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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Status of AVX support
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Wed, 7 Dec 2011 10:47:48 -0500
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2011/12/7 Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>:
> On 06.12.2011 14:01, Benoit Jacob wrote:
>>
>> The difficulty is that taking advantage of AVX without regressing
>> current performance from SSE will require us to handle *both* 16-byte
>> and 32-byte packet size and alignment. We will need 16-byte for e.g.
>> Vector4f, while we will of course want to use 32-byte wherever we can.
>
>
> I'm afraid, you will lose ABI-compatibility if you use 32-byte alignment by
> default. E.g. the size of
> struct { char x; Vector4d y; };
> will be 48 bytes with 16 byte alignment and 64 bytes with 32 byte alignment.
Very good point.
Benoit
>
> W.r.t porting to AVX: Be aware that there might be some pitfalls with
> AVX-performance:
> http://www.agner.org/optimize/blog/read.php?i=142
>
> Christoph
>
>
> --
> ----------------------------------------------
> Dipl.-Inf. Christoph Hertzberg
> Cartesium 0.051
> Universität Bremen
> Enrique-Schmidt-Straße 5
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>
> Tel: (+49) 421-218-64252
> ----------------------------------------------
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