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[netCDF #PKV-308641]: error with growing unlimited dimensions with parallel access

Hello Robert,

Thank you for providing this test program and for doing such a deep dive 
diagnosing the issue.  I'm going to need to kick this around a bit and see what 
I can figure out.  Is this an issue you have experienced only with the latest 
netcdf release? If so, do you know what the last 'good' version was?  I'll do 
some spot checks myself by reverting to previous versions and running your test 
if you aren't sure off the top of your head.  I'm hoping that it worked in a 
previous version; this will make narrowing down the issue much easier.

So, thanks again for the bug report, I just wanted to let you know it's being 
looked at.

Have a great day,


> Attached is a program that reproduces a problem I am seeing.  If I
> create or open a netCDF4 file for parallel access and perform a write
> that grows an unlimited dimension, then it returns an error, the
> dimension is not grown, and no data is written.  The error it returns is
> called "Unknown Error" by the nc_strerror() function.
> The program is an mpi program, but run it on a single process, (e.g.
> "a.out" or "mpirun -n 1 a.out").  The problem shows up even with only
> one process and it's not written for multiple processes.
> The program as it is produces the error, but there are three commented
> out sections that can eliminate the error.  First, if I don't do
> parallel access and use nc_create instead of nc_create_par there's no
> error and everything works.  Second, if I don't use unlimited dimensions
> and instead specify fixed sizes that are large enough there's no error.
> Finally, if I close the created file, open it not in parallel, do a
> write to create space in the unlimited dimensions, then close the file
> and open it again in parallel I can write the data with no error.
> It appears that the error only occurs when I grow unlimited dimensions
> in parallel mode.
> Any help would be appreciated,
> Bob Steinke

Ticket Details
Ticket ID: PKV-308641
Department: Support netCDF
Priority: Normal
Status: Open

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