benchmark program question

[Marty Barnaby]

I'm new to the parallel NetCDF interface, and I don't have much 
experience with NetCDF either. Because of new interest on our part, we 
would like to have a straightforward, benchmark program to get byte-rate 
metrics for writing to a Posix FS (chiefly, some large Lustre 
deployments). I've had some reasonable experiences in this at the MPI-IO 
level, achieving a sustained, average rate of 26 GB/s; this writing to a 
single, shared file with an LFS stripe-count of 160. If anyone is 
interested, I could provide them with more specifics.

I can't find the benchmark-type code that I really need, though I've 
been looking at the material under /test like /test_double/test_write.c
This I've compiled and executed successfully at the appropriate -np 4 level.

There are three dynamics I would like to have that I can't see how to get.

   1. Run on any number of processors. I'm sure this is simple, but I 
want to
       know where the failure is when I attempt it.

   2. Set the number of bytes appended to an open file in a single, atomic,
       collective write operation. In my MPI-IO benchmark program I merely
       got this number by having a buffer size on each processor, and 
the total
       was the product of this times the number of processors. At the higher
       level of PNetCDF I'm not sure which value I'm getting in the def_var
       and put_var.

   3. Be able to perform any number of equivalent, collective write 
operations,
       appending to the same, open file. Simply a:

       for ( i = 0; i < NUMRECS; i++ )

       concept. This is basically what our scientific, simulation 
applications do in their 'dump' mode.


Thanks,
Marty Barnaby