[ODE] Some SSE in Quick step

[Tom Spilman]

 A lot of talk about using D3DX lately, but it isn't a good option in the
long run.  You might get a few small gains quickly, but you won't go far by
optimizing at the math class level.  An effort has to be made to create and
maintain the multiple MMX/SSE/SSE2 versions of some key inner functions like
dxQuickStepper.  So far there isn't an easy solution to getting the most out
of vectorization.  My two cents.

  Tom


> -----Original Message-----
> From: ode-bounces at q12.org [mailto:ode-bounces at q12.org] On 
> Behalf Of Joakim Eriksson
> Sent: Wednesday, June 02, 2004 2:42 AM
> To: ode at q12.org
> Subject: RE: RE : [ODE] Some SSE in Quick step
> 
> > > Well the reason is simple. D3D simply doesnt have 3x3 matrices. It
> only
> > > has 4x4 matrices.
> > 
> > DOH!  I was thinking Vec2/Vec3/Vec4.  However, the question doesn't 
> > change!
> > You shouldn't have an entry at all for D3DX for m3.Identity(), or an
> entry
> > of "1.0(*)", with the * indicating that you had to use the 
> unoptimized 
> > code.
> > What did you do to get 61%?
> 
> The test was made to show the speed diffrence between the 
> diffrent codes so I needed to have the m3 code in there just 
> so I could see the diffrence if we where to go on the D3DX path. 
> It might seem a bit unfair but do realise that if you where 
> to use D3DX then you would be forced to use 4x4 matrices 
> everywhere even though you could do just fine with 3x3 
> matrices (And there are a lot of places 3x3 matrices fits 
> perfecly) so that is the actual speed diffrence you would get.
> 
> The only thing that code does is to call the identity 
> function for the diffrent systems. Now because D3DX doesnt 
> have a 3x3 matrix he will set a  4x4 matrix to identity while 
> I on the other hand only need to set a
> 3x3 matrix to identity. Thats where the diffrence comes from.
> Thats also the reason why the m4.Idenity() takes the exact 
> same time as the m3.Identity & m4.Idenity() for D3DX.
> 
> Cheers
>  Joakim E. - http://www.snowcode.com
> 
> 
> 
> 
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