Forward chaining parallel inference

The completed and ongoing efforts of the parallel inferencing performance evaluation and refinement project (PIPER) are described. PIPER Phase I produced an initial parallel inference engine (expert system tool kit) for the BBN Butterfly Plus. The BBN Butterfly Plus computer consists of up to 256 processor nodes that are interconnected via a butterfly switch. The Phase I inference engine is based on the Merit enhanced traversal engine (METE) algorithm, which is an extension of C.L Forgy´s (1979) RETE algorithm. To evaluate the efficacy of this design and implementation, an iterating 108-rule knowledge base was composed. This rule set was designed to roughly simulate the information-rich nature of its target application domain, Strategic Defense Initiative contact discrimination, and was processed on from 7 to 85 Butterfly Plus processor nodes. Three uniprocessor control groups were also used to gauge speed-up. Using the control group which produced the most conservative speed-up factors, the Phase I inference engine achieved a maximum true speed-up in excess of 29