Category: Conferences

IFORS 2008: Time to get your abstracts in!

I just posted this in sci.op-research and comp.constraints

There is still time to get your abstracts in for IFORS 2008. IFORS
(International Federation of Operational Research Societies) is an
umbrella organization for national OR societies. Every three years,
IFORS holds a conference. Recent past conferences have been in
Edinburgh and Hawaii. In 2008, the conference will be held in
Sandton, South Africa. Sandton is a suburb of Johannesburg, and has
outstanding conference facilities (I am a VP of IFORS, so I visited
the site two years ago). The conference is shaping up to be a very
interesting one, with an emphasis on how OR enhances and links
communities. The dates of the conference are July 13-18 and all the
info you need is at http://www.ifors2008.org

In addition to a top-notch scientific program, Sandton offers some
great outings, before, after, or during (IFORS conferences have a
traditional Wednesday outing) the conference. I particularly enjoyed
visiting Soweto as well as the “Cradle of Humankind”. I also highly
recommend visiting Cape Town (though winter weather there can be a
little dicey: there is a reason all those ships are sunk at the
Cape!). Right now, I am checking out safaris (winter is a great
time, since the animals are easier both to find and to see).

Due to restrictions at the convention center in Sandton, we won’t be
able to keep accepting abstracts after January 31, so get your
abstracts in!

If you have any questions or concerns, please don’t hesitate to write
me.

I really did enjoy the trip two years ago and am very much looking forward to this year’s conference.

ORSNZ Recap

I was at the OR Society of New Zealand conference last week, and failed to blog it.  I am so ashamed!  You can check out some pictures and other information about the conference at its site.  I was one of the speakers, so you can see me in action.

A highlight of the conference for me was the plenary session given by Gerard Cachon of Wharton, who is visiting the University of Auckland this year.  He gave a talk on the use of game theory in operations management.  I have been a little dubious of incredible fad for game theory in the analysis of supply chains.  The assumptions of game theory are pretty strong, and it is not clear that much of the analysis is giving any real insight.  Gerard is very aware of these limitations, and much of his talk was illustrating how difficult it is to conclude things from a game theoretic analysis.  For instance, there is often a huge problem with multiple equilibria, with game theory providing little guidance as to what the “right” equilibrium is.  After the talk, I felt much happier about game theory in OM:  as long as people are talking about the limitations, I can have much more confidence when they make conclusions.

Natashia Boland and Open Pit Mining

I am attending the Australian Society for Operational Research meeting in Melbourne.  I had thought Australia always had wonderful weather, but it is a gray, rainy day here.

The conference was opened with a talk by Natashia Boland, currently at the University of Melbourne (but I hear she is moving) who spoke on her experiences in using integer programming in practice.

The first part of the talk was about modeling excavation in open pit mines.  The goal in this problem is to dig out a mine in the best possible way.  The most critical constraint is, of course, that you can’t dig under stuff that is not already dug away.  There are other constraints on how much ore can be processed in a year, and on other operational requirements.  Of course, the amount of money that is at stake is huge:  these mines generate  hundreds  of millions of dollars of income, and require huge investments (see the wikipedia entry on the Bingham Canyon Mine for one example:  the pictured example is from Russia).  So planning the excavation is an important decision, even if most of the savings are just the time-value of money (getting $100 million this year rather than next is quite a difference!).  The integer programs that Natashia and her colleagues get are very large, so they have had to develop specialized branching rules, along with aggregation approaches to the decisions.

Natashia’s second example had to do with shipping planning for a fertilizer company.  The most striking point she made is that her approach still leaves an 8% gap between the upper bound (feasible solution) and lower bound.  This bound may be because the lower bound is poor (no possible solution can reach that value) but even 1 or 2% of an operation that costs a few hundred million dollars to run is a big deal.

Natashia gives very good, clear, inspirational talks.  The thing I like best is her choice of problems.  They are non-standard, but still involve huge amounts of money.  Every percentage point she saves would be enough to support an enormous research effort in integer programming.  If only she were to get a fraction of the savings!

ISI and Conferences

ISI from Thompson Scientific might be seen as just another scientific article indexing service, just like Google Scholar, Citeseer and many others. But it has a much stronger effect: many universities only “count” ISI-indexed publications. In mainstream operations research, this doesn’t have a very strong effect. Most well-known OR journals are ISI-indexed, and those that are not strive greatly for such indexing. But in some of our newer fields, particularly those related to computer science, this is much more of an issue. In constraint programming, conferences are key outlets for research, particularly such conferences as CP and CP/AI-OR. Both of these conference publish their papers in Springer’s Lecture Notes in Computer Science, which up until recently was ISI-indexed.

The ISI people have recently dropped LNCS and other series from their main ISI-indexing, and created a “conference” version of ISI-indexing. For some, this can have a very strong effect on promotion and tenure.

I have somewhat mixed feelings about this. At one level, I am worried that the ISI-“page count” available for some of our fields has decreased greatly. This will make it harder for some of our subfields to grow and expand. On the other hand, conference volumes are just part of the proliferation of research outlets, and not ISI-indexing them seems appropriate given the sometimes quick level of review that some conferences provide. It is certainly true that the conferences provide reasonably thorough reviews and the rejection rate is high (70% or more rejected), but this still seems different than journals. Perhaps it is just me: as a member of a conference committee, I feel it is my responsibility to review papers somewhat farther from my core interests than I would for journal reviews. As such, I can’t provide the same insights for conferences that I do for journals.

Much of OR doesn’t have this problem. Most OR conferences are “free-for-alls” with no veneer of reviewing. This makes for large conferences of highly-variable quality. It is great for talking about not-fully-formed ideas, or interesting but not publishable results. I wonder if some of the competitive conferences will change in flavor now that the “carrot” of an ISI-indexed paper is not offered. At the very least, people should be working harder to follow up the conference with a journal publication, which seems a good outcome.

Not at INFORMS

I’m not at this year’s INFORMS meeting.  No, it is not because I am in a snit because it looks like Seattle is going to beat the attendance record Pittsburgh set last year (I predicted it, and predict that Washington will set a new record next year that will take a few years to break).  I’m not going because it is 18 hours of flights away from New Zealand, and I needed to cut back on my travel a bit.

So I won’t be live-blogging the conference.  Laura McLay of “Punk Rock Operations Research” will be there so look for her.  If there are any other OR bloggers at the conference, let me know so I can follow the conference vicariously.

Getting cheaper boats and ships

I am in Providence attending this year’s Constraint Programming conference. I’m on the executive and we have developed new bylaws, so instead of listening to all the talks, I am involved in discussions on the minutia of quorums and transition rules. Still, there is some time for the conference itself.

I just saw a terrific talk by Matt Ginsberg of the University of Oregon and On Time Systems, a firm specializing in scheduling optimization. One of the big things they do is shipyard optimization, and he described putting together a system for better scheduling the production of navy submarines (which are boats) and carriers (which are ships). While traditional scheduling involves trying to minimize the amount of time it takes to build something, this sort of scheduling is about minimizing costs (or so he thought). So his firm put together a nice system to minimize the cost of going through the tens of thousands of tasks that go into a boat or ship. If that was the end of the talk, it would have been a fine technical talk on an interesting topic. But he went further.

“Just because a schedule looks good doesn’t mean it is good” is a phrase I wish more people would use. Lots of schedules look good, but when you try to use them they fail for easy-to-see-in-retrospect reasons. One example of this is the highly optimized crew schedules used by airlines. Sure, they look good and they appear to save money, but they are fragile: disruptions can spread throughout the system. Matt brought up two important issues not covered by the “minimize cost” aspects of their schedules. The first is the brittleness seen in airline crew schedules: will delays in one task mess up more? The second is union buy-in. If the goal is to decrease costs, won’t unions naturally be against it?

The brittleness point is important. Indeed, a minimum cost schedule is brittle (though perhaps no more brittle than the schedule currently in place), though it saves about 10.4% on costs. But the methods Matt used can be adapted to make float (the amount any task can be delayed without affecting other tasks) into account. A task with too little float (perhaps just a few work shifts) is at risk of delaying the whole project. But you can combine these objectives: minimize cost and minimize number of tight tasks. It turns out that you can decrease the number of tight tasks by more than 90% (relative to the current schedule) and still save about 10.3% on costs (numbers approximate: I have to learn to take better notes!). So decreasing brittleness comes almost for free!

As for the unions, one fact about shipyards is that they often layoff and then rehire lots and lots of workers. The schedules Matt provides are much smoother in the way they use workers. Certainly far more workers would have consistent jobs under the schedules, and layoffs would not occur near as often.

Overall, the shipbuilders would save money, the unionized workers would have more consistent jobs, and the building process would be less susceptible to delays. What’s not to like?

Well, the firms building the ships are paid by the Navy on a cost-plus basis. The higher the cost, the higher the plus. So they have essentially no interest in saving our money. They like high costs! Next time you see your congressman or -woman, ask “What happened to the ARGOS project to improve ship-building operations? Wasn’t that supposed to save us a few billion dollars?”

While we wait for the companies to work more efficiently, On Time Systems has a scheduling game you can play.

Pecha-Kucha: the Solution to a Conference Problem

I am involved in a number of small (100 attendees or so) conference series: CPAI-OR, PATAT, MISTA, and a number of others. One problem all of these smaller conferences have is getting enough people to attend. Typically, they are competitive, so only accept a limited (30 or so) number of papers. This means we get 30 or so attendees naturally, and then have to struggle to attract more “non-speakers”. Many universities will not fund travel when no talk is given, so getting an audience can be a struggle.

Large conferences like INFORMS have a related problem: there are just not enough rooms for everyone. At the last INFORMS conference in Pittsburgh, we ran 55 parallel sessions and packed 4 talks into practically every 90 minute session. It looked like we might not have enough space. How could we let everyone in who wants to talk (INFORMS conferences are decidedly not competitive: the organization believes that everyone who wants a chance to talk should be able to talk)?

One common way of handling these constraints is poster sessions, where speakers print out a precis of their work, stick it on posterboards, and then stand around hoping someone will come talk to them. For some fields, this works well, but it rarely works in OR. Often the poster sessions are poorly attended or are of somewhat less status.

Wired magazine has an article on a solution to all this: Pecha Kucha. Pecha Kucha was “invented” in Tokyo for architects to show their stuff off. It has now taken off as a form of performance art.

Let us now bullet-point our praise for Mark Dytham and Astrid Klein, two Tokyo-based architects who have turned PowerPoint, that fixture of cubicle life, into both art form and competitive sport. Their innovation, dubbed pecha-kucha (Japanese for “chatter”), applies a simple set of rules to presentations: exactly 20 slides displayed for 20 seconds each. That’s it. Say what you need to say in six minutes and 40 seconds of exquisitely matched words and images and then sit the hell down. The result, in the hands of masters of the form, combines business meeting and poetry slam to transform corporate clich into surprisingly compelling beat-the-clock performance art.

Perfect! Let’s run a conference where every presentation abides by these rules. No more half-hour detailed run-through of proofs (which no-one in the audience is following), but 6 minutes 40 seconds of operations research performance art. Put six of them in an hour-long session, have 20 minutes afterwards for mingling and one-on-one informal questions, ring a bell and move on to the next session. Seven such sessions a day allows time for lunch and a big-shot giving a plenary. Small conferences have room for 120 presentations over 3 days. INFORMS could run with only 20 parallel sessions.

I think it would be a bit exhausting, but I have no doubt attendees would get more out of the conference. And the presentations would then be perfect for YouTube and other uses.

I see from the site that there is a Pecha Kucha event in Auckland: I will have to get over to it (and think about how my research best fits into twenty 20-second slides).

Conference reviews, in perspective

I am just back from Prague: after another 36 hour travel marathon, I think it will take a day or so for my brain to catch up with me!

While I was gone, Scott Aaronson, a graduating doctoral student in quantum computing, had a brilliant article on computer science conference reviewing. From the 1936 Foundations of Computer Science (FOCS) review process:

Dear Mr. Turing,

We regret to inform you that your submission
“On Computable Numbers, With an Application to the Entscheidungsproblem”
was not accepted to appear in FOCS 1936. The Program Committee received a record 4 submissions this year, many of them of high quality, and scheduling constraints unfortunately made it impossible to accept all of them.

The reviews would be a great satire of computer science reviews except they are far too close to the truth:

—————————————- review 1 —————————————-

seems like a trivial modification of godel’s result from STOC’31

—————————————- review 2 —————————————-

The author shows that Hilbert’s Entscheidungsproblem (given a mathematical statement, decide whether it admits a formal proof) is unsolvable by any finite means. While this seems like an important result, I have several concerns/criticisms:

1. The author defines a new “Turing machine” model for the specific purpose of proving his result. This model was not defined in any previous papers; thus, the motivation is unclear.

See Scott’s post for the rest of this and for the other reviews. Many OR conferences are not reviewed (IFORS, EURO, and IFORS conferences accept practically anything submitted on time), but there are some that I am involved with (like CP, CPAIOR, MISTA, and PATAT) that have a review process, and it is clear that the review processes are very hit-and-miss.

With the exception of Scott’s ill-tempered diatribe against babies at conferences (perhaps as forty-something father of three-year-old, I am a little more sympathetic to the pressures of combining parenthood and academia), the entries in Scott’s blog are something I look forward to tremendously: he is opinionated, intelligent, amusing, and self-deprecating by turns, and generally teaches me something when I read him. He is about to join the faculty at MIT: lucky MIT!

IFORS Distinguished Lecturer

I am at the closing session of EURO. This year’s conference was huge with more than 2000 participants. I did attend a good amount of the conference, though Prague has its own attractions.

EURO (along with INFORMS, ALIO, and APORS) have a plenary given by the IFORS Distinguished Lecturer (I chair the committee that recommends the selection to the President of IFORS). This conference’s IDL is Bob Bixby, from Rice University and ILOG. Elise del Rosario introduced Bob, and here are some quotes from her introduction:

The IFORS Distinguished Lecturer for this conference is
Dr. Robert Bixby, an outstanding researcher, innovator, and business
leader. Dr. Bixby received his Ph.D. in the early 1970s from Cornell
University, and looked like he would have a long and distinguished
career in research on combinatorial structures. A sharp turn in the
1980s led him to develop CPLEX, an outstanding large-scale linear
program optimizer. CPLEX led to CPLEX Optimization, Inc, marketing
algorithms for linear and mixed-integer programming. CPLEX was sold
to ILOG in 1997, a company in which Dr. Bixby has served a number of
roles and where he is currently Chief Science Officer.

Dr. Bixby has combined his business success with continued research
success. He, along with his colleagues David Applegate, Vasek
Chvatal, and Bill Cook have just published a book entitled “The
Traveling Salesman Problem: A computational study” that sum up their
20 years of work on solving large scale traveling salesman problems,
culminating the solution of TSPs with tens of thousands of cities.

Dr. Bixby has held a number of leadership roles in our field,
including the presidency of the Mathematical Programming Society, and
has received a number of awards for this work, including the
Beale-Orchard-Hays Prize for excellence in computational mathematical
programming.

The title of his presentation was “From Planning to Operations: the Devil’s in the Details”.  Unfortunately, I had to run out for a plane (for my 42 hour return to New Zealand) so I only got to see the first part, where he reviewed progress in linear programming and integer programming.  A few striking points:

  1. The speed improvement in linear programming from 1996-2004 is a factor of about 5.3 million (3600 due to algorithms and 1300 due to computing).
  2. Not much improvement in linear programming the last few years:  only computer speed improvements.
  3. (Mixed) integer programming is about 13 times fast over the same period.
  4. The next version of CPLEX provides another decrease in time required (by a factor of .6)
  5. The next version of CPLEX is much better at finding feasible solutions to MIP (a test set of about 1300 instances) went from 250 with no solution found in 100 seconds in CPLEX 10 to about 120 in the next version.

The main point of the rest of the talk is that MIP and other optimization models are going to be used increasingly for day-to-day decisions (not as an aid to decision making, but making the decisions directly) and that puts lots of pressure on our models and data.