You can also try the -s option from ncdump, which will tell you about chunking
and compression for each variable. If chunking is too small, for example, then
compression will be limited. (I'm a few versions behind, but I assume that '-s'
is still there.)
-- Ted
On Dec 17, 2013, at 2:55 PM, Frank Fuchs wrote:
> Sorry I did not mentioned that the installation included hdf5 and zlib (I
> think one has to disable the explicitly - otherwise).
> Thank you for the ncdump option - I was looking for something like this to
> check at least that I'm writing Netcdf4 files now.
> Indeed ncdump -k gives me "netCDF-4". - So compression is supposed to work,
> not?
>
> Regards,
> Frank
>
>
>
>
>
>
> 2013/12/17 Nick Papior Andersen <nickpapior@xxxxxxxxx>
> You do not specify whether you have compiled with hdf5 and zlib?
> If you haven't specified this at compile time, you don't have compression
> enabled and you need to install hdf5 and zlib (at least).
>
> You can test your file by this:
> ncdump -k <file>
> '1' or 'classic' => netcdf classic format
> '2', '64-bit-offset', or '64-bit offset' => netCDF 64-bit format
> '3', 'hdf5', 'netCDF-4', or 'enhanced' => netCDF-4 format (enhanced data
> model)
> '4', 'hdf5-nc3', 'netCDF-4 classic model', or 'enhanced-nc3' => netCDF-4
> classic
> model format
>
> What you want is 3 or 4 (as I remember, a netcdf3 installation from a netcdf4
> source would only allow k=1 or k=2).
>
> Kind regards Nick
>
> 2013/12/17 Frank Fuchs <fk.fuchs@xxxxxxxxxxxxxx>
> Hi,
>
> I managed to compile netcdf-4.3.0 using mingw-w64 gcc 4.8.1.
> All I had to disabale was DAP (I have no use for anyway).
>
> I tested that I can read and write netcdf files using the newly build .dll
> Now I wanted to test compression using the cxx4 interface, enabling it by
> ncvar_data.setCompression(true,true,1) for the heaviest of my variables.
>
> However, even for a file filled with constants the files remain as big as
> before.
> Further tests using nccopy -d9 old.nca new.nca did not result in a
> modification of the file size.
>
> Any advise?
>
> Best,
> Frank
>
>
>
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>
>
> --
> Kind regards Nick
>
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