Hi George,

Responses below:

The group query routine that I was thinking of is a local query, which would return information on which processes I know to have failed.

Any particular reason the current get_acked() is not satisfying?

Eek, ok, I had completely forgotten about this function. This is what I was asking for, hopefully my previous message now makes more sense. :)

I am probably going to regret asking this, but is it possible to include an MPI_Comm_resume() function that re-activates a revoked communicator with holes in it?

For many reasons related to the complexities of distributed systems (lack of synchronization in the error detection, divergent view of the entire system from each process) this operation must have a consensus meaning. Thus in terms of cost it is similar to MPI_Comm_shrink (except the reordering of the processes). It might provide some limited benefit, for people that want to use such type of scenario. Now, if by doing the re-enable you expect that the communicator will behave as a freshly new communicator and everything MPI-related, file, one-sided, collective will just work on this communicator with holes … then we're talking about something so complex that I would not even dare considering for inclusion in the standard.

What if MPI_COMM_RESUME duplicated the revoked communicator and left the holes in place? This would preserve the revoked semantic, but allow the user to continue without renumbering the processes.

~Jim.