Re: [boost] [OT?] SIMD and Auto-Vectorization (was Re: How to structurate libraries ?)

Subject: Re: [boost] [OT?] SIMD and Auto-Vectorization (was Re: How to structurate libraries ?)
From: David Abrahams (dave_at_[hidden])
Date: 2009-01-20 19:51:04

on Tue Jan 20 2009, "David A. Greene" <greened-AT-obbligato.org> wrote:

> On Tuesday 20 January 2009 06:58, David Abrahams wrote:
>
>> > Actually, I think you're missing the point (at least from what I'm
>> > saying).
>> >
>> > I'm saying SIMD code generation ought to be the job of the compiler(s)
>> > for the platforms where they make sense.
>>
>> Why are these SIMD operations different in that respect from, say, large
>> matrix multiplications?
>
> A matrix multiplication is a higher-level construct.  Still, most compilers 
> will pattern-match matrix multiplication to an optimal routine.

Not hardly.  No compiler is going to introduce register and cache-level
blocking.

> SIMD code generation is extremely low-level.  
> Programmers want to think in a 
> higher level.  

Naturally.  But are the algorithms implemented by SIMD instructions
lower-level than std::for_each or std::accumulate?  If not, maybe they
deserve to be in a library.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com