1:58 p.m.
Sorry to re-activate this thread, but I was thinking and discussing a lot on this topic
(thanks Sotty and Geoffrey).
And I am still in doubt even after the explanation from Wolfgang. Until now I think there
are more interpretations on how it might be instead of explicit explanation.
Of course the atomicity of fact modification is important thing, but what I am trying to
understand is, why does this error occur in simple conditions (such as a testcase with
domain model of two classes and very few attributes).
The testcase I previously built did not do anything else, there are no additional rules
that would cause side effects, no additional facts in working memory, just four foos and
two bars.
My argument is, that if late update cause retraction, reevaluation and what not, why is
that this example works:
{code}
fooLeft.setBar(fooRight.getBar());
session.update(fooLeftFact, fooLeft);
fooRight.setBar(barLeft);
session.update(fooRightFact, fooRight);
{/code}
I find it weird that even though I did NOT refresh fooRight the error goes away. For me,
such a fix would look feasible:
{code}
fooLeft.setBar(fooRight.getBar());
session.update(fooLeftFact, fooLeft);
fooRight = session.getObject(fooRight);<---- but I don't do this in real example,
still it does not fail
fooRight.setBar(barLeft);
session.update(fooRightFact, fooRight);
{/code}
Second point is that I take that the session.update() is synchronous, so it should NOT
matter if I do this
session.update(fooLeftFact, fooLeft);
fooRight.setBar(barLeft);
session.update(fooRightFact, fooRight);
or this
fooRight.setBar(barLeft);
session.update(fooLeftFact, fooLeft);
session.update(fooRightFact, fooRight);
the difference is just a few millis and i kinda cannot accept that the "correct"
working memory state depend on such sort of things and that it is intended behavior.
kind regards
Reinis
On 03/10/2012 08:24 PM, Wolfgang Laun wrote:
The Rete algorithm imposes severe restrictions on the way fact
updates
may be performed and the when and where these changes are advertised
to the inference engine.
The picture that's in my mind is one of many evaluations of boolean
expressions in parallel on many fact objects, partially being held up
due to lack of additional fact matches or true properties, and
partially waiting for being "fired"; and such evaluations are
"snapshot" as data structures in the Engine's memory. Due to an
announcement of a change in one fact such recorded evaluations may
have to be retracted and retraced, reevaluating conditions with their
unchanged partners. But some of that partner data may have been
represented in Engine memory, and this is what matters for the
reevaluation - not the actual content of that partner's object data.
-W
On 10 March 2012 19:38, Reinis <drools(a)orbit-x.de
<mailto:drools@orbit-x.de>> wrote:
Closing this thread!
Error was in this code-block:
{code}
fooLeft.setBar(fooRight.getBar());
fooRight.setBar(barLeft);
session.update(fooLeftFact, fooLeft);
session.update(fooRightFact, fooRight);
{code}
following fix makes the error go away:
{code}
fooLeft.setBar(fooRight.getBar());
session.update(fooLeftFact, fooLeft);
fooRight.setBar(barLeft);
session.update(fooRightFact, fooRight);
{code}
Pull request retracted and I have a bad taste in my mouth since I
have no technical/logical explanation why so.
Thank you guys for all the help!
On 03/09/2012 02:21 PM, Wolfgang Laun wrote:
> Works also with 5.4.0.Beta2.
>
> Does this really fail in the context of Drools' unit tests?
>
> -W
>
>
> On 9 March 2012 12:23, Wolfgang Laun <wolfgang.laun(a)gmail.com
<mailto:wolfgang.laun@gmail.com>
> <mailto:wolfgang.laun@gmail.com
<mailto:wolfgang.laun@gmail.com>>> wrote:
>
> Can't reproduce the described effect with 5.3.0.Final, will
look at
> 5.4.0.Beta2 later today.
>
> As far as I can see, the test case asserts the correct
result which
> Drools produces anyway?
>
> -W
>
> On 09/03/2012, ge0ffrey <ge0ffrey.spam(a)gmail.com
<mailto:ge0ffrey.spam@gmail.com>
> <mailto:ge0ffrey.spam@gmail.com
<mailto:ge0ffrey.spam@gmail.com>>> wrote:
> > Great work Reinis!
> >
> > --
> > View this message in context:
> >
>
http://drools.46999.n3.nabble.com/rules-users-Drools-Planner-Hard-constra...
> > Sent from the Drools: User forum mailing list archive at
Nabble.com.
> > _______________________________________________
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