Re: [boost] Boost SIMD beta release

Subject: Re: [boost] Boost SIMD beta release
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-12-25 15:54:58

on Tue Dec 25 2012, Mathias Gaunard <mathias.gaunard-AT-ens-lyon.org> wrote:

> On 24/12/12 03:54, Dave Abrahams wrote:
>
>> Well, that is one view.
>
> It's not a matter of view. The definition of the concepts is not
> really subject to interpretation.

I am thinking about the abstract concepts that underly the generic
programming "concepts" in that paper.

>> A simple change to that loop could allow a SIMD-specialized version of
>> fill to kick in.
>
> If we're going to specialize for SIMD anyway, then there is no point
> to the exercise at all.

The problem of using SIMD instructions for these operations *clearly*
requires specialization no matter which approach you choose.  I don't
think that fact makes it a waste of time to explore different approaches
to using such a specialization.

> The solution you're proposing is more about extending our SIMD
> variants to the algorithms to work with segmented sequences, not
> re-using segmented iterator algorithms as defined in the paper to do
> SIMD.

That's a reasonable point of view.

> Those are entirely two different things.

OK

> I can tell you the second is not really conceptually feasible, and in
> the cases it is it is not a good idea.
> The first one is trivial and just a matter of adding the code for it,
> but there isn't really any incentive to do so since there are no
> segmented iterators in existence anywhere.

IMO given the importance of cache effects and hierarchical data
structures, something like segmented iterators *should* be in existence.

-- 
Dave Abrahams
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