[mythtv-users] Re: Problems using MythTV - errors with channel parameters

Joseph A. Caputo jcaputo1 at comcast.net
Wed Jan 26 10:10:34 EST 2005


On Wednesday 26 January 2005 2:12, Michael Obster wrote:
> 
> > As for reading GCC Documentation, what about it?  Did you ever think 
that
> > maybe... just maybe... the build environment might be optimizing for 
the
> > specific platform you are compiling on?   Jeez.
> 
> Thats the point. There are many build kits out which do optimization 
for 
> specific architectures. For example look at Gentoo or ROCK Linux. The 
> build system optimizes the complete build environment for a selected 
> cpu. The only exception on x86 is pentium 4, because this is still 
> experimental *g*.
> If you look at the assembler output ,gcc creates, there is much 
> difference between the different platforms. For example parallel 
working 
> on cpu registers, using SSE, using 3dnow or mmx and so on. Also a 
speed 
> up is between this different optimization.
> This features are in the gcc documentation for example ;-).
> A hardcoded -march=pentiumpro does not recognizes such things, even I 
> know qmake is a little bit tricky here. Personally I prefer autotools 
> for building software.
> So to get an optimal optimization, it is better to let the build 
> determine which option is needed ;-).

Actually, if you read through the mailing list archives you'd find that 
-march=pentiumpro actually generates better performing object code than 
some of the more processor-specific (i.e., -march=athlon-xp) 
optimizations.  It all has to do with the type of operations being 
performed.

Also, as far as non-x86 architectures are concerned... MythTV is not 
supported "out of the box" for anything other than Linux on x86.  There 
is an ongoing effort to support Mac OS X out of the box, as you'll see 
if you examine the settings.pro file.  As for other architectures like 
Linux PPC or *BSD, I believe most of the code has been patched (mostly 
endianness issues), but the build configuration is not supported by 
default (yet).

-JAC


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