I'm in the middle of adding some Rust bindings to the C implementation in github.com/BLAKE3-team/BLAKE3, so that `cargo test` and `cargo bench` can cover both. Once that's done, I'll follow up with benchmark numbers from my laptop (Kaby Lake i5-8250U, also AVX2 with no AVX-512). For benchmark numbers with AVX-512 support, see the Performance section of the BLAKE3 paper (https://github.com/BLAKE3-team/BLAKE3-specs/blob/master/blake3.pdf). Larry, what processor did you run your benchmarks on?

Also, is there anything currently in CPython that does dispatch based on runtime CPU feature detection? Is this something that BLAKE3 should do for itself, or is there existing machinery that we'd want to integrate with?