Walnut356

I feel like it's like pointers.

"Variable" refers to the label, i.e. a box that can contain anything (like *ptr is a pointer to [something we dont know anything about])

Immutable describes the contents, i.e. the stuff in the box cant change. (like int* ptr describes that the pointer points to an int)

Rust makes it very obvious that there's a difference between constants and immutable variables, mainly because constants must be compile time constants.

What do you call it when a variable cant change after its definition, but isnt guaranteed to be the same on each function call? (E.g. x is an array that's passed in, and we're just checking if element y exists)

It's not a constant, the contents of that label are "changing", but the label's contents cant be modified inside the scope of that function. So it's a variable, but immutable.

Saying "non negotiable" doesnt actually hold up in small claims, nor against basic resistance in most cases.

Look up your local laws, in some places carpets must be replaced at the expense of the landlord every X years, or if there is any kind of damage (caused by regular wear and tear) that could be a trip hazard. Pictures from move-in, carpets not being replaced when you moved in, etc. all help your case.

Last place i lived, I spent 30 minutes arguing on the phone with my previous landlord over flooring and got my 700 dollars back. Turns out most of the time they only vaguely know the laws they're quoting, so if you come with confidence, prep, and a willingness to take it to small claims, they'll fold to save themselves the effort.

The freemium and constant "are you sure you dont want to pay?" from some intellij plugins is insulting enough that it's hard to believe any developer would praise it. Presumably this doesnt happen in vscode because it cant happen in vscode, not because people arent shameless enough to do it there.

That depends on your definition of correct lmao. Rust explicitly counts utf-8 scalar values, because that's the length of the raw bytes contained in the string. There are many times where that value is more useful than the grapheme count.

I think it was this issue. Looks like maybe it got fixed some time this year? Iunno, i'll look into it at some point

I did not dismiss it, I said measure the performance yourself.

Then why does anyone ask anything? Just figure it out yourself. Oh you read a book or went to college? Why? Should have just reinvented computers yourself man. Taking advantage of collective knowledge is for suckers /s

This means that the code performance is highly dependent on runtime conditions, and needs to be measured in the place where it's used.

How is that helpful for OP? For example, if his question was about rust i'd say "options 1 or 2 should be identical for speed", but if it's python i'd say "match statements are just chained if/else chains, so a direct array index would be faster". For another example, in python attribute access is a function call. x.y in a loop is slower than assigning z = x.y outside of the loop and calling z in the loop.

You can absolutely generalize and have rules of thumb for performance.

If they already measured, then they would know which one is faster, because they measured it.

Measurements can have unintuitive results based on the dataset used (which, for benchmarks, usually end up being artificial datasets). OP's measurements may not have been consistent with their working understanding, thus they ask outside sources to confirm the truth. Idk why you cant just give them the benefit of the doubt and like... answer the question they actually asked? The explanations for "why" that accompany that answer can also be incredibly helpful.

And all of these optimizations are just as effective after you measure them to see if they're needed, and they're no longer premature.

That implies that these optimizations are harder than doing it the "mundane" way. They're not.

Here's a fun micro optimization for compiled languages: on modern CPUs

x = x * (arr[0] * arr[1]) in a loop has better performance characteristics than

x = (x * arr[0]) * arr[1]

even though they do the same thing (in short, it's because of the data dependencies for out-of-order execution - compilers wont make this optimization automatically for floats). How much harder is it to write the first one compared to the second one? How much harder to read is the first compared to the second?

So why would you not just make the first one your default? Now all your future uses of that pattern will perform better, for no extra effort except the amortized cognitive fee of changing your default option.

Look at OPs question. Could the answer fall under a rule of thumb that they can apply as their default option for a scenario? I'm pretty sure it can. So who cares about "premature" or not?

The particular question asked by the OP is very very unlikely to have any significant performance impact at all, unless it's in an extremely hot loop running millions of times per frame

So instead of answering their question, you assume it isnt impacting performance and they're just asking for no reason?

I literally had this exact question about python like 8 months ago. I had a file parser that needed to process different chunks based on a tag. Performance was critical, several thousand files, each ~3mb), the tag dispatch happened about 100,000-300,000 times per file. The original was implemented with if/else. I switched it to match because i thought it was faster, it wasnt. I looked at a lot of threads with answers like yours until stumbling upon dictionary dispatch (i.e. key = tag, value = first class function to call on the tag's data) and array dispatch.

That change alone was a 15% performance improvement.

You have no idea how their program works, what their hot loop is, if they're just asking out of curiosity, whatever. Just answer their fuckin question my dude. Platitudes are a waste of everyone's time.

Rule number 2: stop dismissing performance questions just because of something some guy said decades ago. Performance matters, learning about performance matters, and answers like yours dont help anyone.

Did they ask if they should optimize, or did they ask which one generates more performant assembly? Which one of those questions did you answer?

Maybe they already measured and already knows this is a bottleneck. Maybe they are curious if match statements are a slow abstraction (e.g. in python, it's essentially a chain of if/else. In rust it's often compiled to an indexable table). Maybe the given example code is only partially representative of the actual code this is being applied to.

It's so irritating to look up performance-related questions when this answer is at the top (and middle, and bottom) of every thread. I swear half the reason every piece of modern software runs like shit is because nobody bothered to learn how to optimize and now everyone just parrots that phrase instead of saying "i dont know".

There's tons of little "premature" optimizations that you can do that arent evil. Choosing the right data structure (how random is the access? Are you using keys? Does it need to be sorted?). Estimating time complexity and load size (e.g. "i'm parsing [11 million | 2] files, i should probably [keep time complexity in mind | ignore time complexity completely]"). Structuring loops in a way that's easy for compilers to auto-vectorize - usually it's not any harder to read what the loop is doing, so why not do it right away?

Yes i'm bitter =(

Is pycharm's semantic highlighting still kinda ass? That's the biggest thing that stopped me from using it over vsc. As of like may this year i remember there still being active issue tracking for it.

Counterpoint, i didnt like the rust book at all (as an inexperienced self taught ~6 months to a year into learning python at the time). Programming Rust and Rust In Action were far better.

Seems you missed the last line

compiles to fast code

Iirc godot uses beta branches and semver, so the only updates you get are the ones that dont break anything.

Obligatory shoutout to Qownnotes for being excellent, fully open source, and with owncloud integration.