Some help for the multi-core world: KNEM

The Open MPI Team has announced the release of Open MPI version 1.5. This release represents over a year of research, development, and testing. Open MPI uses a dual release cycle that includes a "super stable" (currently 1.4 series) and the recent "feature release" (1.5 series). The Open MPI release methodology is explained as follows:

• Even minor release numbers are part of "super-stable" release series (e.g., v1.4.0). Releases in super stable series are well-tested, time-tested, and mature. Such releases are recommended for production sites. Changes between subsequent releases in super stable series are expected to be fairly small.
• Odd minor release numbers are part of "feature" release series (e.g., v1.5.0). Releases in feature releases are well-tested, but they are not necessarily time-tested or as mature as super stable releases. Changes between subsequent releases in feature series may be large.

According to the team, The v1.5 series will eventually morph into the next "super stable" series, v1.6 at which time, they will start a new "feature" series (v1.7).

One feature of note in the 1.5 series is the inclusion of KNEM a Linux kernel module enabling high-performance intra-node MPI communication for large messages (i.e. to improve large message performance within a single multi-core node). KNEM is also used in MPICH2 (since version 1.1.1).

You can find both 1.4 and 1.5 series and full change log on the Open MPI website.