QLogic OFED+ Host Software User Guide, Rev. B

4–Running QLogic MPI on QLogic Adapters
Introduction
PSM
The PSM TrueScale Messaging API, or PSM API, is QLogic's low-level user-level
communications interface for the TrueScale family of products. Other than using
some environment variables with the PSM prefix, MPI users typically need not
interact directly with PSM. The PSM environment variables apply to other MPI
implementations as long as the environment with the PSM variables is correctly
forwarded. See “Environment Variables” on page 4-20 for a summary of the
commonly used environment variables.
For more information on PSM, email QLogic at support@qlogic.com.
Other MPIs
In addition to QLogic MPI, other high-performance MPIs such as HP-MPI version
2.3, Open MPI version 1.4, Ohio State University MVAPICH version 1.2,
MVAPICH2 version 1.4, and Scali (Platform) MPI, have been ported to the PSM
interface.
Open MPI, MVAPICH, HP-MPI, and Scali also run over InfiniBand Verbs (the
Open Fabrics Alliance API that provides support for user-level upper-layer
protocols like MPI). Intel MPI, although not ported to the PSM interface, is
supported over uDAPL, which uses InfiniBand Verbs. For more information, see
Section 5 Using Other MPIs.
Linux File I/O in MPI Programs
MPI node programs are Linux programs that can execute file I/O operations to
local or remote files in the usual ways through APIs of the language in use.
Remote files are accessed via a network file system, typically NFS. Parallel
programs usually need to have some data in files to be shared by all of the
processes of an MPI job. Node programs can also use non-shared, node-specific
files, such as for scratch storage for intermediate results or for a node’s share of a
distributed database.
There are different ways of handling file I/O of shared data in parallel
programming. You may have one process, typically on the front end node or on a
file server that is the only process to touch the shared files, and passes data to
and from the other processes via MPI messages. Alternately, the shared data files
can be accessed directly by each node program. In this case, the shared files are
available through some network file support, such as NFS. Also, in this case, the
application programmer is responsible for ensuring file consistency, either through
proper use of file locking mechanisms offered by the operating system and the
programming language, such as fcntl in C, or by using MPI synchronization
operations.
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