I’m a little dismayed at SODA being outside of North America.  As a graduate student I would have probably been excited in my responsibility-free state.  But now I’m thinking “How much is this going to cost? How can I afford to miss what will probably end up being a full week of teaching?  I’m going to go all that way to just go to the conference and not be able to travel? How are our grossly underfunded faculty and grad students going to afford to go?  Would I justify going if I don’t have a paper?”

SODA is my favourite conference.  And there’s no other conference like it in North America.  Going without it for a year would result in some withdrawal.

I’ve been thinking about what I like about conferences. Of course I appreciate meeting wih friends and colleagues – working on new and old problems. I do enjoy the talks too. But for me, the 20 talk is problematic. I can only imagine two possible uses of 20 minutes: an advertisement to go read the paper, to educate people of the definition of the problem/topic/solution statement, or to actually go into technical details.

For topics that are directly in my area, 20 minutes are too short to delve into any technical details for which I would have questions. Nor do I need an advertisement. I am probably already aware of the paper (thanks archiv and its users) and perhaps already read the paper.

For topics not in my area 20 minutes is probably too long for an advertisment and too short for me to absorb definitions in order to appreciate any technical content.

That said, I miss theory seminars. I am the only traditional TCS person at OSU and am too far from theory strongholds to attend a theory seminar. I would love to get that content from a conference. The plenary talks provide a little of that, but they are not usually on recent results of a technical nature (nor would I want that to change).

What I propose is having two types of talks – short 10-15 minute “advertisements” and long 45-60 minute seminar style talks. The committee could choose the best results to give longer slots to. Perhaps (and probably controversially) longer slots could be biased towards better speakers.

As seen at the Women’s Center on campus at Oregon State University (in the spirit of … is powered by Orange).

Someone at the party suggested that next year they hold a Yankee swap version where, rather than simply draw and donate, people may later “steal” causes by agreeing to donate more than the current donor.  However, I thought this might be unfair to those attending who happen to be unemployed or wracking up student debt.  I was wondering if there is an algorithmic-game-theory person out there who could come up with a way to deal with this that might meet the following conditions:

• the total amount donated is maximized (or at least the price of anarchy is bounded)
• each person ends up matched to a cause (that is not their own)
• each person can cap their donation according to their means
• one’s cap does not hinder the ability to steal a cause
• the game doesn’t take forever and the rules are simple enough for a smart crowd to understand

I suppose one could hide everything and have causes bid on like Google AdWords, but I think a game of stealing in the spirit of Christmas would be more fun.

I gave a version of my talk on constrained knapsack problems (joint work with Brent Heeringa and Gordon Wilfong).  It was a lot of fun!  The discrete math crowd was fun and patiently sat through my discussions of applications and algorithms and approximations until I finally got to the meat of the talk.  I don’t normally attend discrete math events, but this was a great way to meet people in the area who are graph-minded that I otherwise might not meet.  I also hope that all their best undergraduates will be pointed my way for grad school (hint hint hint).

Louis Deaett (University of Victoria) gave a talk on a (orthogonal) generalization of graph colouring to vector colours where one must assign linearly independent vectors to adjacent vertices while minimizing the dimension of the vectors.  This is certainly not something I had ever dreamt of before.  Only after having let the problem stew for a couple of days am I wondering if a notion can be (or already has been) used in the frequency assignment problem.  Rather than a node transmitting over one frequency, transmit over several; use independence to overcome interference.

Omer Angel (University of British Columbia) spoke on graphs that look the same everywhere from a local perspective.  Given a local pattern centred at a vertex, what kind of graph is such that every vertex has the same local pattern?  Can the graph be finite? Must it be infinite?  For example, if the local pattern is a degree-2 star, then the graph could be a cycle or an infinite path – there is no way of telling which it is.  Certainly, I thought, you could never tell if it is finite or infinite.  Not true.

So, thank you Nancy Ann Neudauer for inviting me, Luis Goddyn for arranging the superb location, and Rob Beezer for quickly correcting that I am a proud beaver, not a duck.

* The host institution provides a room and math-fuel (coffee).

In the agonizing months** between interview and job offer at Oregon State University, I gave a lot of thought to “what do I do if I don’t get an academic job?”  I had the option of staying on as a postdoc through summer 2010 – an option that made me cringe.  ”If I stay as a postdoc and next year’s market is terrible and then take another postdoc … where does the cycle end?”

I have many friends in the biosciences where two 3+ year postdocs is the norm.  One has started a blog devoted to advocacy for postdocs; a recent post encourages the cycle of postdocing to end.  I worry that CS could “get worse” and end up like bio.  I hope that the competition offered by industry will help keep the postdocking length down.  But Ph.D. enrollment is going up – where are these students supposed to go?  Does anyone know if there are stats on the average postdoc length in computer science?

* I officially propose postdocking as the verbal of postdoc much like trafficking to traffic.
** Days became months due to budget hoop-jumping.

Unlike my immediate reliance on MathWorld, I have been a slow Wikipedia adopter.  The information on MathWorld seemed more reliable that Wikipedia could ever be, as it is contributed to (exclusively?) by mathematicians.  That said, I can’t imagine Wikipedia going down for a year. (At least, not before the zombie apocalypse starts.)  I find myself more and more using Wikipedia for technical matter.  I don’t think it is solely because I am less likely to look up definitions of groups and more likely to look up definitions of complexity classes.  I think the information on Wikipedia (even for MathWorld-type entries) is richer. Wikipedia entries tend to be more pedagogical than MathWorld’s, handy now that I am teaching.

I still don’t trust Wikipedia, though.  It is a good, quick first reference; a source of examples.  I’m hoping to incorporate Wikipedia participation into my graduate classes once I’ve figured out this teaching thing.  Perhaps I’ll become more trusting of Wikipedia one day, but I wonder if I’ll ever rely on it.

Versions of this talk have been given at the

• School of EECS Colloquium, Oregon State University (November 2, 2009) to an audience dominated by first year EE and CS graduate students.
• Combinatorial Potlatch, Vancouver, BC (November 21, 2009) to a raucous group of discrete mathematicians.

Joint work with Brent Heeringa (Williams College) and Gordon Wilfong (Bell Labs)

Suppose you are planning a party, but you can only invite 20 people, (caviar is expensive).  You can’t invite more than 20 people, but you want to maximize the number (or perhaps worth) of people that will show up.  But an attendee will only come to your party if one of their friends is also attending.  How do you find a set of friends to invite?

More specifically, we are given a knapsack of capacity K and a graph representing constraints (i.e. friendships) between the nodes; each node has a weight and a profit.  The goal is to find a maximum-profit set of nodes of total weight at most K such that if node x is selected, then a neighbour of x is also selected.

It turns out that this knapsack problem models several interesting problems (albeit less important than party planning) such as: network formation, tool magazine management, database storage and strategical investing.  In this talk I will take you on a tour of greedy algorithms, approximation guarantees and hardness of approximation in solving the graph-constrained knapsack problem.

Them: Trick or treat!

Me: I see we have a puppy, Mickey Mouse and, well, you must be a mathematician!

Little girl [defiantly stomping foot]: I’m a princess!

Me: Princesses can be mathematicians too.

I broke a lot of standard rules in giving this job talk.  First and foremost, I did not practice it.  *gasp*  Practice would have removed a lot of my “um”s and “uh”s.  In my defence, when I practice a talk too much, I find it gets stale.  However, practicing it once from start-to-finish would have been a good idea.  In watching this talk (as painful as it is), I think the best thing I could have done was to tape myself once.

Second, I climbed on a chair.  I was offered a laser pointer, but I hate laser pointers.  They are hard to keep steady and the point is very small and hard to see for the audience.  I find it about as useful as the speaker pointing to their laptop screen while they give a presentation.  So, at some point I wanted to point at something that too high for me, so I climbed on a chair.

Another minor thing that I wish I would get in the habit of doing is repeating an asked question. Taking two seconds to summarize the question both confirms that you are answering the intended question and allows the entire audience to hear both the question and the answer.

The slides for the talk are available for Keynote and Powerpoint here.