A Bug of gfortran, g77 and g95 on default optimization

[Tobias Burnus]

Sunjoong Lee wrote:
> I had compiled a legacy fortran77 code and foud a bug;
>    $ gfortran -o TMalign TMalign.f
>    $ ./TMalign 1aquA.pdb 1avaC.pdb | grep ^Ali
>    Aligned length=  89, RMSD=  6.41, TM-score= 0.24257, ID=0.042
>    $ gfortran -O0 -o TMalign TMalign.f
>    $ ./TMalign 1aquA.pdb 1avaC.pdb | grep ^Ali
>    Aligned length=  91, RMSD=  6.35, TM-score=0.24762 , ID=0.024
I find this difference very odd as "-O0" is the default optimization for
gfortran. Other than that I get always the same result  ("91") with all
-O levels I tried with gfortran 4.3, 4.2.0, 4.1.3 and ifort.

Which version of the compiler are you using on which platform. (Use
"gfortran -v" to shows this information.)
Can you also show what "alias gfortran" (or "type gfortran") shows? Just
to make sure there is no alias which adds options.

Tobias