[FFmpeg-devel] [Issue 664] [PATCH] Fix AAC PNS Scaling

[Uoti Urpala]

On Wed, 2008-10-08 at 02:55 +0200, Michael Niedermayer wrote:
> On Tue, Oct 07, 2008 at 05:23:56PM -0400, Alex Converse wrote:
> > Attached is a version that explicitly uses a int32_t.
> 
> i will object to this patch until someone posts a speed comparission
> between it and ff_sqrt.

I tested a simple loop doing "sum += 1/sqrtf(i)" on core2. As expected,
"1./ff_sqrt(i)" is the slowest way to calculate that. Standard
"1./sqrtf(i)" is equally fast with default flags and somewhat faster
with -ffast-math (and has better accuracy). The code from Alex is about
twice as fast.