[Developers] F77 versus F90 compiler

Tom Goodale goodale at cct.lsu.edu
Wed Oct 26 08:44:08 CDT 2005

To keep things in context, the following is what I said earlier on the 
cactusmaint mailinglist.



I think discussing it on the developers mailing list would be appropriate 

We have two things really:

use f90 for f77 compiler, or not
use f90flags when compiling f77 with f90 compiler, or not

which lead to four possibilities.

For the first one, I am happy to use a different f77 compiler from f90 
compiler if the user has specified that (the last patch to do that was 
buggy so I reverted it quickly on the principle we are about to do a beta 
release), and if we do sanity checking to make sure the naming conventions 
are the same.  In the future we could even cope with different naming 
conventions by using an enhanced function aliasing mechanism, but that is 
4.x x>0.

For the latter, I think we should default to the natural flags for the 
compiler (i.e. if using f90 compiler use f90 flags) unless overridden by 
something knowing that the compiler is in fact an f90 compiler;  i.e. if 
user specified f77 and f77 flags but we have overridden f77 with f90, 
using user-supplied f77 flags MAY be erroneous.  This is obviously an 
easier issue to deal with if we can honour the user's f77 choice.

On Wed, 26 Oct 2005, Erik Schnetter wrote:

> (I am trying to take the discussion from cactusmaint at cactuscode to this 
> list.)
> Cactus is currently overwriting the user's choice of F77 compiler with the 
> F90 compiler.  This is necessary on some systems where the autodetected F77 
> and F90 are incompatible.  Unfortunately, in some cases it is necessary to 
> have different F77 and F90 compilers.
> How can we make Cactus work on both kinds of systems?  Here are some 
> suggestions:
> 1. Detect whether the choice of F77 comes from the user or from a 
> configuration script; don't overwrite it if the user wanted it that way.
> 2. Add a new flag that specifies whether to overwrite F77 if F90 is found; 
> make it default to yes.
> Are there other suggestions?  What do you think about these choices?
> Personally I'd prefer 1, as it does not introduce a new flag.
> Tom Goodale raised the question of what to do with F77FLAGS and F90FLAGS.  I 
> would suggest to keep F77, F77FLAGS etc. in sync, i.e., overwrite either all 
> or none of these.
> -erik

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