Hi, NEC MPI uses #1 approach (such as for mpi_register_datarep and mpi_grequest_start). I assume that #2 is more in the Fortran spirit. Hubert Jeff Squyres wrote:

This is related to -- but different from -- MPI 2.2 ticket #55 ("MPI-2.1 Cross-language attribute example is wrong"). Explicitly adding all the #55 CC members to this mail, plus a few others.

I cannot find any text in MPI-2.1 (e.g., p223-225) describing specific behavior regarding the EXTRA_STATE arguments passed to the Fortran keyval copy and delete functions (both the ADDRESS_KIND and deprecated flavors). I see two choices:

1. pass the user's original EXTRA_STATE argument by reference to the callbacks, or 2. copy the user's original EXTRA_STATE into internal MPI storage and pass *that* value by reference to the callbacks

==> Open MPI currently does #1. What do other implementations do?

I raise this issue because the text does not indicate which way is right. And I just ran across an old Sun test that assumed #2. But our internal copy of the Intel MPI tests assume #1 (to be fair: I have no idea if the Intel tests originally assumed #2 and we changed them to #1 over time). Indeed, #2 is actually in-line with the philosophy of storing attribute values in internal MPI storage. E.g.:

INTEGER foo = 4 INTEGER bar CALL MPI_COMM_SET_ATTR(comm, keyval, foo, ierr) foo = 5 CALL MPI_COMM_GET_ATTR(comm, keyval, bar, flag, ierr)

bar should equal 4, not 5 (right?).

So what does that mean (or imply) about the EXTRA_STATE value passed to the Fortran callbacks?

--Jeff Squyres Cisco Systems

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