Politreco

Countdown restarted

Por motivos de força maior, a contagem regressiva foi reiniciada. Nova data: 27 de setembro.

12 dias, e contando…

Suse studio

I was really impressed about the demos I saw in last Novell’s announcement : Suse Studio. So last week I applied to have an account since it’s not open for everybody. Today I received the following email:

Thank you for your interest in SUSE Studio, a new service that makes
it quick and easy to create and test software appliances from your web
browser.  We are pleased to invite you to try SUSE Studio.

To accept this invitation and take SUSE Studio for a spin, please
visit this link:

****************************************

Alternatively you can go to http://www.susestudio.com/account/invitation and manually
enter your invitation code there.  Your invitation code is:

**********************

We hope that you will enjoy using SUSE Studio.  If you encounter bugs,
have general feedback or want to discuss SUSE Studio you can reach us
at feedback@susestudio.com.

Have fun using SUSE Studio!

Best Regards,
The SUSE Studio Team

Woww… amazing!! I’ll try it out and let you know what I think of it in a few weeks. In the meantime you can see some screencasts on their website or on youtube.

Do you have an account?

The final countdown

Em 30 dias estarei pousando no Brasil!!

A contagem final começou.

Preparem a picanha que eu estou chegando.

Compiler’s compiler version

Today I was just wondering… what’s the version of the compiler which compiled my compiler. Quite a strange question to make myself and I really don’t know where this curiosity came from.

Looking in Wikipedia:

Early compilers were written in assembly language. The first self-hosting compiler — capable of compiling its own source code in a high-level language — was created for Lisp by Tim Hart and Mike Levin at MIT in 1962.^[2] Since the 1970s it has become common practice to implement a compiler in the language it compiles, although both Pascal and C have been popular choices for implementation language. Building a self-hosting compiler is a bootstrapping problem — the first such compiler for a language must be compiled either by a compiler written in a different language, or (as in Hart and Levin’s Lisp compiler) compiled by running the compiler in an interpreter.

Interesting, don’t you think? So let’s see the version of your compiler’s compiler. If you use GCC, it will put a comment in section named (surprise!) .comment. Generate the assembly correspondent to a C source code and you are going to see in the end of the file an entry like this:

.size   main, .-main
.ident  “GCC: (GNU) 4.4.1″
.section        .note.GNU-stack,”",@progbits

So, let’s play with our already compiled compiler. First we have to check the compiler version:

[lucas@skywalker tmp]$ gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../configure –prefix=/usr –enable-shared –enable-languages=c,c++,fortran,objc,obj-c++ –enable-threads=posix –mandir=/usr/share/man –infodir=/usr/share/info –enable-__cxa_atexit –disable-multilib –libdir=/usr/lib –libexecdir=/usr/lib –enable-clocale=gnu –disable-libstdcxx-pch –with-tune=generic
Thread model: posix
gcc version 4.4.1 (GCC)

Ok! Version 4.4.1. Let’s use the readelf command to see the content of .comment section:

[lucas@skywalker tmp]$ readelf -p .comment /usr/bin/gcc

String dump of section ‘.comment’:
[     1]  GCC: (GNU) 4.4.0 20090630 (prerelease)
[    29]  GCC: (GNU) 4.4.0 20090630 (prerelease)
[    51]  GCC: (GNU) 4.4.1

[    63]  GCC: (GNU) 4.4.1

(…)

[   237]  GCC: (GNU) 4.4.1
[   249]  GCC: (GNU) 4.4.1
[   25b]  GCC: (GNU) 4.4.0 20090630 (prerelease)
[   283]  GCC: (GNU) 4.4.1
[   295]  GCC: (GNU) 4.4.0 20090630 (prerelease)

I didn’t understand if it’s 4.4.1 or 4.4.0, i.e. if it was used a prior version to compile the current version or if current was recompiled afterwards with this new compiler produced.  Testing random binaries in /usr/bin seems to produce similar effects, having more than one version.

So… no answers yet. Any clues?

Trissa 3D is arriving

I’m proud to release version 0.98 of one of my projects, Trissa. Whilst this is not a version intended for the end-user, I’d like to have some more users to find bugs before releasing 1.0. Be warned: this is intended for developers only. There’s no package yet, so you have to compile it yourself. Some screenshots:

First screen	About menu
Options menu	Start of a 4x4x4 Game
Choosing first position - Human Player	After some time
Minmax Player wins

I’m putting online also a presentation I gave about this project in my university, Politecnico di Milano. Trissa is the name of the Tic-tac-toe game in italian and I made it as part of a course: Laboratory of Artificial Intelligence and Robotics. Thanks to professor Francesco Amigoni who helped me. [ .odp / .pdf ]

Source code is available at Github. To get the last version with git:

git clone git://github.com/lucasdemarchi/trissa.git

You will need some libraries that may or may not be pointed out by the building system:

• scons
• OIS
• Ogre3D
• CEGUI
• Boost

Let me know if you have any trouble to compile it and if you find any bugs. In “TODO” file there are some known bugs.

Awesome!

Just a short post to share a beautiful Brazilian song. Two days ago my friend was playing it, now it just doesn’t get out of my head

Have fun.

Sharing some homeworks

So, I’ve spent some time last weeks doing some homeworks for courses at Politecnico di Milano. One of them is for the course “Image analysis and synthesis” in which I did together with a friend of mine some animations in Blender.

The goal was to make some animations of sport scenes and after apply a kind of “filter” in Matlab to simulate a high exposure of the camera, or, if you prefer, to draw the trace of the ball. As the only object moving in scene was the ball, these two are roughly the same thing. This is done by taking the mean of W frames and making a new one from them, where W is the “window” of the algorithm.

We took four sports: basketball, table tennis, golf and bowling. The amount of things produced is ~ 400MB, so I’m not putting it online for everyone. If anyone is interested in the Blender models, ask me privately (you find my email in the “About” link above). I put some animations in youtube, sou you can see them:
Bowling: http://www.youtube.com/watch?v=YrgkLCTrsVg
Table tennis: http://www.youtube.com/watch?v=HmrDPdDevRM
Basketball: http://www.youtube.com/watch?v=TjeOXhxceWA

3D animation is one of the areas I admire, but definitely isn’t an area I’m good at. Also, this was the first time I did something serious with blender, so don’t expect superb results (and continue reading this post if you gave up after seeing the videos ).

After thinking a while about the time Matlab took to make the final results I decided that it could be better… Two things could be improved: (i) use more threads to calculate the new images and (ii) use CPU optimized CPU instructions. I think it’s a shame to have a dual core with lot of specialized instructions to do things faster and don’t use them. These two goals brought me to code the algorithm in C.

I used pthreads to divide the work among threads (you say at command line the number of threads you want, or just say it to use the number of available processors) and freeimage to load and save images. I did made another version that uses gdk-pixbuf to load and store images and it took me so disappointed. To simply load and save images DIFFERENT images (so, things that are not correlated) it needs to use synchronization mechanisms. This leads to an algorithm not scaling very well as it could. I also tested another one with CImg… and the result was so disappointing too. I think not every developer is performance-ish as I am. Or not everyone cares about it as long as it is easy to use. So, stop talking and show the results:

Time to compute in each implementation

The best version run in less than half of the time required by Matlab! I could also optimize more the algorithm in C to get even better results, but I was already ok with that (read: I have other things to do). It’s also worth noting the improvement when optimizing the code for my CPU: with one thread I got a boost of ~20% and with 2 threads of ~18%. Particularly in this type of algorithm, it’s important to use SSE/SSE2 instructions to get a faster mean of the images. In fact, viewing the assembly code generated in this case we find these instructions as below (the xorps, movaps are SSE instructions that operate with xmmN registers).

 8049517:       0f 57 f6                xorps  %xmm6,%xmm6
 804951a:       8b 41 04                mov    0x4(%ecx),%eax
 804951d:       8b 4d 08                mov    0x8(%ebp),%ecx
 8049520:       39 41 08                cmp    %eax,0x8(%ecx)
 8049523:       0f 82 36 06 00 00       jb     8049b5f <worker_thread+0x6ff>
 8049529:       8d 7d cc                lea    -0x34(%ebp),%edi
 804952c:       0f 29 b5 08 ff ff ff    movaps %xmm6,-0xf8(%ebp)
 8049533:       89 bd 04 ff ff ff       mov    %edi,-0xfc(%ebp)
 8049539:       89 3c 24                mov    %edi,(%esp)
 804953c:       89 44 24 08             mov    %eax,0x8(%esp)
 8049540:       c7 44 24 04 64 a2 04    movl   $0x804a264,0x4(%esp

Awesome!! GCC automatically generated a SSE optimized code. If you got interested, see the wikipedia article about SSE.

The code is available under GPLv2 license at github: http://github.com/lucasdemarchi/imgmean. Let me know if it’s useful to you.

The browser war continues…

One month ago I wrote a post talking about the new Chrome for linux, or better yet, that the Chromium (this one is opensource) is finally working well under Linux, and so fast.

Well, while the Chromium guys are working hard to get a decent browser, the firefox guys didn’t stop working and last week Mozilla released the so waited Firefox 3.5.

Read the rest of this entry »

Benvinda de volta Oficina G3

Creio que nem todos conheçam a banda Oficina G3. Em poucas palavras, é uma banda evangélica de rock muito boa.

O rock pesado nunca foi meu estilo favorito. Passei a ouvir Oficina principalmente quando lá pelo ano 2000 (acho) eles partiram para um estilo mais light com CDs como “Acústico” e “Ao Vivo no Olímpia”. O último CD deles que ouvi bastante foi o “Humanos” quando eles voltaram para o rock que apesar de pesado, era ainda “ouvível”.

Com a saída do vocalista PG do grupo eles deram uma “recaída” e depois de algum tempo sem lançar nenhum CD lançaram o “Além do que os olhos podem ver”. Que decepção! Rock terrivelmente pesado e muito longe do meu gosto.

Bom… esse post é pra falar que, navegando esses dias na internet descobri que eles foram eleitos a melhor banda de rock gospel no “Troféu Talento 2009″. Aí resolvi procurar qual tinha sido o último CD deles e descobri que tinha um novo: “Depois da Guerra”. E que maravilha de CD! Continua no estilo pesado, mas muito, muito melhor do que o anterior que tinha ouvido. As letras não são tão bonitas e poéticas como as do João Alexandre (um dos meus favoritos tanto na parte da letra quanto musicalmente), mas são deveras boas.

Dou destaque para a música “Continuar” que você pode ouvir abaixo, uma das mais calmas do CD.

Descobri também que quando estou programando, ouvir uma música mais agitada como essas me deixa mais acordado – razão pela qual Oficina G3 voltou para a minha playlist e tenho ouvido esse CD várias vezes durante o dia.

Pergunta para meus amigos programadores: vocês escutam alguma música enquato programam? O que?

Meu Brasil brasileiro

Questo post è dedicato ai miei amici italiani. Mi dispiace, ma l’Italia ha giocato troppo male e il Brasile… beh, è il Brasile!!

Sentite la differenza tra il cronista brasiliano e l’italiano.

Italiano:

Brasiliano:

Ci vediamo domani. Io sarò con la maglietta della nazionale brasiliana