I tried searching "SSE2-4.x" and this is the top result in DDG and Google, so I was initially confused what instruction set the article is referring to. However, this appears to be shorthand for SSE2 through SSE4? Perhaps a rephrasing of the article title could be helpful.
AVX2 is slower than SSE2-4.x under Windows ARM emulation
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Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#32I suspected this was because the vector units were not wide enough, and it seems that is the case. AVX2 is 256-bit, ARM NEON is only 128-bit. The big question then is, why are ARM desktop (and server?) cores so far behind on wider SIMD support? It's not like Intel/AMD came up with these extensions for x86 yesterday; AVX2 is over 15 years old.
SVE was supposed to be the next step for ARM SIMD, but they went all-in on runtime variable width vectors and that paradigm is still really struggling to get any traction on the software side. RISC-V did the same thing with RVV, for better or worse.
The only CPU I've encountered that supports SVE is the Cortex-X925/A725 that is used in the NVIDIA DGX Spark platform. The vector width is still only 128 bits, but you do get access to the other enhancements the SVE instructions give, like predication (one of the most useful features from Intel's AVX512).
Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#33AVX2 should be banned anyway. Only expensive CPUs have it, ruining mininum games requirements and making hardware obsolete. Most of the world lives of 300$ per month
Almost every x86 cpu made in the last decade should have avx2. Maybe you're thinking of avx512 or avx10?
Not really, Intel Celeron/Pentium/Atom (apollo lake) that was made in the last decade does not have AVX. These CPUs were very popular for low-cost, low-tdp quad-core machines such as Intel NUC mini PC.
Edit. Furthermore, i think that none of these (pre-2020) low budget CPUs support AVX2, until Tiger lake released in 2020.
Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#34Earlier quoted context omitted.
SVE was supposed to be the next step for ARM SIMD, but they went all-in on runtime variable width vectors and that paradigm is still really struggling to get any traction on the software side. RISC-V did the same thing with RVV, for better or worse.
RISC-V chip designers at least seem to be more bullish on vectors. There is seriously cool stuff coming like the SpacemiT K3 with 1024-bit vectors :)
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Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#35Spoiler is in the conclusion: > Yes, it is absolutely key to build your app as ARM, not to rely on Windows ARM emulation.
Is this actually surprising? Once you use stuff like vectorization you want to get as much performance out of a system. If you're not natively compiling for a system, you won't get any performance.
Using AVX2 and using an emulator have contradictory goals. Of course there can be a better emulator or actually matching hardware design (since both Apple and Microsoft actually exploit the similar register structure between ARM64 and x86_64). However, this means you have increased complexity and reduced reliability / predictability.
Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#36Earlier quoted context omitted.
SVE was supposed to be the next step for ARM SIMD, but they went all-in on runtime variable width vectors and that paradigm is still really struggling to get any traction on the software side. RISC-V did the same thing with RVV, for better or worse.
RISC-V chip designers at least seem to be more bullish on vectors. There is seriously cool stuff coming like the SpacemiT K3 with 1024-bit vectors :)
The 1024-bit RVV cores in the K3 are mostly that size to feed a matmul engine. While the vector registers are 1024-bit, the two exexution units are only 256-bit wide.
The main cores in the K3 have 256-bit vectors with two 128-bit wide exexution units, and two seperate 128-bit wide vector load/store units.
See also: https://forum.spacemit.com/uploads/short-url/60aJ8cYNmrFWqHn...
But yes, RVV already has more diverse vector width hardware than SVE.
Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#37Earlier quoted context omitted.
Almost every x86 cpu made in the last decade should have avx2. Maybe you're thinking of avx512 or avx10?
Yeah, sounds like they're confusing AVX2 for AVX512. AVX2 has been common for a decade at least and greatly accelerates performance. AVX512 is so kludgy that it usually leads to a detriment in performance due to the extreme power requirements triggering thermal throttling.
See this correct comment above: https://news.ycombinator.com/item?id=47061696
AVX512 leading to thermal throttling is a common myth that from what I can tell traces its origins to a blog post about clock throttling on a particular set of low-TDP SKUs from the first generation of Xeon CPUs that supported it (Skylake-X), released over a decade ago: https://blog.cloudflare.com/on-the-dangers-of-intels-frequen...
The results were debated shortly after that by well-known SIMD authors that were unable to duplicate the results: https://lemire.me/blog/2018/08/25/avx-512-throttling-heavy-i...
In practice, this has not been an issue for a long time, if ever; clock frequency scaling for AVX modes has been continually improved in subsequent Intel CPU generations (and even more so in AMD Zen 4/5 once AVX512 support was added).
Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
#38Earlier quoted context omitted.
Almost every x86 cpu made in the last decade should have avx2. Maybe you're thinking of avx512 or avx10?
Not really, Intel Celeron/Pentium/Atom (apollo lake) that was made in the last decade does not have AVX. These CPUs were very popular for low-cost, low-tdp quad-core machines such as Intel NUC mini PC. Edit. Furthermore, i think that none of these (pre-2020) low budget CPUs support AVX2, until Tiger lake released in 2020.
I think the last Intel CPUs that didn't support AVX were 10th gen (Comet Lake) Pentiums and Celerons, released in 2019.
Edit: That's wrong. Jasper Lake from 2021 also came without AVX support.
Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
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Re: AVX2 is slower than SSE2-4.x under Windows ARM emulation
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