[PD] [OT] SSE/MMX tips?

[Mathieu Bouchard]

On Wed, 7 Sep 2011, Mathieu Bouchard wrote:

> On Wed, 7 Sep 2011, Bill Gribble wrote:
>
>> So far iteration on plain floats seems to be the best I can come up with, 
>> but HADDPS is tantalizingly close to what I want to do.  Any hints?
>
> Once I thought that with some commutativity you could speed things up like 
> this :
>
> (f0+f1+f2+f3)+(f4+f5+f6+f7)+...
>
> can be rearranged as :
>
> (f0+f4+...)+(f1+f5+...)+(f2+f6+...)+(f3+f7+...)

But what I said does not apply to your case, because you want a scan, 
whether I didn't really read and assumed a fold.

I don't know how to optimise a scan.

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