From http://www.open-mpi.org/
Open MPI is a project combining technologies and resources from
several other projects (FT-MPI, LA-MPI, LAM/MPI, and PACX-MPI)
in order to build the best MPI library available. A completely
new MPI-2 compliant implementation, Open MPI offers advantages
for system and software vendors, application developers and
computer science researchers.
