Hi Edson, hi all,

To stick to the subject, I have a strange problem (stack trace in PS) with a rule containing two accumulate calls, the result of the first one is re-injected as the input of the second one. Those accumulate functions are "home made".
The first one (tokenize) returns an ArrayList of Token objects built by tokenizing the "text" of the Sentence objects.
The second one (build10windows) returns an ArrayList of Window objects, each one them containing 10 consecutive tokens.
Here is the rule

    when         $budget : ManualAnnotation(text == "something")         $tokens : java.util.ArrayList() from accumulate ($s : Sentence(), tokenize($s))         $windows : java.util.ArrayList() from accumulate ($t : Token() from $tokens, build10windows($t))         # removed a part here but the problem occurs even without this part     then         retract($budget);
Is there anything else one should be aware of when implementing their own accumulate function? I mean things related to the fact that "classical" accumulate functions (sum, average) return an immutable object that does not share anything with the context object.
Although accumulate, reverse, and getResult methods of my functions are unit tested, I suspect something that could be related to stateless/stateful considerations.
What do you think?

Many thanks,

Bruno.

PS :

The stack trace is:
    at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
    at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:927)
    at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:856)
    at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1071)
    at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:785)
    at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:751)
    at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218)
    at org.drools.command.runtime.rule.FireAllRulesCommand.execute(FireAllRulesCommand.java:99)
    at org.drools.command.runtime.rule.FireAllRulesCommand.execute(FireAllRulesCommand.java:33)
    at org.drools.command.runtime.BatchExecutionCommandImpl.execute(BatchExecutionCommandImpl.java:159)
    at org.drools.command.runtime.BatchExecutionCommandImpl.execute(BatchExecutionCommandImpl.java:81)
    at org.drools.impl.StatelessKnowledgeSessionImpl.execute(StatelessKnowledgeSessionImpl.java:262)
    ... 5 more
Caused by: java.lang.NullPointerException
    at org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967)
    at org.drools.reteoo.AccumulateNode.splitList(AccumulateNode.java:920)
    at org.drools.reteoo.AccumulateNode.removePreviousMatchesForLeftTuple(AccumulateNode.java:874)
    at org.drools.reteoo.AccumulateNode.retractLeftTuple(AccumulateNode.java:205)
    at org.drools.reteoo.CompositeLeftTupleSinkAdapter.doPropagateRetractLeftTuple(CompositeLeftTupleSinkAdapter.java:238)
    at org.drools.reteoo.CompositeLeftTupleSinkAdapter.propagateRetractLeftTupleDestroyRightTuple(CompositeLeftTupleSinkAdapter.java:138)
    at org.drools.reteoo.AccumulateNode.retractLeftTuple(AccumulateNode.java:212)
    at org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:240)
    at org.drools.reteoo.EntryPointNode.retractObject(EntryPointNode.java:231)
    at org.drools.common.AbstractWorkingMemory.retract(AbstractWorkingMemory.java:1288)
    at org.drools.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:201)
    at org.drools.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:214)
    at defaultpkg.Rule_Display_windows_0.defaultConsequence(Rule_Display_windows_0.java:21)
    at defaultpkg.Rule_Display_windows_0DefaultConsequenceInvoker.evaluate(Rule_Display_windows_0DefaultConsequenceInvoker.java:29)
    at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:917)
    ... 15 more

Bruno.

Le 24/08/2011 16:21, Edson Tirelli a écrit :

Yes, evaluation is incremental, so for every new fact, it will call accumulate() and getResult().

We do want to reduce the calls to getResult(), improving performance, but it is not easy to figure out a way, as from an engine perspective, it never knows when the application is done inserting facts and it is time to calculate the final result.

Edson

2011/8/24 Bruno Freudensprung <bruno.freudensprung@temis.com>

Hi,

While testing my custom accumulation function I noticed an unexpected
behavior (th'ats of course a personal point of view).
It seems that Drools 5.1 calls accumulate(...) and getResult(...) as
many times as the number of accumulated facts (accumulate, getResult,
accumulate, getResult, etc...).
Is it supposed to work like this?

Best regards,

Bruno.

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Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com
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