On Thu, Dec 24, 2015 at 01:39:36AM +0100, Michael Niedermayer wrote: > On Wed, Dec 23, 2015 at 03:52:50PM -0800, Ganesh Ajjanagadde wrote: > > On Wed, Dec 23, 2015 at 3:38 PM, Michael Niedermayer > > <mich...@niedermayer.cc> wrote: > > > On Wed, Dec 23, 2015 at 10:47:20AM -0800, Ganesh Ajjanagadde wrote: > > >> exp10(x) is superior to pow(10,x). > > >> Note that in some cases, this may affect integers derived from pow > > >> calls. When > > >> spotted, this remark has been added to the relevant commit message. > > >> > > >> Note that if such a thing is troublesome, one can do one of two things: > > >> 1. leave the pow(10,x) call as is in such places. > > >> 2. replace the lavu/libm fallback by the correct pow(10,x) as opposed to > > >> the > > >> sloppy exp2(M_LOG2_10 * x). > > >> > > >> Patches tested with FATE on x86-64, GNU/Linux. > > > > > > some of these fail on arm > > > > > > i suspect thats because exp10 is only available with GNU_SOURCE > > > and we dont define that nor do we want to define that > > > -DGNU_SOURCE often leaks in from pkg_config files though > > > > ah, thanks for this. Out of curiousity, why don't we want to always > > define it? My FFmpeg runs fine, built with GNU_SOURCE. > > it would hide any use of GNU features and FFmpeg should work > on non GNU platforms too. > Its best if any non standard (c99/posix) features trigger immedeate > errors for developers instead of having to depend on the roundtrip > over bug reports to find and remove such uses > > > > > > > my arm setup doesnt include many external libs so GNU_SOURCE doesnt > > > get enabled > > > > It is only with GNU_SOURCE as per man page; I assumed that was handled > > via configure and the like and I thought I mentioned this somewhere > > during the discussion. > > > > > > > > > > > > i didnt think deeply abot it but would it make sense to always enable > > > the fallback even if exp10 is available? that is assuming the fallback > > > is faster everywhere > > > > The fallback is faster everywhere. The trouble is I run into linker > > issues when it is available natively. > > ifdef ... undef ... > #define exp10(x) ... > might work > not sure this has other issues or not
an alternative would be to add and use av_exp10() considering that our implementation is AFAIK much faster than the one from glibc, all the troubble to use it could maybe be avoided [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB You can kill me, but you cannot change the truth.
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