Who won the Netflix Prize? Ensemble or BellKors Pragmatic Chaos?

July 27th, 2009

Who won the Netflix Prize? Ensemble or BellKors Pragmatic Chaos

Who won the Netflix Prize? According to a post in the NYT Bits blog, Netflix Challenge Ends, But Winner Is In Doubt, it’s still very much up in the air.

” So The Ensemble won, right? Not necessarily. In an e-mail message Sunday night, Chris Volinsky, a scientist at AT&T Research and a leader of the BellKor’s team, said: “Our team is in first place as we were contacted by Netflix to validate our entry.” And in an online forum, another member of the BellKor team, Yehuda Koren, a researcher for Yahoo in Israel, said his team had “a better Test score than The Ensemble,” despite what the rival team submitted for the leaderboard.

So is BellKor the winner? Certainly not yet, according to a Netflix spokesman, Steve Swasey. “There is no winner,” he said.

A winner, Mr. Swasey said, will probably not be announced until sometime in September at an event hosted by Reed Hastings, Netflix’s chief executive. The movie rental company is not holding off for maximum P.R. effect, Mr. Swasey said, but because the winner has not yet been determined.

The Web leaderboard, he explained, is based on what the teams submit. Next, Netflix’s in-house researchers and outside experts have to validate the teams’ submissions, poring over the submitted code, design documents and other materials. “This is really complex stuff,” Mr. Swasey said.

A leading member of The Ensemble, Domonkos Tikk, a Hungarian computer scientist, did not sound too hopeful. “We didn’t get any notification from Netflix,” Mr. Tikk said in a phone interview from Hungary. “So I think the chances that we won are very slight. It was a nice try.”

It seems strange that Netflix called the Bellkor team first, since according to the Leaderboard the Ensemble team submitted the top entry.

UPDATE 2/28: Today’s NYT has a good article on the Netflix Prize and the role of teamwork for developing machine learning systems, Netflix Competitors Learn the Power of Teamwork.