HP-MPI User's Guide (11th Edition)

Understanding HP-MPI
MPI options
Chapter 3 157
An alternate remote execution tool, such as ssh, can be used on HP-UX
by setting the environment variable MPI_REMSH to the name or full path
of the tool to use:
% export MPI_REMSH=ssh
% $MPI_ROOT/bin/mpirun <options> -f <appfile>
HP-MPI also supports setting MPI_REMSH using the -e option to mpirun:
% $MPI_ROOT/bin/mpirun -e MPI_REMSH=ssh <options> -f \
<appfile>
HP-MPI also supports setting MPI_REMSH to a command which includes
additional arguments:
% $MPI_ROOT/bin/mpirun -e 'MPI_REMSH="ssh -x"' <options> \
-f <appfile>
When using ssh, first ensure that it is possible to use ssh from the host
where mpirun is executed to the other nodes without ssh requiring any
interaction from the user.
RDMA tunable environment variables
MPI_RDMA_INTRALEN -e MPI_RDMA_INTRALEN=262144 Specifies the size
(in bytes) of the transition from shared memory to interconnect when
-intra=mix is used. For messages less than or equal to the specified size,
shared memory will be used. For messages greater than that size, the
interconnect will be used. TCP/IP, Elan, MX, and PSM do not have mixed
mode.
MPI_RDMA_MSGSIZE MPI_RDMA_MSGSIZE=a,b,c Specifies message
protocol length where:
a Short message protocol threshold. If the message
length is bigger than this value, middle or long
message protocol is used. The default is 16384 bytes,
but on HP-UX 32768 bytes is used.
b Middle message protocol. If the message length is less
than or equal to b, consecutive short messages are used
to send the whole message. By default, b is set to 16384
bytes, the same as a, to effectively turn off middle
message protocol. On IBAL, the default is 131072
bytes.