[rules-users] 答复: 答复: Performance consideration in rule writing

[Wolfgang Laun]

2011/12/26 Zhuo Li <milanello1998 at gmail.com>

> So for #1, you mean it is more from static variable safety to put uncommon
> conditions at the beginning of LHS?
>

A static variable or a DRL global is something that must be used with
caution in a rule's LHS. In any case, if it is read, it  should be used
like a constant; if you modify it, it should be used like a one-way outoing
service.



> On #3, can you elaborate more about " Making your rules depend on salience
> isn't good practice "? in general, what we need to define in every rule
> file
> is a business case, and every case stands for a flow with things like
> if-elseif-else. I guess you mean I may use Drools flow or Java itself to
> control the flow and leave judgment inside Drools?


Think of "flow" (either by Drools or by Java) as a high-level progress
through application stages or phases. Salience is better restricted to
precedence within flow groups, and there I don't recommend more than three
levels.


> If that's the case, the
> original concern we had was it will have too many insert() into
> workingmemory which may impact performance...
>

I don't see how one would require the other. Inserts are indicated if you
derive new facts that need to be evaluated in subsequent rules.

-W

>
> Best
> Abe
>
> -----ÓʼþÔ­¼þ-----
> ·¢¼þÈË: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org] ´ú±í Wolfgang Laun
> ·¢ËÍʱ¼ä: 2011Äê12ÔÂ26ÈÕ 23:15
> ÊÕ¼þÈË: Rules Users List
> Ö÷Ìâ: Re: [rules-users] ´ð¸´: Performance consideration in rule writing
>
> On 26/12/2011, Zhuo Li <milanello1998 at gmail.com> wrote:
> > //Abe: it definitely makes a difference if you put differentiator
> > conditions at the beginning ¨C this way RETE won¡¯t waste efforts
> > constructing networks which will not fulfill. See below example.
> >
> > rule "Evaluation of assignment in r-value position"
> > no-loop true
> > when
> >  $statement:CStatement($value:value)
> >  eval(Matcher.isRVExpression($value))
> >
> >  eval(0==Matcher.getClauseNum())
> > then
> >  System.out.println($value);
> >  modify($statement){
> >   setSemantics(Matcher.getRVSemantics(memory,$value));
> >  }
> > end
> >
> > rule "Evaluation of assignment clause in r-value position without
> > updating memory"
> > no-loop true
> > when
> >  $statement:CStatement($value:value)
> >  eval(Matcher.isRVExpression($value))
> >
> >  eval(0<Matcher.getClauseNum())
> > then
> >  System.out.println("=="+$value);
> >  Matcher.decreaseClauseNum();
> >  modify($statement){
> >   setSemantics(Matcher.getRVSemanticsWithoutUpdate(memory,$value));
> >  }
> > end
> >
>
> This is quite different from the rules in the original post. It is
> generally
> not advisable to access and modify static variables, here:
> clauseNum in class Matcher, i.e., not a fact.
>
>
> >
>
> >  //Abe: I saw below statement from Drools document 5.2.0. As Eval is
> > not indexed, overuse of evale reduces the rules¡¯ clarity and will
> > result in a bad performance.
>
> Needlessly using eval is not good; if you have to use it you won't be able
> to avoid it.
>
>
> >
> >
> > 3.       What¡¯s you guys¡¯ naming convention for rule¡¯s salience?
> >
> > Not clear what you mean by that.
> >
> > //Abe: I mean how do you weight your salience values across different
> rules.
> > I¡¯ve seen various styles in my project ¨C somebody uses 100, 200, 300
> > but somebody uses 90, 100, 110, 120, etc. This is not a big problem as
> > they are working on different rules and won¡¯t pollute each other.
> > However I would still try to make it consistent so maintain each
> > other¡¯s rule files will be easier¡­
>
> Making your rules depend on salience isn't good practice, certainly not
> with
> more than 3 levels (my personal definition). The sort of multi-level
> salience you're indicating could be an indication that procedural style
> if-then-elsif logic has been fitted into rules.
>
> -W
> >
> >
> >
> > ·¢¼þÈË: rules-users-bounces at lists.jboss.org
> > [mailto:rules-users-bounces at lists.jboss.org] ´ú±í Wolfgang Laun
> > ·¢ËÍʱ¼ä: 2011Äê12ÔÂ26ÈÕ 22:20
> > ÊÕ¼þÈË: Rules Users List
> > Ö÷Ìâ: Re: [rules-users] Performance consideration in rule writing
> >
> >
> >
> > See below.
> >
> > 2011/12/26 Zhuo Li <milanello1998 at gmail.com>
> >
> > Hi, team,
> >
> >
> >
> > I have some quick questions here regarding performance best practices
> > of rule writing. See below two pieces of rules:
> >
> >
> >
> > Rule ¡°1¡±
> >
> >          Salience 100
> >
> >          No-loop true
> >
> >          When $txn : data(sourceid == 5&&txnjustify==¡±995¡±
> > &&eval(creditOption($txn)==1)&&eval(isGCSwitch($txn))&&isCurrencyEqual
> > s($txn )==0&&compareToPostThreshold($txn)==2);
> >
> >          Then
> >
> >                    ¡­
> >
> >          End
> >
> >
> >
> > Rule ¡°2¡±
> >
> >          Salience 100
> >
> >          No-loop true
> >
> >          When $txn : data(sourceid == 5&&txnjustify==¡±995¡±
> > &&eval(creditOption($txn)==1)&&eval(isGCSwitch($txn))&&isCurrencyEqual
> > s($txn )==0&&compareToPostThreshold($txn)==1);
> >
> >          Then
> >
> >                   ¡­
> >
> >          End
> >
> >
> >
> > Questions:
> >
> > 1.       Will I gain better performance if I put the rule differentiator
> > condition ¡°compareToPostThreshold($txn)==2¡± at the beginning of both
> > rule
> > 1 and 2?
> >
> > One kind pf Rete optimization is based on evaluating common
> > constraints once, therefore: no.
> >
> >
> > 2.       I saw salaboy¡¯s video claiming that to avoid using eval() in the
> > rule. Do we have any alternative way to do that from a performance
> > consideration
> >
> > Constraints based on fields using == are best. Other things may result
> > in eval-like evaluations anyway. Most of the time, it isn't eval that
> > causes performance setbacks.
> >
> > or I¡¯d better collect/ prepare all the data before I send them into
> > the session?
> >
> > Not clear what you mean by this, but if you can provide attributes
> > that lend themselves to straightforward constraints it might be
> > worthwhile considering some up-front processing of facts.
> >
> >
> > 3.       What¡¯s you guys¡¯ naming convention for rule¡¯s salience?
> >
> > Not clear what you mean by that.
> >
> > -W
> >
> >
> >
> >
> > PS: my Drools version is 5.2.0.
> >
> >
> >
> > Best regards
> >
> > Abe
> >
> >
> > _______________________________________________
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> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
> >
>
>
>
>
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