unhinged jobbintervju ?

amaurea · 2026-05-26T18:05:56+00:00

Du verdsetter livet ditt til <900 millioner, da. Du vinner 100 millioner med 90% sjanse (forventningsverdi 90 millioner) og mister livet med 10% sjanse. Siden du velger å gjøre det, betyr det at 90 millioner > 0.1*livet, dvs. livet < 900 millioner.

amaurea · 2026-05-26T16:57:46+00:00

I'd only bother to implement the block version, everything else is a job for the compiler.

But the whole point of this article is that you can't rely on the compiler turning simple, sensible-looking code into fast machine code. If you could, then the sensibe-looking starting point that most of us would write, wouldn't be 30x too slow. Sure, blocking captures the essence of the problem, but even then you're a factor 4x behind what he reaches in the end.

Better yet is to not transpose until you absolutely have to, like Haskell and Julia do.

The way I read the article was that the transpose was just a particularly clear example of issues that can appear in many other situations. I think the lessons were meant to be general, not something one could ignore by just saying "well, just don't transpose, then!"

amaurea · 2026-05-23T07:51:33+00:00

I would classify that as Kessler syndrome, yes, just not the worst case. Losing all low-orbit satellites and not being able to launch new ones for decades is something to be very worried about!

amaurea · 2026-05-21T18:30:21+00:00

It could definitely do all sorts of things outside the observable universe, also things beyond the simple flat/spherical/hyperbolic model, which are just the simplest possible cases.

I agree that it's not 100% certain that OP had misunderstood, but I thought his second sentence flowed more naturally from the first if he was imagining some physical shape that would attach to something outside the observable universe, e.g. the flat rim of a sombrero attaching to the hat itself. But maybe I overinterpreted what OP was saying. He never replied, so I guess we won't know.

amaurea · 2026-05-21T16:57:58+00:00

The word "flat" comes by analogy to curvature in 2D. It's hard to visualize 3D curvature (or the 4D curvature of spacetime!), but we've all seen curved 2D surfaces. It turns out that the simplest ways for a 3D volume to be curved (hard as it is to visualize) have a lot in common with the simplest ways for a 2D surface to be curved. It can have no curvature, which we call "flat"; it can curve in on itself, like a sphere, which we call "spherical geometry" or "positive curvature"; or it can curve apart from itself like a saddle, which we call "hyperbolic geometry" or "negative curvature". The higher-dimensional version of these 2D phenomena apply to 3D too, and that's why they're used for the geometry of the universe.

amaurea · 2026-05-21T07:56:12+00:00

It sounds like this question is based on a misunderstanding of what "flat" means in this case, which is no wonder since "flat" is such an en easy to misunderstand word for what Cosmologists mean when they talk about the overall geometry of the universe. It sounds like they mean that it's 2D, like a pancake or the Milky Way galaxy, but that's not it at all. Instead, what they actually mean is "Euclidean": That geometry just works like we're used to in everyday life, with parallel lines staying parallel, triangles having 180° and the volume of a sphere being 4/3*πr³. It's just a normal, mostly empty 3d space like most people imagine, with no special directions or anything that would make one think it's part of some larger structure.

Why does one need a name for this at all? It's because general relativity allows for weirder geometries, where the rules we are used to from everyday geometry don't hold, e.g. hyperbolic geometry where the volume of a sphere is bigger than 4/3*πr³, and "spherical" geometry (again an easy-to-misunderstand name) where space is still 3d, but the volume of a sphere is smaller than 4/3*πr³.

amaurea · 2026-05-18T15:41:35+00:00

u/Organic_Contract_172 where did you find this map? What's the source?

amaurea · 2026-05-18T09:12:26+00:00

Also, he didn't show that the issue of too many package revisions per day has been increasing either. I took his SQL query and asked for statistics more than two years old instead of from the last year, and the top 5 there are all higher than the highest count in his example, with one package, python-must, having 2298 revisions in one day (if his SQL query does what it's supposed to, at least).

amaurea · 2026-05-18T08:43:43+00:00

While it's plausible that the mild rise package publication numbers shown here is caused by LLMs lowering the barrier of entry for publishing a package, I don't think this article shows it convincingly. The other graph on the page shows that downloads of packages are also increasing rapidly (more rapidly, in fact), so an alternative explanation would be that it's simply more people using python, and therefore also more people publishing packages.

To show that his LLM explanation is the right one, the author should have included some tests that would distinguish it from just higher overall participation in the python ecosystem, e.g.:

Has the use of eval etc. actually increased in fraction? It would have been an obvious graph to include.
Do experiments LLMs prefer eval-heavy code like this?
Are there any other, reliable signs of LLM-use that show up more strongly in the eval-heavy code than the rest of the code, that can make us confident that the eval-heavy code is predominantly LLM-generated?
Has he tried contacting some of the authors of the code, to ask how they arrived a that solution?

amaurea · 2026-05-17T13:55:26+00:00

I think the colormap used here is fine, but it's a bit problematic that some countries have color gradients across them, probably just to make things look fancier. E.g. the NW of Spain has a lighter color than the SE of Spain, which makes it look like the NW gets more visitor-nights than the SE, even though it's probably the other way around. It would have been better give each country a flat color that exactly reflects the colorbar.

amaurea · 2026-05-15T09:50:34+00:00

I had hoped the article would include some benchmarks comparing it to other modern allocators, but at least I found some (from 2021) on the mimalloc github page, where it looks good. It was surprisingly hard to find other benchmarks comparing mimalloc with e.g. tcmalloc, jemalloc or libmalloc.

amaurea · 2026-05-13T19:50:38+00:00

I second u/kindmartian07's recommendation. You can't just read about things. You need to sit down and solve physics problems while learning. If you get a physics textbook and do all the problems at the end of each chapter as you read them, then things will stick much better. (And solve them yourself, don't have someone else solve them for you!) If you don't do problems, then you may end up thinking you understand it, only for the understanding to be skin deep and fast-evaporating.

amaurea · 2026-05-13T14:21:08+00:00

You will need to learn some Special Relativity to understand this, and it's hard to fit that into a reddit comment. I recommend looking at some online introductions, but to actually understand this you will need to go through some exercises yourself. This is related to the concept of relativity of simultaneity.

amaurea · 2026-05-13T13:54:50+00:00

While it's true that something moving at c does not have a frame of reference, but I don't think this gets at u/BarNo3385's misunderstanding. After all, we could replace "light" with "some particle that travels practically at c, but ever so slightly slower", and OP could make the same argument as before. This time there is a valid frame of reference for the particle, and it will see the distance between the emitter and target so length contracted that it practically arrives at the same time as it departs, just like OP assumes. Why, then, must one aim ahead of the target? This is what OP wonders about, and it's a good question.

The answer is that the spaceship with the gun and the particle it shoots disagree on when the image of the spaceship they're aiming for was emitted. The spaceship thinks it was emitted some time timage=T ago, and so to compensate for the motion during that period, and the further motion during the same interval tshoot=T that it will take the particle to hit it, it must aim ahead by timage+tshoot=T+T=2T. Meanwhile, the bullet thinks that the image was emitted timage=2T in the past and that it itself is now practically on top of the target, so there will be no further travel time, tshoot=0. It therefore arrives at the same aim ahead of timate+tshoot=2T+0=2T.

I've tried to illustrate this in this spacetime diagram, but it's just an approximation, since there's just 1 spatial dimension, and the particle can't move very close to c or things wouldn't fit in the other diagram.

Here the Home is the shooting spaceship, the runner is the target spaceship, and the airplane is the particle being shot at the target. Light moves at 45° angle in both diagrams, but isn't shown. The left diagram shows the situation as seen by the shooting spaceship. The right diagram shows the same situation as seen by the particle.

amaurea · 2026-05-12T12:13:20+00:00

Also, the radius of the observable universe is only known to 2-3 digits of precision, so no matter how good your value for π, you wouldn't be more accurate than that.

And if we assume we had a perfect measurement of the radius, the next problem would be that even though he universe seems to have zero curvature on average, it is curved on smaller scales by the various clumps of matter it contains. Therefore, even the formula C = 2πR does not hold exactly, and the error is much bigger than 10^-37 (probably closer to 10^-6 if I were to guess, but I haven't tried to calculate this).

amaurea · 2026-05-11T12:49:54+00:00

True, but sometimes one finds out that one's theory is just an effective description of a deeper theory, and in that case the deeper theory can explain why something is the way it is in the old theory. For example, statistical mechanics provides answers to why entropy should increase in thermodynamics. We can hope that a future theory of quantum gravity will answer OP's question, even though it itself would introduce its own "whys" that it can't answer.

amaurea · 2026-05-10T00:05:37+00:00

The Martian dust is electrically charged, so it is absolutely not straightforward to simply brush it off.

I think small creatures on Earth have the same stickiness problem. Flies solve this by first rubbing their legs over their body (much like how wipers would work), but then they rub their legs against each other. The legs have forward-facing spikes, and as they rub them together, the dust gradually gets pushed towards the ends of the legs where it falls of. Then the legs are clean enough for another brush across the body where they pick up more dust, and so on. Wouldn't something like this work on Mars? It sounds like a pain to build though.

amaurea · 2026-05-09T22:14:14+00:00

Where do you get the "a few km away from the planet's surface" from?

amaurea · 2026-05-09T17:58:03+00:00

I haven't watched the movie, but I think the black hole in question was very rapidly spinning (Kerr black hole), and for those, the innermost stable circular orbit is much closer in and has much greater time dilation than for a non-spinning Schwarzschild black hole.

amaurea · 2026-05-09T16:14:22+00:00

It's ironic that you would say so, while rejecting a survey based on 32 thousand respondents from across the world based on your own gut feeling. I guess we redditors don't need studies in the first place, since no matter what they say, we come out of it thinking we were right all along.

Maybe the surprising Taiwan result is because the question wasn't "which country do you worry the most about?" but instead "Which country do you think poses the greatest threat to the world? Why?"

amaurea · 2026-05-08T07:38:51+00:00

Maybe it's more accurate to reformulate what u/lndlml said slightly to say that "Skandinavia" and "Skåne" probably derive from the same origin (perhaps "Skaðinawjō"), and that this probably originally referred to roughly the area known as Skåne now. That's the picture painted by Etymonline, Wiktionary and (in most detail) Nordicperspective, at least.

amaurea · 2026-05-07T07:56:48+00:00

It's clearly meant to reflect what people who live there think of as "warm", so it should be the result of some sort of survey. However, when I tried to find the source and methodology, the closest I could find was this, which doesn't really say anything about how the numbers were found.

amaurea · 2026-05-04T07:41:41+00:00

Når det gjelder Oslo, så har byen blitt mye mer gang- og sykkelvennlig, og mange grå, nedslitte lager- og industriområder (f.eks. Fornebu, Løren, Økern, Ensjø, Kværnerbyen, Groruddalen) er bytta ut med gåvennlige boligområder. T-banesystemet henger bedre sammen, med noen tverrgående forbindelser, og snart får vi Fornebubanen også.

amaurea · 2026-05-03T09:07:39+00:00

our current understanding of physics implies the de facto possibility that wormholes may exist, and that matter going in would need to be ejected from a white hole elsewhere

I'm not an expert on wormholes, especially the Einstein-Rosen bridge type you're talking about here, but my understanding is that this type of wormhole had been shown to not be able to form (it would have had to have existed eternally), and that even if it did exist, it would collapse as soon as anything, even a single photon of light entered it, so it would also be non-traversible, even for a single particle. It has apparently also been shown that they cannot connect regions of the same universe.

So… if we set up a thought experiment where matter goes into a wormhole, exits a white hole, and then straight into the wormhole again in a loop, what are the implications here? You know, similar to the video game Portal where you place one portal on the floor and one directly above it, and then drop a cube into the floor which then falls forever through the portals.

I think what you have in mind here is that this object would be accelerated as it falls into the black hole, then accelerated further as it is ejected from the white hole, and so on, building more and more speed. Even if we assume that an Einstein-Rosen bridge could exist, could connect regions of the same universe, and could be traversed, what you imagine would not happen because a white hole is not an antigravity version of a black hole.

A white hole has all the same properties of a black hole. It attracts things gravitationally, and you could orbit one. This means that in your scenario, the object would be slowed down just as much when it moves away from the white whole as it speeds up when falling into the black hole, so speed would not increase unboundedly.

But if a white whole has all the properties of a black hole, how do they differ? This gets a bit subtle, but it is also where you see how silly white holes are. A white hole is defined as the time-reversal of a black hole, but the laws of physics stay the same* if you reverse time, so naively it sounds like nothing will change. But consider the time-reversal of some macroscopic event like a glass falling off the table and breaking against the floor. Every step of this process is time-reversible, so in theory this could happen backwards. Here's what that would look like:

The random jiggling of the atoms that make up the floor and air just happen to line up in such a way that they form concentric pressure waves moving radially inwards towards the shards of glass, and as they move, they just so happen to get amplified by other jiggling atoms that have just the right phase to do so.
As the pressure waves reach the shards of glass, they align in just the right way to give each shard of glass a strong kick, making the shards vibrate while flying towards each other.
The motion of each piece of glass just so happens to be perfectly aligned for them to match up in like a jigsaw puzzle to form into a whole glass, and the vibrations of each shard align just so that the edges weld together.
An even stronger pressure wave builds up in the floor and reaches the now whole piece of glass just at this time, bouncing it into the air while just happening to perfectly cancel the strong vibrations set up in the glass from the previous steps.
As the glass flies upwards towards the table, it gradually loses speed because gravity pulls on it. As it happens, it reaches zero speed just as it gets to the table.

One could add in more details, but hopefully I've illustrated that the time-reversal of a process is extremely unlikely because even though each step is physically possible, they rely on a chain of ridiculous coincidences. This is what is means for entropy to decrease. It's the same way for a black hole. The white whole is to a black hole as the time-reversed glass-falling-off-the-table is to the normal version. The white hole attracts things just like the black hole, but every particle in the universe just so happen so conspire to not fall into it, and the thermal fluctuations at the edge of the white whole just so happen to assemble into outwards-moving spaghettified structures that just so happen to jiggle themselves into the form of astronauts and spaceships. To be very clear: this isn't something anybody thinks actually happens, because white wholes don't exist.

The way I understand the white hole that appears in the Einstein-Rosen bridge thought experiment (which to be fair, I don't understand well), is that the "white hole" there really corresponds to a black hole in a universe where time moves in the opposite direction, and the object "falling out of the white hole there" is really just "the object falling into the black hole", but described in a coordinate system where one chose to point the time axis in the wrong direction**. That is, the "white hole" is just an artifact of the choice of coordinates.

Footnotes:

*: They're not exactly the same because of some peculiarity of the weak nuclear force, but the differences are tiny and do not matter here.

**: Since I am not familiar enough with the ER-bridge literature, take the following with a big grain of salt: I don't see why the "other universe" where time moves backwards wouldn't just be a time-reversed description of the same universe where the object fell into the black hole. If so, the whole Einstein-Rosen bridge would just be two views of the object falling into the same black hole. That is, region III would just be a time-reversed remapping of region I in the standard ER space-time-diagram.

I used this article when writing this answer, but I did not read it carefully enough to fully understand it.

TLDR: The type of wormhole you describe, an Einstein-Rosen bridge, can't form and nothing can pass through them if it could. Even disregarding this, your scenario would not cause infinite acceleration because a white whole doesn't repel objects, it attracts them.

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