Cycle-maximal triangle-free graphs

Thursday 30 October 2014, 12:16

In January of 2011, I had recently arrived at the University of Manitoba to work as a postdoc with Stephane Durocher. One of the first things he asked me to do was find out how many cycles there are in an n-dimensional hypercube graph, for general n. At the time, he and I both assumed that that meant spending maybe half an hour in the library looking up the answer.

Since then it's been more than three years; thousands of lines of computer code and months of CPU time; we added two more co-authors; we didn't solve the original problem, and didn't completely solve the other problem that we ended up working on, either; but here's a journal paper, anyway, and I think it's pretty interesting. The official definitive version will be free to access until mid-December and then will go behind Elsevier's paywall; the authors' accepted manuscript on arXiv is permanently accessible.

Read the paper if you're interested in the math details; in this entry I'm going to try to tell the story behind the paper, in relatively non-mathematical terms. I'm hoping it'll be of interest to my Web log readers and give you some idea, because I often get asked this, of what I actually do at work.

Days since last Biblical plague: 0

Wednesday 15 October 2014, 11:49

Every time I think I've seen it all with regard to Danish excuses, this place surprises me. Today's excuse is tzaraath.

False negative

Monday 6 October 2014, 12:26

I. Fukurou

Bank Account Man

Saturday 4 October 2014, 13:23

I've been in Denmark just over a month, and I'm pretty stressed. This update is going to be somewhat disconnected. You can get some idea of what my experience has been like by watching the famous Bank Account Man commercial.

The Danish excuse list

Thursday 4 September 2014, 12:35

Denmark, being part of Europe, has a great deal of bureaucracy and many rules. However, the Danes are not really rule-followers. That at least is their reputation among people from other Nordic countries and I can see why. This is a list of excuses I've heard from Danish people, mostly government bureaucrats. All are genuine, though some have been paraphrased from their more complicated original forms or to remove personal information. The list will be periodically updated.

A few days in Denmark

Thursday 4 September 2014, 12:32

As I start writing this, it's Thursday aboput 2pm in Copenhagen, and I am in the waiting room at International House Copenhagen, waiting to apply for a Central Persons Register (CPR) number. I have been in Denmark since Monday morning.

Heading for Denmark

Thursday 28 August 2014, 18:59

I don't think I have officially mentioned this here on my Web log yet, but here it is: I am moving to Denmark to work as a postdoc in the Scaleable Similarity Search project at the IT University of Copenhagen. This is a one-year temporary position with a possible renewal for a second year.

As I type this, I am in my apartment in Winnipeg, sitting on top of my modular synthesizer in its Pelican case because that is the closest thing to furniture that hasn't been taken away by either the movers or Goodwill.

Tsukurimashou 0.9

Sunday 17 August 2014, 16:26

I have just posted Tsukurimashou 0.9, the latest version of my Japanese-language font project. After almost a year in development since the last version, this one contains 1754 kanji, including all through Grade Four and 100 from Grade Five (a little more than half of the 185 assigned to that grade). This version also includes extensive infrastructure changes, most notably a bundled interpreter for the FontForge native scripting language, intended to provide insurance of future support as mainline FontForge moves further and further away from that language.

The future of Tsukurimashou development may be tangled, as my commitments and priorities change with my upcoming move to Denmark. This 0.9 release was produced in a bit of a rush to get something out the door before I pack up my computer for shipment. I don't know when I will next get a change to work on it more, but that will be at least two months from now. You can do your bit to support continued work on Tsukurimashou by building it, using it, and above all by writing about it. What the project needs most of all is attention.

The Apollo moon landings were fake

Sunday 20 July 2014, 20:20

The Apollo moon landings were fake.

I don't mean that they did not occur - it was before I was born, but it seems clear that men did at one time walk on the Moon. There are too many independent confirmations of that for it to be in any reasonable doubt. However, the Apollo Moon landings occurred under false pretences. The story told about the factual events, both at the time and now, was and is a dishonest story, carefully constructed to further the goals of the US government and certain other powerful forces.

A read-only root for Slackware ARM

Sunday 20 April 2014, 16:52

In my last posting I described getting Slackware ARM to boot headless on the ODROID U3 single-board computer, and I said that the next step would be to try to make it handle ungraceful shutdown (power loss) better. I plan to put this board into a Eurorack synthesizer module with no easy access to the microHDMI monitor connection, and SSH over the Ethernet connection as the only access to administrative functions. If, when the power is pulled on it, it comes up on next boot in a state where it requires console interaction to do a step like checking the filesystem before it will accept SSH connections, that is a disaster; I'd have to disassemble the whole module to extract the microSDMI card and replace the OS image. To be useful, the ODROID must be guaranteed or almost guaranteed to survive a power drop and come up SSH-able on the next boot. Ideally, I want pulling the plug on it with no shutdown formalities to be the normal expected way of shutting it down too, not just an error condition from which it can recover. A good journalling filesystem can increase the chance of recovery from occasional accidental power drops, but I think the only way to make routine non-accidental power drops safe is to keep the filesystem mounted read-only - which might be desirable anyway, to reduce wear on the flash memory and prevent its being corrupted by other kinds of accidents. So this posting is about my experiences configuring Slackware ARM on the ODROID U3 to keep its root filesystem read-only.