[macstl-dev] Questions on valarray use : non-aligned buffers

[Glen Low]

All:

On 24/09/2005, at 9:15 PM, Ilya Lipovsky wrote:

> Can I propose yet another way of naming?
>
> How about renaming the already existing refarray into  
> "aligned_refarray" and naming the upcoming one as "refarray".  
> Sometimes, I think, it's necessary to break the API (which should  
> be ok here as it's very recent) to do things right rather than be  
> constantly confused later on.
>
> -Ilya
>
> P.S. if not, then arbarray should do it. I don't think you want to  
> make the names similar (for the aligned and the "unknown alignment"
> versions), since this can confuse future novices.

I'm hoping to eliminate some epilogue code in the next version of  
macstl. Particular valarray expressions can stand to use all SIMD  
instead of wasting time in the tail of the array calling scalar  
functions -- e.g. where it can be established that there's enough  
"slop" in the source and target arrays. This would be true of  
valarray and statarray and all strictly parallel functions and  
operators, but unfortunately won't be true for refarray and arbarray/ 
urefarray -- I can't guarantee there's nothing "important" after the  
end of data in a refarray or arbarray/urefarray. I don't want a  
runtime check, not just because it's (slightly) slower but because  
I'm hoping to eventually target the Cell and other embedded scenarios  
where non-use/non-linking of the Standard Library would be an advantage.

Not sure how to address that in the design of refarray. I'm now  
thinking it'd be better to use some default template non-type params  
(similar to policies) to do this e.g.

refarray <float> -- non-aligned, no slop (the default case should be  
the hardest to stuff up, as per Ilya's thinking)
refarray <float, aligned, sloppy>
refarray <float, aligned>

etc.

"sloppy" doesn't accurately capture what I'm thinking, I mean it's an  
assert that the data passed in will have a length divisible by 4 (for  
floats).

What do you think?




Cheers, Glen Low


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