g77 issues
Sven LUTHER
luther@dpt-info.u-strasbg.fr
Thu Apr 19 03:03:00 GMT 2001
On Thu, Apr 19, 2001 at 10:50:34AM +0100, Nick Bailey wrote:
> Ionut Georgescu wrote:
>
> > PS command line: g77 -g -pg -o programm *.f
> > PPS gcc -v:
> > Reading specs from /usr/lib/gcc-lib/alpha-linux/2.95.3/specs
> > gcc version 2.95.3 20010315 (Debian release)
>
> I'm interested... I don't know enough FORTRAN to test this out, but I have been
> seeing Scilab (which has a lot of FORTRAN inside) doing some strange things
> recently. If you were to send me a short program to compile and run on this
> debian PowerPC (Mac G4) I can let you see the results.
>
> >
> > PPS I made another test. In the big programm I have defined a function
> > fermi2:
> >
> > ...
> >
> > and computed the following expression:
> >
> > aux22= 1.0d0-fermi2(enpct)
> >
> > The output was:
> >
> > on x86:
> > tmp_fermi2( -2.20214243)= 1.
> > aux22= 1.11022302E-16 !! should have been 0. !!
> >
>
> This is an engineering department: 1.11022302E-16 == 0 ;-) Can you print out
> the first expression more accuately? I bet it isn't really 1 (actually
> 1.000000000000000111022302 ;-) Maybe there's no bug: it's just truncation
> error? Maybe the maths unit on the alpha is better than the one on the ia32 on
> this test (no suprise there!)
Also, note that alpha is a 64bit plateform, and that as thus it could be that
it handles some things better than ia32 or ppc. Not sure if this influences
floating point values, i guess not.
Friendly,
Sven Luther
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