Saturday, September 27, 2008

The Second Great Depression

To give you an idea of what to look for to know if we have experienced anything similar to the first Great Depression:

August 30, 1929 : Dow @ 382
July 8, 1932 : Dow @ 42

So after ~3 years, the Dow was at ~11% of its peak value.

What would this look like in modern times? The Dow peaked at 14093 on October 12th, 2007. If we experience a similar plummet, then sometime in September of 2010, the Dow would bottom out around 1550.

This gives you an idea of just how bad a "real" depression is. That is an average decline of 6.1% per month. The worst we've seen, since our recent peak of 14093, is about a 3% decline per month, over a 9 month period. Yes, this is quite bad, but it is (so far) only half as bad as the slide experienced during the Great Depression.

It could be worse. A lot worse.

Sunday, September 21, 2008

Clusters are Beautiful

I have a computer cluster living in my living room. Ain't she puurrrrdee?

Saturday, September 13, 2008

MatLab vs Octave Benchmark

I just thought I'd share some informal benchmarking results with the world. This is with Octave 3.0.0 and MatLab 2008a. I'm running on Ubuntu Linux, 8.04, 64-bit, with an AMD Athlon X2, 2.2 GHz processor, and 2 GB of RAM. I wrote a little modulator-demodulator thingy, which is not very fancy at all. Its just a couple of for-loops, some non-vectorized Euclidean-distance calculations, and some comparisons.

Octave : 7.5 Seconds
MatLab : 1.5 Seconds

That's a 5x speed advantage for MatLab. I like open-source stuff, and Octave is lighter-weight, so I'll still use it, but MatLab sure shows off the fact that it has been low-level optimized. When I need a 5x speed boost, I'll certainly power up MatLab, and when I need way more than that, well, then its time to go to C++, and move things over to my cluster :)

Friday, September 12, 2008

Egg Trick

Hate peeling hard-boiled eggs? Try this!

I tried it, and it (pretty much) worked. I think the best part of the advice is to add baking soda to the water before you boil the eggs. Two tablespoons per quart is probably about right. This reduces adhesion, and makes them really easy to peel.

Sunday, September 7, 2008

Pseudo-random Number Generators

Fascinating. I just learned that one can construct a pseudo-random number generator out of any one-way function. Then I tried it out in MatLab with a few simple experiments, and yup, it works. Thats cool.

Gold ion beam-beam collisions

Science sure is purrrdee, ain't it? This image was stolen right off of Wikipedia, because it was so pretty, I just couldn't help myself.

Hadronized Charged Particle Debris

...and here's another Wikipedia article on a different topic, related to some of the research I did as a graduate student. The "pareto perspective" is a pretty helpful one, in many areas of life.

Saturday, September 6, 2008


Well, that sucked.

I just spent about 1 hour breaking my laptop, and another 3 fixing it. To save you the pain, here's how I broke it, and how I fixed it.

As part of debugging another computer, I installed Ubuntu to an external USB drive, using my laptop. This went fine, and I was able to boot the laptop from the USB drive. I unplugged the drive, and tried to boot my laptop the usual way, which gave rise to the error message:

Grub loading, please wait...
Error 21

Oh well hell.

Anyway, like I said above, to "save you the pain", here's the solution:

1) Boot from an Ubuntu live CD
2) Open up a terminal
3) Type the following:
>> sudo grub
>> find /boot/grub/stage1
4) This will tell you something like "(hd0,2)". Use this information for the next step:
>> root (hd0,2) <------ there is a space between "root" and "(hd0,2)"
>> setup (hd0) <------ again, don't forget the space
>> quit
5) Now reboot. It should be fixed.

Tuesday, September 2, 2008

Slow SSH

Is SSH being slow? Are you running Ubuntu (8.04 at the time of this writing)? I've found the following solution fixes slow SSH and Telnet logins. Specifically, the symptom is an annoying ~10 second delay between attempting to log into a remote terminal, and when it prompts you for a password. If this is happening to you, do the following (to the remote machine):

sudo nano /etc/hosts

Then, just add a line with the IP address and host name of the machine you are logging in from. Apparently, the remote machine is trying to do a DNS lookup, or something, and timing out. If it already has your machine in its list of hosts, you can get in instantly. I've found a few other folks discussing this in the forums, but none of their suggestions worked for me.

Happy computing.