> I don't think people's intuitive concept of minutes and seconds is that they vary according to the time of year or the tidal effects on the Earth.
But if you asked people to choose between "seconds vary by an imperceptible amount, less than your clocks naturally drift" and "an hour doesn't have 3600 seconds" I bet most will pick the former.
And it doesn't have to drift day by day, you can average it over a multi-year period.
It's going to be weird once the earth slows down enough that we'd need a leap second every day or two. Once you can't ignore the drift anymore, the system we chose is significantly unintuitive.
> If we didn't care about "relatability", nobody would have gone to all the trouble of trying to determine how many cesium clock oscillations there were in 1/86400 of an epoch day.
I'm not saying we didn't care about it, I'm saying we didn't put it as top priority. We went with a nice clean fixed-length second that will drift away from the Earth over time. And it wasn't/isn't that hard to determine the number of oscillations since "matching" the Earth's unstable speed has a huge margin you can land within.
> Would you also say that getting rid of leap seconds and allowing UTC to gradually drift away from the sun is making the technical side easier at the expense of relatability?
Yes.
I'm in favor of both, to be honest. But it's a tradeoff, and it's a tradeoff that weakens the layman's definition of a second.
I completely disagree. The intuitive meaning is that a day is 24 hours and you can divide that by 60 twice. But that makes the second vary by some parts per billion, so we nailed down the second to make the technical side easier at the expense of relatability.
No, they handle totally different things. Leap seconds handle the earth spinning at a varying speed. They would be a problem even if the sun didn't exist. Leap years handle the fact that earth spins don't evenly divide orbits around the sun. They would be a problem even if clocks didn't exist.
We can imagine a system where leap days are split into mean and variance: This would look like a council coming together every thousand years to decide if that year will have a leap day or not, but otherwise we follow the pattern.
We can also imagine a system where leap seconds are split into mean and variance: Many years from now when the Earth is notably slower, there's a guaranteed leap second every odd month, and sometimes there's an extra leap second in June.
> Um, because it's the prime meridian and that's how UTC is defined?
That's an explanation of how it is, not why we should care to preserve it.
The definitions of hours minutes and seconds have changed before, and in recent history.
> Which is why I was careful to specify mean solar noon.
And "mean solar noon" is meaningless to people's lives. Even in the areas where time zones do follow meridians and not country borders that are many minutes off.
Well CLOCK_MONOTONIC was a bad name for anything that's supposed to do more than be... monotonic, with mild accuracy, so I'm not surprised things became unclear.
But it is just a basic system clock. Being the wrong speed by 15 parts per million shouldn't throw off your data collection. Lots of clocks are more inaccurate by accident.
> The models for this are IIRC trigonometric polynomials of fairly low order, so even if we could model the unpredictability perfectly, truncation error would limit our ability to distribute the model at super high accuracy. The existing models are built in to, eg, satellites, so you can't just make them arbitrarily complex.
What are the satellites doing with the models? They're not deciding leap seconds on their own, I hope. So I don't see why the leap second decision would be locked to low accuracy.
Also I would expect doubling the precision to give you a 3-4x slowdown on the math or adding orders to have less effect, and the amount of available computation spent on those models to be like a tenth of a percent at most, so the extra cycles wouldn't be an issue. What am I missing here?
To me it seems like unpredictability is the only real issue.
> 0x7ffffffffffffffff. The typical argument is that such a value would be “pathological”. Not only is this argument incorrect, it’s even more dangerous which we will see later.
The only later thing I see that's somewhat relevant to that appears to be dealing with 32 bit overflow? That doesn't prove the argument incorrect.
No current OS I'm aware of lets you have a size_t that goes over 2^63. I doubt any OS will ever allow it. It makes things easier if virtual memory is capped to 2^62 or so, and if anyone really ends up with a use case for more I expect them to switch to 128 bit numbers.
Okay, interesting. Also to be clear I do think Z2 makes sense in a lot of situations, but I suspect that it's not very dependant on drive size like a lot of people think. If I wanted high reliability I'd use Z2 even with small drives.
Also to reply to your other comment: Personally one extra drive is a small price to pay for the peace of mind.
I achieve peace of mind via backups. For each copy, once I get the AFR below 2% I'm not too fussed about pushing it lower.
Only a couple percent of websites have a significant need to be "modern web applications".
Yes that is the fallback. That doesn't make it a bad example. Your core functionality should work on almost everything even if it's laid out a bit weird and missing niceties.
So: not bad faith and your accusation is unreasonable
This argument makes sense if learning the language is the default and you require an excuse to get out of it. But I don't think that's true. If you don't want to learn, that's not a big deal. There's no cherry picking involved. Learning the language isn't inherently tied to working somewhere. It's tied to citizenship but this isn't citizenship.
In other words, yes it's illogical to argue that a stay is short and long at the same time but who declared that learning the language is an inherent part of long stays?
My favorite parity trick was how the N64 was designed around ECC RAM chips but didn't bother using ECC, so it has a ninth bit at every address that the CPU ignores and the GPU uses as extra storage.
> - The chance of any given bit (of data on a disk) going bad, in a given time interval, is relatively constant.
We can't just assume this, though. Especially for data that's being checked regularly, because the drive can see how many pre-ECC bits have gone bad and rewrite iffy sectors.
And even if it's true, it's normal to go years without errors. If you have a 15% chance of getting an error each year, and your degraded array has 4 drives without redundancy, then the chance of getting an error in 4 hours is .02% and your chance of getting an error in 48 hours is .3%. Having that risk show up once every few years is pretty negligible compared to everything else that could go wrong with your array.
On top of that, if you don't have a hot spare and it takes 5 days to get a new drive, the difference in resilvering speeds is now 5.2 days versus 7 days and that barely matters.
The main situation where you have to worry about extra drives failing is when you think the resilvering process will greatly accelerate drive deaths. And that depends very much on the specific numbers you have in mind.
> AMD has been allowing ECC on lots of regular hardware for a long time.
Often unsupported or untested by the motherboard manufacturer, because the precedent set quite a while ago has stood so strongly.
> because it costs significantly more [...] and the performance specs are poor
Because it's niche. If a large share of the desktop market was using ECC memory, the extra cost would have been 10-12%, and a typical kit would push the clocks and timings at least as much as non-ECC memory.
> Since DDR5 doesn't include reporting on bit errors (afaik), it likely means much fewer single bit errors, but most experienced errors will be multi-bit. Although, I dunno what proportion of bit errors is on the ram chips and what's on the bus... there's no protection from bus errors.
Yeah that sucks. I'm really hoping that DDR6 standardizes a light form of end to end ECC. (Bursts are 24 bits wide and 24 bits deep, so on top of the 512 bits of payload there's a bunch of extra bits that can be used for ECC. If memory chips would just store 4 extra bits per 128, that's enough for reasonable ECC on a per-burst basis.)
> I don't think people's intuitive concept of minutes and seconds is that they vary according to the time of year or the tidal effects on the Earth.
But if you asked people to choose between "seconds vary by an imperceptible amount, less than your clocks naturally drift" and "an hour doesn't have 3600 seconds" I bet most will pick the former.
And it doesn't have to drift day by day, you can average it over a multi-year period.
It's going to be weird once the earth slows down enough that we'd need a leap second every day or two. Once you can't ignore the drift anymore, the system we chose is significantly unintuitive.
> If we didn't care about "relatability", nobody would have gone to all the trouble of trying to determine how many cesium clock oscillations there were in 1/86400 of an epoch day.
I'm not saying we didn't care about it, I'm saying we didn't put it as top priority. We went with a nice clean fixed-length second that will drift away from the Earth over time. And it wasn't/isn't that hard to determine the number of oscillations since "matching" the Earth's unstable speed has a huge margin you can land within.
> Would you also say that getting rid of leap seconds and allowing UTC to gradually drift away from the sun is making the technical side easier at the expense of relatability?
Yes.
I'm in favor of both, to be honest. But it's a tradeoff, and it's a tradeoff that weakens the layman's definition of a second.