Thanks, Ben! This explains a lot. Also helps me see my way clear to
writing simpler code.
Dave
> Hi Dave,
>
> I'm just learning my way around MPI myself, so please don't take this
> advice as expert. But I hope it's better than the blind leading the blind
> into a ditch.
>
> Again, the book I'm reading suggests that MPI_Comm_create must be called
> with the same arguments on all processes in the original communicator
> (MPI_COMM_WORLD in your example), even those that aren't going to be part
> of the new communicator (&newcomm in your example). Furthermore, whatever
> new communicators are created by the processes, they must all be created
> in the same order, so that this is verboten:
>
> (on process 1)
> MPI_Comm_create(args…,&newcomm1);
> MPI_Comm_create(args…,&newcomm2);
>
> (on process 2)
> MPI_Comm_create(args…,&newcomm2);
> MPI_Comm_create(args…,&newcomm1);
>
> I'm also not sure whether you would need the handles for any purpose. If
> you have run MPI_Comm_create on all the relevant processes, as seems to be
> required, each of those processes should be able to refer to the
> communicator directly, as far as I can make out.
>
> Let me know how you get on, though; I'm interested in learning some of
> this stuff myself!
>
> B.
>
>
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Received on Sat Jan 14 2012 - 22:30:02 PST
