Chainstate seed speed up idea: Parallelize SHA-256 Checksum Verification

[pradel]

The chainstate seed script is quite slow, and the sha256sum check takes a long time to run on the big archives. An idea to improve the process and make it faster would be to parallelize that call, which seems to be possible with smth like openssl dgst -sha256 -parallel 8 or other tools.

[wileyj]

by itself, i don't think this will work (tested as-is, and it exits with 1).

but, the idea could work:

• xargs could be an option, but that would not be posix compliant
• gnu parallel could also do it (but then comparing the output would need some extra work to track the state of the checksum)

will have to think about this more - i think a good starting place is to take that seed-chainstate script and fully rewrite/refactor it. it was quite literally a POC that more or less worked and only minor edits have happened over time.

probably a good idea to just rewrite it better.