FastHamming VS ParPar

Check out https://github.com/BenBE/FastHamming (AGPL license). It should work for all blocks that are a multiple of 15 bytes, I haven't tested all other sizes.

PAR2 creation (file-based error correction): the core routine here is GF(2^16) matrix multiplication. AVX512 has the GF2P8AFFINEQB instruction, which isn't present on any GPU that I know of, but massively accelerates GF multiplication. Without this instruction, you have to resort to emulating it via bitwise operations or lookup tables, which are much slower. I actually have an OpenCL implementation, but its performance is rather meh compared to CPU

Did you tried to use parpar for creating par2 files? Supposed to be much faster. https://github.com/animetosho/ParPar

I've been developing a performance oriented PAR2 tool (used for generating file-based redundancy for error correction), but without access to a lot of hardware, I don't have that much ability to tune it to various microarchitectures. Currently there's no real benchmark setup defined/implemented (though it shouldn't be hard to come up with one), and it certainly isn't tuned for the number of cores on EPYC, but I've never really thought PAR2 benchmarks would interest that many people.

QuickPar is ancient at this stage, however the PAR2 format hasn't changed since, so the concepts are still the same. For a more modern client, I generally recommend MultiPar. I've also written a PAR2 client, ParPar (CLI, or experimental GUI frontend), but it only supports creating PAR2s, not verify/repair.

Also this implementation of par is the fastest I've seen (for creation only thought) https://github.com/animetosho/ParPar

For PAR2, I did a benchmark comparison here of every tool, which you can use to make up your mind. par2j (Multipar) and phpar2 are Windows only, but work via Wine. ParPar only supports create, so you'll need to use a different client for verify/repair.