Q-Logic IB6054601-00 D manual Multiprocessor Nodes, Number of processes to spawn

3 – Using InfiniPath MPI InfiniPath MPI Details

Q

3.5.9

Multiprocessor Nodes

Another command line option, -ppn, instructs mpirun to assign a fixed number p of node programs to each node, as it distributes the n instances among the nodes:

$ mpirun -np n -m mpihosts -ppn p program-name

This option overrides the :p specifications, if any, in the lines of the MPI hosts file.

As a general rule, mpirun tries to distribute the n node programs among the nodes without exceeding on any node the maximum number of instances specified by the :p option. The value of the :p option is specified by either the -ppncommand line option or in the mpihosts file.

NOTE: When the -npvalue is larger than the number of nodes in the mpi hostsfile times the -ppnvalue, mpirun will cycle back through the hostsfile, assigning additional node programs per host.

Normally, the number of node programs should be no larger than the number of processors on the node, at least not for compute-bound problems. In the current implementation of the InfiniPath interconnect, no node can run more than eight node programs.

For improved performance, InfiniPath MPI uses shared memory to pass messages between node programs running on the same host.

3.5.10

mpirun Options

Here is a list summarizing the most commonly used options to mpirun. See the man page for a more complete listing.

-np np

Number of processes to spawn.

-ppnprocesses-per-node

Create up to specified number of processes per node.

-machinefile filename, -m filename

Machines (mpihosts) file, the list of hosts to be used for this job.

Default: $MPIHOSTS, then ./mpihosts, then ~/.mpihosts

-M

Print a formatted list of MPI-level stats of interest for the MPI programmer

3-14 IB6054601-00 D