yes, the result is correct in that case, we must be overrunning a counter or something similar in the ompio code.

Edgar


On 11/6/2017 8:40 AM, Gilles Gouaillardet wrote:
Chris,

Can you try to

mpirun --mca io romio314 ...

And see if it helps ?

Cheers,

Gilles

Christopher Brady <c.s.br...@warwick.ac.uk> 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 d
  emonstra
  ted 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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Edgar Gabriel
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Parallel Software Technologies Lab      http://pstl.cs.uh.edu
Department of Computer Science          University of Houston
Philip G. Hoffman Hall, Room 228        Houston, TX-77204, USA
Tel: +1 (713) 743-3857                  Fax: +1 (713) 743-3335
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