unordered_dense

Shoutout to unordered_dense, a drop-in replacement for C++ unordered_map that uses this: https://github.com/martinus/unordered_dense

On that angle - I like the project structure, overall, CMake use and documentation. It was helpful to understand, high level, before diving into code. I also recall the discussion here related to fast associative containers, like unordered map/set. This is the implementation - https://github.com/martinus/unordered_dense Combined with HFT CppCon talk that emphasizes the impact of node-based STL containers you may benefit from using some optimized hash maps on top of vectors, if you aim at top-performance in runtime. Also, abseil has some flat sets/maps implementation. All of this could be a nice addition if you experiment with performance (I figured that from std::pmr use in your project).

Of libraries that are better than the STL? Or data structures that the STL is missing? Without getting into the weeds of esoteric data structures and algorithms I think there's a few holes that aren't addressed: https://github.com/martinus/unordered_dense provides better replacements for unordered_map/set. The STL is missing B-trees and B-heaps, as well as d-heaps. STL is also missing a radix sort, which is even more sorely missed now that we have std::executor::par_unseq to play with.

I tied adding the maps to the [1] benchmark, but I wasn't able to, since they aren't type generic yet. You may want to benchmark against [2], and [3] which are the best performing ones in the above benchmark. [1] https://github.com/martinus/map_benchmark/ [2] https://github.com/martinus/unordered_dense/blob/main/includ... [3] https://github.com/ktprime/emhash Edit: I had the wrong link for [2] and [3], somehow...

https://github.com/martinus/unordered_dense Check this one out, it's a successor to this idea. Boost also introduced a very performant flat_hash_map in 1.81