Re: [netcdfgroup] What is the "standard" way to use NetCDF from Fortran 90?

• To: Ed Hartnett <ed@xxxxxxxxxxxxxxxx>
• Subject: Re: [netcdfgroup] What is the "standard" way to use NetCDF from Fortran 90?
• From: Russ Rew <russ@xxxxxxxxxxxxxxxx>
• Date: Tue, 14 Jul 2009 15:06:23 -0600

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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• References:
  • Re: [netcdfgroup] What is the "standard" way to use NetCDF from Fortran 90?
    • From: Ed Hartnett