ITA 2014 Talk: MAP Perturbations and Measure Concentration

Due to weather issues, I was unable to make it on time to ITA to give my talk, which is based on an ArXiV preprint with Francesco Orabona, Tamir Hazan, and Tommi Jaakkola. The full work will be presented at ICML 2014 this summer. I decided to give the talk anyway and upload it to YouTube (warning: single take, much stammering):

I have a Mac, so I used the screencast recording features of QuickTime Player, as recommended to me by Manu Sridharan. Worked like a charm.

I plan to post a bit more about this problem later (I know, promises, promises), but in the meantime, this talk is mostly background about the MAP perturbation framework.

More advice on giving talks

I’d like to point out Alex Dimakis’s great post from last week on how to give a great ISIT talk (or any talk, really) and to put in a few bits more about a replicable process for writing talks that might help out students trying to write their first (or second, or third…) talk. As with any form of writing or communication, an unclear talk is usually the product of unclear thought on the part of the presenter. There’s no shortage of advice out there on how to give talks, but I figured I’d write down a process that I use to help streamline the process.

Before I get into the list, I have to issue a disclaimer : it’s not that I think I am super-great at giving talks. I am pretty good at critiquing talks to death, however. It must be the theater critic in me. What I have done is write down a process that has worked for me…

  1. Who is your audience? This is the place to start. If you are giving a talk at a conference, you may have a sense of what the interests of the audience are, but that is only part of it. Do you want your talk to be accessible to only faculty in your sub-area? (Hint : NO). Graduate students? If so, how much background should they have? Most of your talk should be accessible to a certain group — identify that group and target the bulk of the material to them. If you are giving a job talk it’s a different group from a conference or a specialized workshop.
  2. What do you want them to know? You have to be able to summarize what you want to say in one sentence. It’s not going to encapsulate everything, but it should be what you want your target audience to learn from your talk. Write this down and think about it. It’s not easy to summarize your work in a sound bite.
  3. Outlining the talk. Make an outline of the talk that contains one sentence per slide. Each slide should have a single main point that you can write down before adding any content to the slide. Read the sentences in order. It should be a story — does the story flow well? Does it make sense? Do you really need a table of contents slide for a 20 minute talk?
  4. Filling it in. For each sentence, think about how best to explain that point. Pictures are great, loads of equations are not. How can you, in a minute or two, make that point while talking, and what do you need visually to help emphasize that point? This is like storyboarding for a film.
  5. Balancing the content. Now that you have a plan for each slide, check to see that it’s balanced. Too many slides with text will fatigue people. Too many slides with just pictures may lead to confusion.
  6. Fill it in. Fill in the text and make the figures. This will take time, but since you have the sentence on each slide and the plan you should be able to think clearly through what you need to put down on each slide.
  7. Practice. Practice giving the talk once, out loud (not just in your head). You will find mistakes on the slides. Fix those mistakes. Practice again to find more mistakes. You might discover that the story doesn’t flow as well as you thought so you have to go back and retweak things. But always keep in mind the story.
  8. Presentation = Invitation. People say a talk is an invitation to read your paper, but that is not really true, I think. Chances are that more than half the audience will not read your paper anyway, but you still need to teach them something. Of the remaining half, most may skim your paper in the proceedings; you have to make that process easier for them. For the hardcore few who will really spend time reading your paper (because they are reviewing it), you want them to be excited by that prospect.
  9. Planning for contingencies. People get derailed about things like having backup slides with all the details of the proofs. Making backup slides, which are seen 1% of the time, takes away time from making the main presentation, which is seen 100% of the time. Focus on making the main presentation good.

ISIT 2010 : Anthony Ephremides

“The first phase [of life] you believe in Santa Claus, the second you don’t believe in Santa Clause, and in the third you become Santa Claus.” — Tony Ephremides

Prof. Anthony Ephremides gave the third plenary at ISIT, which included an interim report on the consummation between information theory and network coding and many connections between opera and research. He did a great job I think in explaining the difference between throughput region, stability region, and capacity region (under bursty vs. non-bursty use). These are in increasing order of inclusion. Some interesting tidbits (some new, some not):

  • He had a complaint about the way networking handles fading by simply saying the success probability for a packet being received is just \mathbb{P}( SNR > \gamma).
  • Under contention, the capacity region may not be convex, unlike in information theory where you can do time sharing.
  • For wireless network coding it is important to connect the MAC protocol and scheduling issues as well as change the notion of cut capacities. That is, you shouldn’t replace edges with hyper-edges, because that’s not a good model.
  • The information rate is the rate from the payload plus the information in the idleness and the information from the identity of the transmitter. That is, you get data from the actual packet, when the packet was sent, and who is sending the packet.
  • Extending many analyses to more than 2 users has not been done.
  • Can bursty traffic capacity be larger than non-bursty? The NNN (*) community says that would be a contradiction, because you can always then emulate bursty traffic. But this is unfair because idling the transmitter to build up packets and hence create artificial bursts is not allowed in the problem formulation, so there is no contradiction.
  • Relaying is good from a network perspective because it can partially enable a first-come first-serve (FCFS) discipline. So relays bridge a gap to the optimal scheduling policy. This is different than the information theory notion of cooperation yielding diversity gain.
  • Multicast throughput is an interesting thing to think about more rigorously for the future.
  • His prescription : the information theory has to apply its tools more broadly to networking problems and to unorthodox problems. The networking community should use more rigorous modeling and analysis methods.

(*) NNN = Nagging nabobs of negativism (really it should be “nattering nabobs of negativism,” Safire’s famous alliterative phrase wielded with such gusto by Spiro Agnew).