[Mpi3-subsetting] MPI subsetting: charting the way forward atatelecon next week?

[Richard Treumann]

Since an assertion is a statement about the application, made by the
application, I see no need for a query system that preceeds making the
assertion. If the application author is confident enough about the way his
application works to make one of the few predefined assertions, it can
never do any harm to make the assertion.

If he wants to experiment, he can use the query function within the
application to find out if the assertion he made is being exploited by the
MPI implementation. If the query function says the assertion is not being
exploited then it is harmless.  If the query function says it is being
exploited then the application author can try his application with and
without the assertion to see if the payoff is noticable. If he is the
cautious type he can put in a query and issue a warning for any MPI
implementation that exploits the assertion. The warning would say
"Additional testing may be required". When he changes or upgrades his MPI
and the new MPI implementation does exploit the assertion he will be
warned.

I think if there are more than a very few assertions available, the third
party libraries will simply take the defensive actions of disallowing all
assertions. If there are a very few will defined assertions, third party
libraries can decide which ones to allow.

If there are a small number of predefined assertion there is no reason the
standard could not say which bit each one uses. If the standard said
MPI_NO_EAGER_THROTTLE was to be 0x01 there would be no ABI issue.

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

mpi3-subsetting-bounces_at_[hidden] wrote on 06/20/2008 01:05:03
PM:

>
> Yes, but the best approach would be a query/subscribe
> interface, possibly with some set of standard ketwords
> that provide portability.
>





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