Dear Bill,
Thanks. I would agree with you on
that subsets are indeed not required, but their clear definition in
the standard would promote equally clear and uniform implementation of the
memory footprint minimizing approaches you and Dick referred to. I guess static
linkage is the easiest case for this, as the linkers are smart enough nowadays
to load only the required parts of the library, provided it's appropriately
structured. Again, subsets may promote such a structuring.
Best regards.
Alexander
On the memory footprint issue, I'd like to add that it is possible to
structure an MPI implementation to only require the code associated with the
routines that are used in the application, even when the application must be
statically linked (as is the case for Blue Gene/L, for example). This can
be done even if there are actions that the application needs or wants to perform
at the time of MPI_Finalize. There are some things that can be done to
make this easier for the implementation, but (like Dick) I'm not convinced that
a subset is required as a way to limit the memory footprint.
Bill
William Gropp
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign
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