Profile

Cover photo
Andrew Reid
Works at NIST
Attended Queen's University
Lives in Washington DC
133 followers|216,697 views
AboutPostsCollectionsPhotosYouTube

Stream

Andrew Reid

Shared publicly  - 
 
Could a neuroscientist understand a microprocessor?

This has been bubbling away in my various newsfeeds for a while, and I finally got around to reading it. The answer, unsurprisingly, is that the methods of neuroscientists give rise to results which are very, very far from the readily-available engineering understanding of the system.

What I had not appreciated until I finally dove in is that the work builds on the Visual6502 (http://www.visual6502.org/JSSim/expert.html), which I have had a lot of fun with over the years.

The scheme is, they apply activity maps, spike-train analysis, and lesion studies to an operating, simulated 6502 under three behavioral conditions -- Donkey Kong, Space Invaders, and Pitfall. In each case, they are able to identify subsets of transistors in the chip which, when disabled, inhibits one behavior but not others (bottom of page 4, top of page 5, in the section "Lesion a single transistor at a time").

My guess is that the obvious cautionary conclusion applies not only to biological neural systems, but also gene expression, where isolating the "gene for X" often seem to rely on a similar combination of blunt tools and sharp logic.

Hat tip to Alex Tabarrok for an accessible summary (http://marginalrevolution.com/marginalrevolution/2016/05/68515.html)

The full paper is here (PDF link): http://biorxiv.org/content/biorxiv/early/2016/05/26/055624.full.pdf

Tagging +mos6502 in the unlikely event they haven't seen this yet.
1
George Phillips's profile photo
 
I can understand that it probably has no effect on the main point but it bugs me that their 2600 simulation has a fairly gross error. The ladder in Pitfall! should be centered in the tunnel. Because collision detection between sprite and playfield objects is reported back to the 6502 this can go beyond a mere visual difference.

http://blog.visual6502.org/2014/10/atari-2600-simulation.html
Add a comment...

Andrew Reid

Shared publicly  - 
 
Via HN, a story about local vs. nonlocal optimization in a stochastic limited-information game.

The game is Scrabble, and the nonlocal optimizers are a new group of Nigerian players, who have cultivated a thorough knowledge of five-letter words. Playing shorter words gives your opponents fewer openings, allows you to preserve some of your own good letters for later, and also apparently reduces the probability that you'll get a bad draw.

I'm not sure I really understand that last point, it seems like the V and J and the Q have to go somewhere, and while playing shorter words reduces the probability that any given draw will be bad, it also increases the number of draws, so it seems like it would balance out.

HN link: https://news.ycombinator.com/item?id=11747367
1
Add a comment...

Andrew Reid

Shared publicly  - 
 
From the often-excellent BLDGBLOG, a story of the underworld making itself known. Apparently, with a combination of age and increasing rain, various cavities in the Earth are making themselves known in otherwise quiet residential neighborhoods. Many of them are relatively shallow, former chalk or sand excavations, but in one remarkable case, a backyard patio crumbled away to reveal a 300-foot-plus vertical shaft, a legacy of Cornish tin-mining.

The article says the house was being prepared for sale, I wonder if a vertical shaft adds to or subtracts from the value? I'd pay extra for it, but I am not in the Cornish housing market.
[Image: Drone footage of a Cornwall garden sinkhole, via the BBC]. One of the peculiar pleasures of reading Subterranea, a magazine published by Subterranea Britannica, is catching up on British si…
1
James Karaganis's profile photoEd S's profile photo
4 comments
Ed S
+
2
3
2
 
It could be like the Severn Bridge - they can go down the hole for free, but have to pay to come up again.
[Hope that's not insulting to anyone...]
Add a comment...

Andrew Reid

Shared publicly  - 
 
John Baez had this post a few days ago about how some interesting old tech is being preserved through the Historical European Martial Arts group, see the link and interesting comments below.

But he opened with a claim (not his, he credits Kevin Kelly) that "old tools never die", which maybe depends on what you think of as a "tool", but motivated some thoughts.

Lots of knowledge gets lost, the canonical famous example perhaps being Roman concrete, which we still don't really know how to do.

Years ago, I participated in the "Dead Media Project," which is a catalog of various obsolete forms of information storage and retrieval. What really struck me about it was, for most of the 20th century, analog chemical or electro-chemical techniques ruled his space, mostly photography or, later on, xerography. There are some digital media, like Zip drives, that are dead, and a lot of the media in that database are dead because of digital competitors. So the problem of information storage and retrieval remains solved, but in this space at least, the tools absolutely do die.

Ironically, the dead media site itself may be dying, although the medium of websites remains reasonably robust.

The main site is at www.deadmedia.org. My contribution was about the "Contoura" document duplicator, it's here (with an obsolete e-mail address for me): http://www.deadmedia.org/notes/49/495.html
 
Fecht Yeah

Kevin Kelly has claimed that "tools never die" - that any tool ever made is still being made somewhere.   There are interesting arguments about this online.  You can find videos on how to make stone hand axes.  You can find instructions on how make a calcium oxide light - the old-fashioned "limelight" used in theaters until it was replaced by electric arc lamp in the 1890s.  

And you can certainly buy a longsword.  That's a sword with a long double-edged blade and a cross-shaped handle, as shown here.  They reached their height of popularity from 1350 to 1550.  But people still fight with them - mainly for fun.

In fact, this weekend on Staten Island there's a course for women who want to fight with longswords!   And there's a tournament, too!  It's called Fecht Yeah, and it's probably not too late to register.  Bring your weapon.

It's part of the Historical European Martial Arts movement, or HEMA.  Here's the ad:

A weekend of training, learning, and collaboration for women who study HEMA and other sword arts.

This is an event for women of all skill levels with varied interests to come together and develop their skills. Workshops for beginners will be available. Free from tournament pressure and the constraints of classes, we have the ability to workshop teaching methods, rulesets, and learning strategies with other dedicated practitioners.

We will have laurel tournaments in longsword, sword and buckler, rapier, and saber. Prizes will be modest. Attend to learn, not win.

I'm an absurdly nonviolent guy, who will pick up a spider and take it outside rather than squash it.   But I admire skills like sword-fighting, and I'm glad people are keeping those skills alive.   Why?  I'm not completely sure.  I could theorize about it, but never mind.

Check out this video of German longsword fighting:

https://www.youtube.com/watch?v=5zueF4Mu2uM

Register here:

http://www.hema.events/aboutfy/

As you might expect, female swordfighters get flack from some male ones.  There's a nice article about Fecht Yeah here, and it get into that a bit:

http://www.villagevoice.com/news/fecht-club-new-yorks-women-warriors-kick-ass-8601021

Tiby Kantorowitz, one of the women running Fecht Yeah, treats swordfighting as a spiritual exercise:

"It's the flip side to yoga.   It's easy to Zen out with twinkly music, incense, and soft light. But can I maintain the same equanimity when there's some six-foot guy" — she's four-ten — "with a sword who's trying to brain me?"

The woman in this picture is Laura McBride, and she was photographed by Brad Trent.

For Kevin Kelly's claim, try:

http://www.npr.org/templates/transcript/transcript.php?storyId=133188723

KRULWICH: And then he made this ridiculous bet. He said: I bet you can't find any tool, any machine - go back to any century you like - that still isn't being made and made new today. So all I have to do is find a single tool that's not being made anymore, and I win.

(Soundbite of laughter)

KELLY: Yes, that's right.

KRULWICH: You're so going to lose this.

And then the show explores this....
63 comments on original post
1
Add a comment...

Andrew Reid

Shared publicly  - 
 
The mandatory shot. It's actually a very impressive building, the backlit phone camera shot does not do it justice.
2
Add a comment...

Andrew Reid

Shared publicly  - 
 
Today's ride.

It was a bit early in the season for one this long, I definitely over-did it, and in fact for the first time in a few years, had serious difficulties with Heartbreak Hill.
It was also a bit of an exploration, using a slightly different route up to Silver Spring through upper northwest DC.
1
Add a comment...
Have him in circles
133 people
David Larsen's profile photo
Alexander Lobkovsky Meitiv's profile photo
Mark Warren's profile photo
Mark Locatelli's profile photo
Cornus Ammonis's profile photo
faradillah devseven's profile photo
Kate Childers's profile photo
PEAK OIL happened 2006's profile photo
Unique Gifts for Cycling, Camping and Outdoor Enthusiasts's profile photo

Andrew Reid

Shared publicly  - 
 
So apparently Delta has noticed that thing where, if you have more than one server for a single queue, the throughput gets increased by a factor greater than the number of servers in use.

I'm eager to see this get more widely deployed, but I'm not sure "innovation" is the right description. It's a basic result of queuing theory, and arises because, with a single server, the queue is rate-controlled by the slowest transaction, but with multiple servers, you have to have multiple coincident slow transactions to stall the queue. The application of this to airport security isn't even innovative, I saw it at both Heathrow and Barcelona on my recent business trip. It's not a panacea, by any means, my security experience at Heathrow was far from optimal, but that was unrelated to queue management issues.
Delta's 'Inovation Lines' project moves travelers through TSA checkpoints u to twice as fast, reducing wait times and frustration levels.
1
George Phillips's profile photoAndrew Reid's profile photo
3 comments
 
Found a weirdly incomplete analysis here:
http://aix1.uottawa.ca/~glamothe/mat4371/Queues.pdf

The "incomplete" part is that they don't define their notation, but assuming they are using the same scheme as Wikipedia, an M/M/1 queue has a line-up for one server, and an M/M/2 queue has one line-up for two servers. Other undefined parameters seem to be, lambda is Poisson process parameter for the arrival rate, and mu is the exponent of the exponential distribution of service times.

You can only actually compute closed forms for the average waiting time for stationary states of the system.

It seems obvious (although I confess I haven't even done this basic calculation yet) that an M/M/2 queue will outperform an M/M/1 queue with the same parameters -- the M/M/2 queue has more resources, so it had bloody well better do better (and, staying on topic, this seem to be part of what Delta has figured out -- just easing up on the filling-the-bin chokepoint already helps).

Less obvious, but as I recall still true, is that a single M/M/2 queue with arrival rate lambda outperforms two M/M/1 queues, each with half the arrival rate, assuming the same service-time distribution, where "outperforms" means has better throughput, corresponding to a lower average waiting time. I'm less sure that it's better on other metrics, like server utilization.
Add a comment...

Andrew Reid

Shared publicly  - 
 
I haven't actually been on my bike for a while, and didn't participate in "bike to work day" today, so I am suitably ashamed, but this is still awesome.

Extra points for "Cuddleville" and "Nicechester", I plan on stealing those.
 
It is morning. You are slow-rolling off the exit ramp, nearing the end of the long-ass commute from your suburban enclav…
2 comments on original post
1
Add a comment...

Andrew Reid

Shared publicly  - 
 
From the Retrocomputing G+ community (where I'd have posted this if I hadn't been beaten to the punch), some lunatic has built a discrete-transistor 6502.

Perhaps unsurprisingly, it's the same lunatic who build the discrete-transistor 555 and 741.
 
"A new dis-integrated circuit project to make a complete, working transistor-scale replica of the classic MOS 6502 microprocessor."
The MOnSter 6502. A new dis-integrated circuit project to make a complete, working transistor-scale replica of the classic MOS 6502 microprocessor. We'll be showing off our progress at the 2016 Bay Area Maker Faire! Credits. The MOnSter 6502 is a work in progress, designed by Eric Schlaepfer, ...
7 comments on original post
2
Add a comment...

Andrew Reid

Shared publicly  - 
 
Got this via a chain of shares. The gist of it is, it's a math puzzle, you have a box with three six-sided dice in it, and you want to play a game that requires two six-sided dice, what's a good way to map the three indistinguishable six-sided dice roll result into two dice? It's not entirely clear from the puzzle statement, but I assume you want to get the results of the two dice, not just the total -- this might matter in a game like Monopoly where "rolling doubles" matters, the effect of a (2,4) roll is not identical to a (3,3), so just knowing the total is insufficient.

The linked video has a flow-chart based solution that's reasonably interesting, and also has a link to the original video on the standupmaths Youtube channel, where there are a number of other solutions proposed.

I think I have a solution that's simpler than any I have seen, but I am disinclined to wade through comments.

My solution is this: Given the three indistinguishable values, order them from smallest to largest, and assign lables, say v0, v1, and v2. Then, take the sum of the values modulo 3, and exclude that value from the result. The other two values are your two-dice solution.

I think this gives you the same probability distribution for the value pairs as two actual fair six-sided dice. And, in fact, I think the order is arbitrary.
 
What to do if you have 3 dice all inside a transparent cube and you can't take them out but you want to play a game that requires only 2 dice.
8 comments on original post
1
Andrew Reid's profile photoPhillip Landmeier (ᚠ)'s profile photoGeorge Phillips's profile photo
6 comments
 
Glad to see Python is keeping up with old bug traditions. As a teaching assistant way back when I saw quite a few students with the same problem in their C programs. They meant to call function "foo" but wrote "foo;" instead of "foo();". The former is an expression that returns a pointer to the function foo. That evaluating the function has no effect was of no concern to the C compiler so it didn't mention it to the programmer.

Even today gcc doesn't care unless you turn up the warnings. Which seems like a silly default to me. I wonder if Python has some way to check for that error?

I presume the students fell into the trap based on experience from Pascal where one just used the name of a procedure to call it (if the procedure takes no arguments).
Add a comment...

Andrew Reid

Shared publicly  - 
 
Lunch on our "day off" after a conference in Barcelona. The walkway is "La Rambla", a 1.2 km long pedestrian walkway through an amenity-rich (and touristy) part of town.

1
Andrew Reid's profile photoTom Hardy's profile photo
3 comments
 
yeah I didn't get any trouble tbh. Even though we did go looking for it :)
Add a comment...

Andrew Reid

Shared publicly  - 
 
An island off the coast of America....

Strolling the High Line park, we just ran across this sculpture of Manhattan, by Yutaka Sone (according to the label nearby). It appears to be carved from marble, and besides capturing the buildings as surface relief, also has protrusions for the piers and bridges. I was slightly disappointed to note that it does not have holes corresponding to the tunnels that connect things below ground.
2
Add a comment...
Andrew's Collections
People
Have him in circles
133 people
David Larsen's profile photo
Alexander Lobkovsky Meitiv's profile photo
Mark Warren's profile photo
Mark Locatelli's profile photo
Cornus Ammonis's profile photo
faradillah devseven's profile photo
Kate Childers's profile photo
PEAK OIL happened 2006's profile photo
Unique Gifts for Cycling, Camping and Outdoor Enthusiasts's profile photo
Collections Andrew is following
Education
  • Queen's University
    Physics, 1989 - 1994
  • University of British Columbia
    Physics, 1986 - 1989
  • University of British Columbia
    Physics and Computer Science, 1982 - 1986
Basic Information
Gender
Male
Story
Tagline
Clever. Maybe clever enough.
Introduction
I studied computer science and physics at UBC, and have never really let go of either. I read a lot. Geeky, but not in a debilitating way.
Bragging rights
I know how much wood a woodchuck would chuck, but I'm not telling.
Work
Occupation
Scientific computing
Employment
  • NIST
    Scientific computing, present
Places
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Currently
Washington DC
Previously
Canada - Calgary - Vancouver - Chicago