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Parallel Rule-Based Isotach Systems

Srinivasa, Rashmi
Srinivasa, Rashmi
The rule-based system is an important tool used to build expert systems. Much research has gone into trying to speed up rule-based systems, especially by using parallelism, but limited success has been observed so far. Most of the attempts have been in the direction of improving the Match-Recognize-Act (MRA) cycle [BROW85], which is the technique used in the sequential execution of rule-based systems. We present a parallel algorithm (ISORULE) for the execution of rule-based programs, which is based on isotach time [REYN89], and which eliminates the MRA algorithm. We compare ISORULE to a conventional parallel technique based on MRA (PARAMRA). We describe the design and implementation of ISORULE, and analyze the ways in which ISORULE exploits parallelism. We describe a static model to analyze ISORULE performance, and use it to demonstrate that ISORULE exploits most of the statically determinable parallelism in a rule set. We detail our simulation of ISORULE and PARAMRA, and report results obtained by running synthesized as well as real rule-based programs on it. Our experiments with synthetic rule sets reveal order of magnitude performance improvement of ISORULE over PARAMRA. Since our initial analysis suggests that the performance improvement increases with the amount of concurrency in the rule sets, multiple orders of magnitude in performance improvement seem likely with larger rule sets exhibiting a low degree of conflict. Further, we analyze the results obtained from our initial investigation of real rule sets, and explain the more limited performance improvement we observed with these sets.
Date Received
University of Virginia, Department of Computer Science, 1999
Published Date
Libra Open Repository
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