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The compiler will optimize that away

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Re: The compiler will optimize that away

#31

Post by elcapitan »

aparsons wrote: post #4
theamk wrote: post #2

Summary: the computer has changed -- memory latency measured in CPU cycles has grown a lot. So we should not be using traditional struct/class-like programming model, where we put all properties of an object next to each other. Instead, we should be using game-style "data oriented programming" a.k.a. "column databases" for a much higher performance. However, most modern languages (C, C++, Python, Java, etc..) are not…

What do you mean by game-style here? I’m very intrigued. Any place to read more about these?

Look for "Data oriented design" or "Structs of arrays".

Here's a talk on the former by Mike Acton: https://www.youtube.com/watch?v=rX0ItVEVjHc

On the latter, there's Jai, a new programming language for games (WIP, unpublished) by Jonathan Blow, who has been very public in documenting the process creating it, and which is centered around such concepts. There is some unofficial documentation of the ideas on SoA vs AoS and how the language can help switching between the two, e.g. here: https://pixeldroid.com/jailang/overview/Features/SOA/#/overv... and here: https://github.com/BSVino/JaiPrimer/blob/master/JaiPrimer.md...

Edit: Just realized that the articale even mentions Jai towards the end.

Re: The compiler will optimize that away

#32

Post by elcapitan »

> The programming languages listed above are all over 20 years old and their initial design decisions, like Python’s global interpreter lock or Java’s everything is an object mindset, no longer make any sense today

I wonder what general purpose languages (as the mentioned Jai is meant for games primarily) will be the best fit for modern architectures, besides obvious things like doing it in C and just doing everything manually to fit the machine nicely.

Re: The compiler will optimize that away

#34

Post by PixelOfDeath »

TazeTSchnitzel wrote: post #33

The metaprogramming available in languages like Rust and C++ could maybe be leveraged to make the struct-of-arrays model easier. Wouldn't be the same as native support, though.

There is some, lets call them experimental, C++ libraries for that. But C++ not having static reflection is the main show stopper on that frontier.

Re: The compiler will optimize that away

#35

Post by NohatCoder »

elcapitan wrote: post #32

> The programming languages listed above are all over 20 years old and their initial design decisions, like Python’s global interpreter lock or Java’s everything is an object mindset, no longer make any sense today I wonder what general purpose languages (as the mentioned Jai is meant for games primarily) will be the best fit for modern architectures, besides obvious things like doing it in C and just doing everythin…

I don't see any particular reason why Jai shouldn't be usable for other stuff than games, there are no baked-in assumption about any gamey nature of programs.

Re: The compiler will optimize that away

#36

Post by teh_matt »

conradludgate wrote: post #3

If you want to utilise this data oriented approach in rust, check out soa-derive[0]. SoA stands for struct of array, rather than the conventional array of struct. [0]: https://crates.io/crates/soa_derive

I hacked up something similar (https://gitlab.com/mbryant/functiontrace/-/blob/master/src/p...) a while ago. Your variant looks much more useful!

Re: The compiler will optimize that away

#37

Post by jhgb »

theamk wrote: post #2

Summary: the computer has changed -- memory latency measured in CPU cycles has grown a lot. So we should not be using traditional struct/class-like programming model, where we put all properties of an object next to each other. Instead, we should be using game-style "data oriented programming" a.k.a. "column databases" for a much higher performance. However, most modern languages (C, C++, Python, Java, etc..) are not…

> So we should not be using traditional struct/class-like programming model, where we put all properties of an object next to each other. Instead, we should be using game-style "data oriented programming" a.k.a. "column databases" for a much higher performance.

Something like DataDraw (http://datadraw.sourceforge.net/) does with C?

> However, most modern languages (C, C++, Python, Java, etc..) are not making it easy

Funnily enough, it was yesterday when I though about how cool it would be to make an implementation of Oberon-07 (http://oberon07.com , https://people.inf.ethz.ch/wirth/ProjectOberon/index.html - a simple-enough language to experiment with in various ways) that would use something like this as its in-memory data representation.

It came up as a consequence of me wanting to have an implementation of Oberon-07 for WebAssembly, and realizing that the necessity of "restarting" the whole binary at any code change (necessitated by how WebAssembly works) also allows for some liberties in data representation (for example running out of compressed IDs for instances of a type could be handled in exactly the same way as changing the code of the running program - by generating a new binary with expanded space for these IDs and restarting it using the serialized old heap).

Re: The compiler will optimize that away

#38

Post by PixelOfDeath »

Const-me wrote: post #30
moonchild wrote: post #26

Earlier quoted context omitted.

Actually... https://arxiv.org/pdf/1902.04738.pdf On a more serious note, most c programs I see don't do very much of that, preferring to allocate fixed-size buffers on the stack. Additionally, most GC'd languages that aren't java have crappy GCs, and those GC'd languages that are java lack value types. This harms spatial locality quite a bit, and compaction can't fully compensate for that. They are working on adding…

> preferring to allocate fixed-size buffers on the stack When working set is measured in megabytes, it fits in L3 cache of modern CPUs. Memory layout is not too important for these programs. > most GC'd languages that aren't java have crappy GCs C# is good too. It also has value types, native memory spans, SIMD intrinsics, and stackalloc.

Don't forget that good cache locality also can cause data being pulled into cache that the prefetcher did know nothing about.

I can create you a shitty linked list that fits perfectly in L3, but still has terrible cold cache performance because each individual cacheline has to be pulled in one by one.

Re: The compiler will optimize that away

#40

Post by tom_mellior »

theamk wrote: post #2

Summary: the computer has changed -- memory latency measured in CPU cycles has grown a lot. So we should not be using traditional struct/class-like programming model, where we put all properties of an object next to each other. Instead, we should be using game-style "data oriented programming" a.k.a. "column databases" for a much higher performance. However, most modern languages (C, C++, Python, Java, etc..) are not…

> However, most modern languages (C, C++, Python, Java, etc..) are not making it easy,

The article shows how easy it is to declare a struct of arrays in Java: You declare a struct (class). Inside it you declare arrays. Done.

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