I could reproduce this problem only on power4 hardware,
running SUSE linux.
% uname -a
Linux regsuse01 2.6.5-7-pseries64 #1 SMP Thu Apr 8 15:55:41 UTC 2004 ppc64 ppc64
ppc64 GNU/Linux
% ~/gcc/bin/gfortran --version
GNU Fortran 95 (GCC 4.0.0 20041027 (experimental))
Running SIXTRACK spec benchmark results in a miscompare,
even with all optimizations turned off. The miscompare is caused
by the following place in file eig66.f
do 40 i=1,ndim2
if(abs(reval(i)**2+aieval(i)**2 -one).gt.c1m10) then
write(6,*) ' EIG6: EIGENVALUES OFF THE UNIT CIRCLE!'
return
endif
This code checks that the distance from computed complex
eigenvalues to the unit circle is no more than 10**-10.
With g77, the distance is about 10**-14, and I get similar
results on other platforms with gfortran. On power4+gfortran
the distance is about 10**-8, which triggers the error
message and causes miscompare.
There is some possibility that this problem is related
to 17927.
--
Summary: Miscompare in sixtrack benchmark caused by loss of
precision
Product: gcc
Version: 4.0.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: lei at il dot ibm dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: powerpc64-unknown-linux-gnu
GCC host triplet: powerpc64-unknown-linux-gnu
GCC target triplet: powerpc64-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18218
