Calls to the Message Passing Interface (MPI) are a typical part of a parallel application that is meant to run on a distributed memory resource such as Vista. As the name suggests, MPI describes a standard interface together with a set of expected message-passing actions. When the code runs, the expected actions are performed by a system-specific MPI implementation, which usually comes in the form of a library.

Two major MPI implementations ("stacks") are supported on Vista:

• Open MPI
• mvapich-plus (Ohio State University)

Either of these implementations may be selected through the module system. A default MPI module is generally already loaded when you log in, which is openmpi/5.0.5 (December, 2025). To see all the available versions, run:

Regardless of which MPI implementation you choose, the commands you use to compile and link your code are always the same:

The mpiXXX commands are "wrapper" scripts that call the underlying C/C++/Fortran compiler for you, including any compiler options that are needed for properly linking your selected MPI library to your code. If you execute mpicc -show, you can see the full compile line that is generated by the wrapper.

Performance Options

As we saw with serial programs, it is a good idea to supply architecture-specific optimization options to the compiler to ensure you get the best per-core performance for your code: