“Machinenraum? Oh, ja, einen moment bitte, simon?” (war wohl doch wer anders)

“ah.. ein salzstangerl hmm nein, doch eine karotte” (nach 24h durch arbeiten).

“Gibt es einen Zylinder? oder was gibt es sonst noch? einen torus? einen teapot?”

“Das sind dann 16 Marina-steps”

“ Maaaaa Popcorn!”

and this one is for marlene:
“Mit lachgummi, mit lachgummi, da haben wir rießen spaß!”

If anybody else has some good quotes (stefan, plz!!!), please post them here, we can omit names, most of us will remember who it was anyhow.

Simon and I just finished our project for the “Lange Nacht der Forschung” a.k.a “European Researchers Night”. While it was quite exhausting during the last week (~75 workhours from monday – friday) the results where quite satisfying. Thank you to everybody who contributed!

We worked together with quite a team of students from the JKU and Kunstuni on a space game where you had to remove trash from areas to enable the launch of new satellites. The input devices were designed and implemented by the Interface Cultures and consisted of 3 independent controls:

• a turntable-style device for controlling the yaw of your ship and a one-hand, one-axis controller for vertical movement
• a mounted gun that you could turn up, down, left and right to aim at trash. It had a trigger to start the grabbing process
• a bicycle that controlled the forward/backward movement of the ship. This was mostly designed for parents

The fun part of the story was that since you had to collaborate with the 2 other players, so you can imagine it was quite noisy. To bad that the application wasn’t very stable and we had to restart quite often, especially when kids where on the bike and got rid of all the left-over energy they had from the day, resulting in space ships racing around like crazy and crashing into all satellites causing mayhem in our Application, inVRs and probably also ODE (note, ODE doesn’t like fast moving objects, and cylinders .

So, once more, thanks to all contributers that they remained calm even during the crunch time and the final sessions.

I want the the library to connect to a daemon on a port through a connect command which can later disconnect and reconnect to a different host as well. Not that we utterly need it, but it’s always nice if it’s there. So, the thread starts without having a connected socket and waits on a condition for socket to be created by the connect() member function. so, at the beginning of the threads processing loop it locks the mutex and enters a condition.wait(mutex) until the socket is valid. The connect method on the other hand, locks the mutex, creates the socket, unlocks the mutex again and notifies the condition variable. This is afaik the correct pattern to do this, and it works great. There is only one major problem: When you have a thread as a member variable, you better be sure that you have it listed AFTER the mutex (and possible also the condition var) in the class.

Otherwise the thread is created in the constructor and it’s run function immediatly starts running into the condition variable, which waits on a uninitialized mutex (jup, uninitialized). The mutex is uninitialized, because it is declared AFTER the thread variable which is constructed first. BAM. Result: the condition locks the mutex and after that the mutex is constructed in the inializer list (and probably reset). now the connect method does a notifiy via the condition variable (which sits ontop of the mutex) and does not find any waiting threads, even tough the spawned thread is hanging in a system wait somewhere. It won’t ever be notified. Lost. Gone.

All of this only because I declared the thread variable before the mutex / condition variables. nice, huh?. Note that with boost thread being moveable now, I wouldn’t create the thread in the constructor anymore. I’d have a start method which creates a new thread and moves it to the local member variable.

So, rule #1 check your member initialization order when using boost::threads!

So what makes Erlang a concurrent programming language? I first tought that the langauge itself was designed in a way so that it was easy for the compiler to parallelize things because of const-correctness etc. etc. Well, as it turned out, Erlang is not able to do this. Erlang is even better.

1. Erlang makes it easy to use multiple processes within a program. It makes it easy to send and receive messages between processes. Not that Erlang calls them processes. Processes do not share memory. Side-note: there are some tricks you can use to share memory using ETS tables, but you better know what you are doing!
2. Erlang’s runtime system makes process spawning and message passing efficient. On process spawning there are some numbers in Joe Armstrong’s book stating that on his 2.4 Ghz Celeron notebook with 512MiB of memory and Ubuntu installed it takes 3.5 microseconds of CPU time (micro not milli) to spawn a process when spawning 20.000 processes and 9.2 microseconds of elapsed wall-clock time.
3. When programming Erlang you design your methods to be side-effect free, meaning that multiple calls to the same function don’t influence each other (there’s a better definition here). Now because you do this (yes you do!) you can turn a loop that does some expensive operation for every member of a list into a loop that spawns a process for every member of a list and collect the result. Not that this can (and is) encapsulated into a function in the Erlang modules. You don’t have to do any process spawning, message sending, receiving, collecting, etc. All you have to do is to use a pmap (parallel map) instead of map. Side-note: map applies a function to every member of a list.
4. Because Erlang already has built-in mechanism for sending and receiving messages between processes they extended it to allow processes to be on different Erlang nodes (different running instances of the Erlang runtime system). This includes Erlang nodes being on different machines being connected trough a network. Do you get the point ? Distributed programming made easy!
   

What do we do about shared resources? Easy. We write a server that makes sure access to the resource is sequential and atomic. A server is a process that receives messages from other processes, performs and operation and returns the result. Simple enough. I recommend you start reading up on Erlang and get addicted as well!

Side-note: I’m not a highly-experienced Erlang programmer. I am reading Joe Armstrong’s book at the moment and am solely expressing my comments on this. If I get something wrong please contact me and correct me.

Dr. Zemaneck starting telling tales from the stays with the first computers. How they translated their programs to binary before loading it into the computer, how he loved the sound about the rattling of the Mailüfterl, how it clicked and clicked away at every instruction. He mentioned that back then, what you could do was very limited compared to what you can do today. He’s amazed about how he can look at maps from all over the world, look at videos. Yet, he can still hear the computer rattling.

Dr. Chroust continued with his story on the beginnings of software development, the first programming languages and so on and so on… basically the same story we heard in the Software Engineering I and Allgemeine Systemlehre. We’ll old man just loves him self for the wonderful things he did.

Dr. Mössenböck gave a very nice review of how programming languages have evolved over the years. His experiences with the various languages, Cobol and Fortran, how they developed a 7 pass compiler at first because they only had 128k of memory. I really respect Dr. Mössenböck because I know of the work he has done.

Mag. Rabiser started off telling us how he got to programming. He started with a computer in his mom’s office that started with a DOS shell uhuhuhuhuu.. fear! When they first got a computer, it was a used notebook, 286, 10mhz, something like that… monochrome screen. poor guy. they still put down 80.000 schilling back then. He then explained to started studied business-computer-science and that that would explain the Mag. title instead of the Dipl.-Ing. Title. I don’t know if he was bragging or if he was sad about it. I won’t comment.

Anyhow, I really got upset when he mentioned that the best programming language is the one that one is best at. Everybody was like “uh-ah”, “so true”. Bullshit. For every domain there is a should be a good programming language. Some programming languages are really good at low-level programming, like C, some are better for large project with a lot of interconnected componentes (c++/java), some are good at string processing (Perl), some are good for file system scripting (Bash-script), the list goes on and on. It’s as if you’re in a racing tournament where you do one race on every kind of race track. You won’t be using a forumlar1-car in a rally-race etc.

We are now at a point, where programming languages seem to be able to do everything we need and the rest is being solved with tools: Generating Code, filling a few lines here, adding some there. Code reuse is brought to a maximum. Yet I still see programs crashing, not scaling to multiple processors, having to be stopped to be upgraded, the list goes on (readers familiar with a modern functional programming language I won’t name right now). Why don’t we leave that old procedural paradigm behind and follow the path to the light?

I brought up the discussion about what’s the next step in programming. There are quite a few researchers really thinking about the problem programmers have with software stability, especially with multi-threaded applications. They analyzed the most common sources for errors in languages and tried to take them away from the language. This resulted in a programming called Erlang. While I haven’t really writting big projects with it, I’ve been reading Joe Armstrong’s Programming Erlang book and am truly convinced by the concepts of the language.

Then came the moment when I lost a lot of respect for Dr. Chroust: He somehow heard Erlang was a functional programming language and immediately had to comment on performance. “When I got my first laptop, it had 40k auf hard-diskspace!” “you have to think about space usage” bla bla bla. I just commented that at some point nobody tought we would be sending XML documents across the internet, yet we do. Heck, we have lot’s of performance we could use, we just have to make it easier to write our programs with parallelism in mind.

Well, he said that our thinking is sequential. I found that really strange as well. We want to model things they way they are in the real world most of the time and yet we think sequential? Thats not true. And if we do, we have to start thinking in parallel. The world is parallel!

Next he mentioned that they already found out that there is a maximal amount of parallelism you can acheive. Heck yes, everybody having waited all summer for a grade in his parallel computing course knows about Amdahl’s Law. And while Amdahl is basically right that in any given program you can only parallelize a specific amount of instructions, we have to realize that we can handle bigger problems by utilizing more processors. So his law is not wrong, it’s just not relevant. Somebody like Dr. Chroust should have realized this. I am really disappointed.

Side-note: This post is the opinon of Philipp Aumayr. None of the other ebg13 members are responsible for this.

Last Saturday we went to the Project Revolution Tour Concert in San Bernadino. It was such a blast: Placebo, HIM, Taking Back Sunday, My Chemical Romance, 45.000 people. Something like this And that was way up in front. I should have gone for the more expensive tickets and end up in the moshpit! What an awesome day that was (hot as hell during the day as well tough).

Ok, gotta get to bed, waves are calling! -phil

I am happy to report that our friends at Rarebyte Game Development released the public beta of Waterstorm, their fast paced 2D multiplayer submarine action shooter.

I am even more happy and proud to see that a small, independent game developer managed to create a entertaining game and support all major operating systems from the very beginning. Many big developers and distribution companies don’t care about the small (but growing) segment of Linux-gamers (and the apple users … of course ) which makes this project an even larger success.

So don’t wait .. join the fun and tell your fiends!

digg.com news

Rarebyte’s release announcement:

The waiting has found its ending: Rarebyte’s newest incarnation, Waterstorm, a fast paced 2D multiplayer shooter, goes beta. Players from around the world can measure up against each other in a sophisticated ranking system and team up as clans.

A massive variety of sub marines and weaponry rock the boat in Waterstorm. Subaqueous battles with jaw-dropping graphics guaranteed and free of charge!

You can dive into the world of Waterstorm using Linux, Mac OS or Windows. So have no fear and register right this second at www.waterstorm-game.com

To learn more about Rarebyte please visit www.rarebyte.com

Anyway I am looking forward to New Years Eve and partiing with friends.

Matthias

the weather is not too good in venice atm. since we are not bathing thats no problem.

 sorry no pictures … forgotten the cable of my cam.

 have a nice day matthias

Sure it would be nice to see some patent-free technology like ogg/vorbis but its a great first step anyway.

Another cool concept was implemented by finetunes.net, who sell high quality music (DRM free ogg or mp3) in a – in my opinion – fair pricing scheme. They feature many german and international independent-labels for several years now.

I think these facts show once again that great musicians (which happen to be non-mainstream most of the time ) don’t seem to fear piracy or current technologies at all. So lets hope that the big companies won’t destroy it all and there is no problem anymore

Some example bands would be The Dresden Dolls, Clap Your Hands Say Yeah!, ..

One way out of my keyboard-hell would be buying a Happy Hacking Keyboard or one of those OLED ones. Both to expensive … I don’t get them as presents

But! Look at http://capsoff.org/ they try to help me with the CAPSLock problem a little bit.

Regards

Yes ok, phil and myself will have to do paperwork for our bachelor papers. And then of course there is still work, werwurm is starting his summerjob on monday. The rest of us will probably just spend more time on our sparetime jobs.

Anyways … wish you all a great summer, hope we don’t loose touch during the summer breaks.