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List:       kde-multimedia
Subject:    Re: winskin changes / new maintainer
From:       Stefan Westerfeld <stefan () space ! twc ! de>
Date:       2002-01-11 3:50:51
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   Hi!

On Thu, Jan 10, 2002 at 05:45:08PM -0800, Charles Samuels wrote:
> On Thu, 10 Jan 2002, Ryan Cumming wrote:
> > > Actually the last thing I've seen was damn fast already, at least compared 
> > > to the builtin FFT in Noatun (please somebody replace Noatuns FFT with a
> > > faster one)
> > Yes, the one in HEAD is in fact faster, and it has been sorta merged in to 
> > the new code. There is still some work to do with regards to VISCOLOR.TXT and 
> > the new code, but it works fine, apparently.
> 
> Winskin indeed has a nice FFT, but unfortunately, I need LGPL or better.

Well, speaking of FFTs: I suppose (but that is only an assumption), that the
winskin FFT code is not effectively faster than what we could do with the
gsl FFT (which is in kdelibs/arts/gsl already), if used optimally. I think
the main things that influence the speed of an FFT are:

 * the number of samples you use for input (the FFT algorithm takes
   O(N*log(N)) time, which means that for instance 1024 samples vs.
   256 samples gives you more than factor 4 speedup)

 * whether you use a real valued FFT - gsl can do both (compared to the old
   aRts FFT) - which should give another speedup of 2

It would be really great if somebody could realistically compare the new FFT
code with what aRts does right now, and merge all FFT objects (the one used
by artscontrol from kdelibs, the one from noatun and the one from winskin)
into one new in kdelibs, so that all apps could benefit.

As I said, I suppose by optimally using the gsl FFT, it should be at least as
fast as the winskin one. It might be even faster (last time I checked, winskin
did a convert from float to integers, which might slow down things on modern
processors, rather than help).

   Cu... Stefan
-- 
  -* Stefan Westerfeld, stefan@space.twc.de (PGP!), Hamburg/Germany
     KDE Developer, project infos at http://space.twc.de/~stefan/kde *-         
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