OpenGrADS extensions for v1.9.0-rc1

[Arlindo da Silva]

All,

     One of the core activities in OpenGrADS Project (http://opengrads.org)
is the development of high performance user defined commands and functions.
The classic user defined functions (UDFs) in GrADS relies on disk files for
the transmission of data to and from the UDF. While this approach is
somewhat robust and language independent, reading the exchange file is
somewhat tedious and the unnecessary I/O leads to a large performance
penalty.

    Starting with GrADS v1.9.0-rc1, you now can write your own UDF in C or
Fortran and have it dynamically linked to your grads application during
runtime.  (This is similar to "mex" files in Matlab(tm), but for GrADS; the
extension files name have ".gex" in their names.) You can find more
information about these extensions at the OpenGrADS Wiki, including how to
write your own extensions and how to use an extension that someone compiled
for you:

   http://opengrads.org/wiki/index.php?title=User_Defined_Extensions

   As a proof of concept we have uploaded to sf.net a small (but handy)
collection of UDFs and UDCs:


http://sourceforge.net/project/showfiles.php?group_id=161773&package_id=256757

Among these extensions is re(), a very fast regrid function contributed by
B.-J. Tsuang which is meant as a replacement for the classic UDF regrid2()
that Mike Fiorino wrote a few years back.  You can find out more about re()
here:

  http://opengrads.org/doc/udxt/re/

  As Jennifer mentioned, the just released GrADS v2.0.a0 no longer supports
the classic file-based UDFs. A mechanism similar to the dynamic extensions
implemented in v1.9.0-rc1 is being considered for GrADS v2.

  Cheers!

      Arlindo

--
Arlindo da Silva
dasilva at alum.mit.edu
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