[rules-users] Improving Drools Memory Performance

[Wolfgang Laun]

On 9 July 2010 14:14, Mark Proctor <mproctor at codehaus.org> wrote:
>  You have many objects there that are not constrained;

I have an inkling that the functions.*() are hiding just these contraints,
It's certainly the wrong way, starting with oodles of node pairs, just to
pick out connected ones by fishing for the connecting edge. And this
is worsened by trying to find two such pairs which meet at some
DomainSource

Guesswork, hopefully educated ;-)

-W


> if there are
> multiple versions of those objects you are going to get massive amounts
> of cross products. Think in terms of SQL, each pattern you add is like
> an SQL join.
>
> Mark
> On 09/07/2010 09:20, Jevon Wright wrote:
>> Hi everyone,
>>
>> I am working on what appears to be a fairly complex rule base based on
>> EMF. The rules aren't operating over a huge number of facts (less than
>> 10,000 EObjects) and there aren't too many rules (less than 300), but
>> I am having a problem with running out of Java heap space (set at ~400
>> MB).
>>
>> Through investigation, I came to the conclusion that this is due to
>> the design of the rules, rather than the number of facts. The engine
>> uses less memory inserting many facts that use simple rules, compared
>> with inserting few facts that use many rules.
>>
>> Can anybody suggest some tips for reducing heap memory usage in
>> Drools? I don't have a time constraint, only a heap/memory constraint.
>> A sample rule in my project looks like this:
>>
>>    rule "Create QueryParameter for target container of DetailWire"
>>      when
>>        container : Frame( )
>>        schema : DomainSchema ( )
>>        domainSource : DomainSource ( )
>>        instance : DomainIterator( )
>>        selectEdge : SelectEdge ( eval (
>> functions.connectsSelect(selectEdge, instance, domainSource )) )
>>        schemaEdge : SchemaEdge ( eval (
>> functions.connectsSchema(schemaEdge, domainSource, schema )) )
>>        source : VisibleThing ( eContainer == container )
>>        target : Frame ( )
>>        instanceSet : SetWire ( eval(functions.connectsSet(instanceSet,
>> instance, source )) )
>>        detail : DetailWire ( )
>>        eval ( functions.connectsDetail(detail, source, target ))
>>        pk : DomainAttribute ( eContainer == schema, primaryKey == true )
>>        not ( queryPk : QueryParameter ( eContainer == target, name == pk.name ) )
>>        eval ( handler.veto( detail ))
>>
>>      then
>>        QueryParameter qp = handler.generatedQueryParameter(detail, target);
>>        handler.setName(qp, pk.getName());
>>        queue.add(qp, drools); // wraps insert(...)
>>
>>    end
>>
>> I try to order the select statements in an order that will reduce the
>> size of the cross-product (in theory), but I also try and keep the
>> rules fairly human readable. I try to avoid comparison operators like
>> <  and>. Analysing a heap dump shows that most of the memory is being
>> used in StatefulSession.nodeMemories>  PrimitiveLongMap.
>>
>> I am using a StatefulSession; if I understand correctly, I can't use a
>> StatelessSession with sequential mode since I am inserting facts as
>> part of the rules. If I also understand correctly, I'd like the Rete
>> graph to be tall, rather than wide.
>>
>> Some ideas I have thought of include the following:
>> 1. Creating a separate intermediary meta-model to split up the sizes
>> of the rules. e.g. instead of (if A and B and C then insert D), using
>> (if A and B then insert E; if E and C then insert D).
>> 2. Moving eval() statements directly into the Type(...) selectors.
>> 3. Removing eval() statements. Would this allow for better indexing by
>> the Rete algorithm?
>> 4. Reducing the height, or the width, of the class hierarchy of the
>> facts. e.g. Removing interfaces or abstract classes to reduce the
>> possible matches. Would this make a difference?
>> 5. Conversely, increasing the height, or the width, of the class
>> hierarchy. e.g. Adding interfaces or abstract classes to reduce field
>> accessors.
>> 6. Instead of using EObject.eContainer, creating an explicit
>> containment property in all of my EObjects.
>> 7. Creating a DSL that is human-readable, but allows for the
>> automation of some of these approaches.
>> 8. Moving all rules into one rule file, or splitting up rules into
>> smaller files.
>>
>> Is there kind of profiler for Drools that will let me see the size (or
>> the memory usage) of particular rules, or of the memory used after
>> inference? Ideally I'd use this to profile any changes.
>>
>> Thanks for any thoughts or tips! :-)
>>
>> Jevon
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>>
>>
>
>
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