[vorbis-dev] Another good optimization (for PPC only, though)

[David Riley]

"Timothy J. Wood" wrote:
> 
> #if defined(__ppc__)
> // Vanilla PPC code, but since PPC has a reciprocal square root estimate instruction,
> // runs *much* faster than calling sqrt().  We'll use two Newton-Raphson
> // refinement steps to get bunch more precision in the 1/sqrt() value for very little cost.

This should also do nicely with 3dnow, which has similar instructions. 
I dunno about SSE, I don't know the instruction set or have a processor
with which to test it.  If no one else wants to work on this, I'll try
in a few days (once a new CPU comes for my Linux box, which is down ATM).

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