Martin Geisler Online

Well, I’ve done various stuff — Jérémy and I have made the first third of the mandatory assignment in dADS. It’s actually an interesting assignment: we have to design an algorithm that will find the maximum matching in a bipartite graph. The first thing we had to do, was to prove that an algorithm written in pseudo code was valid and correct. The algorithm uses a transition system to color the nodes in the graph, so we had to prove a couple of things about that too.

This week we have to design efficient datastructures that will allow us to color the graph using the transition system in time O(m+n) where m is the number of edges in the graph and n in the total number of vertexes. We will use these datastructures in the final third of the assignment where we have to implement the algorithm in Java. Exciting stuff…

I plan to publish the report here at gimpster.com when we’re finished, so stay tuned. (It’s in Danish, so don’t be too excited if you cannot read that :-)

Manitou and I met yesterday and made a couple of Java assignments which were overdue. We implemented a Heap using the Locator pattern and a Vocabulary using a Trie — it was a very good learning-experience to actually implement these ADTs instead of just talking about them.

We also talked about other things — we met at 14:00 and went home again at 23:30 so there was plenty of time :-) One of the things we discussed extensively was, that he had a book, which said, that the set of all subsets of the empty set, which is denoted 2^∅, is {∅, {∅}}. I don’t believe that this is true — the only subset of ∅ is ∅ itself, so I would say that 2^∅ = {∅}. If 2^∅ = {∅, {∅}}, then that would imply, that ∅ ∈ ∅ which is clearly false, as the empty set is empty. We’ll ask Jørgen Hoffman-Jørgensen about it — he should know as he’s our teacher in Probablility Theory.

It’s Easter and the holidays are near. The holiday starts this Wednesday and lasts for about a week. So I’ll have to be at the University both Monday and Tuesday, which is a little unfair, as I know that others have already started their holidays. Oh, well — at least I’m going to get some more of that sacred thing called spare time. I’ll be in Aalborg the first couple of days, and then back in Århus a day or two before we start again.

For those of you who don’t know this: it only takes 15 minutes to make a cake, when you use one of those almost-done mixtures you can buy in supermarkets. And the best this is, that the cake tastes really good — you might be able to make a better cake by making it yourself from the bottom, but these cakes taste almost just as good, and you’ll only need to invest 15 minutes of your expensive time.

I made a chocolate cake two weeks ago. And since I’m living by myself, I could just eat it whenever I wanted — it’s really cool to be able to say to one self: “Hmm, I wonder if I have anything exciting to eat… Ahh — there’s still some cake left! I’ll just have a nice big piece of that.” I can actually smell my new cake right now — it should be done in about 10 minutes, enjoy your cakes :-)

I’m back from LinuxForum — and to put it short: it wasn’t as good as last year. When Cookie and I arrived at Copenhagen Friday afternoon we started by going to our hostel (I didn’t know that there existed such a word, but a “hostel” is a cheap hotel — you get a bed and that’s about it). After we had checked in, we headed for down-town Copenhagen. It was surprisingly easy to find the right busses and trains, everything went according to the plan Cookie had made from .

We then went to the Tycho Brahe Planetarium where we saw an Omnimaxfilm called Shackleton’s Voyage of Endurance. It was a really good film about how Shackleton managed to save all his men, after his ship was crushed by the ice in Antarctica.

LinuxForum was held the next day. It started out great with Eric S. Raymond who told about the hacker culture. Then there was a speech about Linux mainframe which was OK. But the other speeches were quite boring: they used 45 minutes to talk about something which you could read up on in 10 minutes. So we didn’t learn anything new, they just repeated what we already knew.

It could be, that Cookie and I simply went to the wrong speeches. After the first two speeches, the rest were given in parallel, so you had to choose between them. And it was difficult to judge the speeches beforehand. But we’ll be looking more carefully at the program next year, before we decide if we want to go again.