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:
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.