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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Vectorized quaternion multiplication.
- From: Rohit Garg <rpg.314@xxxxxxxxx>
- Date: Sat, 7 Mar 2009 17:30:06 +0530
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When you put it in, please tell me. :)
I posted this for feedback here and you may be interested.
http://forum.beyond3d.com/showthread.php?t=52840
On Sat, Mar 7, 2009 at 5:16 PM, Gael Guennebaud
<gael.guennebaud@xxxxxxxxx> wrote:
> hi,
>
> thanks a lot,
>
> at a first glance I was not sure about the perf, because it needs a
> lot of shuffle instructions which are quite costly, so benched, and on
> my core2 your version is 1.5 times faster :) Then I changed the
> shuffle_ps for the simpler PSHUFD instr. and now, it is almost 2x
> faster, so really worth it :)
>
> FYI I only changed vec4f_swizzle like this:
>
> #define vec4f_swizzle(v,p,q,r,s) (_mm_castsi128_ps(_mm_shuffle_epi32(
> _mm_castps_si128(v), \
> ((s)<<6|(r)<<4|(q)<<2|(p)))))
Now I see. This instruction takes one operand alone so is perhaps
faster (aka higher throughput).
--
Rohit Garg
http://rpg-314.blogspot.com/
Senior Undergraduate
Department of Physics
Indian Institute of Technology
Bombay