Re: [netcdf-java] 4.0 updates

  • Subject: Re: [netcdf-java] 4.0 updates
  • From: John Caron <caron@xxxxxxxxxxxxxxxx>
  • Date: Sat, 04 Apr 2009 12:43:21 -0600


Bill Moninger wrote:
Hi Robb,

thanks for the information. I'll take a look at regenerating the gbx files.

For what its worth--the *biggest* percentage slowdown is not with grib or grib2 files, but with netCDF files, surprisingly enough. My c routine (using an earlier version of netCDF) reads the files almost instantly--the java-netcdf4 arrangement reads the file much more slowly.
Thats interesting. When you say "read" do you mean read all the data, or just opening the file? I assume netcdf 3 formatted files?

Can you send a sample program that has this slowdown? Are you comparing against a C program or earlier versions of java-netcdf?

BTW, java 1.6 should be 20-30% faster than java 1.5, particularly if you use the -server option.


-Bill

On 3/31/2009 12:56 PM, Robb Kambic wrote:
On Fri, 27 Mar 2009, Bill Moninger wrote:

Hello netcdf-java folks,

Thanks to good help from the netcdf-java staff, I'm now able to read and generate soundings from RUC files in netCDF, grib, and grib2 format. Its really nice to be able to use the same code for all three formats.

Unfortunately, I find that, at least as I've implemented it, netcdf-java is 20% to 50% slower than my previous methods (using C).


Bill,

If you use the the grib index file, those are the files with the gbx suffix that are usually in the same dir as the grib file. You should delete them all and then regenerate them. The new index file read in much quicker. Currently, i working on grib performance issues

Robb...





Moreover, it appears that java 1.6 is slower than 1.5 (though I haven't recompiled the underlying UCAR code in 1.6--only my code).

If folks have any thoughts about how to speed things up, I will be much obliged to hear them.

-Bill
--
William R. Moninger         http://www-frd.fsl.noaa.gov/~moninger/
NOAA / Earth Systems Research Laboratory / Global Systems Division
325 Broadway, R/GSD1                           voice: 303-497-6435
Boulder, CO 80305                              fax:   303-497-3329

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===============================================================================
Robb Kambic                       Unidata Program Center
Software Engineer III               Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx           WWW: http://www.unidata.ucar.edu/
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