[bunderbunder]

I'm no game dev but I have had friends who do it professionally.

Long story short, yes, it's very different in game dev. It's very common to pre-allocate space for all your working data as large statically sized arrays because dynamic allocation is bad for performance. Oftentimes the data gets organized in parallel arrays (https://en.wikipedia.org/wiki/Parallel_array) instead of in collections of structs. This can save a lot of memory (because the data gets packed more densely) be more cache-friendly, and makes it much easier to make efficient use of SIMD instructions.

This is also fairly common in scientific computing (which is more my wheelhouse), and for the same reason: it's good for performance.

[Pet_Ant]

> Oftentimes the data gets organized in parallel arrays (https://en.wikipedia.org/wiki/Parallel_array) instead of in collections of structs. This can save a lot of memory (because the data gets packed more densely) be more cache-friendly, and makes it much easier to make efficient use of SIMD instructions.

That seems like something that could very easily be turned into a compiler optimisation and enabled with something like an annotation. Would have some issue when calling across library boundaries ( a lot like the handling of gradual types), but within the codebase that'd be easy.

[crq-yml]

The underlying issue with game engine coding is that the problem is shaped in this way:

* Everything should be random access(because you want to have novel rulesets and interactions)

* It should also be fast to iterate over per-frame(since it's real-time)

* It should have some degree of late-binding so that you can reuse behaviors and assets and plug them together in various ways

* There are no ideal data structures to fulfill all of this across all types of scene, so you start hacking away at something good enough with what you have

* Pretty soon you have some notion of queries and optional caching and memory layouts to make specific iterations easier. Also it all changes when the hardware does.

* Congratulations, you are now the maintainer of a bespoken database engine

You can succeed at automating parts of it, but note that parent said "oftentimes", not "always". It's a treadmill of whack-a-mole engineering, just like every other optimizing compiler; the problem never fully generalizes into a right answer for all scenarios. And realistically, gamedevs probably haven't come close to maxing out what is possible in a systems-level sense of things since the 90's. Instead we have a few key algorithms that go really fast and then a muddle of glue for the rest of it.

[rcxdude]

It's not at all easy to implement as an optimisation, because it changes a lot of semantics, especially around references and pointers. It is something that you can e.g. implement using rust procedural macros, but it's far from transparent to switch between the two representations.

(It's also not always a win: it can work really well if you primarily operate on the 'columns', and on each column more or less once per update loop, but otherwise you can run into memory bandwidth limitations. For example, games with a lot of heavily interacting systems and an entity list that doesn't fit in cache will probably be better off with trying to load and update each entity exactly once per loop. Factorio is a good example of a game which is limited by this, though it is a bit of an outlier in terms of simulation size.)

[bunderbunder]

Meh. I've tried "SIMD magic wand" tools before, and found them to be verschlimmbessern.

At least on the scientific computing side of things, having the way the code says the data is organized match the way the data is actually organized ends up being a lot easier in the long run than organizing it in a way that gives frontend developers warm fuzzies and then doing constant mental gymnastics to keep track of what the program is actually doing under the hood.

I think it's probably like sock knitting. People who do a lot of sock knitting tend to use double-pointed needles. They take some getting used to and look intimidating, though. So people who are just learning to knit socks tend to jump through all sorts of hoops and use clever tricks to allow them to continue using the same kind of knitting needles they're already used to. From there it can go two ways: either they get frustrated, decide sock knitting is not for them, and go back to knitting other things; or they get frustrated, decide magic loop is not for them, and learn how to use double-pointed needles.

[djmips]

Very much agree and love your analogy but there is a third option - make a sock knitting machine.

[at_compile_time]

> verschlimmbessern

Thank you for this delightful word.