[rules-users] Rule performance with accumulate

Tue Jan 15 10:27:08 EST 2013

Update:

Turns out I was looking in the wrong place. All along I had been looking
for a rule with accumulate based on AccumulateNode showing up in the stack
trace. By setting a conditional breakpoint in AccumulateNode that only
breaks when the result is AbstractList (I knew AbstractList.hashCode was
causing the performance problem) I was able to find the rule that caused
the problem...

The problem rule actually used "collect" not "accumulate"! Appears that
"collect" is implemented using "accumulate" under the covers. This explains
why I had trouble narrowing down my search.

In the problem rule "collect" was the last condition in WHEN. Additionally
the first condition matches a fact that is not inserted until late in rule
processing. It was clear from my investigation the work associated with
"collect" was happening much more frequently than I had expected (maybe
even as often as every fact inserted).

Once I found the problem rule it was straightforward to accomplish the same
effect without a "collect". In the heavy workload use case (hundreds of
thousand facts) this resulted in a 99% performance improvement.

I have not had the chance to create a simple rule set to reproduce the
problem so I can understand WHY this rule was so detrimental to
performance. For now I am happy reporting to my team the performance issue
is fixed and to be very careful when using collect and accumulate in the
future.

Thanks for the pointers.

On Wed, Jan 9, 2013 at 10:38 AM, Ryan Crumley <crumley at gmail.com> wrote:

> Thanks Geoffrey.
>
> I have a few rules that have two accumulates. Upgrading to 5.5 shouldn't
> be a problem so I will give that a try and see if it helps. Thanks for the
> tip!
>
>
> On Wed, Jan 9, 2013 at 8:37 AM, Geoffrey De Smet <ge0ffrey.spam at gmail.com>wrote:
>
>>  I 've also seen that accumulate and statefull don't always mix as good
>> as they could.
>> The new algorithm for 6.0 sounds promising to improve this (with "set
>> based propagation").
>>
>> Do you have any rule that has 2 accumulates in 1 rule?
>> That used to kill my statefull performance (3 times slower etc), but a
>> recent experiment with 5.5 showed that that's no longer the case IIRC.
>>
>> Op 09-01-13 15:09, Ryan Crumley schreef:
>>
>>  Hi,
>>
>>  I am investigating performance of a Drools 5.4 stateful knowledge
>> session. This session has about 200 rules, 200k facts and takes about 1
>> hour to run to completion. Looking at the profile there is a hotspot that
>> consumes almost 65% of the cpu time: java.util.AbstractList.hashCode().
>>
>>  Here is the full stack:
>>
>>
>>  com.company.rules.engine.Rule_Set_weights_08b44ce519a74b58ab3f85735b2987cbDefaultConsequenceInvoker.evaluate(KnowledgeHelper,
>> WorkingMemory)
>>
>>  com.company.rules.engine.Rule_Set_weights_08b44ce519a74b58ab3f85735b2987cbDefaultConsequenceInvokerGenerated.evaluate(KnowledgeHelper,
>> WorkingMemory)
>>
>>  com.company.rules.engine.Rule_Set_weights_08b44ce519a74b58ab3f85735b2987cb.defaultConsequence(KnowledgeHelper,
>> List, FactHandle, GradingFact, FactHandle, ReportNode, FactHandle,
>> WeightsHolder, FactHandle, Logger)
>>    org.drools.base.DefaultKnowledgeHelper.update(FactHandle, long)
>>    org.drools.common.NamedEntryPoint.update(FactHandle, Object, long,
>> Activation)
>>    org.drools.common.NamedEntryPoint.update(FactHandle, Object, long,
>> Activation)
>>
>>  org.drools.common.PropagationContextImpl.evaluateActionQueue(InternalWorkingMemory)
>>
>>  org.drools.reteoo.ReteooWorkingMemory$EvaluateResultConstraints.execute(InternalWorkingMemory)
>>
>>  org.drools.reteoo.AccumulateNode.evaluateResultConstraints(AccumulateNode$ActivitySource,
>> LeftTuple, PropagationContext, InternalWorkingMemory,
>> AccumulateNode$AccumulateMemory, AccumulateNode$AccumulateContext, boolean)
>>    org.drools.common.DefaultFactHandle.setObject(Object)
>>    java.util.AbstractList.hashCode()
>>
>>  I believe the following clues can be extracted:
>>
>>  - "Rule_Set_weights" was fired and a fact was modified (confirmed by
>> examining the rule definition)
>> - The fact modification caused the pre-conditions for other rules to be
>> computed.
>> - One of these rules has an accumulate condition that accumulates into an
>> AbstractList.
>> - This list is very very large. So large that looping through the
>> elements in the list and aggregating the hashCode of individual elements
>> dominates execution time (the individual element hashCode doesn't even show
>> up in the profile… either its very fast or maybe its identify hashCode
>> which the profiler might filter?).
>> - Accumulate is either working on a large set of data or the same
>> accumulate is evaluated many many times.
>>
>>  Is my analysis correct? Are there clues that I am missing?
>>
>>  I have 15 rules that use accumulate… However none accumulate with a
>> result of List. Most accumulate using sum() and count() (result of Number).
>> A few use collectSet(). A few more aggregate into a result with a custom
>> type.
>>
>>  A few other notes:
>> - All accumulate conditions are the last condition in the WHEN clause.
>> - I use agenda groups to separate fact processing into phases. Rules that
>> accumulate are in a separate agenda group from rules that modify/insert
>> facts that are used in accumulation. I hope this prevents the accumulate
>> condition from being evaluated until all the rules that modify the facts
>> accumulate needs are done firing. I suspect this may not be working as I
>> expect. I haven't put together an example to investigate.
>> - When accumulating into a set, the rule condition looks like this:
>>     $factName : Set() from accumulate( FactMatch( $field : field ),
>> collectionSet( $field ) )
>>
>>  How can I narrow down this further?
>>
>>  Are there any general rules to follow to optimize use of accumulate in
>> conditions?
>>
>>  Thanks,
>>
>>  Ryan
>>
>>
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