Merging, sorting and matrix operations on the SOME-bus multiprocessor architecture

Due to advances in fiber-optics and VLSI technology, interconnection networks which allow multiple simultaneous broadcasts are becoming feasible. This paper presents the multiprocessor architecture of the Simultaneous Optical Multiprocessor Exchange Bus (SOME-Bus), and examines the performance of representative algorithms for matrix operations, merging and sorting, using the message-passing and distributed-shared-memory paradigms. It shows that simple enhancements to the network interface and the cache and directory controllers can result in communication time of O(1) for the matrix-vector multiplication algorithm using DSM. The SOME-Bus is a low-latency, high-bandwidth, fiber-optic interconnection network which directly links arbitrary pairs of processor nodes without contention, and can efficiently interconnect over 100 nodes. It contains a dedicated channel for the data output of each node, eliminating the need for global arbitration and providing bandwidth that scales directly with the number of nodes in the system. Each of P nodes has an array of receivers, with one receiver dedicated to each node output channel. No node is ever blocked from transmitting by another transmitter or due to contention for shared switching logic. The entire P receiver array can be integrated on a single chip at a comparatively minor cost resulting in O(P) complexity. The SOME-Bus has much more functionality than a crossbar by supporting multiple simultaneous broadcasts of messages, allowing cache consistency protocols to complete much faster.