[rules-users] Limiting rule evaluation--not firing

Edson Tirelli ed.tirelli at gmail.com
Mon Mar 21 12:26:44 EDT 2011 

   All,

   Please let me re-emphasize something from my e-mail: "for the general
case [eager evaluation] is still better than doing selective evaluation".
Unless you are having performance problems for your specific use case, you
should not be worrying about this, as the engine is optimized for the
general use case.

   If you *are* having performance problems, then there is a number of
possible factors that need to be analyzed, one of which is the possible use
of control facts to prevent beta evaluation. So, don't think that control
facts are a general solution that will work for everybody... it is quite the
opposite, control facts are only worth for a minority of very specific
cases, because depending on your situation, it might be very costly to do
the phase switch on a control fact.

   Regarding the question on the rule-flow optimizations, there are
optimizations there... for instance, activations don't go into the main
agenda until the rule-flow group is activated, and it is usually much
cheaper to maintain activations in the separate groups than it is to
maintain them on the main agenda...

   Edson

2011/3/21 FrankVhh <frank.vanhoenshoven at agserv.eu>

> Hi all,
>
> This is a very interesting discussion, so I re-read the Drools Flow manual.
> IN section 8.1, it is stated as one of the reasons to use rules in your
> process:
>
> Performance: Rule evaluation is optimized.
>
> How do I have to understand this? Does rule evaluation only happens for the
> rules that are in the current ruleflowgroup? Because the above conversation
> seems to imply it isn't.
>
> Regards,
> Frank
>
>
> Swindells, Thomas wrote:
> >
> > That's probably the best way to go. I think it's a case of
> experimentation
> > to work out what runs best (and please report your results). Things to
> > consider are what order you have the conditions in the rules (the control
> > fact first is probably most efficient but may be worth comparing with it
> > at the end) and the order you insert facts - do you insert the control
> > fact first or last.
> >
> > Thomas
> >
> > From: rules-users-bounces at lists.jboss.org
> > [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Vincent
> Legendre
> > Sent: 21 March 2011 13:47
> > To: Rules Users List
> > Subject: Re: [rules-users] Limiting rule evaluation--not firing
> >
> > ok.
> > So the only way to do that is to add a control fact, and update it at
> > runtime...
> > Do you think that using the &quot;control fact&quot; method will speed up
> > the execution time for a large ruleset that have different ruleflow-group
> > ?
> > My feeling is yes, especially if &quot;first&quot; rules does many
> > updates, but I haven't done any tests.
> >
> > Le 21/03/2011 14:37, Swindells, Thomas a écrit :
> > The thing to remember is that fact evaluation occurs at object
> > insert/update time, not at the point you call fireAllRules. Salience,
> > Agenda and rufeflow control on the other hand are runtime conditions
> which
> > control which rules are actually activated in what order.
> >
> > Thomas
> >
> > From:
> > rules-users-bounces at lists.jboss.org&lt;mailto:
> rules-users-bounces at lists.jboss.org&gt;
> > [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Vincent
> Legendre
> > Sent: 21 March 2011 13:34
> > To: Rules Users List
> > Subject: Re: [rules-users] Limiting rule evaluation--not firing
> >
> > And what about ruleflow-group ?
> > There is no network filtering for that too ? The ruleflow-group behaves
> > like an agenda filter, but still evaluate all nodes ?
> > Could we imagine setting &quot;tags&quot; to nodes, and stop propagation
> > for node that does not declare the current task tag ?
> >
> >
> > Le 21/03/2011 14:20, Edson Tirelli a écrit :
> >
> >    The algorithm as is does eager evaluation, as for the general case
> that
> > is still better than doing selective evaluation.
> >
> >    If, in your case, the decision of which rules to fire is an arbitrary
> > application decision, and not based on the actual constraints of the
> rules
> > themselves, then the only way would be by creating a control fact:
> >
> > rule 1
> > when
> >    ControlFact( phase == Phase.ONE )
> > ...
> >
> > rule 2
> > when
> >    ControlFact( phase == Phase.TWO )
> > ...
> >
> >    This way, if the control fact is the first pattern in each rule it
> > effectively disables all the beta evaluations for rules of phases other
> > than the current one. Just be aware that by blocking the eager evaluation
> > this way, phase switches are heavier than without the control fact, where
> > most constraints were already previously evaluated. Obvious, but worth
> > saying out loud... :)
> >
> >    There is also a feature that Leonardo is working on that makes the
> > engine automatically unlink and relink parts of the network, based on the
> > existence and possibility of matching the other required facts in a rule
> > LHS. It might achieve similar results to what you are looking for in some
> > cases, but that is totally based on the constraints in there and not on
> > any arbitrary application decision.
> >
> >    Edson
> >
> >
> >
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-- 
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com
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