[FFmpeg-devel] [PATCH] fix add_bytes_mmx and add_bytes_l2_mmx for w <= 15
Mon Jun 23 19:48:18 CEST 2008
On Mon, Jun 23, 2008 at 06:52:48PM +0200, Reimar D?ffinger wrote:
> On Mon, Jun 23, 2008 at 01:08:32AM +0200, Michael Niedermayer wrote:
> > On Sun, Jun 22, 2008 at 09:34:08AM +0200, Reimar D?ffinger wrote:
> > > Like in attached patch? Unfortunately the benchmark number seem
> > > completely unrealistic to me, going by them there would be 4x speedup in
> > > some cases...
> > > Though I tested with png images, maybe they are a horrible testcase.
> > >
> > > Example numbers:
> > > previous code:
> > > 39350 dezicycles in blub, 1 runs, 0 skips
> > > 24925 dezicycles in blub, 2 runs, 0 skips
> > > 16242 dezicycles in blub, 4 runs, 0 skips
> > > 11603 dezicycles in blub, 8 runs, 0 skips
> > > 9407 dezicycles in blub, 16 runs, 0 skips
> > 16 runs? Dont you have a file that uses that code more than 16 times?
> Well, the pngs created with e.g. mplayer -vo png do not use it at all,
> but I used some other png files.
> > and patch ok if it works (same and correct output)
> Well, in that respect it works, but with a "proper" benchmark it seems
> to be slower - I strongly suspect that the png code hardly ever uses
I suspect it would be faster if the code would not work from the end to
the begin but the normal way around.
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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