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 11:11:57

On 11/06/2016 06:25 AM, Joaquin M López Muñoz wrote:
 > A couple of years ago I wrote two blog entries about high-performance
 > data structures
 > for polymorphic objects:
 >
 > http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections.html
 > 
http://bannalia.blogspot.com/2014/05/fast-polymorphic-collections-with.html
 >
 > that spurred some interest in the community. Now I've had the time to
 > turn these
 > ideas into something resembling a full-fledged library:
 >
 > https://github.com/joaquintides/poly_collection
 > 
http://rawgit.com/joaquintides/poly_collection/website/doc/html/index.html
 >
 > and I'd be very grateful if people could give their opinion on
 > usefulness, design, etc.
 > so as to determine potential interest in an eventual official submission
 > to Boost.
 >
 > Thank you,
 >
 > Joaquín M López Muñoz
 >
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

which made me wonder how it would perform in the benchmark
mentioned in that thread:

   https://github.com/cppljevans/soa/blob/master/soa_compare.benchmark.cpp

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>...>;

where the separate pointers would be the data() pointer for
each element in soa_tuple.  IOW, the storage would be like
that of particles here:

 
https://github.com/cppljevans/soa/blob/master/soa_compare.benchmark.cpp#L278

Hence, I'm wondering what's the advantage of your library's
base_collection compared to the soa_tuple.  Now, if you say
soa_tuple contains duplicate entries of size(), then I could
ask what's the advantage of base_collection vs that of the
particles at:

 
https://github.com/cppljevans/soa/blob/master/soa_compare.benchmark.cpp#L456

where there's just a single pointer to a contiguous block of
storage:

   https://github.com/cppljevans/soa/blob/master/soa_block.hpp#L30

and the pointers to the specific types are given by the
soa_block::begin_all function:

   https://github.com/cppljevans/soa/blob/master/soa_block.hpp#L294

in the soa_block<Ts...> type of the particles?

Maybe you could provide another implentation of the
emitter_t using your base_collection to see how they
compare.

-regards,
Larry