John the Ripper: OpenMP mode vs using the “–fork=N” option?

Clang on OSX doesn’t support OpenMP by default, so I could not compile JtR with OpenMP support without another Clang installation.

However, after looking at the below option, I wonder what the difference is compared to OpenMP mode:

--fork=N fork N processes

If I invoke JtR using --fork=2, then JtR will run with two processes, executed on different physical processor cores (same as OpenMP)?

John the Ripper known part of password

For migration purposes i need to get the plaintext password for all our accounts.

Our system uses usernames in the format “firstname.lastname” and password is either “firstname + single_number + single_letter” or “lastname + single_number + single_letter”, like “firstname3p” or “lastname3p”

What is the correct way to use filters to extract firstname or lastname and try every combination of number + letter on them?