On Thu, 3 Aug 2006, Kyle Wheeler wrote:
> >> MPI_Group world, cur;
> >> int globalrank;
> >> PMPI_Comm_group(comm, &cur);
> >> PMPI_Comm_group(MPI_COMM_WORLD, &world);
> >> PMPI_Group_translate_ranks(cur, 1, &rank, world, &globalrank);
> >
> > The simplest way is to call MPI_Comm_rank twice.
> >
> > PMPI_Comm_rank( MPI_COMM_WORLD, &world_rank );
> > PMPI_Comm_rank( comm, &comm_rank );
> >
> > PMPI_Group_translate_ranks() becomes more efficient if you have a group
> > of ranks to be translated (i.e. save you a Comm_group() call).
>
> Really? Umm... I'm not sure that does what I want (or maybe I'm just
> not understanding what PMPI_Comm_rank() does). I *have* an arbitrary
> rank (the destination argument of an MPI_Send, for example) and I want
> to, inside the profiling layer, convert that destination rank into a
> rank in MPI_COMM_WORLD. I don't see where it's taking my arbitrary
> rank as input somewhere.
My 2 comm_rank calls relate rank of local processs in 2 different
communicators. For translation of remote process' rank, you probably need
Group_tranlate_ranks.
>
> If PMPI_Group_translate_ranks() is inefficient... perhaps I should
> build up my own translation tables?
I would think that Group_translate_ranks is less efficient than
Comm_rank because it involves a "group" translation (That statement
depends on the MPI implementation of communicator and group). If you need
to do rank translation often in profiling, building your translation
table may not be a bad idea.
A.Chan
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