I'll have a look at it. I can confirm that I can replicate the problem,
and I do not see an obvious mistake in your code for 1 process
scenarios. Will keep you posted.
Thanks
Edgar
On 11/6/2017 7:52 AM, Christopher Brady wrote:
I have been working with a Fortran code that has to write a large array to disk excluding
an outer strip of guard cells using MPI-IO. This uses two MPI types, one representing an
array the size of the main array without its guard cells that is passed to
MPI_File_set_view as the filetype, and another that represents the subsection of the main
array not including the guard cells that is used as the datatype in MPI_File_write (same
result with MPI_File_write_all). Both subarrays are created using
MPI_Type_create_subarray. When the file size (per core) reaches a value of 512MB the
final output size diverges from the expected one and is always smaller than expected. It
does not reach a hard bound, but is always smaller than expected. I have replicated this
behaviour on machines using Open-MPI 2.1.2 and 3.0.0, and am attaching a simple test code
(in both C and "use mpi" Fortran) that replicates the behaviour on a single
core (the test codes only work on a single core, but I have demonstrated the same problem
on multiple cores with our main code). While I've replicated this behaviour on several
machines (every machine that I've tried it on), I'm also attaching the ompi_info output
and config.log files for a machine that demonstrates the problem.
If anyone can tell me if I've made a mistake, if this is a known bug that I've
missed in the archives (very sorry if so), or even if this is a previously
unknown bug I'd be very grateful.
Many Thanks
Chris Brady
Senior Research Software Engineer
University of Warwick
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