[netCDF #XRV-955693]: core dump preparing a moderate size netcdf file

["Unidata netCDF Support" <support-netcdf@xxxxxxxxxxxxxxxx>]

Hi Stephen,

> As I have problems with writing a moderate size netcdf file, I decided
> to try one of your examples. it is pres_temp_4D_wr.f90. I compile this
> code on our aix power 6 machine and for the parameter settings you
> provide with the code there is no problem. The problem start if I
> increase the dimensions of the arrays to something more interesting: in
> my case nlats 300, nlons 300 and nlvls 1738. This causes a core
> dump.

Hmmm, I just tried this and it worked fine, writing a netCDF "classic"
format file of about 2.5 Gbytes:

  -rw-r--r--   1 russ     ustaff   2502722808 Jun 30 14:39 ptw.nc

You should be able to write such a file with no special flags from any
version of netCDF since about 3.5.1.  Check the possible causes in the
answer to this FAQ:

  Why do I get an error message when I try to create a file larger than 
  2 GiB with the new library?

  http://www.unidata.ucar.edu/netcdf/docs/faq.html#Large%20File%20Support12

You don't need a 64-bit library (or a 64-bit computer) in order to write
larger (netCDF 64-bit offset) files, as explained here:

  http://www.unidata.ucar.edu/netcdf/docs/faq.html#Large%20File%20Support7

So you should be able to create even larger files using the 64-bit offset
format by using the correct creation mode in the call to nf90_create, as
in:

  ! Create the file. 
  call check( nf90_create(FILE_NAME, or(nf90_noclobber,nf90_64bit_offset), 
ncid) )
 
> No special compilation flags (so on our machine xlf90 as I use the ibm
> compiler) however, in order to make use of max.ram i edit the loader
> file /usr/ccs/bin/ldedit -bmaxdata:0x60000000 name.of.executable

You should not need larger RAM, but you have to have a file system that
supports large files, as explained in the first FAQ above.

> The question I have is do I hit a limit within netcdf itself.
> 
> to my knowledge we are running a standard netcdf library (so not the
> one for 64 bit).

Do you know what version library you have?  If it's pre-3.6 (about Feb 2005),
there were some problems with large file support that were fixed in later
releases.

--Russ

Russ Rew                                         UCAR Unidata Program
russ@xxxxxxxxxxxxxxxx                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: XRV-955693
Department: Support netCDF
Priority: Normal
Status: Closed