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Archive for July, 2012

Deep Learning reads Wikipedia and discovers the meaning of life – Geoff Hinton.

The above quote is from a very interesting talk by Geoffrey Hinton I had the chance to attend recently.

I have been at a summer school on Deep Neural Nets and Unsupervised Featured Learning at the Institute for Pure and Applied Mathematics at UCLA since July 9 (till July 27). It has been organized by Geoff Hinton, Yoshua Bengio, Stan Osher, Andrew Ng and Yann LeCun.

I have always been a “fan” of Neural Nets and the recent spike in interest in them has made me excited, thus the school happened at just the right time. The objective of the summer school is to give a broad overview of some of the recent work in Deep Learning and Unsupervised Feature Learning with emphasis on optimization, deep architectures and sparse representations. I must add that after getting here and looking at the peer group I would consider myself lucky to have obtained funding for the event!

[Click on the above image to see slides for the talks. Videos will be added at this location after July 27 Videos are now available]

That aside, if you are interested in Deep Learning or Neural Networks in general, the slides for the talks are being uploaded over here (or click on the image above), videos will be added at the same location some time after the summer school ends so you might like to bookmark this link.

The school has been interesting given the wide range of people who are here. The diversity of opinions about Deep Learning itself has given a good perspective on the subject and the issues and strengths of it. There are quite a few here who are somewhat skeptical of deep learning but are curious, while there are some who have been actively working on the same for a while. Also, it has been enlightening to see completely divergent views between some of the speakers on key ideas such as sparsity. For example Geoff Hinton had a completely different view of why sparsity was useful in classification tasks than compared to Stéphane Mallat, who gave a very interesting talk today even joking that “Hinton and Yann LeCun told you why sparsity is useful, I’ll tell you why sparsity is useless. “. See the above link for more details.

Indeed, such opinions do tell you that there is a lot of fecund ground for research in these areas.

I have been compiling a reading list on some of this stuff and will make a blog-post on the same soon.

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I have never done anything useful. No discovery of mine has made or is likely to make, directly or indirectly, for good or for ill, the least difference to the amenity of the world. Judged by all practical standards, the value of my mathematical life is nil. And outside mathematics it is trivial anyhow. The case for my life then, or for anyone else who has been a mathematician in the same sense that I have been one is this: That I have added something to knowledge and helped others to add more, and that these somethings have a value that differ in degree only and not in kind from that of the creations of the great mathematicians or any of the other artists, great or small who’ve left some kind of memorial behind them. 

I still say to myself when I am depressed and and find myself forced to listen to pompous and tiresome people “Well, I have done one thing you could never have done, and that is to have collaborated with Littlewood and Ramanujan on something like equal terms.” — G. H. Hardy (A Mathematician’s Apology)

Yesterday I  discovered an old (1987) British documentary on Srinivasa Ramanujan, which was pretty recently uploaded. I was not surprised to see that the video was made available by Christopher J. Sykes, who has been uploading older documentaries (including those by himself) on youtube (For example – The delightful “Richard Feynman and the Quest for Tannu Tuva” was uploaded by him as well. I blogged about it a couple of years ago!). Thanks Chris for these gems!

Since the documentary is pretty old, it is a little slow. But if you have one hour to spare, you should watch it! It features his (now late) widow, a quite young Béla Bollobás and the late Nobel Laureate Subrahmanyan Chandrasekhar. The video is embedded below – in case of any issues also find it linked here.

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[Ramanujan: Letters from an Indian Clerk]

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I could have written something on Ramanujan, but decided against it. Instead, I’d close this post with an excerpt from a wonderful essay by Freeman Dyson on Ramanujan published in Ramanujan: Essays and Surveys by Berndt and Rankin

Ramanujan: Essays and Surveys (click on image to view on Amazon)

A Walk Through Ramanujan’s Garden — F. J. Dyson

[…] The inequalities (8), (9) and (10) were undoubtedly true, but I had no idea how to prove them in 1942. In the end I just gave up trying to prove them and published them as conjectures in our student magazine “Eureka”. Since there was half a page left over at the end of my paper, they put in a poem by my friend Alison Falconer who was also a poet and mathematician. […]

Short Vision

Thought is the only way that leads to life.

All else is hollow spheres

Reflecting back

In heavy imitation

And blurred degeneration

A senseless image of our world of thought.

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Man thinks he is the thought which gives him life.

He binds a sheaf and claims it as himself.

He is a ring through which we pass swinging ropes

Which merely move a little as he slips.

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The Ropes are Thought.

The Space is Time.

Could he but see, then he might climb.

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Not only is it not right, it’s not even wrong! – Wolfgang Pauli

I just found a delightful joke concerning Pauli while rummaging through my email, thought it was worthy of sharing!

The phrase “Not Even Wrong” ofcourse was famously coined by Wolfgang Pauli, who was known to be particularly acerbic to sloppy thinking. The wiki entry for the phrase has the following story on how it originated. Rudolf Peierls writes that “a friend showed Pauli the paper of a young physicist which he suspected was not of great value but on which he wanted Pauli’s views. Pauli remarked sadly,”Not only is it not right, it’s not even wrong!”

Coming to the email which centers around being “Not even wrong”:

Wolfgang Pauli

Exactly, Pauli could be pretty scathing in his reviews. Visiting physicists delivering a presentation would dread seeing him in the audience. Pauli would sit and listen and scowl, arms crossed, and shake his head. The faster he shook his head, the more he disagreed with you.

The joke goes that when Pauli died he asked God why the fine structure constant has the value 1/(137.0) … God went to a blackboard and began scribbling equations. Pauli soon started shaking his head violently…

Note: I didn’t write this but apparently I read it somewhere a few years ago and mailed it to somebody. I googled for parts of it, but couldn’t locate the source. If you happen to know, then please link me up!

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