QLogic OFED+ Host Software User Guide, Rev. B

4–Running QLogic MPI on QLogic Adapters
MPD
mpirun Tunable Options
MPD
There are some mpirun options that can be adjusted to optimize communication.
The most important one is:
-long-len, -L [default: 64000]
This option determines the length of the message that the rendezvous protocol
(instead of the eager protocol) must use. The default value for -L was chosen for
optimal unidirectional communication. Applications that have this kind of traffic
pattern benefit from this higher default value. Other values for -L are appropriate
for different communication patterns and data size. For example, applications that
have bidirectional traffic patterns may benefit from using a lower value.
Experimentation is recommended.
Two other options that are useful are:
-long-len-shmem, -s [default: 16000]
This option determines the length of the message within the rendezvous protocol
(instead of the eager protocol) to be used for intra-node communications. This
option is for messages going through shared memory. The InfiniPath rendezvous
messaging protocol uses a two-way handshake (with MPI synchronous send
semantics) and receive-side DMA.
-rndv-window-size, -W [default: 262144]
When sending a large message using the rendezvous protocol, QLogic MPI splits
it into a number of fragments at the source and recombines them at the
destination. Each fragment is sent as a single rendezvous stage. This option
specifies the maximum length of each fragment. The default is 262144 bytes.
For more information on tunable options, type:
$ mpirun -h
MPD Description
The complete list of options is contained in Appendix A.
The Multi-Purpose Daemon (MPD) is an alternative to mpirun for launching MPI
jobs. It is described briefly in the following sections.
MPD was developed by Argonne National Laboratory (ANL) as part of the
MPICH-2 system. While the ANL MPD had some advantages over the use of their
mpirun (faster launching, better cleanup after crashes, better tolerance of node
failures), the QLogic mpirun offers the same advantages.
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