> to properly articulate their problems using the jargon of mathematicians and programmers
I once distilled a real-life problem into mathematical language exactly like how the Introduction to Algorithms book would pose them only to have the quesiton immediately closed with the explanation "don't post your CS homework".
(My employer at the time was very sensitive about their IP and being able to access the Internet from the work computer was already a miracle. I once sat through a whole day of InfoSec and diciplinary meetings for posting completely dummy bug repoduction code on Github.
"don't post your CS homework" is exactly the type of toxic comments that are not allowed on the site. Such a comment should have been flagged and would be deleted by moderators. Homework questions are welcome on SO.
If this were true, then treating any question as an X-Y problem shouldn't be allowed at all. I.e. answers should at least address the question as posed before/instead of proposing an alternative approach.
In reality the opposite is encouraged. For countless times, I've landed on questions with promising titles/search extracts, only to find irrelevant answers because people grabbed onto some detail in the question irrelevant to my case and provided X-Y answers.
This often also causes subsequent useful questions to be marked as dups even though they no longer contain that irrelevant detail. The appeal process is so unfriendly that most would not bother.
Really not sure what/who this is for. There aren't many 3-phase LV AC + DC use cases apart from industrial load + control. I can't imaging the DC part can be transmitted at a voltage that will make the system efficient while avoiding an expensive step-down conveter.
Many supermarket chains (in the West at least) have satellite links at their major locations because they can't afford to close a store just because the local ISP had an issue.
The real question is how long can some of the smaller banks' datacenters stay up.
Firstly and most importantly, a cash register needs a power outlet. It is highly contestable that every single Western supermarket out there has a diesel generator down in the back / storage room that will kick in in an instant if a power outage begins.
Lest also forget the Crowdstrike drama where many supermarkets simply went dark, in some instances for nearly 24 hours, despite working communication links. But I digress.
Crowdstrike was an interesting one. Just as it was going down I went out to the supermarket and found half of the self checkouts had bluescreened. Then a few hours later they were all back and functioning again. The supermarket had remote management at a level below the OS that could restore the whole countries self checkouts rapidly.
I would not be surprised if they simply booted an image from the network. It would significantly simplify maintenance, as for any change you'd just need to update a single image and push it downstream to an in-store management server. The individual terminals essentially become disposable.
> It is highly contestable that every single Western supermarket out there has a diesel generator down in the back / storage room that will kick in in an instant if a power outage begins.
Literally true. However:
- If it takes them 10 minutes to fire up the generator, then 5 minutes to restart the network and registers, that is no big issue (in a many-hour outage)
- At least in my part of the USA, many supermarkets do have generators - because storm damage causes local outages relatively often, and they'd lose a lot of money if they couldn't keep their freezers and refrigerators powered. Since the power requirements of the lighting and registers are just (compared to the cooling equipment) a rounding error, those are also on generators.
Plus, there are backup-power lories and refrigerated trailers. If your shop doesn't have enough backup power for duration, you might see several of these pull into the carpark all at once. If not all of the chillers can be powered, shop's staff will schlep stuff to the refrigerated lories.
Seen it done in USA, for a Target next to a Kroger grocer. Kroger lost everything that needed cold after reserve either ran out or wouldn't start, but Target had a contingencies contract and lost no product.
Well,in my experience it was the case for the 2 largest supermarket chains. We lost electricity at 12:30pm and only got it back during the night at 3am.
But both major supermarkets nearby worked on diesel generators and payment by card worked flawlessly. I guess they had satellite connection.
It might have been more complicated in small villages but people living in rural areas ually still use a lot of cash.
In my local area of Spain/portugal, 2/3 supermarkets and 2/3 gas stations had generators up and running within a couple of hours. We’re pretty rural, though - I don’t know that urban areas faired as well
We're outside Mataro, had to make a trip into Barcelona yesterday. I'd say most gas stations north of Barcelona/Maresme area were 100% offline, some (we found only two, from 6 visited) gas stations still had operational pumps but huge queues and cash only. None of the TPVs seemed to work anywhere in the afternoon yesterday here, even the battery powered/mobile network ones.
That's true, I went shopping cca. 4-5 hours after the blackout started and had no issues, even card transactions worked. Whoever designed the retailer, they clearly had this scenario in mind. Even the "self-service" computer kiosks all worked.
A true black start has several factors (which make it difficult and notable):
1. The grid has to fully collapse with no possibility of being rescued by interconnection
2. As a result, a generation asset has to be started without external power or a grid frequency to synch to
3. An asset capable of this is usually a small one connected to a lower voltage network that has to then backfeed the higher voltage one
4. Due to the difficulty of balancing supply/demand during the process, the frequency can fluctuate violently with a high risk of tripping the system offline again
None of this applies in yesterday's case:
The rest of the European synchronous grid is working just fine.
News reports stated Spain restored power by reconnecting to France and Morocco.
By reestablishing the HV network first, they can directly restart the largest generation asset with normal procedures.
As they bring more and more load or generation online, there's little risk of big frequency fluctuations because the wider grid can absorb that.
Is not that OpenJDK developers can't prevent these, but there's a forbidding cost for doing so.
The simplest "safe" way of doing this involves defensively copying the input argument. However, the `compress` function will likely make yet another smaller copy, making the constructor very allocation and CPU intensive.
In fact, due to the fixed array size in Java, all thread-safe implementations must either allocate two arrays to hold the two possible encodings, which guarantees one piece of garbage, or iterating the input array twice.
For such a core class like String, this is probably unacceptable cost. And the constructor is not documented to be thread-safe, so no one should expect it to.
In reality, there are much more impactful data structures to abuse in Java.
I once distilled a real-life problem into mathematical language exactly like how the Introduction to Algorithms book would pose them only to have the quesiton immediately closed with the explanation "don't post your CS homework".
(My employer at the time was very sensitive about their IP and being able to access the Internet from the work computer was already a miracle. I once sat through a whole day of InfoSec and diciplinary meetings for posting completely dummy bug repoduction code on Github.