In my post yesterday, I briefly mentioned the problem with simulations
as a replacement for animal testing. But I’ve gotten a couple of self-righteous
emails from people criticizing that: they’ve all argued that given the
quantity of computational resources available to us today, of course
we can do all of our research using simulations. I’ll quote a typical example
from the one person who actually posted a comment along these lines:
This doesn’t in any way reduce the importance of informing people about
the alternatives to animal testing. It strikes me as odd that the author of
the blogpost is a computer scientist, yet seems uninformed about the fact,
that the most interesting alternatives to animal testing are coming from that
field. Simulation of very complex systems is around the corner, especially
since computing power is becoming cheaper all the time.
That said, I also do think it’s OK to voice opposition to animal testing,
because there *are* alternatives. People who ignore the alternatives seem to
have other issues going on, for example a sort of pleasure at the idea of
power over others – also nonhumans.
I’ll briefly comment on the obnoxious self-righteousness of this idiot.
They started off their comment with the suggestion that the people who are
harassing Dr. Ringach’s children aren’t really animal rights
protestors; they’re people paid by opponents of the AR movement in order to
discredit it. And then goes on to claim that anyone who doesn’t see the
obvious alternatives to animal testing really do it because they
get their rocks off torturing poor defenseless animals.
Anyway: my actual argument is below the fold.
Remember a while back, I wrote about a crackpot who pestered me both about
converting to Christianity, and his wonderful, miraculous compression system? He
claimed to be able to repeatedly compress any file, making it smaller each time.
Well, he’s back pestering me again. Repeatedly asking him to leave me alone,
shouting at him, etc., hasn’t worked. (His current claim is that he doesn’t know how
to delete me from his gmail contacts list.) So I’m resorting to another round of
public humiliation, which I hope will be informative and entertaining as well.
Like a lot of other bloggers, I often get annoying email from people. This week, I’ve been dealing with a particularly annoying jerk, who’s been bothering me for multiple reasons. First, he wants me to “lay off” the Christians (because if I don’t, God’s gonna get me). Second, he wants to convince me to become a Christian. And third, he wants to sell me on his brilliant new compression scheme.
See, aside from the religious stuff, he’s a technical visionary. He’s invented a method where he can take a source document, and repeatedly compress it, making it smaller each time.
This is a stupid idea that I’ve seen entirely too many times. But instead of just making fun of it, I thought it would be interesting to explain in detail why it doesn’t work. It touches on a bunch of basic facts about how data compression works, and provides a nice excuse for me to write a bit about compression.
The basic idea of data compression is that you’re eliminating redundancies in the original text. You can’t discard information. Mathematically, a compression function is an invertible function C from an array of characters to an array of characters (or you could use bits if you prefer), such that if y=C(x), then on the average input, the length of y is smaller than the length of x.
An ideal compression system is one where for all possible values of x, C(x) is shorter than x. C is your compressor; and since C is reversible, it has a unique inverse function C-1 such that C-1(C(x)) = x. An illustration of this basic compression system is in the diagram to the side.
I’ve been getting a lot of emails asking about the so-called “Z2K9” problem.
For those who haven’t heard, the software on a particular model of Microsoft’s Zune music player froze up on New Year’s eve, because of a bug. Apparently, they didn’t
handle the fact that a leap year has 366 days – so on the 366th day of 2008, they froze up for the day, and couldn’t even finish booting.
Lots of people want to know why on earth the player would freeze up over something like this. There was no problem with the date February 29th. There was nothing wrong with the date December 31st 2009. Why would they even be counting the days of the year, much less being so sensitive to them that they could crash the entire device for a full day?
The answer is: I don’t have a damned clue. For the life of me, I can’t figure out
why they would do that. It makes absolutely no sense.
I’ve been getting a lot of requests from people to talk about the recent Excel bug. For those of
you who haven’t heard about this, in Excel 2007, floating point calculations that should result in
a number very, very close to either 65,535 or 65,536 are displaying their result as 100,000.
It’s only in the display though – the underlying number is actually represented correctly, so if you subtract 2 from 65,536, you’ll get the correct answer of 65,534 – not 99,998.
I can’t give you the specifics – because without seeing the Excel code, I can’t tell exactly what they got wrong. But I’ve got some pretty good suspicions, so I’ll do my best to explain the background that leads to the problem, and what I think is probably going on. (Another excellent explanation if this
is in the Wolfram blog post that I mentioned in my fast arithmetic fractals post this weekend.)
As of 2/24/2008, Sewell has just responded to this, pretending that he just noticed it. To make discussions easier to follow, I have responded with a new post here, and I would appreciate it if comments could be posted there, to keep it all in one place.
My SciBling Mark Hofnagle over at the Denialist blog wanted me to take a look at the pseudo-mathematical ramblings of Granville Sewell. It actually connects with some of the comments in the thread about the paper by Dembski and Marks – Sewell uses part of the article to make the same kind of quantum nonsense claims that showed up here.
Sewell claims to have written a simulator which simulates the Universe, and is complaining that his supposed simulation didn’t produce things like computers or aircraft carriers. I say claims because I’m pretty convinced that he did no such thing. Actually programming a simulator like the simplest of the several he claims to have done, which produces the results that he claims it produced, would be an absolutely astonishing feat of programming, involving a quantity of data that’s more on the scale of Google than on the scale of Granville Sewell’s laptop.
I came across a link to an excellent article that provides an example of one of my professional bugaboos: the truly awful way that we often design software in terms of how the implementer thinks of it, instead of how the user will think of it.