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

Subject: Re: [boost] interest in structure of arrays container?
From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2016-10-21 01:48:45

On 10/20/2016 10:02 PM, Larry Evans wrote:
> On 10/19/2016 11:59 PM, Michael Marcin wrote:
>> On 10/19/2016 7:32 AM, Larry Evans wrote:
>>>> 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.
>>>>
>>> Code has been updated to implement most of the "essentials" of
>>> soa_block.  You can now call begin<Index> to get the begin
>>> iterator for the Index'th vector.
>>>
>>> The code now is on github at:
>>>
>>> https://github.com/cppljevans/soa/blob/master/soa_block.cpp
>>>
>>
>> Still digesting this but one small tidbit I stood out for me
>>
> [snip]
> I uploaded a modification of your benchmark:
>
>   http://codepad.org/eol6auRN
>
> to:
>   https://github.com/cppljevans/soa/blob/master/codepad.eol6auRN.cpp
>
> The modification added soa_emitter_block_t which uses soa_block.
> Unfortunately, this soa_emitter_block_t takes about twice as long as
> your soa_emitter_static_t.
>
> I've no idea why.  Any guesses?
>

2x is quite an abstraction penalty.
I can only assume your compiler is failing to optimize away some part of 
the abstraction.

FWIW on vs2015 I'm not seeing nearly as much of a difference.

particle_count=1,000,000
AoS in 6.34667 seconds
SoA in 4.26384 seconds
SoA flat in 4.16572 seconds
SoA Static in 5.4037 seconds
SoA block in 5.5588 seconds