Fastest container or algorithm for unique reusable ids in C++

Question

I have a need for unique reusable ids. The user can choose his own ids or he can ask for a free one. The API is basically

class IdManager {
public:
  int Allocat         


        

Answer 1

So a friend pointed out that in this case a hash might be better. Most OpenGL programs don't use more than a few thousand ids so a hash with say 4096 slots is almost guaranteed to have only 1 or 2 entries per slot. There is some degenerate case where lots of ids might go in 1 slot but that's seriously unlikely. Using a hash would make AllocateID much slower but a set could be used for that. Allocating being slower is less important than InUse being fast for my use case.