Hi Keith Say the MPI implementor for the Cell SPE version of MPI did a good job of organizing his functionality (perhaps by making subsetting decisions that work for the structure of his implementation). Say there is an MPI application that only makes calls to the 6 essential MPI routines plus MPI_Allreduce and MPI_Bcast. When that application is statically bound to the MPI implementation by a smart linker that follows dependancy chains and only brings in needed subroutines don't you get the desired result? What more do you get in this case from having the MPI standard dictate the subsets and asking the user to declare what subsets he will need? If you leave it to the implementor to devise the subsets and change them as some ways of slicing and dicing libmpi prove more useful than others it may be better than having the standard lock down the dividing lines based on today's best guess. It does occur to me that the linker cannot tell if the MPI_Bcast call will need the code that supports MPI_Bcast on intercommunicators even though that is rarely used. That means if the application has an MPI_Bcast call, both (probably needed) intracomm- and (probably not needed) intercomm support enter the footprint. Dick Dick Treumann - MPI Team/TCEM IBM Systems & Technology Group Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601 Tele (845) 433-7846 Fax (845) 433-8363 mpi-22-bounces_at_[hidden] wrote on 05/09/2008 02:34:33 PM:
Imagine, for example, MPI running on a Cell SPE. Yes, it sounds crazy, but people are working on it. If you look at the state in MPI-2 today, and assume it will grow proportionally with complexity, MPI-3 could be really nasty in that context. So, while I agree that an arbitrarily large number of permutations is a terrible idea for everyone involved (implementers wouldn’t leverage all of the options, ISVs wouldn’t test them, people who write third party libraries would have a huge headache dealing with the arbitrary combination of features chosen by the application), it seems like it would be prudent to try to figure out how to provide some mechanisms in this direction. I don’t know if this overlaps with your idea about assertions or not, but they do seem to be related.
Keith
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