[netcdf-java] Opening a GridDataset for large NcML aggregations

[John Caron]

HiJon:

Are these JoinExisting or JoinNew ? How is the coordinate value specified? You are doing this in your own application, not in TDS?

Jon Blower wrote:
> Hi all,
> 
> Using the Java NetCDF libraries, version 2.2.22, we have notice that
> opening a GridDataset using TypedDatasetFactory.open() is slow when
> the dataset in question is an NcML aggregation over a long timeseries
> (around a thousand timesteps, with one timestep per file).  The call
> to TDF.open() takes around 3 seconds every time, which is a problem
> for our application, where performance is important.
> 
> We are using the NetcdfDatasetCache, which doesn't seem to help with
> this problem.  Is there something we can do to speed up the process of
> creating a GridDataset?  I don't think this was a problem for us in
> previous library versions, where we used a different syntax
> ("GridDataset gd = new GridDataset(nc);").
> 
> I guess we could cache the GridDataset object in memory at the
> application level, but is there a reason not to do this (e.g. if this
> is a very large object)?
> 
> Here's what we do using version 2.2.22:
> 
>    NetcdfDataset nc = NetcdfDataset nc = NetcdfDatasetCache.acquire(filename);
>    GridDataset gd =
> (GridDataset)TypedDatasetFactory.open(DataType.GRID, nc, null, null);
> 
> Thanks, Jon
>