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mnw21cam commented on “Are you the one?” is free money   blog.owenlacey.dev/posts/... · Posted by u/samwho
jncfhnb · 2 days ago
If you can only check pairings one at a time I’m not sure it’s possible to do better than greedily solving one person at a time.
mnw21cam · 2 days ago
Agreed. There's an argument elsewhere about how a truth booth can possibly have an expected return of more than 1 bit of information, but in reality most of the time it's going to give you way less than that.
mnw21cam commented on “Are you the one?” is free money   blog.owenlacey.dev/posts/... · Posted by u/samwho
stevage · 2 days ago
You also learn about other pairings now being impossible.
mnw21cam · 2 days ago
No, that doesn't make sense either. For a truth booth, you're taking all the possible pairing arrangements, and dividing them into two sets. After the answer, one of those two sets is false. There is no way that this can provide more than 1 bit of information.

The match-ups can however give more information, as it isn't giving a yes/no answer.

mnw21cam commented on “Are you the one?” is free money   blog.owenlacey.dev/posts/... · Posted by u/samwho
cgriswald · 2 days ago
> If the group can correctly guess all the perfect matches, they win a cash prize of $1M.
mnw21cam · 2 days ago
Is that each, or divided between 20 people?
mnw21cam commented on The stack circuitry of the Intel 8087 floating point chip, reverse-engineered   righto.com/2025/12/8087-s... · Posted by u/elpocko
johngossman · 8 days ago
Sometime in the 80s, I implemented the core of the Mandelbrot Set calculation using assembly on an 8087. As the article mentions, the compilers did math very inefficiently on this stack architecture. For example, if you multiplied two numbers together and then added a third, they would push the first two numbers, multiply, pop the result, push the result back onto the stack (perhaps clearing the stack? after 40 years I don't remember), push the third number, add, pop the result. For the Mandelbrot loop this was even worse, as it never kept the results of the loop. My assembly kept all the intermediate results on the stack for a 100x speed up.

Running this code, the 8087 emitted a high-pitched whine. I could tell when my code was broken and it had gone into an infinite loop by the sound. Which was convenient because, of course, there was no debugger.

Thanks for bringing back this memory.

mnw21cam · 8 days ago
The idea of listening to hardware running a program to tell what it is doing is surprisingly old. On the EDSAC computer[0] a little speaker was connected across one of the serial data lines, which allowed the progress of a program to be listened to. Skilled operators could immediately tell when a program had triggered a bug and either gone off into the weeds or entered a tight loop.

[0]: https://en.wikipedia.org/wiki/EDSAC

mnw21cam commented on 1D Conway's Life glider found, 3.7B cells long   conwaylife.com/forums/vie... · Posted by u/nooks
mnw21cam · 13 days ago
Pretty please with a cherry on top use standard SI multipliers for numbers like this. I can't be sure without reading the article whether you mean 3.7G cells or 3.7T cells. Billion is ambiguous having different meanings to different people and should not be used as a word any longer.
mnw21cam commented on China reaches energy milestone by "breeding" uranium from thorium   scmp.com/news/china/scien... · Posted by u/surprisetalk
pdpi · 25 days ago
My understanding is that reactors will use that plutonium just fine, so the energy you get from a fresh fuel rod is almost exclusively from uranium fission but, as time goes on, an increasingly large share is from plutonium fission.

In principle, using Thorium would give you the energy from Thorium fission, then Uranium fission, then plutonium fission, which is pretty cool. However, I suspect you might hit an issue here where such a low conversion rate would make the reactor go sub-critical.

mnw21cam · 25 days ago
No, this is a misunderstanding of how fission works.

When a nuclear reactor is run with mildly-enriched Uranium, which is a mixture of Uranium 235 and Uranium 238, it forms a self-sustaining chain reaction with the Uranium 235 (which is fissile) and a load of the spare neutrons get absorbed by the Uranium 238 (which is fertile), converting it into Plutonium 239, which is also fissile. But most Uranium 235 reactors use a moderator which slows down the neutrons, which makes them more likely to cause fission in Uranium 235 but less likely to transmute Uranium 238 to Plutonium 239. So most modern reactors don't produce much Plutonium. In any case, the fission you get from Uranium and the fission you get from Plutonium is from different source materials. Once an atom is fissioned, it is split into smaller atoms and can no longer be fissioned.

Thorium isn't fissile, it's fertile. That is, if you fire a neutron at Thorium 232, you get Thorium 233, which decays to Protactinium 233, which then decays into Uranium 233, which is fissile. You then fire another neutron at Uranium 233, which then fissions into much smaller nuclei, giving you energy and the neutrons to do the above. The Uranium is no longer around after that to form Plutonium. There is no way to get any significant amount of Plutonium 239 from this, because that would require adding 7 more neutrons to the original Thorium 232 and having none of them trigger a fission event. The fissions that do occur don't provide 7 neutrons anyway, so it wouldn't be possible to get a self-sustaining conversion of a significant amount of Thorium into Plutonium for final fission even if the previous sentence weren't true - it would have to be enhanced with some other provider of lots of neutrons.

mnw21cam commented on Nearly all UK drivers say headlights are too bright   bbc.com/news/articles/c1j... · Posted by u/YeGoblynQueenne
delichon · a month ago
It does appear to be a UK thing. This is from the UK Highway Code. I'm not finding a US equivalent.

  114 You MUST NOT use any lights in a way which would dazzle or cause discomfort to other road users, including pedestrians, cyclists and horse riders use front or rear fog lights unless visibility is seriously reduced. You MUST switch them off when visibility improves to avoid dazzling other road users (see Rule 226).

  In stationary queues of traffic, drivers should apply the parking brake and, once the following traffic has stopped, take their foot off the footbrake to deactivate the vehicle brake lights. This will minimise glare to road users behind until the traffic moves again.
https://www.gov.uk/general-rules-all-drivers-riders-103-to-1...

mnw21cam · a month ago
Well found, though I'll also point out that the highway code uses "MUST" and "should" in the same way as the RFCs do.
mnw21cam commented on Nearly all UK drivers say headlights are too bright   bbc.com/news/articles/c1j... · Posted by u/YeGoblynQueenne
delichon · a month ago
> When you're waiting at a red light, you're meant to have the hand brake on (which does not illuminate the brake lights), not your foot on the brake, unless you know that the light is going to turn green very soon

I was definitely not taught this as a US driving student. Is this a UK thing?

mnw21cam · a month ago
I can't see how it would be country-specific. How else would you have any control of the forward motion of the vehicle otherwise, especially when starting on an uphill slope? You're meant to raise the clutch to the biting point and apply some accelerator and release the handbrake when you are confident that the engine will prevent the car from moving backwards. Taking the foot off the brake and hoping you can move it over to the accelerator quickly enough doesn't give you that control. Drifting backwards into the car behind you when setting off is rather an embarrassing thing to do.
mnw21cam commented on Nearly all UK drivers say headlights are too bright   bbc.com/news/articles/c1j... · Posted by u/YeGoblynQueenne
jeffwass · a month ago
I don’t understand the seeming lack of regulation for flashing bike lights.

I don’t mean a simple “normal” flashing light, but the super bright ones that are like a camera flash strobe going off 2-3x per second which hurts your eyes and kills your night vision, making it hard to see anything including the actual cyclist.

mnw21cam · a month ago
It used to be law that a bicycle had to have a solid on light front and back at night, and any extra flashing lights were optional extras that didn't count, but they scrapped that law several years ago.
mnw21cam commented on Nearly all UK drivers say headlights are too bright   bbc.com/news/articles/c1j... · Posted by u/YeGoblynQueenne
sanex · a month ago
Honestly I'm seeing the opposite. Some new cars, I THINK Camry's, have taillights so bright it's blinding to wait behind one at a stoplight. They don't need to shine just glow so you can see them.
mnw21cam · a month ago
I have never understood why everyone seems to immediately forget everything in their driving lessons as soon as they pass their test. When you're waiting at a red light, you're meant to have the hand brake on (which does not illuminate the brake lights), not your foot on the brake, unless you know that the light is going to turn green very soon, or you're trying to catch the attention of someone coming up behind who looks like they haven't seen that you have stopped.

u/mnw21cam

KarmaCake day5954October 29, 2013View Original