parallel netCDF question

[Daniel S. Katz]

Hi,

I have a parallel code/machine which uses the standard netCDF library to 
write data to a single file system NFS-mounted on the compute codes.  As 
I got this code, it uses a fairly simple MPI send/recv mechanism 
(similar to token passing) to allow output files to be written by 
multiple processors in a serialized fashion (each opens, writes, then 
closes the file).  This is slow, and bad!

As I don't know the netCDF library well, my first thought is simply to 
have all the processors write at once, since they are going to write to 
separate parts of the file.  However, depending on how the library does 
buffering, this may not work.  (I know it wouldn't work with the cfitsio 
package, for example.)  Does anyone know if this will work, will not 
work, or will have uncertain behavior?

Assuming that this will not always work, is parallel netCDF the next 
choice, even when the file system is question is not a parallel file system?

Any other thoughts or suggestions?

Thanks,
Dan

-- 
          Daniel S. Katz                Daniel.S.Katz at jpl.nasa.gov
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California Institute of Technology          or dsk at computer.org
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