Machine Learning (Theory)

12/1/2013

NIPS tutorials and Vowpal Wabbit 7.4

At NIPS I’m giving a tutorial on Learning to Interact. In essence this is about dealing with causality in a contextual bandit framework. Relative to previous tutorials, I’ll be covering several new results that changed my understanding of the nature of the problem. Note that Judea Pearl and Elias Bareinboim have a tutorial on causality. This might appear similar, but is quite different in practice. Pearl and Bareinboim’s tutorial will be about the general concepts while mine will be about total mastery of the simplest nontrivial case, including code. Luckily, they have the right order. I recommend going to both :-)

I also just released version 7.4 of Vowpal Wabbit. When I was a frustrated learning theorist, I did not understand why people were not using learning reductions to solve problems. I’ve been slowly discovering why with VW, and addressing the issues. One of the issues is that machine learning itself was not automatic enough, while another is that creating a very low overhead process for doing learning reductions is vitally important. These have been addressed well enough that we are starting to see compelling results. Various changes:

  • The internal learning reduction interface has been substantially improved. It’s now pretty easy to write new learning reduction. binary.cc provides a good example. This is a very simple reduction which just binarizes the prediction. More improvements are coming, but this is good enough that other people have started contributing reductions.
  • Zhen Qin had a very productive internship with Vaclav Petricek at eharmony resulting in several systemic modifications and some new reductions, including:
    1. A direct hash inversion implementation for use in debugging.
    2. A holdout system which takes over for progressive validation when multiple passes over data are used. This keeps the printouts ‘honest’.
    3. An online bootstrap mechanism system which efficiently provides some understanding of prediction variations and which can sometimes effectively trade computational time for increased accuracy via ensembling. This will be discussed at the biglearn workshop at NIPS.
    4. A top-k reduction which chooses the top-k of any set of base instances.
  • Hal Daume has a new implementation of Searn (and Dagger, the codes are unified) which makes structured prediction solutions far more natural. He has optimized this quite thoroughly (exercising the reduction stack in the process), resulting in this pretty graph.
    part of speech tagging time accuracy tradeoffs
    Here, CRF++ is commonly used conditional random field code, SVMstruct is an SVM-style approach to classification, and CRF SGD is an online learning CRF approach. All of these methods use the same features. Fully optimized code is typically rough, but this one is less than 100 lines.

I’m trying to put together a tutorial on these things at NIPS during the workshop break on the 9th and will add details as that resolves for those interested enough to skip out on skiing :-)

Edit: The VW tutorial will take place during the break at the big learning workshop from 1:30pm – 3pm at Harveys Emerald Bay B.

11/21/2013

Ben Taskar is gone

Tags: Announcements,Machine Learning jl@ 12:13 pm

I was not as personally close to Ben as Sam, but the level of tragedy is similar and I can’t help but be greatly saddened by the loss.

Various news stories have coverage, but the synopsis is that he had a heart attack on Sunday and is survived by his wife Anat and daughter Aviv. There is discussion of creating a memorial fund for them, which I hope comes to fruition, and plan to contribute to.

I will remember Ben as someone who thought carefully and comprehensively about new ways to do things, then fought hard and successfully for what he believed in. It is an ideal we strive for, that Ben accomplished.

Edit: donations go here, and more information is here.

11/9/2013

Graduates and Postdocs

Several strong graduates are on the job market this year.

  • Alekh Agarwal made the most scalable public learning algorithm as an intern two years ago. He has a deep and broad understanding of optimization and learning as well as the ability and will to make things happen programming-wise. I’ve been privileged to have Alekh visiting me in NY where he will be sorely missed.
  • John Duchi created Adagrad which is a commonly helpful improvement over online gradient descent that is seeing wide adoption, including in Vowpal Wabbit. He has a similarly deep and broad understanding of optimization and learning with significant industry experience at Google. Alekh and John have often coauthored together.
  • Stephane Ross visited me a year ago over the summer, implementing many new algorithms and working out the first scale free online update rule which is now the default in Vowpal Wabbit. Stephane is not on the market—Google robbed the cradle successfully :-) I’m sure that he will do great things.
  • Anna Choromanska visited me this summer, where we worked on extreme multiclass classification. She is very good at focusing on a problem and grinding it into submission both in theory and in practice—I can see why she wins awards for her work. Anna’s future in research is quite promising.

I also wanted to mention some postdoc openings in machine learning.

9/20/2013

No NY ML Symposium in 2013, and some good news

There will be no New York ML Symposium this year. The core issue is that NYAS is disorganized by people leaving, pushing back the date, with the current candidate a spring symposium on March 28. Gunnar and I were outvoted here—we were gung ho on organizing a fall symposium, but the rest of the committee wants to wait.

In some good news, most of the ICML 2012 videos have been restored from a deep backup.

7/24/2013

ICML 2012 videos lost

A big ouch—all the videos for ICML 2012 were lost in a shuffle. Rajnish sends the below, but if anyone can help that would be greatly appreciated.

——————————————————————————

Sincere apologies to ICML community for loosing 2012 archived videos

What happened: In order to publish 2013 videos, we decided to move 2012 videos to another server. We have a weekly backup service from the provider but after removing the videos from the current server, when we tried to retrieve the 2012 videos from backup service, the backup did not work because of provider-specific requirements that we had ignored while removing the data from previous server.

What are we doing about this: At this point, we are still looking into raw footage to find if we can retrieve some of the videos, but following are the steps we are taking to make sure this does not happen again in future:
(1) We are going to create a channel on Vimeo (and potentially on YouTube) and we will publish there the p-in-p- or slide-versions of the videos. This will be available by the beginning of Oct 2013.
(2) We are going to provide download links from TechTalks so that the slide-version (of p-in-p- version if availbale) of the videos can be directly downloaded by viewers.This feature will be available by Aug 4th 2013.
(3) Of course we are now creating regular backups that do not depend on our service provider.

How can you help: If you have downloaded from TechTalks the ICML 2012 videos using external tools, we will really appreciate if you can provide us the videos, please email at support@techtalks.tv .

Thank you,
Rajnish.

« Newer PostsOlder Posts »

Powered by WordPress