Have you been programming with the Zen 4? I bought one, and I've been using the avx512 intrinsics via C++ and Rust (LLVM Clang for both), and I've been a little underwhelmed by the performance. Like say using Agner Fog's vector library, I'm getting about a 20% speedup going from avx2 to avx512. I was hoping for 2x.
Not really. The "pure" computations are double pumped but some of the utility instructions you use with the computations are native AVX-512. And there has been a lot of analysis out there about this and AFIK the conclusion is that outside of very artificial benchmarks most (not all) applications of AVX-512 will never saturate the pipeline enough for it (being double pumped) to matter (i.e. due to how speculative execution, instruction pipeling etc. work in combination with a few relevant instructions being native AVX-512).
Even more so for common mixed workloads the double pumped implementation can even be the better choice as using it puts less constraints on clock speed and what the CPU can do in parallel with it internally.
Sure if you only look at benchmarks focused on benchmarks which only care about (for most people) unrealistic usage (like this article also pointed out many do) your conclusions might be very different.
I think the notion of double pumping is only in the VMOV operation. Looking at Agner[1], the rest of the instructions have similar Ops/Latency to their avx2 counterparts.
