this post was submitted on 05 Nov 2024
300 points (96.9% liked)

Open Source

31358 readers
206 users here now

All about open source! Feel free to ask questions, and share news, and interesting stuff!

Useful Links

Rules

Related Communities

Community icon from opensource.org, but we are not affiliated with them.

founded 5 years ago
MODERATORS
[email protected]
[email protected]
[email protected]
[email protected]
300
FFmpeg devs boast of up to 94x performance boost after implementing handwritten AVX-512 assembly code (www.tomshardware.com)
submitted 2 weeks ago by [email protected] to c/[email protected]
20 comments fedilink hide all child comments
 

Unfortunately, due to the complexity and specialized nature of AVX-512, such optimizations are typically reserved for performance-critical applications and require expertise in low-level programming and processor microarchitecture.

all 22 comments
sorted by: hot top controversial new old
[–] [email protected] 144 points 2 weeks ago* (last edited 2 weeks ago) (1 children)

Whomever wrote this article is just misleading everyone.

First of all, they did this for other kinds of similar instruction sets before, so this is nothing special. Second of all, they measure the speedup compared to a basic implementation that doesn't use any optimizations.

They did the same in the past for AVX-2, which is 67x faster in the test where avx-512 got the 94x speed increase. So it's not 94x faster now, it's 1.4x faster than the previous iteration using the older AVX-2 instruction set. It's barely twice as fast as the implementation using SSE3 (40x faster than the slow version), an instruction set from 20 years ago....

So yeah, it's awesome that they did the same awesome work for AVX-512, but the 94x boost is just plain bullshit.... it's really sad that great work then gets worded in such a misleading way to form clickbait, rather than getting a proper informative article.....

[–] [email protected] 48 points 2 weeks ago (1 children)

Even more ridiculous since a 1.4x performance increase is already incredible news for anyone who makes regular of this.

If someone found a software optimization that improved, say, blender performance by 1.4x people would be shouting praises from the rooftops.

[–] [email protected] 8 points 2 weeks ago

Indeed, it's a very nice boost, and great work, but this clickbait nonsense is just so stupid....

And i'm really bothered how it's just parrotted everywhere... Doesn't anybody wonder "94x faster is like.... really a LOT.... that can't be true"

[–] [email protected] 39 points 2 weeks ago (1 children)

There is an issue, though: Intel disabled AVX-512 for its Core 12th, 13th, and 14th Generations of Core processors, leaving owners of these CPUs without them. On the other hand, AMD's Ryzen 9000-series CPUs feature a fully-enabled AVX-512 FPU so the owners of these processors can take advantage of the FFmpeg achievement.

Intel can't stop the L.

As for the claims and benchmarking, we need to see how much it actually improves. Because the 94x performance boost is compared to baseline when no AVX or SIMD is used (if I understand the blog post correctly). So I wonder how much the handwritten AVX-512 assembler code improves over an AVX-512 code written in C (or Rust maybe?). The exact hardware used to benchmark this is not disclosed either, unfortunately.

[–] [email protected] 5 points 2 weeks ago* (last edited 2 weeks ago) (1 children)

Someone else in the comments mentioned it is about 40% faster than the AVX-2 code and slightly more than twice as fast as the SSE3 code. That's still a nice boost, but hopefully no one was relying on the radically slow unoptimized baseline.

[–] [email protected] 1 points 2 weeks ago

But my question is, how much faster is it that its written in assembly rather than "high" level language like C or Rust. I mean if the AVX-512 code was written in C, would it be 40% faster than AVX-2?

[–] [email protected] 16 points 2 weeks ago

As someone who has done some hand coding of AVX-512, I appreciate their willingness to take this on. Getting the input vectors setup correctly for the instructions can be a hassle, especially when the input dataset is not an even multiple of 64.

[–] [email protected] 11 points 2 weeks ago (1 children)

When this comes to the BSD's, it will be interesting to see if there is a significant difference in multimedia. I bought Intel 11th gen over 10th for it's AVX-512.

[–] [email protected] 4 points 2 weeks ago (1 children)

Why, do you expect a difference on bsd?

[–] [email protected] -1 points 2 weeks ago

Does the BSD's heavy emphasis on code correctness, that's when the quality and security of the code will be revealed. I will watch what the OpenBSD developers say when they try to port the new code for FFMpeg.

[–] [email protected] 9 points 2 weeks ago* (last edited 2 weeks ago) (2 children)

nice.

can usually get a pretty good performance increase with hand writing asm where appropriate.

don't know if its a coincidence, but i've never seen someone who's good at writing assembly say that its never useful.

[–] four 5 points 2 weeks ago (1 children)

To be fair, people who don't find assembly useful probably wouldn't get good at writing assembly

[–] [email protected] 5 points 2 weeks ago* (last edited 2 weeks ago)

for sure, its perfectly reasonable to say "this tool isn't useful for me"

its another thing to say "this tool isn't useful for anyone"

[–] [email protected] 3 points 2 weeks ago (1 children)

Though you'd get the same speedup if you used SIMD intrinsics. This is just comparing non-SIMD to SIMD.

[–] [email protected] 2 points 2 weeks ago* (last edited 2 weeks ago) (1 children)

from the article it's not clear what the performance boost is relative to intrinsics (its extremely unlikely to be anything close to 94x lol), its not even clear from the article if the avx2 implementation they benchmarked against was instrinsics or handwritten either. in some cases avx2 seems to slightly outperform avx-512 in their implementation

there's also so many different ways to break a problem down that i'm not sure this is an ideal showcase, at least without more information.

to be fair to the presenters they may not be the ones making the specific flavour of hype that the article writers are.

[–] [email protected] 7 points 2 weeks ago

Absolute madness. I cringe at the thought of making modern x86 asm code.

Great work!

[–] [email protected] 7 points 2 weeks ago

I worked in the media broadcasting, we had an internal lib to scale/convert whatever format in real time, and it went from basic operation, to SSE3, to AVX512, to CUDA, and yes crafting some functions/loops wit assembly can give an enormous boost.

[–] [email protected] 1 points 2 weeks ago

And how many people have access to avx 512? Genuine question, iirc Intel discontinued it right?