This is really awesome work! Thank you for sharing, and good luck for what’s ahead. Several source files are referenced through the post (emu.c, emuC.c, emuJit.c, patchpace.c, etc.), but I could not find them. Where can these be accessed please?

Set family {{1,2,3,4}, {1}, {2}, {3}, {4}} has all 4 elements appearing in exactly 2 sets out of the 5, that is 40%. What am I missing?

Your example is not union-closed.

"A collection, or family, of sets is considered “union-closed” if the union of any two sets in the family equals any existing set in the family."

EDIT: In your hypothetical collection of sets, the union of "2" and "3" would produce the set "2,3" which is not an enumerated set in your list.

Check out the replies to this comment [1] with the same attempted counterexample. Your set isn't union closed because {1}U{2} = {1, 2} isn't in it (same for {1}U{3} etc.).

[1] https://news.ycombinator.com/item?id=34236889#34240381