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.

Open MPI is based on an open component architecture allowing modular
replacement of many system components without recompilation.

This is the legacy version, but the latest one with support of 32 bits
platforms.