Maintenance

Short notice: The site was just migrated to a new server and finally gets to use PHP 5 and MySQL 5.1. This is nice, but due to some subtle compatibility issues, there are some minor problems around. I’ll fix them soon enough, in the meantime, please don’t be surprised about them, I do know about it.

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December 28th, 2009 at 04:09 am 0 Comments

Bildungsstreik - Impressions

Today was the main day of the Bildungsstreik protests, and I happened to have some time for it, so I thought I’d post some pictures.

The event was shifted from the original location, the Elisenbrunnen, to the Theaterplatz because someone forgot to think about a market. What surprised me was the sheer number of people. The call did not resonate strongly (as far as I could tell) within the RWTH, but the AStA (the official executive of the student representation body) of the FH completely supported it. Police estimates talk about 2500 people, and that does not feel fully unrealistic to me.

Many protest signs were done in the style of comic speech bubbles, but there weren’t a lot of them in total.

About 13:30 the demonstration started their trek through Aachen’s city centre.

The leaders.

I’m not quite certain whether this sign (which asks for a revolution) was meant seriously, or whether I just couldn’t read it properly, but it did seem rather odd to me. But then, left-wing parties were very quick to embrace this all…

Of all the signs protesting against the german tuition fees, this one (calling for rich parents) and it’s variations were my favorite.

My absolute favorite protest sign. And people who like photographers.

The rear end. Not that interesting, but someone has to take that picture. For bus enthusiasts, notice the doubly articulated bus in the background.

I had to leave about then, for a lecture (yes, I’m not on strike, I’m just observing), but I did get back in time for the final demo in front of the cathedral.

There wasn’t much New in terms of content. However, the occupation of Fo3 did end this morning, as the university fulfilled the request of the protesters to give them a room for debating once a wekk.

In other news, there’s also an occupation in Brunswick. Sorry that I can’t permalink.

Tags: planetrwth

November 17th, 2009 at 10:28 pm 0 Comments

Besetzung oder Kaffeekränzchen

Seit gestern hat auch die RWTH Aachen einen besetzten Hörsaal wo Leute für bessere Studienbedingungen demonstrieren, also dachte ich mir, ich gehe mal hin und dokumentiere, was ich dort so sehe.

Außerhalb des Hörsaals ist praktisch nichts los, außer dem Banner natürlich. Der tatsächliche Bildungsstreik findet am 17. November statt, in Aachen mit Kundgebung um 13:00 am Elisenbrunnen, wenn ich das richtig mitbekommen hab. Mal schauen, ob ich davon auch berichten werde. Erst mal was anderes aber.

Als Hörsaal für die Besetzung hat man sich den Fo3, einen der vielen im Kármánn-Auditorium, ausgesucht. Das halte ich persönlich fü eine schlechte Wahl, denn der Hörsaal ist recht klein und seine Besetzung stört nur wenige Leute.

Quelle: Hörsaalübersicht der RWTH Aachen für Bereich Mitte

Der Hintergrund davon ist anscheinend, dass die Fachschaft 7/I eine außerordentliche Vollversammlung angemeldet hatte und dafür diesen Hörsaal erhielt und dann einfach dort blieb. Das macht zwar Sinn, aber trotzdem wirkt es etwas komisch, wenn man alle 20.000 Studenten der RWTH aufruft, sich in solch eine Sardinenbüchse zu zwängen.

Und so sieht das ganze dann in echt aus:

Als ich da war war nichts los, mit Ausnahme von einigen Leuten (wie mir) die immer mal wieder hineinschauten, sich wunderten und dann wieder gingen. Laut aktuellen Nachrichten auf Twitter wurde in dem Saal bevor ich da war und nachdem ich wieder gegangen bin viel wichtige Arbeit und Diskussionen geführt, da hatte ich wohl gerade Pech.

Was soll man nun davon halten? Ich halte davon relativ wenig. Grundideen wie die Abschaffung von Studiengebühren, bessere Studienorganisation, weniger überfüllte Hörsäle und mehr Stipendien, dagegen habe ich nichts einzuwenden. Aber ist das beste Mittel dafür wirklich, die anderen Kommilitonen zu nerven? Es gibt tatsächlich Leute, die dann noch darauf kommen, sich darüber zu beschweren, dass manche Studenten in dem Hörsaal lieber etwas lernen würden. Ist überhaupt Lehre nicht allgemein besser als gar keine Lehre?

Dass die Hochschulleitung der RWTH das Problem kennt sollte ja eigentlich auch bekannt sein. Betrachten wir doch das Beispiel der überfüllten Hörsäle mal: Die Baustelle hinterm Super-C, das werden neue Hörsäle, und es ging gerade ein Architekturwettbewerb für ein neues Hörsaalzentrum in unmittelbarer Nähe zum Audimax zu Ende. Das Problem ist Geld, welches vom Land kommt, und dass heißt im Zweifelsfall in Düsseldorf protestieren.

Aber selbst, wenn man meint, man hätte am meisten Erfolg die Lehre zu verbessern in dem man sie gewaltig stört: Mir fällt es schwer, eine so furchtbar kleine Aktion wie diese hier (im Vergleich zur Größe der Uni) ernst nehmen zu nehmen.

Update

In den Kommentaren wurde behauptet, dass keine Veranstaltungen durch das sogenannte Dauerplenum ausgefallen sind. Allerdings gibt es Berichte von Veranstaltungen, die tatsächlich ausgefallen sind, und auch die Kármán-Hochschulzeitung berichet von einer Höhere-Mathematik-Übung, die so nicht statt finden konnte und deren Teilnehmer und Dozenten statt dessen zu einer Debatte eingeladen wurden. Das betrachte ich persönlich auch als eine Störung der Lehre.

Tags: planetrwth

November 13th, 2009 at 12:21 pm 5 Comments

Single Instruction, Multiple Data

A quite interesting technology for video games is SIMD, spelled out Single Instruction Multiple Data, meaning that one computer instruction processes more than one value. This may be best illustrated by an example. A normal piece of code that every game needs will look vaguely like this:

positionX += time * velocityX;
positionY += time * velocityY;
positionZ += time * velocityZ;

The += means increase the value to the left by the value on the right. So we have six calculations, consisting of three additions and three multiplications, and we can approximately say that they take six units of time. With SIMD, though, the pseudocode looks as follows:

position += toVector(time) * velocity

Here, the two variables are both vectors consisting of multiple components (by default four). Not counting the toVector-method (which can often be removed by some means) we are down to only two operations. The result is still the same, but the additions and multiplications are now happening in parallel.

Different versions of SIMD are known as Altivec on PowerPC CPUs, various versions of SSE on Intel and, interestingly, NEON on ARM CPUs. ARM CPUs are not as well known as those by Intel, but are used for just about everything, including as the CPUs in iPhones and iPod touches. The first two generations of either (up the iPhone 3G) have a so-called ARMv6 CPU, without NEON, but the iPhone 3GS and the third-generation iPod touch both have an ARMv7 “Cortex” CPU which does feature this SIMD extension.

Apple doesn’t acknowledge this anywhere, neither for users nor for developers, but if you follow the instructions on http://monkeystylegames.com/?p=82 then it is possible to write NEON code that works on an iPhone. If you also happen to have a non-NEON-version (as I already did for my rail simulator), then you can create code for both plain ARMv6 and the extensions of the ARMv7 and get, as in the days of the PowerPC to Intel transition, an universal binary that’ll run on both. I did test that with my railroad simulator and it works

Whether I’ll actually use that, though, is a different question. It does make the application slightly larger (about 80 kB at the moment, but I plan on writing more code, increasing this difference), and I have to test on both. Since I don’t actually plan to develop two versions of the game at the moment, though, I have no actual advantage, because the iPhone 3GS is much faster than an older device without such tricks already. Finally, it doesn’t really matter either: Most of the performance-critical work my game does is drawing things, which is of course done by the completely separate GPU. The parts that I did optimize with NEON never were important for the performance in any way. In the end, it is a nice research project for me, but not truly useful.

Tags: software

October 18th, 2009 at 07:17 pm 0 Comments

The Switches are Lined Up

University is fully active again, so my progress is now somewhat slower and will remain so. Still, I was able to implement a number of nice (as in essential) features, which means it’s time for a new Video!

Making this video and getting it to work in all browsers was a great deal more involved than I had thought, so if it happens to fail to work, please tell me! As before, it was taken from the simulator only because I don’t know how to make a good video from the iPhone, but it does run there.

So what are the changes precisely?

• Driving in general works, including around curves (which turned out to be a great deal more difficult than you’d expect). There’s no physics at all behind it yet, though.
• There are also fully functional switches, including signs indicating their directions.
• On the graphics side, there is now a real sky (using a skybox) instead of the old gray.
• In addition to that, I’ve changed texturing: The color is now combined from a large texture without much detail for the general colors, and a small, highly detailed but extremely often repeated texture modifying it, to give the impression of far more detail than I have or want (obviously not my idea, lots of games that render large landscapes have that).

I’m pretty content now, but obviously still a long way from done.

Tags: software

October 17th, 2009 at 10:16 pm 4 Comments