Comparing to ska::flat_hash_map or khash wouldn't be fair, because the F14 hash tables use SIMD intrinsics to lookup 14 buckets at once (and thus the name) whilst the former two don't have that advantage. A fairer comparison would be against Swiss tables[1] from Google's abseil library, which uses the same trick. Also, std::unordered_map is slow because its interface requires a chaining based collision resolution strategy.

[1]: https://abseil.io/blog/20180927-swisstables