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Edsger Dijkstra, Computer Scientist

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Wikimedia Commons

In our Retrobituaries series, we highlight interesting people who are no longer with us. Today let's explore the life of Edsger Dijkstra, who died at 72 in 2002. 

If you’ve used a computer or smart phone in the last few decades, you’ve come into contact with the work of Edsger Dijkstra. Since his death in 2002, his research in the field of computer science has in many ways only grown more important. Here are a few things you didn’t know about his life and his science. 

If you took his computer science class, you probably didn’t touch a computer.

Professor Dijkstra once said, “Computer science is no more about computers than astronomy is about telescopes,” and he taught his courses accordingly. He was a proponent of elegance in mathematical proofs, whereby puzzles are solved with efficiency and aesthetic sensitivity.

Grades were determined by the final exam, which was neither written on a piece of paper nor typed on a computer. Rather, students were given individual oral examinations in his office or at his home. The conversational exams lasted hours at a time, and students were asked how they might prove various mathematical propositions. They were then challenged to write out their proofs on a chalkboard. After the exam, students were offered a beer if they were of age, or a cup of tea, if they were not. 

He didn’t use email. Or a word processor.

Dijkstra was famous for his general rejection of personal computers. Instead of typing papers out using a word processor, he printed everything in longhand. He wrote well over a thousand essays of significant length this way, and for most of his academic career, they proliferated by ditto machine and fax. Each essay was given a number and prefixed with his initials, EWD.

Students who emailed Dijkstra were asked to include a physical mailing address in the letter. His secretary would print the message, and he would respond by hand.

Computers weren’t the only technology he shunned. He refused to use overhead projectors, calling them “the poison of the educational process.”

 

Use Google Maps? You can thank Dijkstra.

Among his profound contributions to computer science is a solution to the “single source shortest-path problem.” The solution, generally referred to as Dijkstra’s algorithm, calculates the shortest distance between a source node and a destination node on a graph. (Here is a visual representation.) The upshot is that if you’ve ever used Google Maps, you’re using a derivation of Dijkstra’s algorithm. Similarly, the algorithm is used for communications networks and airline flight plans. 

He “owned” a nonexistent company.

In many of his more humorous essays, he described a fictional company of which he served as chairman. The company was called Mathematics, Inc., and sold mathematical theorems and their maintenance. Among the company’s greatest triumphs was proving the Riemann hypothesis (which it renamed the Mathematics, Inc. Theorem), and then it unsuccessfully attempted to collect royalties on all uses of the mathematical conjecture in the real world. Evidence was never given of the proof, of course, because it was a trade secret. Mathematics Inc. claimed to have a global market share of 75 percent.

He was the first programmer in the Netherlands.

In the 1950s, his father suggested that he attend a Cambridge course on programming an Electronic Delay Storage Automatic Calculator, or EDSAC. Dijkstra did, believing that theoretical physics (which he was studying at the time at Leiden University) might one day rely upon computers. The following year, he was offered a job at Mathematisch Centrum in Amsterdam, making him the first person in the Netherlands to be employed as something called a “programmer.” (“A programmer?” he recalled of the moment he was offered the position. “But was that a respectable profession? For after all, what was programming? Where was the sound body of knowledge that could support it as an intellectually respectable discipline?” He was then challenged by his eventual employer to make it a respectable discipline.) 

This would later cause problems. On his marriage application in 1957, he was required to list his profession. Officials rejected his answer—”Programmer”—stating that there was no such job.

Previously on Retrobituaries: Albert Ellis, Pioneering Psychologist. See all Retrobituaries here.

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technology
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Health
One Bite From This Tick Can Make You Allergic to Meat
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iStock

We like to believe that there’s no such thing as a bad organism, that every creature must have its place in the world. But ticks are really making that difficult. As if Lyme disease wasn't bad enough, scientists say some ticks carry a pathogen that causes a sudden and dangerous allergy to meat. Yes, meat.

The Lone Star tick (Amblyomma americanum) mostly looks like your average tick, with a tiny head and a big fat behind, except the adult female has a Texas-shaped spot on its back—thus the name.

Unlike other American ticks, the Lone Star feeds on humans at every stage of its life cycle. Even the larvae want our blood. You can’t get Lyme disease from the Lone Star tick, but you can get something even more mysterious: the inability to safely consume a bacon cheeseburger.

"The weird thing about [this reaction] is it can occur within three to 10 or 12 hours, so patients have no idea what prompted their allergic reactions," allergist Ronald Saff, of the Florida State University College of Medicine, told Business Insider.

What prompted them was STARI, or southern tick-associated rash illness. People with STARI may develop a circular rash like the one commonly seen in Lyme disease. They may feel achy, fatigued, and fevered. And their next meal could make them very, very sick.

Saff now sees at least one patient per week with STARI and a sensitivity to galactose-alpha-1, 3-galactose—more commonly known as alpha-gal—a sugar molecule found in mammal tissue like pork, beef, and lamb. Several hours after eating, patients’ immune systems overreact to alpha-gal, with symptoms ranging from an itchy rash to throat swelling.

Even worse, the more times a person is bitten, the more likely it becomes that they will develop this dangerous allergy.

The tick’s range currently covers the southern, eastern, and south-central U.S., but even that is changing. "We expect with warming temperatures, the tick is going to slowly make its way northward and westward and cause more problems than they're already causing," Saff said. We've already seen that occur with the deer ticks that cause Lyme disease, and 2017 is projected to be an especially bad year.

There’s so much we don’t understand about alpha-gal sensitivity. Scientists don’t know why it happens, how to treat it, or if it's permanent. All they can do is advise us to be vigilant and follow basic tick-avoidance practices.

[h/t Business Insider]

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