Everything largely looked fine to me, except for some style issues.  For the moved code, I checked the PR versions, and then spot checked that they matched the removed versions (method signatures, etc).

Did my approach to implementing multiprocessing seem reasonable to you?

I had to stop and think about the locking, but this seemed like a reasonable solution.  I have a suspicion that a randomized list of inputs would run faster than one that's sequential (as processes in the pool shouldn't have lock collisions), but that probably isn't a big deal in the long run.

Watching the CPU load on my desktop when generating my Gaia test set, I could see file contention appear as occasional dips, but it was pretty consistent otherwise. When I made some estimates of speed, it was roughly a factor of 7 faster with 8 process than with 1 process, so it seems to be doing a decent job.

Thanks for the quick review, Christopher Waters.

Merged and done.