Ed,
Nice answer!
--Russ
> Magnus Hagdorn <Magnus.Hagdorn@xxxxxxxx> writes:
>
> > F90 source code is portable (as long as it is standard conforming and
> > you have a decent compiler...)
>
> Howdy Magnus!
>
> As noted, fortran compilers do not produce compatible .mod files. This
> can be a pain.
>
> In practice it means you must build netCDF for every fortran compiler
> you want to use on the machine. That is, if you want to use ifort and
> gfortran on the same machine, you need to build the library twice, and
> install them in different places. Then you have to use the correct one
> when compiling fortran.
>
> As you have also noted, sometimes a compiler will change (as gfortran
> did a few years back), so you would need to recompile your netCDF
> library. However, in practice, this seems to be rare. The gfortran case
> is the only one I know of.
>
> >> Basically this means I need to include the NetCDF library into my
> >> model source. When there is no reliable external source to use, this
>
> Including netCDF in your distribution is probably a bad idea. You don't
> want to take this on, believe me.
>
> What happens when we update netCDF in some important way, and you are
> still distributing an older version? Not good.
>
> Getting and installing netCDF is a well-solved problem. Just tell your
> users to go to the Unidata web site and get the latest stable
> release. (Always found here:
> ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf.tar.gz)
>
> In any case the idea of shipping netCDF with your code will not
> scale. Starting with version 4.0 we (optionally) make use of other
> libraries, like the HDF5 library. You don't want to have to distribute
> all this too.
>
> >> Now, perhaps that mess with Fortran libraries could be cleaned up when
> >> there is a nice package of the Fortran wrapper part (for use with
> >> NetCDF C API from some version up) that easily can be integrated in
> >> custom build systems (in an automated way).
>
> The mess with the fortran libraries is even worse than you imagine. The
> F90 library is based on the F77 library, which is really a C library
> pretending to be Fortran 77 for your compiler, and which then calls the
> "real" netCDF C library.
>
> This was all necessary because there was (until F2003) no standard
> C/Fortran interoperability.
>
> The conversion of the current system to one based on Fortran 2003 will
> clear away much of the confusion, but will not eliminate the requirement
> for the netCDF fortran compiler to match the fortran compiler for your
> particular application.
>
> To fully implement your idea, you could distribute all the fortran code
> from a revised, 2003 compliant, netCDF fortran API. But I would not
> recommend this.
>
> Thanks,
>
> Ed
>
> --
> Ed Hartnett -- ed@xxxxxxxxxxxxxxxx
>
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