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Subject: Re: [boost] [gsoc] boost.simd news from the front.
From: MaximYanchenko (MaximYanchenko_at_[hidden])
Date: 2011-06-12 05:51:32

Hi David,

> - Programmer tries to run the compiler on it, examines code
> - Programmer restructures loop nest to expose parallelism
> - Try compiler directives first, if available (tell compiler which
> loops to interchange, where to cache block, blocking factors,
> which loops to collapse, etc.)>
> - Programmer tries compiler again on restructured loop nest
> - Programmer adds directives to tell the compiler which loops
> - Programmer uses boost.simd to write vector code at a higher level
> than provided compiler intrinsics
> Does that seem like a reasonable use case?

In theory, yes.
In practice, the code can stop working when you change a compiler (sometimes
just a new version of the same compiler), or something changes in the code
around the loop, not mentioning the very usual case when somebody makes a simple
and innocent-looking change to the loop code, and the auto-vectorizer silently
switches off.

I think explicitly using Boost.SIMD (or any other explicit solution like
BLAS/MKL/whatever) is much more robust in practice.


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