The Static World of MPI

As previously stated, many systems provide only a static process control model. The nodes in such a model may be fixed at compile, download, or spawn time; and once started, an application cannot usually change size or migrate during its execution. Failure of a single program module causing the entire application to fail by invalidating its message communicators.

Because of the wide range of possible initialization options, the MPI forum decided against standardizing process control. This decision had several advantages:

• The process model was easy to reason about. A fixed number of processes existed: either all processes existed or none.

• Collective operations could be optimized, since the members taking part were known beforehand and were not subject to change.

• Contexts or application tags could be implemented efficiently.

• MPI Process Control
• Contexts, Process Groups, and Communicators
• Static Separate Worlds