Every time some computer scientist interviews me and shows off their O(n) knowledge (it's always an o(n) solution to a naive o(n**2) problem!) I mention that in the Real World, engineers routinely do O(n**7) calculations (n==number of basis functions) on tiny systems (up to about 50 atoms, maybe 100 now?) and if they'd like to help it would be nice to have better, faster approximations that are n**2 or better. Unfrotunately, the process of going from computer scientist to expert in QM is entirely nontrivial so most of them do ads ML instead