8.1.1. Features Needed to Support Libraries

The key features needed to support the creation of robust parallel libraries are as follows:

• Safe communication space, that guarantees that libraries can communicate as they need to, without conflicting with communication extraneous to the library,
• Group scope for collective operations, that allow libraries to avoid unnecessarily synchronizing uninvolved MPI processes (potentially running unrelated code),
• Abstract naming of MPI processes to allow libraries to describe their communication in terms suitable to their own data structures and algorithms,
• The ability to ``adorn'' a set of communicating MPI processes with additional user-defined attributes, such as extra collective operations. This mechanism should provide a means for the user or library writer effectively to extend a message-passing notation.