InterWeave: A Middleware System for Distributed Shared State

As an alternative to message passing, Rochester’s InterWeave system allows the programmer to map shared segments into programs spread across heterogeneous, distributed machines. InterWeave represents a merger and extension of our previous Cashmere and InterAct projects, combining hardware coherence within small multiprocessors, Cashmere-style lazy release consistency within tightly coupled clusters, and InterAct-style version-based consistency for distributed shared segments. In InterWeave, each shared segment evolves through a series of consistent versions. When beginning a read-only critical section on a given segment, InterWeave uses a programmer-specified predicate to determine whether the currently cached version, if any, is “recent enough” to use. Inter-segment consistency is maintained by means of hashed vector timestamps. Automatic data conversions allow each program to employ its own natural data format, byte order, and alignment, with full support for intraand inter-segment pointers. Timestamping is used to determine and communicate only those pieces of a segment that are different from the cached copy. A preliminary implementation of InterWeave is currently running on our AlphaServer cluster. Driving applications include data mining, intelligent distributed environments, and scientific visualization.