Abstract: "We map structured connectionist models of knowledge representation and reasoning onto existing general purpose massively parallel architectures with the objective of developing and implementing practical, real-time reasoning systems. SHRUTI, a connectionist knowledge representation and reasoning system which attempts to model reflexive reasoning, serves as our representative connectionist model. Realizations of SHRUTI are developed on the Connection Machine CM-2 -- an SIMD architecture -- and on the Connection Machine CM-5 -- an MIMD architecture. Though SIMD implementations on the CM-2 are reasonably fast -- requiring a few seconds to tens of seconds for answering queries -- experiments indicate that SPMD message passing systems are vastly superior to SIMD systems and offer hundred-fold speedups. The CM-5 implementation can encode large knowledge bases with several hundred thousand (randomly generated) rules and facts, and respond in under 500 milliseconds to a range of queries requiring inference depths of up to eight. This work provides some new insights into the simulation of structured connectionist networks on massively parallel machines and is a step toward developing large yet efficient knowledge representation and reasoning systems."