Re: [boost] [poly_collection] Request for comments: fast polymorphic collections

Subject: Re: [boost] [poly_collection] Request for comments: fast polymorphic collections
From: Larry Evans (cppljevans_at_[hidden])
Date: 2016-11-06 15:35:58

On 11/06/2016 02:22 PM, Joaquin M López Muñoz wrote:
> El 06/11/2016 a las 17:11, Larry Evans escribió:
>> Thanks for the update Joaquin.
>>
>> I noticed you also mentioned this library in reponse to
>> another thread here:
>>
>> http://lists.boost.org/Archives/boost/2016/10/231186.php
>
> Mmm... on that particular thread I mentioned a different set of blog
> entries related to
> DOD, SOA/AOS etc. This is rather a different beast having to do with
> dynamic
> polymorphism, which I think the SOA/AOS discussion is not particularly
> concerned about.

Ah.  Thanks for clarifying.
>
>> [...]
>>
>> But then, I looked at the documentation here:
>>
>> http://rawgit.com/joaquintides/poly_collection/website/doc/html/poly_collection/an_efficient_polymorphic_data_st.html
>>
>>
>> and it looked like there was a separate pointer for each
>> type.  Hence, the storage looks like it would be simllar to:
>>
>>    template<typename... Ts>
>>    soa_tuple=std::tuple<std::vector<Ts>...>;
>
> The data structure in (candidate) Boost.PolyCollection is not meant to
> be used
> as a SOA structure where the different attributes of an entity are laid
> out contiguously,
> but as a decomposition of a linear sequence of polymorphic objects into
> several segments
> dedicate to each of the concrete types being dealt with. In particular,
> traversing the entire
> sequence is done by traversing each segment in succession, which looks
> to me hardly
> similar to SOA access patterns. Maybe I'm missing something?
>
No, you probably got it right.  I was jumping to conclusions.
Sorry :(