Could it be worse?

Health problems. Lost mobile phone SIM card. Flight delay of 24 hours. Notebook got a virus and cannot boot. Fuse in power adaptor of notebook blown. Then the adaptor itself. I don't even know where to start blogging all these. Maybe not until I get some reasonably-working computers. I mean, this one I am using in the office is populated with 7 viruses and has some other strange problems...

terrorists in arithmetic progression

Forget about the years for the moment:

30/6 Glasgow airport
7/7 London (tube and bus)
14/7 ?
21/7 London (failed)

What happens in 14/7? Nothing important except that I will be flying...

Scaling down the marks?

For the other modules I gave in the past, the problem of exam marking is to give out as much marks as possible. This time however, the cryptography module has an average that is so so high and we almost have to scale it down. Although, at the end, it was not done. I really don't know why the marks are so high. (Can I just say my teaching is very good?) I don't think the exam paper is too simple. If the same paper is given to the batch of students last year, I'm pretty sure the situation would be entirely different...

annoying project reports

I was reading the pile of project reports, and I'm getting more and more annoyed about their English. Perhaps as a non-native speaker myself I shouldn't complain, but they are just... almost disgusting. Unlike many HK students who write things overly formally, sometimes to the point of being ridiculous, the most common situation here is they write in a very chatty way - not complete sentences, going on and on without even a comma when it should have 3 full stops, wrong spellings of similarly-sounding words, etc. These are the relatively better ones. The worst ones are simply incomprehensible. I believe many of them are, although not ethnic-British, born and educated in UK. How they survived the exam system I don't really understand. Does GCSE test any writing skills?

Speaking of the projects, some of them are just way too weak. It is as if the students only spent half a day doing it. They have "successfully" implemented things like a seat booking system for a football stadium allowing you to book the same seat (for the same match) an infinite number of times, or a webshots-like photo sharing system where the owner/uploader is the only person who can view the photos, etc. In fact, the front webpage of the project is a template with words like "put your company name here" and "this is some dummy text"...

What you can do in ten months

We have been experiencing a severe shortage of secretarial support for some time. As if that's not enough, two of the secretaries somehow coordinated themselves into getting pregnant at roughly the same time. So they are off for ten months of maternity leave. Ten months!

Chicken

The infamous chicken paper now comes with a talk...

MSN

Ok, I finally gave up my insistence on not using msn. Perhaps I've been asked just once too often about this. In case you care to know, the email is a gmail account. The rest should be pretty obvious.

new home

This new place appears to be better than I thought. However, as regular readers of this blog will know, I am quite negative and only look at bad things. The main problem is with the shower heater. Ok it doesn't "burn" the fuse this time (I mean, hasn't). But the product of rate of water flow and the temperature of water is a constant, which is not a problem by itself, but this constant is just too small...

moved

So I finished moving house, and came off the days without Internet at home a bit sooner than I thought!

Snooker championship 2007

Time runs so quickly and it is another snooker championship already. Not unexpectedly, Marco Fu loses pretty quickly. Whenever you have any expectations on him, he will not perform. In fact, his mistakes are sometimes so embarassing to watch.

It is the second time that I watched a O'Sullivan-Ding match. This Ding Jun-hui simply doesn't look like wanting to win. Whenever a few frames behind, he will behave like this so that, like some school students, he can subconsciously give himself the excuse "it's not my standard too low, it's only I choose not to perform".

to view and be viewed

Yesterday a (continental-European?) couple viewed my flat. I don't know whether it is obviously too good or obviously too bad, but they spent less than 2 minutes here.

Today I viewed another flat, although I'm supposed to have committed to the one I mentioned last time. It is a brand new flat, the interior of which is furnished to the highest standards. What's more, the rent is exactly the same as my current one. On the down side, it is immediately next to a construction site, and the building (or group of buildings) itself is not completely finished, so you feel somewhat living in a construction site. But other people are apparently rather happy with it. This is also a bit too far from the university, which means extra travel costs. If not for this I would be very happy to take this...

Moving house?

My current tenancy contract is about to expire and I want to find some cheaper place to live. (Actually, the real problem is this. There are still some unexplained ways for them to possibly get in. And rumour is that they have the same problem two years before. Another rumour is that there was even wasps...) So I viewed a couple of flats.

The first one I viewed was a complete joke.

I was advised long ago that "the other side" of London road is not as safe. Wondering why just the other side makes a difference, I arrived and noticed that, just a few blocks off the road, it clearly is a poorer part of the city.

When I found the house, the first thing to notice is that the house next door had its windows smashed. For the flat itself, there was still someone living and was in a mess, but let's forget about it. When I walked into the bathroom the biggest surprise came: one of the walls was only halfly built. The other side of the wall opened to the next flat, which was then visible from outside the house. The landlord said this is "renovation" and "will be finished within days". Then why don't you just wait a few more days before letting people view it? It's a complete waste of my time. And the most bizarre thing is that, as mentioned above, there was still someone staying there, although he was going to leave in a few days... I just wondered, how on earth does he use the toilet these days?

The second flat I viewed is much more reasonable. Its on the busiest road, near the train station, and directly above a restaurant, and should be very noisy. Other than this, it looks a reasonable place, but certainly not as good as the one I am living. The furniture etc. are not as complete/good and I will need to spend some money. I am actually looking for something with smaller area but similar quality (comparing with my current one), but it looks like all available out there is similar area but poorer quality.

I have some psychological struggle to move to a clearly worse place. I need to keep on reminding myself, "imagine a hundred wasps all burst into your flat through the ceiling!"...

LSD 2007

So I went to London again, this time for the LSD 2007...

(1) Obviously, you can't expect stringology people to be interested in online scheduling algorithms. Not much happened in the talk.

(2) It was announced that I made an important discovery. No, I didn't prove any important theorems. It was only about "discovering" a new toilet...

(3) We went to Chinatown again. Most stuff there are more expensive than those in here (the only problem here is that brands and choices are rather limited), but it turns out that instant noodles are cheaper.

Matchings, algorithms and problems

Some time ago I heard a presentation of a final year project. Somehow the student believed the project involves stable matchings. It is good that they attempt these things, and at first sight it appears to make sense. But when you think about it for a bit more you will realize that it actually does not make any sense to use stable matching in that problem. I won't go into the details here, but basically, the input arrives online rather than a batch, and only perhaps one side has preferences (and even that is arguable).

But this is not the point I want to make. The student did not understand the difference between a problem and the algorithms that solve the problem. His presentation showed a stable matching algorithm, but did not say anything about stable matching itself. So I asked, "So what is stable matching?" Then he showed that slide with the algorithm and is about to explain, when I interrupted and asked the matching itself, not the algorithm. He couldn't answer, and at the end said "a matching that everyone is happy". Other students there, even though they also don't know what a stable matching is, can at least appreciate that this answer cannot be correct.

And of course, he is not the only student with similar problems. Last year I had a project student whose project involve matching papers to referees, and the problem is to find a maximum matching. He just proceeded directly to invent some algorithm to find a "large" matching. I attempted to explain but he couldn't understand that there is a "maximum" matching independent of what algorithm you might what to use.

More recently, a student is doing a project on timetabling. I have nothing to do with his project, but anyway he came to ask me how to find the "optimal solution". I asked, "So what is the optimal solution you want to find?" and he wanted me to tell him what is the optimal solution. He has no idea of different "objective functions".

And I wonder, is all these because of me teaching too badly, or are they simply impossible to be understood by some people?

Almost an issue 3

Within less than 6 months I lost it again! Except this time I discover it within 10 minutes, so rushing back to the supermarket to get it back...

I will now seriously consider not to use it in supermarkets, at least not in Sainsbury's.

Algorithms exam

At St. Valentine's day we had a dreadful meeting about the arbitrary manipulation of some numbers that are important to students (many of whom I don't know) in modules (many of which I don't care). I think it is now time to say something about the algorithms exam paper.

The exam paper has 6 questions and students answer 4. (I don't have any say about this.)

(1) I think I did an ok job of getting an average mark close to whatever number they want. You can easily estimate marks of students on different questions: if you want them to know how to answer, you must give them the exact same question beforehand, with only different numbers. This is the only way they know how to do something. Changing anything else would result in a very low mark.

(2) I included several straightforward (i.e. non-tricky) true/false questions, which are answered satisfactorily. (Never do tricky questions: the correct rate would be far lower than 50%).

(3) You might think that questions asking for simple counterexamples are easy, but they are not. I think this holds true for HK students as well.

(4) I believe no students can ever understand what "lower bound" means. Majority thinks "If the fastest known algorithm of a problem runs in O(n^2) time then the problem has a lower bound of Omega(n^2)" is a correct statement.

(5) There is only one dynamic programming question that you can expect people to do it correctly (and hence I put it in the exam paper) - working out longest common subsequences. They are fairly competent in filling in the tables, perhaps without knowing what they are actually doing.

(6) The divide and conquer question is a "difficult" one and as expected very few people do it. In an earlier assignment they did a question which has similar flavor - the standard maximum-sum contiguous subarray problem - and almost no one can get it correct. In fact, many do not even attempt to do it. It looks like if they decide that a question is difficult, they don't even bother to plagiarize - just leave it blank. I must say that I don't quite understand why they consider this very difficult, as I think this is a rather "natural" D&C problem - even when I first saw it in my first DAA assignment. Having said that, interestingly, a few actually accidentally discovered the linear-time algorithm.

LAW 2007

I went to the London Algorithmic Workshop, held at King's College London a few days ago. The main purpose is to see people, and to have some feeling of being in a city. (I don't expect to understand things like counting runs in a string using automata and such; although there is a talk about my ex-boss and his student's previous work.)

For all sorts of reasons, the cost of going there had increased considerably from the original estimate.

One thing is that I ended up staying at a hotel. Finding a cheap hotel in central London is like 買大細, for you never know how bad it can be. There are always terrible comments on the web for whatever hotel you pick. At the end, I picked one which seem to have not-too-bad comments. When I arrived I was relieved - it was very small as expected, but tidy and clean. From outside, the room is like a storage room or so at a turn of the stairs, but as long as you shut yourself inside it feels alright. There is no toilet/bathroom inside - have to use the shared ones outside. Apparently, this is the default for cheap hotels.

The return trip coincided with the heaviest snow of UK in 10 years (or something like that). You look out of the train window and it is white everywhere. But while the weather was bad enough, the train was very accurately on time.

Gaim Internet messenger

On the school linux computer I am using Gaim as the ICQ client (I don't have much choices). Somehow it doesn't look like they can block people not in your contact list. And so every day I receive dozens of authorization requests or even direct messages from Russians... and also, HK people. And this does not happen with my Windows ICQ (which is a very, very old version). I think no one uses ICQ anymore these days and perhaps they connect through other protocols when I use gaim...

Chinese food at co-op

I don't really know when these all started but the co-op at the student union here start selling many Chinese food, including all varieties of instant noodles, vitasoy milk, and even 王老吉. I suspect this might be something one-off as I don't think the Chinese student population here is large enough to support it...

(PS. I know, I haven't blogged for some time. But I promise some interesting stuff are coming. Like a detailed analysis of the course evaluation. Only that it takes some time...)

Christmas holiday

Alright, I was back in HK once again. Somewhat too frequent is it, when there is no particular reason to go back...

At Heathrow, it is very fortunate that the plane could actually take off with all the fog. I looked out the window at the airport, saw a plane and couldn't saw the next one. Other than the fact that they had no personal TV, I was quite happy with the airline.

In HK I went to a hospital to visit someone. Also I witnessed the last day of Hardee's. I should say that I'm not a big fan of it. However apparently quite some people do, and lots of people were gathering inside or taking photos.

And about the earthquake, I didn't sense anything at all. At that time I was probably staring at a bunch of equations...

Finally. It was not 5am or so at Heathrow, but still there was absolutely no one whatsoever in the Customs, again. Next time I will bring some "white powder"...