GlenTheMachine

If you had no idea what a restorable sequence is the takeaway is about halfway down the OP:

“This is why Linux now provides rseq() which is a much more enlightened solution. With restartable sequences, you actually can get rid of both the mutex and atomics, while the OS continues to fully abstract scheduling. The way it works is you advise the kernel whenever your program enters a critical section of code that you don't want interrupted. It's probably going to be maybe 10 assembly instructions tops. The first assembly opcode should be a move instruction that sets the rseq_cs field. The last instruction needs to be the thing that makes the modification to your global data structure. Think of it sort of like a really tiny database transaction. What makes it go fast, is that the bidirectional communication with the kernel happens via shared memory.”

I am firmly convinced that, in the long course of time, Pratchett will be recognized as a modern Shakespeare.

Maybe that’s the protocol?

It's more complicated than that.

"The system" almost always consists of mid-level bureaucrats. Maybe not this particular one, but her bosses -- a job which, if she sticks around long enough, she will eventually get promoted into. A large amount of what the government does isn't formally law, it's policy, which is often decided by those mid-level managers.

And like individual bureaucrats, "the system" in this case finds it easy to make demands of people if those demands do not result in increased workload for the agency. But if they do result in increased workload for the agency, then the policies that result in that increased workload often get rethought, or the agencies suddenly discover that they can make allowances, and so on.

In this case, I'm confident that "agency X cannot accept pdf documentation" isn't actually law. It might be guidance issued by an agency lawyer, but that isn't the same thing. It is likely to be a policy decided fundamentally by the IT department, which is estimating a high cost for securing the agency IT system to securely handle pdfs. That cost is compared to the cost of accepting faxes, which is significantly lower, and so a policy is issued that the agency cannot accept pdfs, and the legal guidance is offered as justification.

What is not factored in to the decision is the cost to the taxpayer. That's an externality.

So, if the taxpayers can magically make it much more expensive for the agency to accept faxes, so that it is suddenly not an externality any more -- which is what happened in this case -- then the above calculus changes, and the agency discovers that, you know what, actually we can accept pdfs. The IT department is ordered to make the necessary improvements, and it all works.

In my particular case, we were told for literally decades that we could not telework. It wasn't secure enough. Then COVID happened, and suddenly we had a telework system in place, with all the necessary Microsoft licenses purchased and servers stood up and laptops issued and VPN accounts activated, in less than three weeks, and nobody said anything about telework not being secure enough ever again. Because the original justification wasn't true. Setting up telework was more expensive, so we didn't want to do it, and we came up with reasons why we "couldn't". As soon as it was cheaper, we found out that we could do it after all.

“ It reads like an indictment of the government employee personally”

As a government employee: it often is the employee personally. Not always, but surprisingly often. There is a type of mid-level bureaucrat who just can’t be bothered to make anyone else’s life easier, even if they can. It’s just easier not to, and over time that becomes its own form of malice. The tales I could tell you about security officers basically abusing their power in order to make their own lives as easy as possible, while making everyone else’s live almost impossible…

As a government employee, enmeshed in the bureaucracy:

This is the way.

The problem is that it took Karen zero effort to say “we only accept fax”. She doesn’t care about how much effort it takes you you — in fact, as implied, it taking you a tremendous amount of effort actually reduces her effort. In order to make a dent, you have to figure out a way for the idiotic policy to impact the person making and/or enforcing it. That’s the only way it ever changes.

So after almost 50 years of hacking, I'm starting to feel it in my hands. But I don't have any wrist problems -- no carpal tunnel. What I have is tendonitis in my fingers, primarily in my middle fingers and my right pinky (from slamming Enter several million times).

I've had steroid injections into the tendon sheaths of my fingers a couple of times, which hurts like a bugger when it's done but definitely improves things after a few days. It isn't a cure, though, and my hand doctor thinks I'm going to need surgery eventually.

I have to assume that a split keyboard won't help this. Is there anything that might, short of a voice interface?

“Extendible” —> extensible, I believe

That’s certainly an opinion. I’m not convinced that it's a good one, but it’s an interesting one.

I think it’s probably important to remember two things: 1) the novel is a relatively modern invention — Don Quixote is often thought of as the first novel, and it was written in 1605, but 2) fiction clearly is not. The Iliad, for instance. In fact, what we think of as “history”, a recounting of events strongly tied to facts, is also a relatively new invention. It is my understanding that ancient authors were more interested in telling you what was true, in a spitirual, philosophical, or moral sense than in telling you strictly what happened. Obviously this is more clear when reading e.g. religious texts like the Bible, but my understanding is that it’s also true of more “straight” histories — Roman historians were not above inventing entire speeches for which there were not extant records and placing them in the mount of a Julius Caesar or whoever. So strictly speaking if you’re reading sources as old as the OP suggests, there’s no getting away from what we would call fiction.

My wife and I have an ongoing conflict of taste in matters of literature. She prefers what I consider to be absolutely depressing high literature. One of her favorites is The House of Mirth, wherein the protagonist starts out wealthy, slowly goes into debt, ends up impoverished and addicted to morphine, and ends the book by committing suicide. She says she likes these stories because they’re “more realistic”. I claim that no, they aren’t, and even if they were I read specifically because I get enough realism by waking up in the morning, thank you very much, and although I’m not averse to deep thoughts in my literature I usually prefer it with a side of likeable characters.

Anyway, my point is: to pick an example, LOTR is a book of fiction written after WWII, and although Tolkien was an expert on and was drawing from a deep pool of literary traditions that predate written language, he was also addressing modern concerns, and that’s what makes the book more interesting than Beowulf. It’s don’t care that it’s labeled “fiction”; the concepts it explores are as true, in the ancient sense, as straight Greek philosophy, and maybe even as applicable. And if you want to read for information, you’re almost certainly going to get better information by reading a modern history of Rome than by reading Polybius.

I was a grad student in Dave Akin's lab from 1994-2003. Like many labs, we had a journal club. Once a week (Wednesday, I think) somebody would give a presentation over lunch on a paper they'd read. We would get takeout Chinese and eat while discussing the paper.

On this particular Wednesday the presentation was on a failed spacecraft program. It's been a long time, but I think it was probably this paper:

https://llis.nasa.gov/llis_lib/pdf/1009464main1_0641-mr.pdf

which is the initial failure analysis of the Mars Climate Orbiter (1999), which famously crashed into Mars during its orbital insertion burn because JPL specifications were in metric, but Lockheed wrote code in imperial units, and as a result there was a failure to properly convert between newtons and pounds. One fact of note was that the the team responsible for spacecraft navigation had already observed anomalous trajectory data but their reports were ignored because they didn't follow program guidelines for filling out the paperwork to document the observations, so the insertion burn went ahead heedless of what the spacecraft's behavior was trying to tell them.

Ultimately, the loss of mission was a result of unclear responsibility for ownership of the orbital maneuvering software, including the mission requirements that traced to the software, the development of the software derived from those requirements, tests to validate the software, and reports from users of the software that it was behaving unexpectedly.

I was trying to be funny, and turned the statement around from "clear lines of responsibility" to "clear lines of blame".

I’m Henshaw (#37). AMA.

I travel internationally all the time. Someone tell me why I need this.

I wrote code to do this between a C64 and a 1541 disk drive when I was in high school. It got me to the international science fair and (probably) earned me a full tuition scholarship for undergrad.

I called MS support once because some random dude managed to get my son's account registered under his "family", and then locked my son out of being able to update his own machine.

The MS support guy literally tried to get me to password crack the random dude's account. Like, he wanted me to help him guess the guy's password so we could log in as him and change his family settings.

That was the only "help" he could provide.

We don't want it.

My Operating Systems class as an undergrad used a book written by the Multics guys.

I hated it. It would present a bunch of apparently incompatible techniques for e.g. job scheduling, and then say that Multics implemented all of them. I immediately understood why UNIX came about: the Multics designers appeared incapable of having opinions, which led to an OS that was bloated and hard to understand.

That class was a long time ago, and I was a young, arrogant, and uninformed programmer, and maybe that take was wrong. But it left a strong impression at the time, and it was one of the few books from my undergrad days that I sold back instead of keeping.

Space roboticist here.

As with a lot of things, it isn't the initial outlay, it's the maintenance costs. Terrestrial datacenters have parts fail and get replaced all the time. The mass analysis given here -- which appears quite good, at first glance -- doesn't including any mass, energy, or thermal system numbers for the infrastructure you would need to have to replace failed components.

As a first cut, this would require:

- an autonomous rendezvous and docking system

- a fully railed robotic system, e.g. some sort of robotic manipulator that can move along rails and reach every card in every server in the system, which usually means a system of relatively stiff rails running throughout the interior of the plant

- CPU, power, comms, and cooling to support the above

- importantly, the ability of the robotic servicing system toto replace itself. In other words, it would need to be at least two fault tolerant -- which usually means dual wound motors, redundant gears, redundant harness, redundant power, comms, and compute. Alternately, two or more independent robotic systems that are capable of not only replacing cards but also of replacing each other.

- regular launches containing replacement hardware

- ongoing ground support staff to deal with failures

The mass analysis also doesn't appear to include the massive number of heat pipes you would need to transfer the heat from the chips to the radiators. For an orbiting datacenter, that would probably be the single biggest mass allocation.

Two things… one, they didn’t sail across the Atlantic. They hired ships and professional sailors to sail them across. They were passengers. That crossing wasn’t necessarily an easy one, but it was much more like what happens today with wealthy people who pay sherpas to help them climb Everest. The climbers have to have some knowledge and experience, but they aren’t the experts, and without the sherpas they'd be pretty lost.

Second, the point of this whole thread is that even at home, these were not people who were living off the land. They were wealthy Londoners. They lived in the city. They weren’t even raising their own kitchen gardens, they had people for that.

Wealthy Londoners bought their food just like you and I do. They had food markets. They used currency to buy grain, vegetables, and meat.

FYI, salted meat and fish will last for years and, if stored in a reasonably cool place like a root cellar, for decades. I personally have had Virginia hams that were over ten years old. Dried corn will last for centuries if stored properly.

The reason the settlers made so many diplomatic mistakes with the natives was because their leadership was primarily former military, and they saw the natives as a military problem. This made some sense because when they set out, they thought their primary challenge was going to be fending off military attacks from the Spanish. But that assumption turned out to be tragically wrong.

I'm not saying these people were all incompetent buffoons. Some of them were trained military officers. Some were craftsmen — there’s ample evidence of metal work and glassmaking at Jamestown. They were all experienced horsemen, and they were comfortable with firearms and bladed weapons. But what they weren’t was outdoorsmen, or even farmers, and in hindsight that’s what they needed to be. Once they got actual farmers on site, their immediate problems started to clear up.

Like most disasters, there were many causes for this one. The general unpreparedness of the Jamestown settlers is, however, an important one, and probably the primary causative one (although see edit #2 for a strong contrary argument).

We know for a fact that the proportion of wealthy nobles to manual laborers was really, really high compared to the population of England at the time, and there werent' enough of the latter to keep the colony afloat (source: https://encyclopediavirginia.org/the-myth-of-living-off-the-... and https://www.jyfmuseums.org/visit/jamestown-settlement/histor...). These were largely second sons of wealthy families (source: https://en.wikipedia.org/wiki/First_Families_of_Virginia). Most of the rest were the gentlemen's manservants, e.g. they were also urbanites (source: https://bandbwilliamsburg.com/jamestown-settlement/#:~:text=...

Regarding the quote from the paper:

   The colonists’ performance in fishing in the first years, in common with all other activities, must also have been severely hampered by their generally poor health, malnutrition and subsequent lack of energy.

Note that a primary reason for the poor relationship with the native Americans was that the settlers didn't have their own food sources, and resorted to theft and assault to get native's food supplies -- which, as a result of the drought, weren't all that great (source: https://www.loc.gov/classroom-materials/united-states-histor...)

They also didn't have the skills necessary to (for instance) prepare acorns or harvest pine bark cambium. Survival foods would have been foods that noble Englishmen hadn't ever even eaten, much less prepared themselves.

From the Wikipedia article on "The Starving Time":

    Although they did some farming, few of the original settlers were accustomed to manual labor or were familiar with farming. Hunting on the island was poor, and they quickly exhausted the supply of small game. The colonists were largely dependent upon trade with the Native Americans and periodic supply ships from England for their food.

As a consequence of the deteriorating relationship with the natives, the Jamestown colonists' ability to do any land-based (as opposed to water-based) subsistence activities was severely curtailed, and, one assumes, their ability to hire natives to fish for them also eroded. But they did have one major advantage, an actual oceangoing ship that they could have sailed into the Bay and used to fish. The natives had only canoes and could not possibly have constituted a major threat on the waters of the Bay. But that only works if you know how to fish, which they didn't. Once the nets rotted due to the colonists not understanding the importance of drying them, that advantage was also neutralized, and starving was inevitable in the absence of relief supplies from England or the Caribbean.

   Probably also worth remembering how parasite ridden all of the food supplies you are mentioning would be.

The colonists were ill primarily because they didn't practice good hygiene wrt situating their toilet facilities away from their drinking water and ended up with dysentery, a problem that the native Americans managed to avoid (source: https://encyclopediavirginia.org/the-myth-of-living-off-the-...).

Summary: the original contingent of Jamestown settlers had bad luck (drought, several supply ships being wrecked or otherwise not showing up on time) but their primary problem was that they didn't intend to live off the land at all, either by fishing and farming or by foraging. They didn't have the right supplies to do so, and mostly didn't have the knowledge needed to do it as a backup plan when the original plan of trading with the native Americans failed (due to poor diplomatic skills and poor diplomatic decision making.)

EDIT: to head off argument on this score, the poor relationship with the native Americans wasn't inevitable. The Roanoke Colony settlers, when their food ran low, joined the local tribe and the evidence indicates that they were adopted as members, intermarried, and survived there. (source: https://www.whro.org/arts-culture/2025-01-20/new-artifacts-o... and https://nypost.com/2025/06/07/us-news/researchers-discover-e...)

EDIT: Here's the best contrary argument, that it was primarily the drought that was to blame and not the incompetence of the English settlers: https://www.smithsonianmag.com/history/rethinking-jamestown-...

From the article:

‘They suffered fourteen nets (which was all they had) to rot and spoil, which by orderly drying and mending might have been preserved. But being lost, all help of fishing perished.’ (25)

(25) Strachey, W. 1998b [1610], ‘A True Reportory of the wrack and redemption of Sir Thomas Gates, knight, upon and from the Islands of the Bermudas; his coming to Virginia, and the estate of that colony then, and after under the government of the Lord La Warre’, in Haile 1998, p. 441

I originally learned this by talking with a Jamestown National Historical Park docent. I said that, having grown up in Virginia in the 20th century and knowing what tidewater Virginia was like in the 17th century, it would have been very hard to starve to death. American chestnut was still the dominant forest tree, and provided literally tons of nuts per tree. Black walnut and acorn were also plentiful and make good survival foods if you know how to prepare them. The Chesapeake Bay had enormous oyster beds, with oysters being described as "the size of dinner plates", and John Smith said that he thought he could have walked across it on the backs of fish, and if you know how to dry or salt fish it doesn't matter that the sturgeon and rockfish are seasonal. Mussels and crab, likewise, would have been plentiful, and unlike fish, accessible year round. Deer, turkey, rabbit, groundhog, squirrel, opossum and raccoon were plentiful, and passenger pigeon were also around, not having suffered the overhunting they did in the early 20th century.

She indicated that the majority of the English settlers weren't farmers or fishermen and didn't have the hands-on experience to make use of the resources at their disposal. I went home and did a bit of internet research on that statement, and it seemed fairly accurate.

I do not claim to be a trained historian of colonial Virginia; I just grew up there.

The Jamestown colonists starved to death literally living on the shore of the most productive marine environment on earth. They didn’t know how to care for the fishing nets, so they rotted, and then didn’t know how to fix them.

The issue was that many of the colonists were second sons of relatively wealthy families, and weren’t all that familiar with fishing or farming. The first son inherited everything, and the second son had to make his way in the world, and colonizing was an enticing prospect for making your fortune. Poorer families, at the very early stages, weren’t sending their sons on these ventures because they needed the labor at home.

https://historicjamestowne.org/wp-content/uploads/Subsistenc...

Also, for the type of work I'd do with an arm like this, I'd be more than happy to just have the follower arm. You need a leader arm to do some types of teleoperation or imitation learning, but not really to do reinforcement learning or learn about control theory.

What you do need is an articulated rigid body model that you can import into e.g. NVIDIA Isaac Lab or Gazebo. The availability of a good digital model is a HUGE selling point.

   • Adding one DOF to match ARX kinematics is doable, with a price increase of $30–40.

   • A tool changer is a great suggestion. A few of my friends are working on kinematic couplings, which would be ideal for this. I’ll need to give some thought to how to pass electrical signals and power to the tool, while also keeping it lightweight.

   • Could you share what functionality you want in terms of encoders? The ST3215 uses 12-bit magnetic encoders, which can retain position after power loss. Are you looking for higher resolution? For torque sensing, if the order volume is large, I can add this for just a $20-30 price increase.

You'd also ideally add torque sensing at the joints because it opens up a whole world of control techniques that you can't get with just joint position sensing. You can do compliance or force control, which lets the arm act as if it had a spring at the joints, so when it hits something the impact is nice and gentle, and importantly, so you can do things like e.g. a bolt insertion task where you have to control the position of the arm in x and y but you want to exert a small positive insertion force in z.

   • Finger tip force sensing: Is this for applications like picking up an egg?

Or if you're folding clothes or handling cables or wires or anything else flexible, you really need to have a sense of touch. You can't really do these tasks very well with position sensing and vision alone.

Another idea: Maybe add a passive mounting adapter and power leads at the end effector so people can add their own vision or lidar sensors, and just let them connect via bluetooth, so you don't have to route signal cables?

FYI, I am a space roboticist by trade and I teach a graduate level class in robotics at the University of Maryland.

They did ask for suggested upgrades.

“I’d love your feedback! Beyond manufacturing, cleaning up the codebase, and writing docs, I’m considering: a force-controlled gripper, a parallel-jaw gripper, an extra wrist DOF (matching the new Trossen and ARX arms), full force feedback on the leader arm (though that may triple the price), a more affordable version with lower resolution each joint, and a longer-reach variant. Which of these—or something else—would be most useful to you?”

You need some technical specs on the website. How many DOF does it have? Does it have joint angle sensing? If so, what's the resolution? What's the interface to the servos? What's the payload capacity? Does it have integrated motor controllers? How long is it, and what does the dexterous workspace look like?

As a roboticist, what I'd vote for, in order, is:

- more degrees of freedom

- interchangeable tools, either an actual tool changer (unlikely at the price point) or a fixed bolt pattern with electronic passthroughs

- better joint sensing, e.g. absolute encoders, joint torque sensing

- fingertip force sensing

Yep, and in 1986 I had just interned at a NASA lab where they were investigating multiprocessors, which at the time was a wild and crazy idea. I had the epiphany that I could bit-bang a driver between a C64 and one or more 1541s and make my own little multiprocessor, so I did. I made it all the way to the International Science Fair and ended up getting a college scholarship. I've written a lot of code but I'm probably the proudest of that couple of hundred lines of 6502 assembly I wrote when I was 17.

So my kid has ARFID. I am not a doctor, but what I have learned is that eventually, anything that causes nausea associated with eating can progress into ARFID, even if the original underlying cause resolves. ARFID is technically an eating disorder, like anorexia, but it isn't related to poor body image; it is, basically, a food aversion to, well, food. All food, or nearly all. This is what happened to my kid; there’s an underlying disorder that can be treated with meds, but when not treated causes nearly constant nausea. Once we diagnosed and treated the underlying cause, the nausea didn’t go away. My kid's brain had learned to associate eating with being sick, and that association persisted even when the original illness resolved.

My kid at one point was admitted to the hospital for two weeks because said kid had lost so much weight. They inserted a gastric tube, and kid discovered that kid did not become nauseous when fed through the tube. We knew kid had ARFID, but this was ah “a-ha” moment for kid, because it showed kid irrefutable proof that the problem was not a physical issue with kid's gut. It was very clearly related to the experience of eating. Kid has subsequently learned to “eat through the nausea” as described in the post.

That's what this sounds like. There was likely an underlying physical cause of the nausea; that cause may or may not have resolved, but the nausea is now it's own thing. The OP indicates a series of consults with a behaviorist; I would imagine being screened for eating disorders is what that was about, but ARFID is not a common eating disorder, and may or may not have been considered.

I work at NRL, east of DCA and about 500 yards south of the crash. Can confirm that it is not unusual for flights to pass directly overhead of us, however I don’t understand the statement that this was a new flight path.

I work at a Navy installation on the Potomac just south of DCA. As of 10 am EST today there was a moderate police and rescue presence on the water. There is a significant amount of debris visible floating in the river, and the boats are fishing it out piece by piece. The only things in the air are a handful of helicopters, presumably related to the search operation.

I desperately wish I had been introduced to Forth when I was learning assembly circa 1984 on my Commodore. Would have changed my life.