[mpiwg-rma] Synchronization on shared memory windows

[Rolf Rabenseifner]

Dear all,

I tested MPI-3.0 1-sided synchronization on shared memory windows.
A lot didn't worked as I expected:

 - assertions fail with MPI_Win_fence
   (there is no restriction defined on MPI-3.0 p452:8-19),

 - Post-Start-Complete-Wait fully fails
   (compare MPI-3.0 p410:16-19, especially the ref to Sect.11.5),

 - and MPI_Free_mem also fails for the shared memory windows
   (compare MI-3.0 p409:23-24, especially that MPI_FREE_MEM
   is mentioned here).

Attached are some files:
- halo_1sided_put_win_alloc_20.f90

   This is the basis and works. 
   It is with normal (distributed) windows.

- halo_1sided_put_win_alloc_shared_20.f90

   It is the first shared memory example.
   It causes several errors with the test on our Cray system:
    - The assertions on MPI_WIN_FENCE do not work
    - The MPI_FREE_MEM does not work for the shared buffers

   Is my program wrong? it is a simple left and right 
   1-dim halo exchange.

- halo_1sided_put_win_alloc_shared_20_w-a-cray.f90

   This is a workaround that works on our Cray:
    - assertions MPI_MODE_NOPRECEDE and MPI_MODE_NOSUCCEED removed
    - MPI_FREE_MEM removed

- halo_1sided_put_win_alloc_shared_pscw_20.f90

   With Post-Start-Complete-Wait, nothing works!
   No work-around.

- halo_1sided_put_win_alloc_shared_othersync_20.f90

   In this example, I fully substituted the RMA synchronization
   by point-to-point synchronization with Irecv, send and waitall.
   Is this allowed?
   Was it intended?
   Is there any wording about in MPI-3.0?
   Will we have any wording in MPI-next? (3.1 or 4.0)?

I hope, someone knows the answers.

Best regards
Rolf

-- 
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)
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