Van Snyder wrote:

On Fri, 2009-01-23 at 01:56 -0800, N.M. Maclaren wrote:

...

In theory, but not in practice. Not merely is the identifier an integer value (and may be the result of arbitrarily complicated extraction), the WAIT statement may be inside an external procedure.

That's what the ASYNCHRONOUS attribute for arguments is supposed to address.

Since a WAIT statement could occur in a subprogram (at least ones the compiler does not know about, such as ones not intrinsic or inlined) then it is part of the required implementation that operations on a variable with the asynchronous attribute not be moved across such a call. Included in the class of calls that block code motion would be those to the MPI routines. Having the asynchronous attribute in the caller scope effectively solves the code motion problem. Having it on the corresponding dummy probably solves it as well. Jim pointed out that asynchronous may not be that useful in the end. I think this is an important point. As noted above, asynchronous can solve the code motion problem. It is not clear what you mean by "solve" in regard to the other main problem - copy-in/copy-out of actual arguments. What the asynchronous attribute will do is cause a program that would otherwise have to include copy-in/copy-out code at the call to the MPI_Ixxx routine to, instead, get a hard error at compile time based on a constraint violation. It does not make the program "work", which is probably somewhere on the user's agenda. To get a working program, there are two possible solutions that I see: 1) Require that the user always supply a contiguous actual argument corresponding to the buffer dummy (in which case it seems to make more sense for THAT to be the requirement on the user in the first place), or 2) Provide a Fortran interface than can handle non-contiguous sections by having assumed-shape corresponding dummies. This solution off-loads the bulk of the work to the MPI folks. But is does seem more robust. It would be useful to hear feedback from the MPI group on these alternatives. Cheers, Bill -- Bill Long [email protected] Fortran Technical Support & voice: 651-605-9024 Bioinformatics Software Development fax: 651-605-9142 Cray Inc., 1340 Mendota Heights Rd., Mendota Heights, MN, 55120