Vardhan, Sundara (GE Infra, Energy) wrote:
Recently I added the -O3 flag to compile gfortran code. The application
uses OPEN() call to open files. These calls are made in a sequence, one
after another to open about 4 files before any operation on any of these
files are performed. This code works fine when compiled with no
Optimization flags. However upon adding the Optimization flags (be it -O
or -O3), the first OPEN() works fine and the next OPEN() call fails. I
suspect that the optimization flag turns on some check which may be
causing this failure.
It looks more likely you have a bug in your program whose ill effect is
worsened with optimization. Perhaps you could find it by setting -O
along with -Wall and subscript range checking.
It may also be useful to assure that you have a more stable version of
gfortran than would be furnished by some of the "enterprise" linux distros.
