= jb_am_i_irank0 =

== Name ==

//jb_am_i_irank0// - singles out one compute node process per BGAS IO node.

== Synopsis ==
{{{
#include <mpi.h>
#include "jbcnl.h"

int jb_am_i_irank0();
}}}

Include with //-I/bgsys/local/bgas/jbrt/jbcn/include//, link with //-L/bgsys/local/bgas/jbrt/jbcn/lib -ljbcn//.

== Description ==

//jb_am_i_irank0()// chooses one compute node process (i.e. MPI task) out of the set of processes living on compute nodes connected to a given IO node. That is, for each IO node, there is exactly one MPI task which lives on a compute node connected to it and on which //jb_am_i_irank0()// returns TRUE (1).

== Return value ==

//jb_am_i_irank0()// returns 1 if and only if the caller's MPI rank is lowest among the MPI ranks of tasks connected to the same IO node as the caller, 0 else.

== Errors ==

None.

== Thread safety ==

//jb_am_i_irank0()// is thread-safe.