[FFmpeg-devel] FATE & Regressions (and PPC is broken)

Michael Niedermayer michaelni
Sun Mar 16 18:21:09 CET 2008

On Sun, Mar 16, 2008 at 03:14:08PM +0200, Siarhei Siamashka wrote:
> On 16 March 2008, M?ns Rullg?rd wrote:
> [...]
> > > It still would be nice to keep C code as a reference implementation, so
> > > that it could be always possible to check if an assembly optimized mdct
> > > produces bitexact results.
> >
> > Floating-point isn't bit-exact, as has just been demonstrated.
> Yes, it also demonstrates that md5 check in this particular regression test
> does not make much sense :) It can break any time on any platform after, for
> example, compiler upgrade which could result in changes in codegenerator.
> Is it even worth fixing with your patch (also introducing performance
> regression on some platforms)? Maybe a more intelligent regression test which
> just verifies PSNR (taking some possible varuiation in last digits into
> account) would be more suitable in this case?

Maybe compile float codecs with -O0 -ffloat-store for regression testing.

This might reduce the differences between architectures.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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