initial timings

[John Tannahill]

Some initial timing results for parallel netCDF =>

File size:  216 MB
Processors:  16 (5x3+1; lonxlat+master)
Platform:   NERSC IBM-SP (seaborg)
2D domain decomposition (lon/lat)
600x600x150 (lonxlatxlev)
real*4 array for I/O
Fortran code

Method 1:  Use serial netCDF.
            Slaves all read their own data.
            For output:
              Slaves send their data to the Master (MPI)
                (all at once, no buffering; so file size restricted)
              Master collects and outputs the data
                (all at once)

Method 2:  Use ANL's parallel-netcdf, beta version 0.8.9.
            Slaves all read their own data, but use parallel-netcdf calls.
            For output:
              Slaves all output their own data
                (all at once)

Read results =>

   Method 2 appears to be about 33% faster than Method 1.

Write results =>

   Method 2 appears to be about 6-7 times faster than Method 1.

Note that these preliminary results are based on the parameters given
above.  Next week, I hope to look at different machines, different
file sizes (although I am memory limited on the Master as to how big
I can go), different numbers of processors, etc.

Anyway, things look promising.

Regards,
John

-- 
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John R. Tannahill
Lawrence Livermore Nat. Lab.
P.O. Box 808, M/S L-103
Livermore, CA  94551
925-423-3514
Fax:  925-423-4908
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