On 11/14/05, David Sharp <[EMAIL PROTECTED]> wrote:
> On 11/14/05, The Rasterman Carsten Haitzler <[EMAIL PROTECTED]> wrote:
> > On Tue, 15 Nov 2005 05:58:52 +0000 Mike Frysinger <[EMAIL PROTECTED]> 
> > babbled:
> >
> > > On Tue, Nov 15, 2005 at 06:38:33AM +0100, Vincent Torri wrote:
> > > >
> > > > maybe one should test in configure.in if the processor is an mad64 or 
> > > > not,
> > > > then define a specific flag according tot the arch and add it to the 
> > > > flags
> > > > when one compiles.
> > >
> > > gcc bugs change greatly between releases ... trying to track which CFLAGS
> > > are 'safe' and which ones are not is a huge pita
> > >
> > > a lot easier to say to the user:
> > > dont use stupid optimizations
> >
> > -funroll-loops... ummm (i just HAD to say that!)
> >
> > um.. the main problem is gcc4's amd64 build usies sse math by DEFAULT - 
> > thats
> > the problem.
>
> not just gcc4, i have gcc 3.4.4 here, and it compiles sse by default.
>
> > i frankly dont know what exactly the problewm is - someone being
> > able to print a list of results, variables over a series of calculations and
> > plot the difference (errors) in them all at all stages (all intermediate
> > variable values too) would be useful.
>
> this is exactly what i did. i'll attach my boneheaded program and
> results, including binaries in case you want to disassemble or
> something. Hopefully it will be useful to you.
>
> Right off the bat, the first thing i notice is that all errors are
> introduced in divisions, but not all divisions.

forgot, i was going to include my gcc -v output for reference, too:

[EMAIL PROTECTED] development $ gcc -v
Reading specs from /usr/lib/gcc/x86_64-pc-linux-gnu/3.4.4/specs
Configured with:
/var/tmp/portage/gcc-3.4.4-r1/work/gcc-3.4.4/configure --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/3.4.4
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/3.4.4/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/3.4.4
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/3.4.4/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/3.4.4/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/3.4.4/include/g++-v3
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu
--disable-altivec --enable-nls --without-included-gettext
--with-system-zlib --disable-checking --disable-werror
--disable-libunwind-exceptions --enable-multilib --disable-libgcj
--enable-languages=c,c++,f77 --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)


>
> > i personalyl suspect its a bug in the sse
> > math either in the processor or compiler simply losing excess precision
> > somewhere - either just by the way the fpmath sse is used or by a real 
> > "silly"
> > bug. as the fp math seems fine on ARM (emulated fp math), ppc fp math, x87
> > fpmath etc. and i dont really use extremes of the fp range in calculation as
> > best i know... but then again - a good analysis of the situation might be
> > useful.
> >
> >
> > --
> > ------------- Codito, ergo sum - "I code, therefore I am" --------------
> > The Rasterman (Carsten Haitzler)    [EMAIL PROTECTED]
> > 裸好多
> > Tokyo, Japan (東京 日本)
> >
> >
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>
>
>


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