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From: Tom Rosmond (rosmond_at_[hidden])
Date: 2006-08-15 17:24:40

I am continuing to test the MPI-2 features of 1.1, and have run into
some puzzling behavior. I wrote a simple F90 program to test 'mpi_put'
and 'mpi_get' on a coordinate transformation problem on a two dual-core
processor Opteron workstation running the PGI 6.1 compiler. The program
runs correctly for a variety of problem sizes and processor counts.

However, my main interest is a large global weather prediction model
that has been running in production with 1-sided message passing on an
SGI Origin 3000 for several years. This code does not run with OMPI
1-sided message passing. I have investigated the difference between this
code and the test program and noticed a critical difference. Both
programs call 'mpi_win_create' to create an integer 'handle' to the RMA
window used by 'mpi_put' and 'mpi_get'. In the test program this
'handle' returns with a value of '1', but in the large code the 'handle'
returns with value '0'. Subsequent synchronization calls to
'mpi_win_fence' succeed in the small program (error status eq 0), while
in the large code they fail (error status ne 0), and the transfers fail
also (no data is passed).

Do you have any suggestions on what could cause this difference in
behavior between the two codes, specifically why the 'handles' have
different values? Are there any diagnostics I could produce that would
provide information?

T. Rosmond