Re: large netCDF file writing

From: Josh Hacker <hacker_at_nyahnyahspammersnyahnyah>
Date: Wed, 18 Oct 2006 13:38:25 -0600

This is an interesting point:

David Ian Brown wrote:
> I don't know if this applies here but one potentially troublesome and
> perhaps
> not well-known point about using the '(/ var /)' assignment is that
> while it
> generally means that attributes are not copied, the '_FillValue'
> attribute is
> an exception (necessary if you think about it) and is copied. If your
> originally
> defined file has variables without the _FillValue attribute this could
> cause
> a huge loss of performance because all the previously defined data is moved
> to make room for a new attribute at the beginning. This may occur
> whether or
> not you originally defined the variables with 'PreFill' set False (or
> the equivalent
> using ncgen or any other tool). When the file is read in NCL and the
> NetCDF library
> can make no assumptions about whether the data is valid or not.

I don't see a _FillValue in the file header even after I have written a
variable. I have added it in anyway to see if it makes a difference in
this case.


Joshua Hacker
Research Applications Laboratory
voice: 303-497-8188
fax: 303-497-8401
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Received on Wed Oct 18 2006 - 13:38:25 MDT

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