Re: [boost] interest in structure of arrays container?

Subject: Re: [boost] interest in structure of arrays container?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2016-10-19 02:26:36

On 10/18/2016 10:24 PM, Michael Marcin wrote:
> On 10/18/2016 10:55 AM, Andreas Schäfer wrote:
>> On 10:29 Tue 18 Oct     , Larry Evans wrote:
>>> The purpose of item:
>>>
>>>    * sizeof...(Ts) allocations could be a single large block
>>>
>>> is to just require 1 heap allocation instead of N, where N
>>> is the number of vectors in soa<T1,T2,...,TN>?
>>
>> One benefit of this would be that transferring such a container to
>> another address space (think MPI or CUDA) would become much simple.
>>
>
> It also reduces the size of your handle structure (the structure the
> holds the pointer to the data). Otherwise every additionally member adds
> ~24 bytes for a simple tuple< vector<Ts>... > or sizeof(T*) bytes at a
> minimum for separately allocated blocks.
>
> It also can reduce the size of an iterator to a view of the data or
> remove an indirection from it depending on implementation.
>
> It has a nice benefit that the size of the handle + body (alloc'd data
> block) for a soa_vector would be identical to that of a normal AoS
> vector containing the same data.
>
>
> If a solution ticked all the other boxes and dropped this one, I'd be
> fine with that. There's quite a bit of complexity involved with
> calculating the offsets with a dynamic capacity and potentially
> arbitrary alignment requirements on internal subarrays.
>
[snip]
Michael, the attached is an outline of how to do it.
As noted in the comments, a lot of member functions still need
implementation; however, the offset calculations I think are
correct.

HTH.

-regards,
Larry