This. For the OP’s use case, replacing std::unordered_set<T> with CAtlMap<T,bool> improves the hashtable method performance by a factor of ~4, consistent over

This. For the OP’s use case, replacing std::unordered_set<T> with CAtlMap<T,bool> improves the hashtable method performance by a factor of ~4, consistent over different input sizes.