Re: [boost] Accelerating algorithms with SIMD - Segmented iterators and alternatives

Subject: Re: [boost] Accelerating algorithms with SIMD - Segmented iterators and alternatives
From: Jeffrey Lee Hellrung, Jr. (jhellrung_at_[hidden])
Date: 2010-10-13 15:18:13

On 10/13/2010 10:50 AM, David Abrahams wrote:
> At Wed, 13 Oct 2010 17:38:56 +0100,
> Mathias Gaunard wrote:
[...]
>> Segmented iterators are only useful if the iteration of all my
>> segments is done with the exact same logic but at different locations,
>> since they all must have the same type. They don't allow to circumvent
>> the problem I exposed with normal iterators at all.
>
> I think they do.  However, you might find that you need some dynamic
> dispatching to get it to work.  In other words,
>
>    if (operating on complete segment)
>       SIMD algorithm
>    else
>       elementwise algorithm

That doesn't seem any better than what I would imagine the 
range_detail::join_iterator does.  I.e., I don't see what segmented 
iteration buys us here over what I'd imagine Mathias is currently doing 
(which, I'd imagine, is some variant on a joint_iterator that returns 
aligned packets).

- Jeff