December 22, 2011
Calculation of greatest common divisors is a quite complex problem for a digital computer, but not for pendulums:
The pendulums line up at the edge with frequencies given by the common divisors of their individual frequencies. For example, here is diagram of a 6Hz and a 4Hz signal, you can see that they line up with a frequency of 2Hz:
The algorithm it solves it is thought to be NP (it gets slow pretty quickly). Even though the problem it solves is difficult in the usual sense, the python code to calculate it is actually quite short (though I have deliberately made it so here):
return a if b == 0 else gcd(b, a%b)
June 3, 2011
Well, actually, they probably did it for fun, but that doesn’t mean that it doesn’t benefit us. jellymatter should be the kind of place that has an opinion on the recent hacking of Sony by Lulz Security (the name make me laugh when I heard it on BBC news last night). So here is my opinion on the matter…
Good Job. That’s the jist of what I have to say. Well done for doing before someone with worse intentions. Well done for publicly shaming Sony.
For those of you who don’t know the details, LulzSec used an SQL injection, an attack so simple that it shouldn’t really be called hacking. The way this works is: first someone designs a website really badly, so that when someone types in a speech mark followed by, in effect, “give me all you data”, the website gives you all its data. Second, someone does this. Seriously, it’s that easy – and making a website that doesn’t have this vulnerability isn’t much harder. Sony users should be insulted that a company they trusted treated their private data with such disregard.
So, hats off to LulzSec for their reckless benevolence.