In addition to what Howard said, there's actually two other metrics that are
used, as well. Each BTL exports a priority and an exclusivity value.
IIRC (it's been a while since I've looked at this code), the PML gathers up all
BTL modules that claim that they can communicate between a pair of
HI Gary,
The decision occurs within the MPI processes themselves (during the call to
MPI_Init) - so
after the orte daemons have started on the nodes.
The BTL's report their "latency" and "bandwidth" - up the stack to the
PML/BML layer which
then decides based on these metrics which BTL to use to
I'm not having any trouble getting it to start, and it's definitely
using the openib btl. I was just wondering how it decided whether the
openib btl was appropriate before going down the btl list to tcp when
all mpirun gets is a hostname and no other information about
connectivity on the
Hello Gary,
It depends on how the Open MPI was built, and on mca parameters passed to
the job either via settings in an mca params conf
file or the mpirun command line or env. variables. If you have mxm (MLNX)
or psm (qlogic/intel) installed on the system
where your open mpi was built, you may
