Q-Logic IB6054601-00 D Manuel D’Utilisation

3 – Using InfiniPath MPI
InfiniPath MPI Details

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IB6054601-00 D

Q

Another command line option, 

-ppn

, instructs 

mpirun

 to assign a fixed number 

 

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 

-ppn

 command 

line option or in the 

mpihosts

 file.

When the 

-np

 value is larger than the number of nodes in the mpi hostsfile 

times the 

-ppn

 value, 

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.

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.

-ppn processes-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