Today I’ve been rearranging a bit the links at the blog, mainly rearranging links and adding new ones

But while doing that, something I noticed and found amusing was that google reader has a very neat “Your stuff” page listing:

• a neat profile complete with photo and links to other homepages
• shared and starred posts, with a comment
• shared notes, which is a very simple way to do blogging, with a title, a body and tags

That page is available also via RSS, so I’ve also syndicated it to the side of this blog.

Maybe it could even be made to replace the blog itself?

I find the blog keeps mixing both big posts with deep content with smaller “what’s up” posts, and maybe separating these smaller ones to the reader page would be better. But then just using the blog for posting big deep content doesn’t ring so well with the format, and maybe moving that content to a different format such as a proper webpage would be better.

All in all, I have to think a bit more about all this…

EDIT: I’ve created a homepage at google sites with a news frontpage, a links part and also a part for longer articles… let me know how you feel about that! :)

One of the things I’ve felt missing since being an ex-patria is a lack of my own language. It is true that there is many people from all over the country, and of course I keep chatting daily with many people from home, but I still lack the immediate warm of a quick good laugh or word play in andalusian :)

It may be for this reason, then, that lately I’ve listened quite a bit more than usual to Chambao. While not the overall best sellers nor the best known, the group managed to ride the flamenco-fusion fashion quite well and gave us quite a few memorable songs.

I found out quite a few videos and even an official chambao video channel, so let me link to a few of my prefered songs like the famous ahí estas tú or pokito a poko (concert in wroclaw^poland?!?).

Just like they say…

Volveré a encontrarme con vosotros
Volveré a sonreír en la mañana
Volveré con lágrima en los ojo
Mirar al cielo y dar las gracias

ps. kudos para chambao por decidir apostar por la tecnología y permitir los videos en lugar de bloquearlos :)

Me encuentro por el youtube unos videos del vaya semanita, y vaya si me ha gustado, ese humor puntiagudo y esas frases 100% made in spain, un ejemplo rápido:

anchon: pero maite! dios nos dijo que no cogieramos el fruto del arbol de guernica!

maite: PRINGAO! tu te haces llamar vasco? a que no hay HUEVOS de comerte la manzana?

anchon: que no? a ver trae paca y que no coja carrerilla a ver si voy a inventar la sidra!

1000% recomendable :)

Apparently Perlin noise, even the real Ken Perlin one that no demoscener ever uses due to being too compute intensive, is long dead in the high end and has been replaced by wavelet noise.

What I find really amazing is that all these variants shown on the paper describing good noise look somewhat different to the naked eye but are amazingly different when analyzed via frequencies at page 7.

I think it may be cool to try doing inverse noise synthesis by creating an spectral texture and doing an inverse frequency transform, something that I remember hearing was sometimes done for sound synthesis.

ps. paper found via the Pixar online library

One of the most used tricks for space optimization on 4k intros is to mangle floating point values on the executables before compressing.

Recap on standard floating point number storage

To recap, a float is stored in memory using 4 bytes, with bit-fields packed like this:

• 1 bit for sign, s
• 8 bits for exponent, e
• 23 bits for mantissa, m

The exponent is stored with 127 added to it, so the final value is basically

• value = power(2, e - 127) * (1.0 + m)

What this means is that the exponent is used to select which bracket to use:

• e = 125 –> value is between 0.25 and 0.5
• e = 126 –> value is between 0.5 and1
• e = 127 –> value is between 1 and 2
• e = 128 –> value is between 2 and 4
• e = 129 –> value is betweem 4 and 8

And then the mantissa is used to select a number inside than bracket.

Shaving off bits

Compressor engines work by detecting repeating patterns and encoding them in non-obvious ways. The most obvious pattern to detect are strings of zero bits or zero bytes.

That can be used in our advantage: the executable or datafile will compress better if there are many zero bytes, and that is easy to do if we somehow force some bits on the float values to zero. Let’s say we blank out the 2 lower bytes on a float. That means that we end up with this floating point representation:

• 1 bit for sign
• 8 bits for exponent
• 7 bits for mantissa

You could say that this forces us to use numbers other than what we wanted, but that was already the case since floats are only an approximation. How do you store π on a normal float? You can’t, since a float is just a 23-binary digits approximation to the value we want!

I really need a value that is not available by using fewer bits… Help!

That’s so wrong it hurts, you don’t really need them for making a demo. A demo is created by faking, fudging and tweaking until it looks good. You can probably achieve what you want by mangling either that number, another number or the whole formula in a random way.

How to shave bits, the shiny way (aka “in the future the compilers will obsolete the coders”)

Ideally, we would want to automate the whole process of shaving off bytes. One of the nicest parts of C++ is that compilers can detect and eliminate operations at compile time if they can prove that the result will be the same as doing it at run time. Given C++ templates and reasonably modern C++ compilers such as gcc 4, we can try this way:

class f16 {
private:
union {
mutable unsigned int _iv;
mutable float _v;
};
public:
inline f16(float const v) {
_v = v;
_iv = _iv & mask;
}
inline operator float() const {
return _v;
}
inline operator unsigned int() const {
return _iv;
}
};


What is happening here is that we create an object from a float, and the constructor stores that value with the lower 16 bits forced to zero. As the real storage place is marked as private and thus hidden from any other code, the compiler is able to optimise it and the resulting executable only has the masked value.

How to shave bits, the reliable way (aka “compilers are evil and does things behind my back”)

A big problem with the previous method is that it depends on the compiler realizing that he can optimize the code that way. If you need to be sure that the compiler only stores truncated numbers in the executable, the easiest way is to simply never feed him numbers other than the ones that are already in the format we want.

There are two ways:

1. Place the proper numbers my hand or by preprocessor macros
2. Make a filter that reads the source code, detects the floating point values and outputs the code to another file with truncated numbers.

How to shave bits, the backhanded way (aka “compilers are dumb, I better fix their output afterwards”)

Nowadays the leading executable compressor Crinkler is capable of automatically truncating bits. This is done by using the name of the variable as a hint to the compressor, which dutifully takes the variable and masks off lower bits before starting to compress anything. While nice and really automatic, I’d consider this a catch-all rule and just use any of the previous techniques in addition to achieve better control of the numbers.

Relevant links:

Wikipedia article on floating point numbers

IQ/RGBA article on truncating floating point numbers by hand

in4k article on truncating floating point numbers both by hand and by script

Crinkler executable linker and compressor

Since starting to use my new home network at Dbulin, I had noticed that loading anything on the browser always took ages, and my first suspect was of course the isp-provided dns servers. So, today I’ve installed maradns a local dns resolver for my home network on my mac, and it is like… infinitely better???

El otro día de vuelta del curro, me pare a comer en uno de los n-mil restaurantes asiáticos de la calle castro. En verdad este es de los pocos que es de comida japonesa, dado que la mayoría de los bares de la zona son indios, chinos o coreanos…

Mini-review:

• +1 chicas guapas atendiendo, nunca está de más ;)
• +2 comida excelente
• +1 tienen comida para llevar
• +1 precio: $16 (recordemos el restaurante aya de 36€ == $55)
• -1 el huevo duro con los palillos es un poco complicado

sitio: maru ichi en mountain view

fotos: winden en el maru ichi de mountain view

Update domingo 15:

• Ayer volví a cenar allí, y ahora si me explico pq en la entrada decía “espere aquí hasta que le den una mesa”… Sábado a las 6 y media y el restaurante estaba lleno hasta la bola! Fue curioso cenar de mientras en el tele tenían puesto un programa de la tele japonesa acerca del fútbol de japón…
• Corregido el nombre a Maru Ichi

So, having already been for 1 week at Silicon Valley… how is this place?

• weather: Nice, sunny, malaga-like “fresquito” but not “joder que frio copón!”
• food, part 1: enjoy the overwhelming amount of asian restaurants
• food, part 2: chinese restaurants have the infamous fortune cookies with random messages inside
• places, part 0: Typical highschool-teen-film-like neighbourhoods: wide streets, trees, houses with lawns and garages
• places, part 1: Enjoy the beer garden at zeitgeist on valencia street
• places, part 2: Marvel at the computer history museum, full of classic toys to marvel at!
• places, part 3: Free wifi while waiting for the bus shuttles at the Mountain View caltrain station
• people, part 1: Some random names encountered so far: Alicia, Vijay, Crystal, Fernando, Molly, Owen or Erika
• people, part 2: At some parts of the place, you are going to find a quite high density of not-so-random Dubliners
• people, part 3: Amongst the biggest differences to Europe, here you can and will find girls driving taxis
• drink, part 1: All bars will ask you for some age identification to check for 21+ age
• drink, part 2: there is no guiness here :( …
• drink, part 3: … but there are bars with sangria! :)

BTW, don’t forget take advantage of your +16 spanish ability:

• spanish tip 1: you can buy “picos” at the big supermarkets, just smile and ask any spanish-speaking 50s-looking mama
• spanish tip 2: many cooks here are from spanish-speaking families, take advantage and ask for treats

El Jet Lag es cuando vas de viaje muy lejos y estas con el horario tó cambiao. Entonces cuando es de dia tienes un sueño del copón, y luego a mitad de la noche te despiertas y no puedes dormir.

Hay formas de evitarlo, pero parecen mas una lección de masoquismo que otra cosa:

• Dormir bien antes de empezar su viaje: Vale, parece razonable excepto que siempre hay que arreglar la maleta a última hora.
• Evita las bebidas alcohólicas y la cafeína: Esta frase no me queda clara. No beber ni café ni cerveza… no lo entiendo.
• Beber mucho agua: La tónica lleva agua, no?
• Intentar dormir durante el viaje: El que hizo la lista se ve que no viaja en clase turista.
• Comer fruta y verduras frescas en vez de la comida del avión: Esta lista debe ser vieja, seguro que hoy día te meten el pakete por intentar traficar con fruta fresca.
• Llevar ropa cómoda: Hala, todos en shandal.
• Intentar pasear por el avión: Esto debe ir con lo de beber mucha agua, por aquello de ir a mear 15 veces durante el viaje.
• Usar gafas de sol: En Irlanda no hay de eso, tendría que hacer otro viaje antes para poder comprarlas!

Lo dicho, esta lista de trucos tiene menos usabilidad que el mando a distancia de un DVD.