Juan,
if you need synchronization after MPI_Reduce, you can reimplement the
function like this
int MPI_Reduce(...) {
PMPI_Reduce(...);
return PMPI_Barrier();
}
Cheers,
Gilles
On Friday, July 8, 2016, Juan Francisco Martínez <
juan.francisco.marti...@est.fib.upc.edu> wrote:
> Hi everybody!
>
> First of all I want to congratulate all of you because the quality of
> the community, I have solved a lot of doubts just reading the mailing
> list.
>
> However I have a question that I can not solve... Until now I though
> that all the collective operations have an implicit sincronization, but
> I can see that this is not true at all (because optimizations?). Then,
> after searching a little bit on the web I saw that there are several
> implementations of the reduction in openmpi, in fact there are 6
> possible algorithm (at least on OMPI 1.6) that you can use by mean of
> the mca parameters...
>
> I thought that one of them behaves as a synchronization but after
> execute a test with each one, no one behaves as it. Then my question
> is, there is any possibility, by tuning ompi, the reduce operation
> syncrhonize all the ranks that are involved at the end of the
> operation?
>
> Also I would like to know if there is any mechanism to know at runtime
> which algorithm is being used.
>
> Thanks for all!
> - Fran
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