On Sep 21 2012, Anthony Skjellum wrote:
What has been elusive, is concrete agreement beyond the 8-16 range of basic MPI functions, are there really subsets of functions that can be agreed on to form 'compliance points'... those could come with or without restricted semantics (e.g., no tags in point-to-point).
It's a good question, and I don't know. Only last week, someone persuaded me that I need to add a topology lecture to my course. Tags are more useful than data conversion, which is something that I have never seen used, though I would be surprised if nobody used. There are quite a lot of similar features.
Another point was made that if you use a layered library, then you don't know what MPI functions it has used, and that subset could be quite different from what the main application uses.
That is a soluble problem, but experience is that you have to require all components to declare their subset (and not understate it) if you want that to work. A mandatory argument to MPI_Init would do, so a subsetted MPI could not be fully compatible. Regards, Nick Maclaren.