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Re: 19980902: NetCDF Java package

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  • Subject: Re: 19980902: NetCDF Java package
  • Date: Thu, 3 Sep 1998 16:44:04 -0600
> I have a question which you should be able to answer easily, and it has
> to do with the writing speed of the NetCDF file.  It takes about one
> minute to write four arrays of size 41200 each on a Sparc Ultra 1, which
> seems to me to be pretty slow.  The odd thing is, the first array takes
> the majority of that time; after that, the other 3 are written quickly.
> Is this just a function of the NetCDF file format?  It seems to write
> empty data in the other 3 arrays after it writes the first.

I don't have enough info about what you are doing to answer definitively.
I would need to know the netcdf schema and the exact access pattern.

When a netcdf file grows to accept new data, data positions beyond the old end
of file which are not covered by the data 'put' underway are written with
the 'fill value'. This is the default behavior. This behavior can be toggled
by use of the 'setFill()' method of NetcdfFile and by a boolean argument
to some of the NetcdfFile constructors.

The java netcdf is not yet particularly speedy.
This week we announced a release which has some speedups
by using a buffered RandomAccessFile underneath NetcdfFile.

> My final question is this: how much traffic is on the Java-NetCDF list?
> I haven't gotten any messages from it, but I have noticed that the
> NetCDF package is updated regularly.

There hasn't been much traffic.
This week you should have gotten a notice of the release with
buffering I mention above.

-glenn