[netcdfgroup] Ann: NCL/PyNIO now have support for netCDF-4 classic format

[David Brown]

Hi Jeff,

Currently NCL and PyNIO turn on the shuffle filter whenever  
compression is requested.
My reading of the docs suggested that there were no disadvantages to  
having shuffle set on all
the time, and so I did not make it an option in the interest of  
keeping things simple.

So is this okay as far as you (or anyone else with knowledge of these  
things) are concerned,
or do I need to make this something the user controls? It would be  
easy enough to make it optional,
  -dave


On Aug 27, 2007, at 9:39 AM, Jeff Whitaker wrote:

> Mary Haley wrote:
>> Hi all,
>>
>> This is a bit of a late announcement, but NCL V4.3.1 and PyNIO V1.2.0
>> have support built-in for reading and writing netCDF-4 classic files
>> on systems where netcdf-4.0-beta1 is supported.
>>
>> With NCL, you can write a netCDF-4 classic file by calling the
>> "setfileoption" procedure with the "format" option before you call
>> "addfile" to create a netCDF-4 classic 4 file:
>>
>>    setfileoption("nc","format","netcdf4classic")
>>    a = addfile("file.nc","c")
>>
>> You can further specify a compression level:
>>
>>    setfileoption("nc","compressionlevel",5)
>>
>> Similar code exists for PyNIO:
>>
>> import Nio
>> opt                  = Nio.options()
>> opt.Format           = "netcdf4classic"
>> opt.CompressionLevel = 5
>>
>> fout = Nio.open_file("file.nc","c",opt)
>>
>> For more information, see the NCL "setfileoption" or PyNIO  
>> documentation:
>>
>>    http://www.ncl.ucar.edu/Document/Functions/Built-in/ 
>> setfileoption.shtml
>>    http://www.pyngl.ucar.edu/Nio.shtml
>>
>> For download:
>>
>>     http://www.ncl.ucar.edu/Download/
>>     http://www.pyngl.ucar.edu/download.shtml
>>
>> Cheers,
>>
>> --Mary
>>
>>
>
> Mary:  Can you turn the shuffle filter on with setfileoption?  I've  
> found that it can really improve the compression ratios when used  
> in conjunction with zlib compression in netcdf-4 files.
>
> -Jeff
>
> -- 
> Jeffrey S. Whitaker         Phone  : (303)497-6313
> Meteorologist               FAX    : (303)497-6449
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