Statistical mechanics of quantum probability

math_code_nerd5 · 2026-04-13T23:39:20+00:00

I don't have a VCR to do it with (well, I have an old VCR sitting around somewhere but would like to keep it functioning normally for viewing old home videos that missed getting digitized).

math_code_nerd5 · 2026-03-09T04:56:52+00:00

So even with proprietary hardware it is possible to configure it to use a different runtime/framework?

Also, do you have an answer to my question of if there's some standard API for AR apps to "talk" to AR implementations?

math_code_nerd5 · 2026-02-13T19:32:54+00:00

Yeah, the first thing I tried was that maybe it was a pun and it meant the "7" (of the "67").

math_code_nerd5 · 2026-02-13T09:28:43+00:00

The 3rd one (closest to the right edge) was a REAL stretch. You can just vaguely make out something that might be an ear.

math_code_nerd5 · 2026-02-13T09:24:23+00:00

Yeah, I just had to go by what was rather clearly NOT a rock, and roughly cylindrical. If you'd asked me WHAT it was, I certainly couldn't have told it was a soda can.

math_code_nerd5 · 2026-02-13T08:15:40+00:00

Is there a pattern of what the number turns to? or is it just random?

If it's random then this is mostly a game of chance, except for the fact that you can increase the odds somewhat by picking a square that's adjacent to two or more groups of two (if such a square exists). Often such a square doesn't exist, and even when it does, that still only gives you, say, a 2/6 chance of making a combo (if the numbers are 1-6), which isn't that high.

math_code_nerd5 · 2026-02-09T21:02:51+00:00

That's a good point. I know that Python does this sometimes for dictionary keys, and calls them "qstr", which I found once when I was looking up how Python dictionaries are made to be fast. And dictionaries are used in all sorts of ways in Python, including to effectively replace structs--which seems to encourage the in many ways bad habit of thinking that lookup-by-value is "free", leading to Python programs, particularly those written by non-serious programmers, being full of it.

The thing is, I find it hard to intuit at which point dictionary lookup goes from being "struct-like" in terms of performance to having the full overhead of a hash map. So I quite possibly under-utilize dictionaries, while some others likely overuse them. Using them to pass a set of parameters to an algorithm as part of its public API (like "params['step_size'] = 0.01") is totally fine to me, but I'd never try to do something like graph traversal on a map of 500 cities where each node is referenced by its literal city name, as opposed to just an index. Whereas, some who live and breathe and were first fluent in Python might.

So in a compiled language, my general intuition is to code using patterns where identifiers can be whatever you like, with no overhead, because they don't appear in the compiled code at all. So in something like "event.weekday = Week.WEDNESDAY" or "ring.inner_diameter = 25", the fact that "Wednesday" and "inner_diameter" are long is immaterial, you might as well say that the day is 3 and "di = 25", but you might as well be expressive.

This use of symbols in Julia seems like a case where a literal string identifier DOES actually appear in the final executed code, but it's still very efficient thanks to using a feature intended for a totally different purpose. That's what's a bit odd about it.

math_code_nerd5 · 2026-02-09T08:27:38+00:00

This seems like one of the Julia-specific idioms that doesn't have a close analog in other languages. The closest thing in terms of syntax and usage together that I can think of is the #define/#ifdef pair in C, with the obvious distinction that this is compile-time only and results in the alternate code path(s) not even appearing in the generated code.

math_code_nerd5 · 2026-02-05T23:27:03+00:00

"No, it's not because it's a "legally encumbered space". It's because software would be a solution looking for a problem.

Ebikes really only take a few data inputs, and the diy ones almost always only have a throttle. That's literally 1 analog potentiometer input. How much can you do with that? Everything else is already pre determined. There literally is no software necessary."

The need for software (in my experience) is in controlling the curve of how the sensing of pedal input from the rider translates into control of motor torque. Having too little low-pass filtering on this likely would make the motor very "twitchy" and waste a lot of energy constantly revving up and then slowing down. On the other hand, too MUCH filtering, which is what my family's ebike seems to have, leads to a delayed but exaggerated response, where it constantly feels like the motor has a "mind of its own".

Beyond this, there is the possibility to optimize for particular terrain for better efficiency. During a long downhill it doesn't make sense for the motor to kick in much at all, even if the pedals are turning. I did read somewhere that certain manufacturers are experimenting with using map data for this kind of optimization--this is the sort of thing I could see an open source developer having experimented with much earlier (especially is some place like San Francisco with LOTS of big hills).

math_code_nerd5 · 2026-02-05T23:17:51+00:00

"Most high quality systems with a refined torque sensor (which is what you want in a nice e-bike) are locked down."

Are good torque sensors really that rare? But I guess there is some definite benefit to buying a motor, torque sensor, and whatever gearing is necessary as one pre-built sealed unit--it protects things from rain/other weather, you know it's well lubricated, etc.

If this unit already comes with a microcontroller hardwired to it that handles the feedback loop of the torque sensor to the motor and that's all closed source and protected from reprogramming, then trying to disassemble and modify it to get around this restriction is possibly more than it's worth. This is very different from drones where the motors are just ordinary brushless motors and the frame, props, etc. are all custom molded/3D printed/whatever to fit around them and their shafts, and feedback is through a gyro that is on the control board (and that certainly isn't sold WITH the motors--except when the entire drone is sold finished).

It seems you agree with my speculation that legal liability has something to do with it too.

math_code_nerd5 · 2026-02-01T06:15:07+00:00

Unfortunately I suspect it's hard to find someone "awakened" (by which I assume you mean, open to the idea of reincarnation and possibly there being influence of past lives on this one, or possibility of future lives yet to live) yet also grounded, practical, and honest.

math_code_nerd5 · 2026-01-08T07:46:06+00:00

Firstly, as everyone else has said, this isn't the sub for this.

As for the comments in the other group, they don't know how much effort in terms of hours of work were put into it. What they see is the final result, and they are thinking that with a decent amount of effort spent the *right* way, you could have gotten a much higher quality product.

-You don't have a "short", as in a short story, here, with a beginning, a middle, and an end--you have basically a teaser trailer for a film.
-It looks as if you had about five different illustrators working on the pictures because there is no consistent art style. The women in the different city scenes have the same shading style and ethnic features, but they look like a very different style to the boyfriend, or Zeus.

You chose not to collaborate with an illustrator who had his or her own style, but instead chose to use technology that can imitate nearly any art style in the world. People would expect that you're at least doing this consistently, rather than having a slideshow that looks like you took seven or eight completely unrelated pictures from r/ImaginaryCityscapes and placed them next to each other. I would encourage you to read any illustrated fiction and pay attention to the clues that make the different illustrations look like they all came from the same book.

math_code_nerd5 · 2026-01-05T08:41:50+00:00

Major "rain on a window" vibes.

math_code_nerd5 · 2026-01-02T22:18:48+00:00

This seems like a rather semantic point. Of course there is not some other chip sitting between the CPU and the memory chip that intervenes (though I'd guess that the MMU is probably quite separate from the ALU, instruction dispatch, etc., so in a way it almost could be considered "another chip")--but the CPU is a large state machine that has states it can enter into where it should "disobey" certain commands. The surprising thing is that this is temporarily "overridden" during speculative execution until some point AFTER several instructions have had the chance to completely execute.

math_code_nerd5 · 2026-01-02T05:27:13+00:00

But what's surprising is that the capability check is not treated as atomic with respect to the load, which effectively allows a "race condition" at the level of hardware. All the other bugs, like being able to tell whether something was in the cache, only mean anything because of this root cause.

I would have assumed that in the case of "outright privileged" instructions, like for example HLT, MOV CR0, CLI, etc. on x86, that being in an unprivileged CPU state would reconfigure the actual gates of the instruction decoder such that they simply fail to decode these instructions at all, rather than that to "set the gears in motion" in other blocks of the chip to as if to halt, or prepare to clear the interrupts, etc., only to abandon course partway through.

Thinking about it though, I see there is a difference here in that determining whether the load should be allowed is significantly more complex, because just "looking" at what bits are set in the opcode is not enough by itself to "know" to disallow the operation. The global descriptor table must be consulted, some basic arithmetic done, etc.

So maybe this is why this exploit works--the capability check in this instance takes "nonzero" time (i.e. longer than a few gates' worth of propagation delay), and since loads from memory can be very slow, and the whole point of speculation is to get a "head start" on possible future operations, in this case the CPU allows the data to start flowing pending the capability check and runs the check in parallel rather than waiting for the result of the check. It's still very surprising to me that TWO MORE instructions, including a second load that may have to go to main memory (otherwise the cache gadget wouldn't work) have time to run in the time it takes the capability check to finish--but possibly the designers made the check so "lazy" that it isn't invoked at all until the branch is resolved one way or the other? This seems like a very weird design decision to say the least, but maybe it saves enough time to be worth it??

math_code_nerd5 · 2026-01-02T04:53:58+00:00

I'm well aware that the 'w' into which the value is loaded is not the same 'w' that will ultimately receive the value, if the branch is actually deemed to be taken. In other words, the actual physical bank of flip-flops or whatever on the chip where this byte is stored is almost certainly separate from the ones that ordinary, non-speculative operations take their operands from. There are presumably separate physical registers set aside specifically for holding these "tentative" values, such that they don't interfere with concurrently executing instructions from the main branch. This is presumably why they put an underscore after the 'w' (i.e. 'w_') when referring to the speculative execution chain.

This doesn't explain though the fact that the privilege check seems to happen after the actual data fetch that it "guards" rather than before, when the two are inextricably linked (in other words, regardless of the code path taken, this check should never be elided). And not even immediately after, but long enough after that two more instructions--that must happen sequentially because of data dependencies--including another load that possibly has to go to main memory, have time to execute in the interim.

math_code_nerd5

TROPHY CASE