[vorbis-dev] Optimization and doubles vs. floats

[Timothy J. Wood]

On Tuesday, August 29, 2000, at 02:31 PM, Segher Boessenkool wrote:
>Those 4 ops have to be the same, and the data must be in the right order
>in your registers (or I don't know Altivec well enough; that's quite
>realistic).

  Yes.  The ordering is a little flexible since the Altivec unit can pair  
a normal operation with a vector permute operation in a single cycle.  So,  
if your data isn't to far out of order, you can reorder it for 'free'.

>Because of this, the choice of mdct algo gets different.
>Even a plain matrix mult can be fast, you know...

  I need to look around at the various Altivec resources on the net again  
-- I think there was an implementation out there already (although it  
probably isn't under the right license).  Obviously I'm still in the  
research phase :)

-tim

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