f77 optimization

[gravishanker at eagle.wesleyan.edu]

Hi

I have a general question on using any of the Optimization options for f77
on SG Irises. We have several programs used for molecular modelling that were
written in old Fortran IV style and they all work great with -O option and work
fine. We also have some recent programs written to run on a VAX. Strangley most
of these programs do not run correctly if -O is used and the only way they can
be made to behave the same way as on a VAX is to use -g. We know that these
programs mostly assume that the variables local to subroutines are saved and
used in subsequent calls, a property that is the default in VAX/FORTRAN. We use
-static option to emulate this on our Irises along with -O, but no luck. 

We have not seriously worried about optimizing these programs because they run
fast anyway. However, we are at a point now where we want to look into why is
this happening. When we called the SG hotline, after various questions the
person wanted to see our code. These programs have several hundred lines of
code and it is not going to help much. What I would like to know is if there
are any general troubleshooting guidelines one can follow to locate the
problems. Also, if there are others who convert their VAX/FORTRAN programs over
to the Irises who have encountered similar problems and have found out
solutions. Thanks in advance for any help.

Ravi