On Aug 10, 2018, at 6:27 PM, Diego Avesani <diego.aves...@gmail.com> wrote:
> The question is:
> Is it possible to have a barrier for all CPUs despite they belong to
> different group?
> If the answer is yes I will go in more details.
By "CPUs", I assume you mean "MPI processes", right? (i.e., not threads inside
an individual MPI process)
Again, this is not quite a specific-enough question. Do the different groups
(and I assume you really mean communicators) overlap? Are they disjoint? Is
there a reason MPI_COMM_WORLD is not sufficient?
There are two typical ways to barrier a set of MPI processes.
1. Write your own algorithm to do sends / receives -- and possibly even
collectives -- to ensure that no process leaves the barrier before every
process enters the barrier.
2. Make sure that you have a communicator that includes exactly the set of
processes that you want (and if you don't have a communicator fitting this
description, make one), and then call MPI_BARRIER on it.
#2 is typically the easier solution.
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