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16.5 Conclusions

Zipcode currently provides portable message-passing capability on a number of multicomputers. It also works on homogeneous networks of workstations and will soon be supported on heterogeneous networks and for heterogeneous multicomputers, when such systems are created. The key benefits of Zipcode are its ability to work over process lists designated by the user, to define separate contexts of communication so that message-passing complexity can be managed, and to allow different notations of message-passing appropriate to the concurrent algorithms being implemented. Tagged message passing is seen as a special case of the notations supported by Zipcode.

We see notational abstraction as helpful in dealing with issues of non-uniform memory access hierarchy and heterogeneity in multicomputers and distributed computers. Abstraction is a way to help Zipcode find additional runtime optimizations, rather than a tacit source of inefficiency. We believe that Zipcode implementations will be competitive in performance to tagged message systems whenever vendors make low-level access to their hardware and system calls available to us during our implementation phase.

Guy Robinson
Wed Mar 1 10:19:35 EST 1995