how boost multi_index is implemented

Question

I have some difficulties understanding how Boost.MultiIndex is implemented. Lets say I have the following:

typedef multi_index_container<
    employee,
           


        

Answer 1

Conceptually, yes.

From what I understand of Boost.MultiIndex (I've used it, but not seen the implementation), your example with two ordered_unique indices will indeed create two sorted associative containers (like std::map) which store pointers/references/indices into a common set of employees.

In any case, every employee is stored only once in the multi-indexed container, whereas a combination of map and map would store every employee twice.

It may very well be that there is indeed a (dynamic) array inside some multi-indexed containers, but there is no guarantee that this is true:

[Random access indices] do not provide memory contiguity, a property of std::vectors by which elements are stored adjacent to one another in a single block of memory.

Also, Boost.Bimap is based on Boost.MultiIndex and the former allows for different representations of its "backbone" structure.