a) No access to variables contained in common block from the debugger
(actually no "easy" access, there is a way that I have yet to
make work....but I'll let you know when I do)
b) Lack of support for many VAX extensions, like structures (shudder)
c) Slow progress, the present version of g77 is 0.5.21 Yes it hasn't
even made it to beta yet and we are using it for analysis (well at
least some of us are).
The main problem I see is item a) which will really hinder debugging
efforts on Linux boxes.
There are several commercial compilers (C and FORTRAN) for Linux and I
was interested in trying them to see if they address any of the issues
and I just wanted to see how efficient g77 compiled code is.
I contacted the Portland Group (PGI) for a test suite (actually I was
attempting to
purchase a license but the price overran the JLAB credit card, not
that it is expensive just that we have a low limit on credit card
purchases) so instead they offered a two week trial.
The installation was a piece of cake and PGI is to be commended for
making a product that works with and doesn't break existing compilers.
I trial run on a simple prime number generator showed that the PGI
compiled code was actually a bit slower than g77. I then linked
the CLAS
reconstruction code with PGI compilers. The fortran code linked without a
hitch. The C code barfed and I could not decode the warning to figure
out which PGI flag to throw. So I returned to gcc for the C code.
On 5000 REAL data events the reconstruction code compiled with the PGI
compiler was slightly faster than g77
O-flag PGI g77
-O2 16.149 18.246
-O3 16.109 18.289 millisec/event
To test item a) I compiled the prime number code with the -g flag and
tried ddd/gdb on the executible....this failed. One of PGI products
is a debugger but this was not part of the test suite....
Summary, the PGI FORTRAN compiler offers some advantage over g77, for
example: Professional documentation, FORTRAN 90 support plus many
VAX extenstions. Unfortunately the one area they could really blow
away g77, professional debugger, was untestable. The resulting
executibles are ~10% faster than those compiled with g77.
Just thought I'd let you all know.....
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