Re: Simultaneously opening many NCL files

From: David Brown <dbrown_at_nyahnyahspammersnyahnyah>
Date: Fri, 14 Sep 2007 16:37:00 -0600

Sorry, the first line is backwards. It should say:

With the newest version of NCL we made the decision to change the
default for the NetCDF file option 'SuppressClose'
from ***False to True***.

   -dave

On Sep 14, 2007, at 4:19 PM, David Brown wrote:

>
> Hi all,
>
> With the newest version of NCL we made the decision to change the
> default for the NetCDF file option 'SuppressClose'
> from True to False. This changes NCL's behavior such that instead
> of closing a file after each operation it keeps the
> file open until the user (1) deletes the file variable (2)
> reassigns the file variable or (3) exits from NCL.
> This can help to dramatically improve NCL's efficiency particularly
> when writing large files with many variables,
> and, since we had never noticed any adverse effects, we saw no harm
> it making it the default.
>
> However, we have recently encountered situations where there is a
> drawback to keeping files open in this manner.
> Users whose scripts open many files simultaneously (using
> 'addfiles' or 'addfile' in a loop) may find they fail with
> NCL 4.3.1. This is because they are bumping up against limits
> imposed by the operating system on the number of
> file descriptors available to a single process. Although the limit
> varies, it is often set to 1024.
>
> If you have a script that opens many files at once, that worked
> prior to 4.3.1, and seems to be having problems now,
> you should be able to fix it by adding, prior to your calls to
> 'addfile' or 'addfiles' , this call:
>
> setfileoption("nc","SuppressClose", False)
>
> We are sorry for any inconvenience resulting from this change.
> -dave
>
>
> _______________________________________________
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> ncl-talk_at_ucar.edu
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Received on Fri Sep 14 2007 - 16:37:00 MDT

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