@NovaX it's worth noting that swapping out the underlying hash map that evmap uses is really easy, which is one of the advantages of the design as far as I'm concerned! For example, here's the diff for moving to someone else's custom hash map implementation: https://github.com/jonhoo/rust-evmap/compare/hashbrown. A better benchmarking harness is a good idea, though I'd like to see something that is somewhat disconnected from evmap! Pre-generating the randomness is something I've done in the past, but it does have the downside that you end up not actually exercising the distribution well (unless you generate vast amounts of keys)...