The NYU ultracomputer—designing a MIMD, shared-memory parallel machine

The design for the NYU ultracomputer, a shared-memory MIMD parallel machine composed of thousands of autonomous processing elements is presented. This machine uses an enhanced message switching network with the geometry of an omega-network to approximate the ideal behaviour of Schwartz's paracomputer model of computation and to implement efficiently the important fetch-and-add synchronisation primitive. The hardware which would be required to build a 4096 processor system using 1990s technology is outlined. System software issues are discussed and analytic studies of the network performance are presented. A sample of efforts to implement and simulate parallel variants of important scientific programs is included. 37 references.