Reference counting has deterministic timing, you can run a deconstructor without registering objects for deletion and running any known finalizers (what you need to do in all GC langs I’m aware of.)
Define “deterministic timing”.
- One object going out of scope may mean calling free once, but it also can trigger calling free billions of objects, even for the exact same object
- Even freeing one object can have largely varying running time, e.g. to coalesce free blocks or, because it happens to be the last block in a virtual memory region, to unmap a block of virtual memory, blocking the program potentially for an arbitrary time
- With garbage collection (as with reference counting), lots of the overhead of objects going out of scope can be moved onto a specialized thread.
> you can run a deconstructor without registering objects
Not requiring finalizes does make reference counting easier, yes. The downside is have to store the reference counts somewhere, and keep them up to date (enough)
You can even use the same ownership model as rust (borrowing et al.) with non copyable types.
What does this mean? Who told you that?
They largely don't deeply elaborate, which is sad because I am a professional game developer who is interested in precisely presented knowledge so I can apply it to my work.
My interpretation is that games want to allocate large pools of resources, like GPU buffers, cpu memory, etc, and reuse that memory over and over. Ie: Reinitialize it.
In my experience, RAII is my preferred pattern for certain things (std::lock_guard), and you can almost certainly express the majority of these "uber game dev patterns" using RAII/smart pointers/etc, but the c++ implementation of these "uber game dev patterns" tends to be more complicated (and imo esthetically ugly) compared to really well written C.
These new languages (zig, odin, jai) appear to be attempts to improve C to allow an alternative to C++ that doesn't have the ugly baggage that C++ has.
As on some references, Ryan Fleury did an episode on Wookash podcast on RAD debugger showing ECS like approach.
IMO, their RAII critique is a but nuanced, but because of their personality the discourse often gets polarising.
Edit: the sibling comment just proved my last point.
on the other hand there are no constructors (just normal functions) so you cant initialize values in place, only stack allocate and return. i think rust needs to add in place init and change the rules from "always init at declaration site" to "must be initialized at first use" like kotlin.
the big missing piece is custom allocators that let you use something like a bump arena with the same convenience as system malloc. they already exist on nightly but nobody knows when they will land on stable.
honestly thats the biggest problem with rust, they come up with a lot of useful changes but then take ages to stabilize because the core team is overworked. they also have a kind of perfectionist culture as a reaction to all the half baked features shipping in C++.
there should be a stage between nightly and full release where feature is in stable toolchains behind a cfg flag and you get a warning if upstream crates use it. show commitment to shipping it in time but still make it clear that it can change (in minor incompatible ways) before release.
This isn't true and doesn't make any sense. Smart pointers don't need to enter into it. If you need a lot of something you make a vector and allocate once.
Also I remember they mentioned it’s not necessary to free memory if you’re about to close your program, because the OS will take the memory back.
It is an extremely niche scenario to need a program to shut down so much faster that you can't even deallocate memory. If you don't make lots of small allocations in the first place the deallocations won't take any time.
Obviously you need to gracefully deinitialise some things, like audio or other devices, but that’s beyond the discussion.
It's actually a pretty big advantage to destructors to deal with stuff like this as well as memory and locks.
IMO, their RAII critique is a but nuanced, but because of their personality the discourse often gets polarising.
I think it gets polarizing because they are both undeniably sharp programmers but don't have any real evidence of this stuff, they are just grasping at rationalizations.
But a lot of languages aren't like that, and so this doesn't translate. Obviously in Rust with Vec<Goose> that's only 8 allocations, each local Goose lives in the stack - or, if you knew up front there were 500 geese, you Vec::with_capacity(500) and it's a single allocation - but similar is true in many languages, Java is an outlier.
Besides, as mentioned java's allocations are much closer to something like using an arena in a low-level language, then a "slow" malloc. It uses thread-local allocation buffers, where you have a large buffer with a pointer pointing to the start of the free region. Allocation is just a pointer bump, not even needing synchronization since it is per a single thread. As it gets full, the GC moves out still alive objects in the background and resets the buffer.
This is pretty much the most efficient one can be after per-object type arenas and simply not allocating.
Allocations are really really cheap in Java by the way, so I don't get how 500 allocations would even be an issue.
Goose jim = make_a_goose_somehow(); // Java, so jim is on the Heap, no way around it
let jim : Goose = make_a_goose_somehow(); // Rust, jim is on the stack
ArrayList<Goose> geese = new ArrayList<Goose>();
// ... some loop eventually
Goose a_goose = somehow_get_this_goose(); // That's an allocation
geese.add(a_goose);
let geese: Vec<Goose> = Vec::new();
// ... some loop eventually
let a_goose : Goose = somehow_get_this_goose(); // But this is not
geese.push(a_goose);Jon Blow worked on numerous AAA games that required “that level” of optimization. And he’s one of the very few developers in the last 15 years who have managed to sell more than a million copies of a game running on a scratch built 3D engine.
You can disagree with their opinions, but they certainly have the experience to back those opinions up.
My interpretation is that games want to allocate large pools of resources, like GPU buffers, cpu memory, etc, and reuse that memory over and over. Ie: Reinitialize it.
They might say this, but there isn't a good technical rationalization here since anyone can create a global data structure just as easily in C++.
People who are motivated by a superiority complex or by the wish to impress a herd of twitter followers hardly if ever produce a thought I want to read.
Ah... The school of what I like to call "maximum opinions and minimal evidence". Aggressive arrogant dismissal of anything except their exact view (and for Muratori, you're also "woke" for good measure), coupled with a complete lack of _hard evidence_ to back up their views. In that regard, they're not unlike "investment advice" instagram influencers.
Didn't Casey Muratori write a proof of concept windows terminal to highlight Microsoft's substandard implementation? And Jonathan Blow has spent the past decade+ developing his own programming language and funding the development of a game. Seems like they are backing their views.
My angle is systems programming, and there, it absolutely matter. If you are performance sensitive, then you try to avoid crossing the user-space -> kernel boundary more than you have to.
Eg, ask for lots of memory, manage with arenas.
Interestingly Odin and Zig both lean into this heavily. Rust went a different route but has tried later to bolt on pluggable allocators.
Building a database, operating system, etc. absolutely requires fine tuned control over allocation. You can get around some of these things in Rust, but it will fight you. You'll effectively have to turn your back on the containers in std and build your own vectors, maybe even your own Box, etc.
Odin looks really appealing to me at one level, but I'd have a hard time switching to any language at this point that doesn't have a borrow checker story.
This gives the misleading impression that ordinary memory allocators are materially different from arena allocators. They aren't. Both types of allocators first ask for a big block of memory from the kernel, then dole that memory out in userspace. There's no need to cross the userspace/kernel boundary more often than you need to, especially when you consider that you can replace the standard platform allocator with whatever you want.
To wit, C doesn't emphasize arena allocation anywhere near as much as Zig et al do, and yet nobody alleges that C is somehow less suitable for systems programming than these languages. Have you considered why that is? Because, for the most part, arena allocation doesn't make a significant difference, and in the places where it actually does make a difference, you can trivially build an arena allocator on top of the standard allocator.
The perf argument against RAII is very abstract and is less "RAII causes bad performance" and more "the kind of design that leads you to reach for RAII is the kind of design that's bad for performance." There exist similar hand-wavy arguments against many other C++/Rust features.
More generally, "you shouldn't even want that" is basically a meme at this point in programming language design. Every new-ish language has some version of it.
That said. You asked about C, which I use for my job. Most every large C code base end up abandoning the stdlib (such as it is) and inventing their own. Since they do, we aren’t as hurt by abandoning it as you would be in e.g. Rust - the rust stdlib is useful, the C stdlib is.. not great.
Once you abandon the stdlib, a likely first stop is writing your own routines for allocating and freeing memory. There are different approaches here, from glib’s or sqlite’s alloc and free routines to people writing an allocator abstraction (basically a struct with a vtable for allocating/realloc/free) and when you build your own “stdlib” around this abstraction, you are fine.
As for why you may want arenas vs other allocation strategies, that again deals with how often you are comfortable going across the user-space/kernel boundary and how clever you can be with your allocations or how much internal fragmentation you can accept.
As with all other stuff, it depends. But arenas are often great when you can assert that a series of objects share the same lifetime (death time, rather). In these cases, your amortize the syscall cost, have nearly no additional work to manage the memory (contrast to e.g. the complexity of jemalloc) and can free a series of objects in constant time.