Sorry, I have forgotten to send my answers to the netcdf group. My comments are
in the e-mail below, after your answers.
Thanks for your help !
Regards,
Gérald
De : Gérald Mercadier
Envoyé : mercredi 17 juillet 2013 12:20
À : 'David W. Pierce'
Objet : RE: [netcdfgroup] Compound type and Fortran90
Thank you for your answer Dave !
Please see my questions/remarks in your e-mail and thank you in advance for
your help.
Regards,
Gérald
De : davidwilliampierce@xxxxxxxxx<mailto:davidwilliampierce@xxxxxxxxx>
[mailto:davidwilliampierce@xxxxxxxxx] De la part de David W. Pierce
Envoyé : mardi 16 juillet 2013 20:01
À : Gérald Mercadier
Cc : netcdfgroup@xxxxxxxxxxxxxxxx<mailto:netcdfgroup@xxxxxxxxxxxxxxxx>
Objet : Re: [netcdfgroup] Compound type and Fortran90
Hi Gerald,
When the documentation says that the data to be written "may be of any type",
it means, any fortran90 native type (real, double precision, integer, etc.) The
netcdf library does not know how to write out a derived type that you create
yourself.
è (Gérald) In the documentation about compound types (see
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90/Compound-Types.html#Compound-Types),
on can read "To write data in a compound type, first use nf90_def_compound to
create the type, multiple calls to nf90_insert_compound to add to the compound
type, and then write data with the appropriate nf90_put_var1, nf90_put_vara,
nf90_put_vars, or nf90_put_varm call." I know how to define compound types in
netCDF but I don't understand how to write data in a compound type as described
in the doc.
è But you confirm me that one cannot write in a compound type, using netCDF
functions in Fortran90. In this case, the documentation is not correct. Is an
evolution planned to make the user defined type supported by the writing
function ?
My personal advice is that you will save yourself headaches down the line, and
your netcdf files will be more widely compatible with the world of software
already out there, if you avoid netcdf compound types. Some problems really
mandate a compound type, so it's great that they are available, but it's just
limiting the usefulness of your files if you use compound types gratuitously.
I.e., if you're writing a velocity field, just write U and V fields rather than
making a compound type that has U and V components.
è (Gérald) Is it possible to manage compound types in C language ?
(define/write/read ?) Your remark about the compound types is a general remark
? I mean not only for Fortran90 using ? In a general way and whatever the
programming language, what are the recommendations on this matter ? The
compound type should be avoided ? what is the technical status ? (particular
convention ? portability problems ? programming difficulty when using it ?)
è I don't know very well netCDF but do you recommend to use the lib in C or in
Fortran90 ? What would be the limitations/constraints in a Fortran90 using ?
If you do absolutely need compound types, the solution would be to write your
own version of nf90_put_var() that would take as the argument your derived type
and write it appropriately into a netcdf compound type using lower level calls.
Regards,
--Dave
On Tue, Jul 16, 2013 at 10:14 AM, Gérald Mercadier
<Gerald.mercadier@xxxxxxxxxxx<mailto:Gerald.mercadier@xxxxxxxxxxx>> wrote:
Dear all,
I am using netCDF 4.1.3 in a Fortran90 code which is compiled with gfortran
4.4.5. I want to use the compound types. I have no problem to define a compound
type, but I am currently encountering a problem when I try to put values into a
well-defined compound type. The problem occurs at the compilation, when using
nf90_put_var. The compilation fails with the error "Error: There is no specific
function for the generic 'nf90_put_var' at (1)"
In my code, I have defined a compound type using nf90_def_compound and
nf90_insert_compound. This type contains variables of int/double/string type or
another user defined type.
The definition works well, the .nc file created is correct. Unfortunately, the
call of nf90_put_var leads to this compilation error. The third argument of the
routine is "values", which is the derived type (or Fortran90 structure) in my
case, containing variables of different types. The documentation of
nf90_put_var (see
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90/NF90_005fPUT_005fVAR.html#NF90_005fPUT_005fVAR)
says that "the data may be of any type, and may be a scalar or an array of any
rank". I just call nf90_put_var with 3 arguments, like this "nf90_put_var(ncid,
varid, values)".
I would like to know how put a value of a derived type variable into a compound
type variable with netCDF, in a Fortran90 code. Can someone help me please ?
Thank you for your help !
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