Thanks. I think I was the one that introduced the bad wording into the text. :/ Thanks for catching it. On Fri, Sep 9, 2011 at 4:39 PM, Darius Buntinas <[email protected]> wrote:

OK, that makes sense. �I'll fix up that text.

Thanks, -d

On Sep 9, 2011, at 3:36 PM, Josh Hursey wrote:

...

I think that we want to say that an implementation may provide uniform return codes from collectives, but are not required to do so. So this makes then fault tolerant-ish - in the sense that they have to work around failure to return error codes consistently, but not that they finish the collective successfully even if new process failures emerge during the collectives (that would undermine the semantic protections we are putting in place).

We should probably not say 'fault tolerant collectives' in the current proposal so we don't confuse things. Maybe 'collectives that provide uniform return codes'?

If we want truly fault tolerant collectives (like those described below), then I think we should introduce a different set of functions. The functions should probably return a group of processes that either did or did not participate in creating the final result. Something like: �MPI_Reduce_ft(..., &group);

I think the true fault tolerant collectives should be left to a follow on ticket since there is a need, but can be easily added as a second step.

-- Josh

On Fri, Sep 9, 2011 at 4:17 PM, Darius Buntinas <[email protected]> wrote:

...

We discussed the option of allowing an implementation to provide fault tolerant (not just fault-aware) collectives. �The idea is that even when a process fails, collectives will continue to operate correctly (modulo the failed process).

Does this imply that the communicator will never become collectively inactive?

If no, then what's the point of ft collectives?

If yes, then the application may never get notification that a process has failed and collectives are now running one short. �Is this what we really want?

-d _______________________________________________ mpi3-ft mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-ft

-- Joshua Hursey Postdoctoral Research Associate Oak Ridge National Laboratory http://users.nccs.gov/~jjhursey

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-- Joshua Hursey Postdoctoral Research Associate Oak Ridge National Laboratory http://users.nccs.gov/~jjhursey