Ensemble leads Netflix Prize contest, besting BellKors Pragmatic Chaos

July 26th, 2009

The race for the Netflix Prize is still on.

With just one day left in the 30 day last call period before BellKor’s Pragmatic Chaos (BKPC) was awarded the $1M Netflix Prize for a better movie recommender system, another team has broken the 10% improvement threshold and taken the lead by one hundredth of one percent — The Ensemble.

The Ensemble was formed by the merger of two existing Netflix Prize teams that had been ranked second and third behind BKPC: ‘Grand Prize Team’ and ‘Opera Solutions and Vandelay United’. Here’s how The Ensemble describes it’s genesis.

The crowd is indeed wiser than the individual.

The 10% barrier once seemed distant and insurmountable. But when the contest’s “last call” heralded the heroic achievements of BellKor’s Pragmatic Chaos, the rest of the crowd pondered, and asked why the barrier couldn’t be broken twice.

And lo, as if powered by gravity, Grand Prize Team and Vandelay Industries! began to draw in more and more members. And Vandelay went on to join forces with Opera Solutions, and then Vandelay and Opera united with Grand Prize Team, and then … and then … well, things got so complex we decided just to call ourselves The Ensemble.

We can be sure that there will be a lot of Netflix Prize activity in the coming weeks and maybe months as these two teams compete and perhaps more mergers create super-teams. BKPC and Ensemble could even decide to merge and share the prize. Watch the Netflix Leaderboard for the latest ranking.

UPDATE: I had assumed the 30 day last call would reset with each new leader, like auctions on ebay. Not so. The prize will be won (and lost) today! Here’s the relevant section in the rules:

“To qualify for the Grand Prize the RMSE of a Participant’s submitted predictions on the test subset must be less than or equal to 90% of 0.9525, or 0.8572 (the “qualifying RMSE”). After three (3) months have elapsed from the start of the Contest, when the RMSE of a submitted prediction set on the quiz subset improves beyond the qualifying RMSE an electronic announcement will inform all registered Participants that they have thirty (30) days to submit additional candidate prediction sets to be considered for judging. At the end of this period, qualifying submissions will be judged (see Judging below) in order of the largest improvement over the qualifying RMSE on the test subset. In the case of tied RMSE values on the test subsets, the submission received earliest by the Site will be judged first.”

The August 2009 CACM has a short note, Just for You (pdf), on recommender systems and the Netflix prize by BKPC member Don Monroe that includes a visualization by Ensemble member Chris Hefele.

Spotted on Hacker News. See Techcrunch also.

UPDATE II: The Netflix Prize contest has closed.