[OMPI users] OMPIO correctnes issues

[Paul Kapinos]

Dear Open MPI developers,
did OMPIO (1) reached 'usable-stable' state?





Is that a bug in OMPIO or did we miss something?

Best
Paul Kapinos


1) http://www.open-mpi.org/faq/?category=ompio

2) http://www.open-mpi.org/community/lists/devel/2015/12/18405.php

3) (ROMIO is default; on local hard drive at node 'cluster')
$ ompi_info  | grep  romio
                  MCA io: romio (MCA v2.0.0, API v2.0.0, Component v1.10.1)
$ ompi_info  | grep  ompio
                  MCA io: ompio (MCA v2.0.0, API v2.0.0, Component v1.10.1)
$ mpif90 main.f90

$ echo hello1234 > out.txt; $MPIEXEC -np 1 -H cluster  ./a.out;
 fileOffset, fileSize                    10                    10
 fileOffset, fileSize                    26                    26
 ierr            0
 MPI_MODE_WRONLY,  MPI_MODE_APPEND            4         128

$ export OMPI_MCA_io=ompio
$ echo hello1234 > out.txt; $MPIEXEC -np 1 -H cluster  ./a.out;
 fileOffset, fileSize                     0                    10
 fileOffset, fileSize                     0                    16
 ierr            0
 MPI_MODE_WRONLY,  MPI_MODE_APPEND            4         128


--
Dipl.-Inform. Paul Kapinos   -   High Performance Computing,
RWTH Aachen University, IT Center
Seffenter Weg 23,  D 52074  Aachen (Germany)
Tel: +49 241/80-24915

program example
use mpi
integer:: ierr
integer(MPI_OFFSET_KIND) :: fileOffset
integer(KIND=MPI_OFFSET_KIND):: fileSize
real :: outData(10)
integer :: resUnit=565
 call MPI_INIT(ierr)
 call MPI_file_open(MPI_COMM_WORLD,  'out.txt',   MPI_MODE_WRONLY + 
MPI_MODE_APPEND,  MPI_INFO_NULL,  resUnit, ierr)
 
 call MPI_FILE_GET_SIZE (resUnit, fileSize, ierr)
 call MPI_file_get_position(resUnit,fileOffset,ierr)
 print *, 'fileOffset, fileSize', fileOffset, fileSize
 
 call MPI_file_seek (resUnit,fileOffset,MPI_SEEK_SET,ierr)
 call MPI_file_write(resUnit, outData, 2, &
                         MPI_DOUBLE, MPI_STATUS_IGNORE, ierr)
                         
 call MPI_file_get_position(resUnit,fileOffset,ierr)
 call MPI_FILE_GET_SIZE (resUnit, fileSize, ierr)
 print *, 'fileOffset, fileSize', fileOffset, fileSize
 
 
 print *, 'ierr ', ierr
 print *, 'MPI_MODE_WRONLY,  MPI_MODE_APPEND ', MPI_MODE_WRONLY,  
MPI_MODE_APPEND
 
 
 call MPI_file_close(resUnit,ierr)
 call MPI_FINALIZE(ierr)
end

As we reported in (2) we had some trouble in building Open MPI with ROMIO, which fact was hidden by OMPIO implementation stepping into the MPI_IO breach. The fact 'ROMIO isn't AVBL' was detected after users complained 'MPI_IO don't work as expected with version XYZ of OpenMPI' and further investigations. Take a look at the attached example. It deliver different result in case of using ROMIO and OMPIO even with 1 MPI rank on local hard disk, cf. (3). We've seen more examples of divergent behaviour but this one is quite handy.

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