[Mpi3-bwcompat] MPI timer requests

[Fab Tillier]

Jeff Squyres wrote on Mon, 7 Mar 2011 at 12:31:41
> 
> Dave's point about generalized requests is a good one, though -- I need to go
> think about that and convince myself that what we're talking about isn't
> syntactic sugar and/or why it's better to be in the MPI implementation.

In a MPI_THREAD_SERIALIZED implementation, you can't use call MPI_GREQUEST_COMPLETE if you're already calling MPI_WAITANY.  Depending on generalized requests would require MPI_THREAD_MULTIPLE support for this functionality.

Note that for some implementations, making MPI_GREQUEST_COMPLETE thread-safe could be trivial, but there's no MPI_THREAD_MOSTLY_SERIALIZED option so there's no standard way of noting that some things are thread safe while others are not - it's either all or nothing.

-Fab