ncgen does not preserve unlimited dimensions

[BobPortmann]

ncgen does not preserve unlimited dimensions in the ncdf files it produces. And I could not find a function to set a dimension to unlimited. Is there one?

[Alexander-Barth]

It should work as it is part of the test-suite:
https://github.com/Alexander-Barth/NCDatasets.jl/blob/master/test/test_ncgen.jl

The resulting file is:

netcdf juliauJUfOc {
dimensions:
        lon = 3 ;
        unlimited = UNLIMITED ; // (0 currently)
variables:
        float lon(lon) ;
                lon:string = "degrees_east" ;
                lon:float32 = 1.f ;
                lon:float64 = 1. ;
                lon:float32_vector = 1.f, 2.f, 3.f ;
                lon:float64_vector = 1., 2., 3. ;
                lon:int32_vector = 1, 2, 3 ;

// global attributes:
                :dollar = "a dollar $ stop" ;
                :backslash = "a backslash \\ stop" ;
                :doublequote = "a doublequote \" stop" ;
}

Can you provide a minimal netcdf file and julia script that show the error that you are seeing?

[BobPortmann]

Here is an example using the file used in the documentation:

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.0.3 (2018-12-18)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using NCDatasets

julia> ncgen("sresa1b_ncar_ccsm3-example.nc", "ncgen-sresa1b_ncar_ccsm3-example.jl")

julia> include("ncgen-sresa1b_ncar_ccsm3-example.jl")

julia> run(pipeline(`ncdump -h sresa1b_ncar_ccsm3-example.nc`, `head`));
netcdf sresa1b_ncar_ccsm3-example {
dimensions:
        lat = 128 ;
        lon = 256 ;
        bnds = 2 ;
        plev = 17 ;
        time = UNLIMITED ; // (1 currently)
variables:
        float area(lat, lon) ;
                area:long_name = "Surface area" ;

julia> run(pipeline(`ncdump -h filename.nc`, `head`));
netcdf filename {
dimensions:
        lat = 128 ;
        lon = 256 ;
        bnds = 2 ;
        plev = 17 ;
        time = 1 ;
variables:
        float area(lat, lon) ;
                area:long_name = "Surface area" ;

julia> 

Note that the time dimension is unlimited in the original file but not in the ncgen file.

[Alexander-Barth]

Thanks a lot, I could reproduce the issue and commit a fix to the match branch. Does it work for you?

[BobPortmann]

Yes, that works. Thanks!

[Alexander-Barth]

Thanks for confirming. I just made a new release with the fix.