New Leader In Netflix Prize Race With One Day To Go

brajesh writes "The Netflix Prize, an algorithm competition to improve the Netflix Cinematch recommendation system by more than 10%, has a new leader — The Ensemble — just one day before the competition ends. The 30-day race to the end was kicked off after BellKor's Pragmatic Chaos submitted the first entry to break the 10% barrier, with the results showing a 10.08% improvement. The Ensemble, made up of three teams who chose to join forces ('Grand Prize Team,' 'Opera Solutions' and 'Vandelay United), has managed to overtake BellKor with a score of 10.09% — an improvement of .01% over the former leaders. From the article on Techcrunch: 'The competition will end [today], so teams still have a little bit of time left to make their last-second submissions, but things are looking good for The Ensemble. This has to be absolutely brutal for team BellKor.'"

It's not Uve

[thetoadwarrior]

Uwe Boll. It only sounds like a v because he's German.

Re:Ensemble learning

[Stile 65]

Many teams actually combined multiple methods to get a better score. In fact, "BellKor's Pragmatic Chaos" is a combination of three teams, I'm guessing - BellKor, BigChaos and Pragmatic Theory.

Also, it helps to remember that what's posted on the leaderboard is the result of the "quiz" set - half of the actual set of recommendations you're asked to make. The other half, the "test set," is used for final judging. With such a small difference between BellKor's Pragmatic Chaos and The Ensemble on the quiz set (.0001 RMSE), the test set rank may actually end up reversed.

Re:Why now?

[brian_tanner]

It's also true that the winner is not the person who gets the highest score on the leaderboard. Most people seem to miss this.

The leaderboard gives score on the QUIZ dataset, which is half of the answers that the team submits. The WINNER of the million dollars is the person who does best on the TEST dataset, the other half of the answers they submit. Nobody knows how good these guys are doing on the TEST set, either team could be overfitting [wikipedia.org] the quiz set.

Re:Sometimes better design beats better algorythms

[Hawke666]

Yeah, they do. see "Your account", "Account profiles". And then there's a dropdown on the top of the page. I don't see how they could make it much easier.

Re:Why now?

[currivan]

In fact, according to the second post by Yehuda Koren in this thread, it looks like BelKor does have the best test error rate and will be declared the winner. http://www.netflixprize.com/community/viewtopic.php?id=1498 [netflixprize.com]