Managing Multiple Methods in Heterogeneous Computing Systems

Modern networked computing environments and applications often
require---or can benefit from---the use of multiple communication
substrates, transport mechanisms, and protocols, chosen according to
where communication is directed, what is communicated, or when
communication is performed.  We propose techniques that allow multiple
communication methods to be supported transparently in a single
application, with either automatic or user-specified selection
criteria guiding the methods used for each communication.  We explain
how communication link and remote service request mechanisms facilitate
the specification and implementation of multimethod communication.
These mechanisms have been implemented in the Nexus multithreaded
runtime system, and we use this system to illustrate solutions to
various problems that arise when implementing multimethod
communication.  We also mention briefly how Nexus is used in the
Globus metacomputing toolkit.