Entropy

9 Jun 2009
coffee coup

The conversation went approximately like this:

Barista: Careful, the glass is hot, and since we're out of insulating cardboard sleeves, I can only offer you this napkin, a poor substitute.

Me: Fear not, for I have amassed a hefty collection of coffee sleeves, and I have them right here in my bag! I will use one of mine, as I planned, and leave the rest with you.

Barista: My hero!

Approximately.

24 Feb 2009
loose ends

A funny thing happened at the DMV fourteen years ago. I'd recently paid off my car loan, and in a comedy of paperwork, the DMV swallowed up my only copy of the proof without recording it. California thought the bank owned my car, and I couldn't prove otherwise.

Considering how infrequently the bank asked to borrow the car for the weekend, this didn't seem like a big deal. It might be a problem when I tried to sell or otherwise dispose of the car, but in the meantime, getting it straightened out wasn't particularly urgent.

It sat quietly at the bottom of my to-do list for a dozen more years, in the company of other important chores like "learn French" and "prepare for earthquake", until a friend pointed out that the bank might not even exist anymore. Or maybe they'd had a fire. Or perhaps they discard old files once it's been so long that no reasonable person could possibly need them. If none of these things had happened yet, it might be a good idea to sort things out before it became impossible. All good points, I thought, resolving to deal with it soon. In fact, the bank did exist. I jotted down their phone number.

One morning just two years later, in a burst of industriousness and prepared for an arduous struggle, I called the bank. I quickly reached a real person and told her what I needed, without regaling her with the fascinating tale of how I came to be in such a pickle. Without any fuss at all, she told me what I needed and set off to mail it to me.

I thought this smooth service was a little unfair, given the length of my run-up. After putting it off for so long, it would have been polite to make it more difficult, to help me feel my delay was warranted. But no, I soon received a single notarized sheet of paper that essentially said "he paid us, we're good". I immediately made a photocopy.

With the bank out of the way, I no longer had any reason to rush things. The task had taken on symbolic significance on my to-do list, a shining example of procrastination I might enjoy vanquishing, but this only resulted in a vague desire to take care of it one of these days, once again without any sense of urgency.

I might have let it sit another fourteen years if the DMV hadn't asked me to drop by. They had a funny notion I might have aged visibly since my last photo, ten years prior. This was the motivation I'd been waiting for. If I dealt with it now, I might be able to avoid returning to the DMV until 2019, or until I upgrade my license to include flying cars, whichever comes first.

So I brought everything in, and without any fanfare at all, it was done. The clerk even made me a copy of the bank's document, just in case.

18 Feb 2009
the direct approach

I've been enjoying coffee's energizing effects, but today I learned that it's counterproductive to pour it directly onto the computer.

11 Jan 2009
Happy Pedantic New Year

No, today is not the new year by any reckoning I know. Most people call January 1 the start of the new year, but really it depends on the calendar you use. The vernal equinox always seemed like a more meaningful choice to me, but though the equinox is a global phenomenon, spring is not, so maybe an arbitrary day is as good as any.

The Chinese new year, celebrated by perhaps 1.3 billion people, is coming up on January 26, and it's the last in a run of major new year holidays. I often hear people call it "the lunar new year", which always bugs me because the Chinese calendar is just one of many popular lunar calendars, and because I'm a pedantic nitpicker. (And really, if we're going to nitpick, the Chinese calendar is not strictly lunar, because it tracks the tropical solar year.)

Around 1.5 billion people follow the Islamic calendar, the only truly lunar calendar I've ever heard of (probably because lunar calendars are not useful for any practical purpose), which celebrated its new year on December 28. September 29 marked the Jewish New Year, celebrated by a vocal minority of 15 million.

(Population estimates gleaned from the always-reliable internet.)

16 Dec 2008
advancing the art

A friend and I went to SF MOMA yesterday and spent most of our time looking at early scientific photography from the 1800s. Not exactly modern art, but all the more fascinating. I had no idea people back then had made such high quality photos of the moon, solar eclipses, Saturn, Jupiter, and also microscopic things like bacteria and plant cells.

In many cases, the pioneering photographers of the day were personally engineering better equipment: chemical treatments to increase the sensitivity of the photographic plates, lenses designed to focus the high frequency light the plates responded to, and shutter mechanisms that facilitated making multiple exposures on different regions of a single plate (since changing plates took a while).

Most of my photography is of circus acrobats, who tend to move fast on dimly lit stages, which means my photos are often too dark, motion-blurry, or grainy. A couple days ago, I had an idea for how to get more value from the meager light in my photos: apply a simple convolution filter to add to each pixel some of the light from neighboring pixels. This comes at a cost of image sharpness, but for some photos it's a huge win, especially when I'm just putting low resolution copies online.

I'm advancing my own art, which is nice, but I'm several decades behind the actual frontier for these kinds of tricks. Perhaps it's time to catch up a bit.

14 Dec 2008
moral compass bearing down

Today is cold and rainy, and after being rudely awakened before dawn by my alarm clock, I spent the day outdoors, teaching navigation skills to search and rescue trainees (today, rainees). As cold and rainy as it was, it wasn't as bad as I thought it would be, and I found it quite pleasant. Apparently, half the battle is having the right expectations. The other half is made of fleece and Gore-Tex, in large quantities. Also helpful: a thermos of coffee, still hot five hours in.

26 Nov 2008
echoes and explanations

I haven't posted here in months, and only ten times in the past year. I'm not trying to lull you into a false sense of complacency; your complacency is justified. Embrace it. I have, however, been posting lots of photos (here and on Flickr) and sharing links through Friendfeed (visible in a sidebar on my own site). I have been up to interesting things, but mostly not things I want to share with the whole world.

Yesterday, Rafe pointed out a NY Times article about the Netflix competition and called out this quote:

[W]hile the teams are producing ever-more-accurate recommendations, they cannot precisely explain how they're doing this. Chris Volinsky admits that his team's program has become a black box, its internal logic unknowable.

That's a little misleading. The programmers do know the details of how their programs work, but those details are a collection of statistical optimizations that don't neatly follow how people consciously make or explain their own decisions. That makes the overall effect unintuitive, even though the internal logic itself is known.

It reminded me of some work I heard about in grad school, presented by a guest lecturer in my machine learning class (whose name and affiliation I sadly don't recall). He'd worked on a system that made medical diagnoses. You enter the patient's symptoms and perhaps other personal data, it tries to guess what's wrong with them, based on data from previous cases.

They'd made two systems. One used k Nearest Neighbor (kNN), which works by finding the most similar prior cases (k of them, where k is some relatively small number you like) and guessing that the case in question is probably like those cases.

The other system used a simple neural network, and it was more accurate. The problem was that doctors didn't trust the results of any automated diagnosis and wanted the computer to make a coherent argument supporting its decision. The neural network could explain itself, but not in a useful way. ("I think the patient has pneumonia, because when you add up these fifty thousand numbers using these weights that I computed from your training data, then combine them in this way, you get the following matrix, which ...") The kNN system could present the similar cases it found, which was easy to understand, but its predictions weren't as good.

The dichotomy is mildly interesting, I guess, but the fun part is how they solved it with a hybrid system.

First, a little background. Their neural net was a fairly common topology: a feed-forward network with a single hidden layer with fewer internal nodes than inputs or outputs. The inputs might have been the patient's symptoms (coughing? feverish? blue?) and background (age, sex, personal or family history of various things), and the outputs could have been likelihoods of various diagnoses, the highest of which would be the system's best guess. For any given set of inputs, the activation pattern of the hidden layer can be thought of as a summary of the case. It's not a summary a doctor would want to read, but it's a projection of the data into a lower dimensional space that simplifies the data in a way useful for making predictions, similar to how people are using Singular Value Decomposition in the Netflix contest.

And now the clever trick. They used the neural net to make the diagnosis, and used kNN to justify its prediction, but instead of finding cases similar in the high dimensional space of the inputs, they ran kNN on the hidden layer activations of all the training cases. The system couldn't explain in a non-numerical way how those particular cases were similar to the one in question, but generally it didn't have to, because the doctors could see the similarities for themselves once the relevant cases were pointed out.

In one sense it's just dimensionality reduction, which is something you always do with kNN if you want decent results, but the neural net was probably still more accurate than kNN operating on its hidden layer, and I thought it was clever to use one algorithm for the prediction (the primary objective) and piggyback another on its internal state to argue for its validity (a related task that turned out to be required). It's a bit like handing your brain to a friend so he can explain something from your point of view.

30 Jun 2008
giant explosions and roads not taken

00:14 UTC this morning (which for me was 5:14pm yesterday), marked the 100th anniversary of the Tunguska blast. Some friends and I mixed up white Russians, raised our glasses, and from the comfort of my living room, toasted the lack of any large explosions currently transpiring in our neighborhood.

I noticed the impending anniversary a few years ago and put "visit Tunguska site on 2008-06-30" on my list of travel ideas. I had only a vague idea of where it was. A few months ago I started to get serious about it and begun to research the event and the region's travel logistics. I even fixed the Wikipedia article, which was off by two weeks due to a calendar translation error.

The beauty of such a pilgrimage is that, as far as I know, the time and place are completely ordinary. There would be no parades, no parties, and no reason to believe anyone else would show up. The site would be the same the day before or after, and after 100 years, is probably indistinguishable from any other random patch of forest in central Siberia. But I liked the idea of flying to Irkutsk and finding slow passage 1000km north, meeting people along the way, and finally standing in a clearing early that morning (7:14am local time), watching nothing happen. If anyone else did turn up, we'd have shared something special, but in any case the journey would probably make a pretty good story.

I've had good and bad experiences traveling alone, and what it came down to this time was that I was kind of busy and didn't really feel like going. It's a little disappointing to miss a once in a lifetime chance to make a pilgrimage to the site of a large mysterious explosion on its 100th anniversary, but at the same time it seemed a little pointless and the reality of solo travel is often more laborious than entertaining. Ah, well. I'll be sure to cook up other excuses to travel, and will post stories and photos upon my return.

Since I wasn't in remote Siberia, I took some pictures at the two big shows at the circus center: Pratfalls and Rising Stars and the annual student showcase.

11 Jun 2008
moving violation

I'm moving this week, to a place about 155 meters around the corner. Ask me for my new address and coordinates if you're not a creepy stalker. Non-creepy stalkers are welcome (but good luck qualifying).

Strolling through the new place, a friend of mine found an old discarded note:

There's a feeling inside that I want you to know you are the one and I can't let you go.

* Just before that.

Apparently it's (nearly) a quote from Back Here, a song by by BBmak, who I'm not cool enough to have heard of. I've no idea what the footnote means, but most interesting is that above all that is an address in Yuma, Arizona. I guess I'll have to mail it there.

28 May 2008
obsolete habits

I just picked up my cell phone, opened it, and held it to my ear to listen for a dial tone. I haven't had a land line in years. Where was that reflex hiding all this time?

16 Apr 2008
don't try this at home

This year, paying taxes turned out to be a little more painful than usual. On my way home from the post office, I accidentally got off my bike before I came to a complete stop. I was going about 55kph. There I was, apparently not minding my own business as well as I should have been, when suddenly, in the middle of a major intersection, my bike and I went our separate ways. I suppose we must have been growing apart for some time and I simply hadn't noticed, just as I hadn't noticed any obstacles until the front wheel ran into what I can only assume must have been a tear in the fabric of space itself, or maybe that pothole I always forget about.

It all went pretty well, considering. I wore out the knees of my pants a bit faster than I'd planned and here and there I'm missing some skin I'd been taking for granted. Several bystanders got to watch me fly through the air then surf the asphalt on my wonderful biking gloves, whose virtues I can't praise loudly enough and without which I wouldn't be typing today.

When I finally ground to a halt, I got up, picked up my bike (which I was very pleased not to have gotten tangled up in), walked out of the street, and assured everyone I was fine and told them how happy I was to be wearing gloves, not realizing as I showed off my leather-clad hands that one of my arms was shouting "he's not fine, he just doesn't feel it yet". But escaping with just a few scrapes is pretty good, and it was nice that I was just a few blocks from home. I can't say that I recommend a biking accident, but if you do find yourself in one, I hope it goes as well as mine.