Although it "may" be obvious to some people, I thought I'd mention this well known lesson.
Do not load huge knowledge base into memory. This lesson is well documented in existing literature on knowledge base systems. it's also been discussed on JESS mailing list numerous times over the years, so I would suggest searching JESS mailing list to learn from other people's experience. It's better to intelligently load knowledge base into memory as needed, rather than blindly load everything. Even in the case where someone has 256Gb of memory, one should ask "why load all that into memory up front". If the test is using RDF triples, it's well known that RDF triples produces excessive partial matches and often results in OutOfMemoryException. The real issue isn't JESS, it's how one tries to solve a problem. I would recommend reading Gary Riley's book on expert systems to avoid repeating a lot of mistakes that others have already documented. On Thu, Jun 9, 2011 at 11:41 AM, Md Oliya <md.ol...@gmail.com> wrote: > Thank you Ernest. > I am experimenting with the Lehigh university benchmark, where i transfer > OWL TBox into their equivalent rules in Jess, with the logical construct. > Specifically, I am using the dataset and transformations, as used in the > OpenRuleBench. > As for the runtimes, I missed a point about the retractions. The fact is, > even if the session does not contain any rules (no defrules, just > assertions), loading the same set of retractions takes a considerable time. > This indicates that the high runtime is mostly incurred by jess internal > operations. > but still, when the number of changes grows high (say more than 10%) the > runtime is not acceptable, and rerunning with the retracted kb would be > faster. > I have another question as well: what type of truth maintenance method is > implemented in jess? Do you solely rely on the Rete memory nodes and tokens > for this purpose? > > --Oli. > > > On Mon, Jun 6, 2011 at 7:37 PM, Ernest Friedman-Hill <ejfr...@sandia.gov> > wrote: >> >> I don't think there's a particular reason in general. Retracting a fact >> takes only a little longer than asserting one, on average. But if we assume >> liberal use of "logical", retracting a single fact could result in a sort of >> "cascade effect" whereby retracting a single fact would result in many other >> facts, and many activations, being removed also due to dependencies. Â All of >> that would take time. Â Still, your case seems extreme. Maybe there's >> something pathological about this particular case. >> >> >> On Jun 5, 2011, at 3:18 PM, Md Oliya wrote: >> >>> Hi, >>> >>> I am doing some experiments with a set of rules which contain the >>> "logical" CE. >>> I intend to see the performance of Jess on a set of assertions as well as >>> retractions. >>> >>> After some experiments, I found that the runtime for assertions is much >>> less than that of retractions. >>> In fact, the performance on retractions is so bad that I would rather re >>> (run) jess on a retracted kb. >>> >>> >>> A sample test case: >>> The KB size, Â number of assertions, number of retractions, and number of >>> rules are 100K, 50K, 1k, and 100, respectively. >>> runtimes are >> initial run: 860ms, Â assertions:320ms -- Â retractions: >>> 4s. >>> >>> >>> Would you please give some hints on the reason? >>> >>> >>> Thanks in advance. >>> --Oli. >> >> --------------------------------------------------------- >> Ernest Friedman-Hill >> Informatics & Decision Sciences, Sandia National Laboratories >> PO Box 969, MS 9012, Livermore, CA 94550 >> http://www.jessrules.com >> >> >> >> >> >> >> >> -------------------------------------------------------------------- >> To unsubscribe, send the words 'unsubscribe jess-users y...@address.com' >> in the BODY of a message to majord...@sandia.gov, NOT to the list >> (use your own address!) List problems? Notify owner-jess-us...@sandia.gov. >> -------------------------------------------------------------------- >> > > -------------------------------------------------------------------- To unsubscribe, send the words 'unsubscribe jess-users y...@address.com' in the BODY of a message to majord...@sandia.gov, NOT to the list (use your own address!) List problems? Notify owner-jess-us...@sandia.gov. --------------------------------------------------------------------
