thanks Ernest to clarify our concerns of "modify" function! Gang
>From: [EMAIL PROTECTED] >Reply-To: [EMAIL PROTECTED] >To: [EMAIL PROTECTED] >Subject: Re: JESS: Threads. >Date: Thu, 5 Sep 2002 14:01:33 -0700 (PDT) > >I think Gang Liu wrote: > > > It is expensive to retract that fact and create a new one if that > > fact holds many entities. > >I think you're assuming that calling "new Fact" and a bunch of >setSlotValue()'s is "expensive". That may well be, but for a >nontrivial rule base and a decent-sized working memory, creating the >Fact object itself is a trivial amount of work compared to the pattern >matching that will be done on that fact during retraction and/or >assertion. This is neither here nor there, in any case, because Jess's >current implementation of "modify" actually reuses the same Fact >object, and the fact-id is unchanged. The manual just hasn't been >updated to specifically reflect this, because it's an implementation >detail. Jess behaves "as if" modify were equivalent to a retract >followed by an assert. > > > > > Performance of (modify) function: > > ======================== > > It seems (modify) = (retract) + (assert) with new value. If this is > > true, this will be against our "Benifit of modification". > >Remember that the first rule of software optimization is "don't". The >second rule is that if you really have to, profile first, and fix >things that are actually problems. You're worrying about >micro-optimizations here, and in general, about things that should be >transparent to you as someone programming with Jess. A lot of work >goes into making Jess as performant as possible when used as >recommended, amortized over a whole application. Jess is a fairly >complicated system, and a lot is going on behind the scenes. If you >develop a prototype and it's slower than you need it to be, that's the >time to start worrying about this stuff. Otherwise, assume that Jess >is going to try to do the right thing as long as you program it >according to standard practice. > >--------------------------------------------------------- >Ernest Friedman-Hill >Distributed Systems Research Phone: (925) 294-2154 >Sandia National Labs FAX: (925) 294-2234 >Org. 8920, MS 9012 [EMAIL PROTECTED] >PO Box 969 http://herzberg.ca.sandia.gov >Livermore, CA 94550 > >-------------------------------------------------------------------- >To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]' >in the BODY of a message to [EMAIL PROTECTED], NOT to the list >(use your own address!) List problems? Notify [EMAIL PROTECTED] >-------------------------------------------------------------------- _________________________________________________________________ Join the worlds largest e-mail service with MSN Hotmail. http://www.hotmail.com -------------------------------------------------------------------- To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]' in the BODY of a message to [EMAIL PROTECTED], NOT to the list (use your own address!) List problems? Notify [EMAIL PROTECTED] --------------------------------------------------------------------
