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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Use of streaming loads in eigen
- From: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>
- Date: Fri, 27 Mar 2009 16:08:23 +0100
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On Fri, Mar 27, 2009 at 2:57 PM, Rohit Garg <rpg.314@xxxxxxxxx> wrote:
> In the PacketMath.h file, the only eigen function to send the sse
> registers back to memory is the _mm_store_ intrinsic. Has anybody
> looked at using the _mm_stream intrinsics instead. They should help
> atleast in BLAS 1 and BLAS 2 codes where the code is fundamentally
> bandwidth bound. For a pseudo benchmark. look here
>
> http://humus.name/index.php?page=Comments&ID=244
>
> Even for BLAS 3 it should only help. However, for small sized stuff,
> it will definitely not be helpful as one will want to have the item in
> the cache as long as possible as it doesn't pollute the cache because
> of it's small size.
that's exactly why we cannot use it in Eigen: we cannot know if the
data are going to reused soon or not, and even in the best case
scenario the improvement would be pretty low...
> --
> Rohit Garg
>
> http://rpg-314.blogspot.com/
>
> Senior Undergraduate
> Department of Physics
> Indian Institute of Technology
> Bombay
>
>
>