On Mon, Jan 18, 2016 at 12:18:09PM +0100, Mats Peterson wrote: > On 01/18/2016 12:02 PM, Michael Niedermayer wrote: > > >thats unrelated and should be in a seperate patch if it is faster > >if its not faster it should not be done > > > >you can test the speed with START/STOP_TIMER > > > Pure logic tells me it's faster to just increment than involve a > series of multiplications.
its not so simple theres a optimizing compiler between you and the CPU the multiplication is a shift really, and the compiler may very well change this to dst++, buf++ and buf < buf_end or it might use something like p[8*i] and q[i] i++ and a i<=0 check, the 8* can on some architectures be free as part of addressing memory if you are interrested in optimizing code see http://www.agner.org/optimize/ and intels Intel 64 and IA-32 Architectures Software Developers Manual is invaluable as a reference but not useable for other purposes than as a reference (its too huge) [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are too smart to engage in politics are punished by being governed by those who are dumber. -- Plato
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