[rules-users] Rule set execution performance and memory consumption issues

[Joe Ammann]

On 08/05/2013 09:04 AM, Wolfgang Laun wrote:
> Fine. Although occasionally useful, "from <expression>" is often used
> as a cover-up for inadequate design of fact types. (from
> collect/accumulate is a different matter.) 
That was exactly the case before we found out how to make fact types
"more rule friendly". Luckily we are generating the fact classes from a
model, so we could implement some "rule helper functionality" quite
easily. For example, we generate all fact classes in 2 incarnations:
once as fully featured implementation classes with Hibernate, JAXB and
god-knows-what dependencies for the runtime system, and once as "almost
pure Java beans" for using them as models in Guvnor.
> Hmm, there isn't much. Perhaps I should consider writing another white
> paper on monitoring.
That would be an excellent idea, me thinks ! I think with the
Annotations coming in Drools 6 one could put together a really useful
set of monitoring annotations (I have some experience doing this for
Java/Spring, but not for Drools, obviously. But I could be a good tester :-)
>
> Activations are created whenever WM changes (or rule base changes)
> make LHSs true for some fact set. At first, an activation is added to
> the agenda. Firing removes an activation, but so does any change to
> the set of facts in the WM. For instance:
>    rule AB when
>       A( $aid: id )
>       not B( id == $aid )
>    then ... end
> Inserting 100k As and *then* 100k matching Bs before calling
> fireAllRules creates and deletes 100k activations; with Bs before As
> nothing is wasted.
Aha! That could be my problem, I'm doing exactly that in one case.
Wasn't really aware the the sequence of fact insertion can have such a
great impact...
> Activations can be destroyed by calling clear() on the Agenda, and
> they can "evaporate" by being filtered away by an AgendaFilter that's
> passed to the fireXY method.
>
I can see use cases for using an AgendaFilter (like "eliminating"
certain rules without changing the rule set and without clobbering the
LHS with guard facts.

But what would be a good example where I would use clear() on the Agenda
? Can't really think of one, but maybe I still did not understand the
concept fully...

-- 
CU, Joe