to submit a new set of predictions today ....
So now I am trying a movie x customer-style model. Each customer is modeled to have his/her own rating scale. This produces 480,189 Rasch-Masters partial credit scales. First time out, this blew up Facets. Facets had a maximum of 16,000 partial credit scales. But now that is fixed and various other optimizations made. Facets is running again, about one iteration per hour, and 20 iterations to converge. Perhaps I will be able to submit a new set of predictions today ....
