2
points
rwallace
Joined 3,522 karma
russell.wallace@gmail.com
- rwallaceSure. If you feel the need to write "this is shitty code", fair enough, I'm fine with making allowances for that kind of language. But please leave it at that, instead of also insulting the people who wrote it. There are, unfortunately, plenty of ways for bad incentives to result in competent people creating bad products.
- In general, if a program is not a Web browser, I do not want that program getting clever with displaying a URL as an active link. Just show it as the URL, https prefix and all, so I can see where it will be taking me if I copy it into the browser. (This is one of my very few gripes with Google docs.)
- Fair enough! If you ever have the time and inclination to write it up as a blog post or such, I would love to read it.
- I disagree with your second sentence above. I think it is shallow dismissals that are inappropriate here. Conversely, I have upvoted a number of long explanations of interesting topics.
If you don't have time to write a detailed refutation, that's entirely understandable! But if you do, I would love to read it.
I did appreciate your paragraph length comment on the matter elsewhere in this thread.
- Or unless delete is a rare operation. So yeah, to make the best decisions here, you need to know expected numbers as well as expected access patterns.
As far as I can see, you are indeed going to incur one extra memory access apart from the object itself, for any design other than just 'Temporarily flag the object deleted, sweep deleted objects in bulk later' (which would only be good if deleted objects are uncommon). It still matters how many extra memory accesses; deleting an object from a doubly linked list accesses two other objects.
It also matters somewhat how many cache lines each object takes up. I say 'somewhat' because even if an object is bulky, you might be able to arrange it so that the most commonly accessed fields fit in one or two cache lines at the beginning.
- No problem!
As to what would be better - this is also a reply to your sibling comments above - I don't have a single across-the-board solution; the equivalent of std::vector everywhere is fine for some kinds of application code, but not necessarily for system code. Instead, I would start by asking questions.
What kinds of entities are you dealing with, what kinds of collections, and, critically, how many entities along each dimension, to an order of magnitude, p50 and p99? What are your typical access patterns? What are your use cases, so that you can figure out what figures of merit to optimize for? How unpredictable will be the adding of more use cases in the future?
In most kinds of application code, it's okay to just go for big-O, but for performance critical system code, you also need to care about constant factors. As an intuition primer, how many bytes can you memcpy in the time it takes for one cache miss? If your intuition for performance was trained in the eighties and nineties, as mine initially was, the answer may be larger than you expect.
- To clarify a couple of things:
I'm aware of the reasons Linux uses doubly linked lists. I'm still of the opinion this design decision made a lot of sense in the 1990s, and would make less sense in a new project today. You may disagree, and that's fine! Engineering is constrained by hard truths, but within those constraints, is full of judgment calls.
I'm not a member of the evangelical Rust community. I'm not proclaiming 'thou shalt rewrite it all in Rust'. Maybe you have good reasons to use something else. That's fine.
But if you are considering Rust, and are concerned about its ability to handle cyclic data structures, there are ways to do it, that don't involve throwing out all the benefits the language offers.
- Yes, that was exactly the reason. CJK unification happened during the few years when we were all trying to convince ourselves that 16 bits would be enough. By the time we acknowledged otherwise, it was too late.
- I read that paragraph, but my reading of it was different from yours. As far as I can see, it only discusses training time and experience. No mention of time for sleep.
Though yes, I do give it credit for going at least a little of the way - not far enough, but a little - in pushing back on the 'human error' scapegoating, in favor of asking questions about procedures and policies.
- In several similar incidents, it was clear that the, or at least a major, cause of the accidents, was that the officers on watch had been forced to work overtime and deprived of sleep to the point of cognitive impairment.
How many hours had the officer on watch in this case worked that week? How many hours of sleep did he have?
And why is no one except me asking those questions?
- I predict that it will never make sense for artificial neural networks to directly generate machine code, for most of the same reasons it doesn't make sense for biological neural networks to do so.
- That's an interesting question about the number of levels of address translation. Does anyone have numbers for that, and how much latency and energy an extra layer costs?
- I'm not aware of any CPU invented since the late eighties that doesn't have paged virtual memory. Am I misunderstanding what you mean? Can you expand on where you are getting the 4x number from?
- As I understand it, the philosophy dates from centuries before that, and was inspired at least in large part by the frequency of earthquakes there.
- 4 points
- I'd like to apply, but the job pages just offer 'see open positions' in a loop, no clear way to get to an application form, and the 'contact us' page doesn't accept a Gmail address. Am I missing something?
- I'm seeing quite a few people on this site recently talking about their Kagi subscriptions, claiming it is sufficiently better than Google to be worth the money.
- I leave a handful of actually important notifications on, like the one that says 'someone just made a purchase using your bank account, making sure it was you', but most of them, I do indeed turn off.
- Beware of concentrated benefit and diffuse cost. Sure, let a seconds clock be available to call up the 0.1% of the time when you want it. But it shouldn't be in the system tray presenting a small but ongoing attention drain the other 99.9% of the time.