Radiation equipment

John Tukey said that the best thing about being a statistician is that you get to play in everyone’s backyard. This morning I got to play in IsoTherapeutics‘ backyard. The most photogenic thing on the tour they gave me was their box for working with highly radioactive material with robotic arms. (There was nothing hot inside at the time.)

 

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Time exchange rate

At some point in the past, computer time was more valuable than human time. The balance changed long ago. While everyone agrees that human time is more costly than computer time, it’s hard to appreciate just how much more costly.

You can rent time on a virtual machine for around $0.05 per CPU-hour. You could pay more or less depending on on-demand vs reserved, Linux vs Windows, etc.

Suppose the total cost of hiring someone — salary, benefits, office space, equipment, insurance liability, etc. — is twice their wage. This implies that a minimum wage worker in the US costs as much as 300 CPUs.

This also implies that programmer time is three orders of magnitude more costly than CPU time. It’s hard to imagine such a difference. If you think, for example, that it’s worth minutes of programmer time to save hours of CPU time, you’re grossly under-valuing programmer time. It’s worth seconds of programmer time to save hours of CPU time.

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What would Donald Knuth do?

I’ve seen exhortations to think like Leonardo da Vinci or Albert Einstein, but these leave me cold. I can’t imagine thinking like either of these men. But here are a few famous people I could imagine emulating when trying to solve a problem

What would Donald Knuth do? Do a depth-first search on all technologies that might be relevant, and write a series of large, beautiful, well-written books about it all.

What would Alexander Grothendieck do? Develop a new field of mathematics that solves the problem as a trivial special case.

What would Richard Stallman do? Create a text editor so powerful that, although it doesn’t solve your problem, it does allow you to solve your problem by writing a macro and a few lines of Lisp.

What would Larry Wall do? Bang randomly on the keyboard and save the results to a file. Then write a language in which the file is a program that solves your problem.

What would you add to the list?

 

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Open source dissertation

Three cheers for Brent Yorgey! He’s finishing up his dissertation, and he’s posting drafts online, including a GitHub repo of the source.

Cheer 1: He’s not being secretive, fearing that someone will scoop his results. There have been a few instances of one academic scooping another’s research, but these are rare and probably not worth worrying about. Besides, a public GitHub repo is a pretty good way to prove your priority.

Cheer 2: Rather than being afraid someone will find an error, he’s inviting a world-wide audience to look for errors.

Cheer 3: He’s writing a dissertation that someone might actually want to read! That’s not the fastest route to a degree. It’s even actively discouraged in some circles. But it’s generous and great experience.

 

 

 

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Twitter news

Starting next week, @MedVocab will post two tweets a day, once in the morning and once in the afternoon (CDT).

I’ve stopped posting to @DailySymbol. It was a fun experiment, but it was time to wrap it up.

My most popular account, @CompSciFact, now has over 100,000 followers. It’s interesting how some Twitter accounts take off and some don’t. CompSciFact has done quite well but I’ve shut down several other accounts that never gained much of a following.

You can find a list of my accounts here with a very brief description of each. Some of the accounts are a little broader than the name implies.

 

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Engineering a waterpark

This weekend my family went to Schlitterbahn, a waterpark in New Braunfels, Texas. (The German-sounding name of the park and the city are evidence of the large number of Germans that settled in this part of Texas.) I thought about several engineering questions while we were there.

Most of the rides involve sitting in an inner tube and floating down a course with rapids, waterfalls, swells, etc. At many points there are back currents. You could be headed toward a fall but then find yourself reversing direction. It’s surprising to have to work to make yourself go downhill. At most if not all these points there are employees standing in the water to grab hold of rafts and pull people in the right direction who need a little help.

One question I had is what causes the back currents. Ultimately you could solve Navier-Stokes equations, but it would be nice to understand at a more rule-of-thumb level how these currents work. It would also be interesting to see whether a park could reduce the number of guides while keeping the rides as fun. The guides also serve as lifeguards, so the park may need to position people in all the same spots even if they didn’t need as many guides.

The slowest person in the family was consistently yours truly. I’d start out in front and inevitably end up bringing up the rear. I was curious how I could be so inept at a mostly passive activity.

I was also curious how they designed the rapids to be so safe. You’re repeatedly tossed straight toward rocks — perfectly smooth artificial rocks, but still not not things you want to hit your head on — at a fairly high speed, and yet you never hit one. It has something to do with how they position jets to push you away from the rocks, but that would be interesting to understand in more detail.

Another thing I was curious about is what the park does with its water in the off-season. Schlitterbahn in New Braunfels is actually two parks, an older park that uses untreated water from the Comal river, and a newer park that uses treated water. When the parks close for the season, the older park must just let its water return to the river. (At least one of the rides ends in the river, so they’re already returning water to the river.)

The question of what to do with the treated water in the new park is more interesting. I assume they cannot just dump a huge volume of chlorinated water into the river. Aside from ecological consequences, I wonder whether they’d even want to dump the water. Is it economical to store the water somewhere when the park closes for the year? If not, do they store it anyway because they have no way to dispose of it, or do they treat it so that they can dispose it? I suppose they could circulate the water occasionally while the park is closed, though that seems expensive. I wonder whether different waterparks solve this problem different ways.

If I could propose a new ride for Schiltterbahn, it would be a video presentation about how the park was designed followed by Q&A with a couple engineers. This would be a terrible business decision, but a few visitors would love it.

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Software development becoming less mature?

Michael Fogus posted on Twitter this morning

Computing: the only industry that becomes less mature as more time passes.

The immaturity of computing is used to excuse every ignorance. There’s an enormous body of existing wisdom but we don’t care.

I don’t know whether computing is becoming less mature, though it may very well be on average, even if individual developers become more mature.

One reason is that computing is a growing profession, so people are entering the field faster than they are leaving. That lowers average maturity.

Another reason is chronological snobbery, alluded to in Fogus’s second tweet. Chronological snobbery is pervasive in contemporary culture, but especially in computing. Tremendous hardware advances give the illusion that software development has advanced more than it has. What could I possibly learn from someone who programmed back when computers were 100x slower? Maybe a lot.

Related posts:

A brief note on Moore’s law
Moore’s law and software bloat

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