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Entries from February 2020

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Leap day! (29 Feb 2020 at 23:28)

It's leap day, which gives me an extra day in the short month to write this boring blog post! Alas, I spent most of the month traveling for work and vacation, and didn't finish my main-series project(s). Is the monthly shaming even motivational for me? Yes, of course, though I am skilled at filling my life up with whatever is currently catching my fancy.

For example, earlier this month I finally got working this fairly straightforward raspberry pi project, which I built to try to diagnose wtf is going on with my overcomplicated 4-zone hot water (hydronic) home heating system. It has a problem whereby my bedroom gets annoyingly hot under certain conditions, even though the thermostat is not being triggered. Just the "boiler room" looks like this:

Boiler Room

Of course I could pay someone money to tinker with it but the true satisfaction of problem solving is in suffering that problem for multiple years while you pick up the necessary skills and data to solve it yourself and work up the mental energy to apply the solution. In the above you can perhaps barely make out the diagnostic device hanging from the scary bundle of wires (not my fault) with some of its heat sensors zip-tied to pipes. The needlessly hand-built software can give me one of these:

System Diagram

(I was pretty happy with the cheap but fairly maintainable way I decided to do this, with a templated SVG file. Since they're text, I just left placeholders like [[alice]] (the name of temperature probe "A") and just string-replace it with the temperature string as I deliver the SVG over HTTP. Will use this trick again some day.) Here you can see Floor 2 source is hotter than the others even though its thermostat isn't even on. It also produces time-series graphs of course, which are decidedly more retro (but really is only visible at full size):

Click for full 1080p pixel glory

I have succeeded in catching it in the act and have some theories about what's happening (the heat appears to be convective but I don't yet understand why the boiler keeps putting out heat in this situation). But I haven't solved it yet, and certainly haven't fixed it.

SIGBOVIK 2020 is in about a month, and so the deadline is coming up imminently. Consider submitting if you have anything to share! I have a few ideas partly done but it looks like the writing will be coming at the last minute, of course.

Stay safe out there!

(4 comments — almost 5 years ago) [ comment ]

Entries from January 2020

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174627560650599227+100919519*23#*n for n=0..24 (31 Jan 2020 at 19:10)

Hello again! I got a little bit stuck on my most recent project because I don't have the right tools to do it the best way, which has created a sort of analysis-paralysis, but I like to think that one is wrapping up. Of course I still need to make a video which will take 9999 hours. Winter's computational space heater made a decent discovery, which is an Arithmetic Progression of Primes. An AP is some starting number x, and some positive stride s, where a progression of numbers in this sequence are all prime:

x, x + s, x + 2s, x + 3s, x + 4s, ...

For example with x=3 and s=2, we have 3, 3+2, 3+2+2 prime (and then 3+2+2+2=9 is not prime), yielding an Arithmetic Progression of length 3, or "AP3". The longest such progression known is an AP27, the only one yet known found last year:

x=224584605939537911, s=18135696597948930

for 27 consecutive primes! Only twelve AP26s are known,^* and my computer found an AP25:

x=174627560650599227, s=22514425132729530

i.e. 174627560650599227, 197141985783328757, 219656410916058287, 242170836048787817, ...

only 133 AP25s are known^* so it's a pretty lucky find, although of course people care a lot less about finding these than about finding huge primes (AP1s, if you will.)

^* Technically an AP27 contains two AP26s, and three AP25s (etc.) so these numbers undercount a little.

Aside from the secret projects and winter hibernation, I played a slightly-old puzzle game called Closure which was pretty good. Definitely an interesting mechanic that they get plenty out of, if perhaps with slightly sluggish controls. I also just started Luigi's Mansion 3 for the cozy-factor, but you probably don't need me to tell you about AAA franchise Nintendo titles. I rarely recommend TV on here, but the second season of Castle Rock was unexpectedly good, if you like that sort of thing (first season is fine but there's no reason to watch them in any particular order). OK byeeee

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Entries from December 2019

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HNY 2020! (31 Dec 2019 at 22:14)

Hello and happy new year! I’m currently at a party and basically forgot to post, which is fine because I didn’t finish anything this month! I did make progress on my project, but then also expanded the scope (as is my way) and then also ruined a part of it, both activities pretty much consuming all the free time of the holiday break with such excursions. I've still been running the prime-finding space heater as described in post 1175 but my luck has regressed to the mean and I have no new primes despite running for 30x longer than last time. The winter slows me down for sure. In the melancholy I played a few video games, which were unremarkable except for Fidel Dungeon Rescue, which I really like. It’s described as a roguelike, but it’s really a puzzle game. It won my heart when I convinced myself that one level was impossible, then implemented a solver for it, which made me realize I was missing something, but then convinced myself that it was still impossible, but then the solver solved it and proved my brain is soft.

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Entries from November 2019

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2609 * 2^1549069 + 1 (30 Nov 2019 at 21:42)

Happy Thanksgiving!

One interesting thing that happened this month: A few weekends ago it was feeling cold in my office, so I thought about turning on a space heater, but why do that when I've got a 850W power supply hooked up under my desk that can provide a "useful" resistive load? My current projects don't have any long-running computations, so I fired up PrimeGrid, which is a distributed computing project that lets you hunt for prime numbers (etc.) using your stupidly overpowered home computer. Amazingly, the next day, I had discovered this prime:

2609×2^1549069 + 1

It's a Proth prime, one of the several special forms of numbers that have efficient primality tests. This particular one is 466,320 decimal digits long, in fact big enough that when I discovered it, it was the 3461^st largest prime number known to mankind (see its entry in the list of Top 5000 Primes). As you know, computers are pretty fast these days, and there exist many nerds, so this number has already slipped 62 places to #3523.

Finding this on my second day was pretty lucky, although not really beginner's luck since in college I ran Prime95 ("Great Internet Mersenne Prime Search") on any computer I could get my hands on. You can see my historic page exhorting internet strangers to join the Tom7 prime team for example. Apparently we were once in the top 100 teams in the world, so I think I deserve a prime 20 years later, right?

I finally assembled my current project and it is kind of working! There are several things I can do to improve it, which I am trying, but at this point it at least does something interesting/funny enough to make into a video. Next the trick will be finding the right stopping point. I was hoping to get a lot done over Thanksgiving break (mercifully, not traveling this year), but (not mercifully) I immediately got sick and have spent most of my time playing Pokémon in bed or warming my toes on the prime-powered heat sink. So sad to finally have some free time but not have the energy. Oh, well!

Category: momentous

(5 comments — almost 5 years ago) [ comment ]

Entries from October 2019

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The Kentucky Bourby (30 Oct 2019 at 23:12)

Well, not that much to say about October. This is the busiest time of the year at work, and this year for some reason particularly so, and I don't get much time to do anything but that.

Two running-related things. The Shadyside (that's my neighborhood in Pittsburgh) 5k was earlier this month, and I finished with a time of 20m21s, which is pretty good for a 40 year-old (6m33s/mile). This continues the recent theme of coming close to PRs I set as a 30 year-old, with some dubious excuse (in this case, I "felt sick that morning") to explain the gap, and to motivate myself to keep trying to match/beat those old times and "just lose 15 pounds" etc.. We also traveled to Kentucky, my first time there, for the Ragnar "Bourbon Chase", which event is a relay race from Louisville to Lexington, which route passes through the sites of various bourbon whiskey distilleries. William calls it the "Kentucky Bourby," which IMO should be canonical. Ragnars sound like a lot when you say it's a 200 mile relay, but that's split over 12 people, and honestly the running is not really the hard part (it's all the sleep deprivation and van logistics). Two of my legs were kind of monotonous but one was very scenic, almost "Kentucky" pastiche, with the rolling hills and perfect fences and horses and grasses. It was also cool to visit these distilleries (and e.g. Four Roses was moderately open for us at 3am), but this kind of running and sleep deprivation doesn't really set the best mood for drinking whiskey and touring the grounds (e.g. in the dark), so maybe it is not the best way to visit Kentucky's whiskey scene. Still, was a good trip.

Games-wise, I finished RAGE 2 (IMO a fine game as far as dumb shooters go, I think underrated even) and a little bullet hell roguelike called "Monolith," which I liked. This weekend I unwisely installed Call of Duty: Modern Warfare (distinct from "Call of Duty 4: Modern Warfare" and "Call of Duty: Modern Warfare Remastered"; cf. related joke) and have been saving America over and over. It's exactly what you'd expect.

I've found some time to spend on my ongoing engineering project, and made some impossible-to-undo steps (e.g. cuts into irreplaceable pieces), which is an unarguable sign of progress. This weekend I finally did one of those integration steps where I first tested a bunch of things together, and unnervingly it worked on the first try. I still have one mechanical part that I think has a pretty good chance of not working due to my naivety, in which case I will have to get creative, which is part of the fun!

Happy halloween! see you soon!

Category: races

(1 comment — almost 3 years ago) [ comment ]

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