[vorbis-dev] Modification requests / question
segher at wanadoo.nl
Tue Dec 26 16:21:24 PST 2000
> My experiences say that such "it's enough for the current purpose" are seeds
> for long term bugs. They are hardly to find.
That's where the macro's are for: they isolate this "hack". And it's
documented as well.
> If you really need fast code, use good code, not such hacks. The time you
> need to find errors which are a result of such hacks you can investigate in
> real optimization.
gcc is bad at converting floating point to integer on x86; this is mostly
Intel's fault, and made worse by some of the weird things of C. This macro
is there to have Vorbis on x86 just do a "fistp" for doing
"i = (int)(f+.5f);"
So there's nothing wrong in having the macgine-independent version
of the code just doing that.
> BTW: There's code available, which is:
> - 5 times faster (on Intel)
This is done by Vorbis (10-15 times faster, actually).
> - works always correct (0.5 => 0, 0.51 => 1, 1.5 => 2, -1.5 => -2)
This is not an issue.
Please read the source.
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