[rules-users] Drools stateless session question

Wolfgang Laun wolfgang.laun at gmail.com
Tue Mar 23 05:05:16 EDT 2010 

All right, so the id attributes are unique? Try the preferred way of
writing this:

when
   Obj_A: A( $id : id, a !=1 )
   Obj_B: B( id == $id, b != 2 )
   Obj_C: C( id == $id, c != 3 )

Drools uses indexing, and this is automatically utilized by using
<field> == <value> ( or != )

-W

2010/3/22 Shah, Malay <Malay.Shah at morganstanley.com>:
> It will be 1 trillion activations unless there is an index on the "id"
> property of the classes. If the right index is used, it should scan all
> objects of one class, and through indexes figure out the corresponding
> related objects of other classes. I am not sure if we can somehow tell rete
> to create indexes on certain attributes. I read a nice article on indexing
> in drools, which mentioned about Rete Beta node indexing. I am not sure if
> this is what drools is doing internally. Any suggestions/ideas?
>
> http://blog.decaresystems.ie/index.php/2008/02/24/rete-nodes-indexing-in-drools/
>
> Thanks,
> Malay
> ________________________________
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Wolfgang Laun
> Sent: Monday, March 22, 2010 3:17 PM
> To: Rules Users List
> Subject: Re: [rules-users] Drools stateless session question
>
> You have calculated it correctly: 10000 A's * 10000 B's * 10000 C's results
> in 1,000.000,000.000 activations, which is (almost) a mind-boggling figure.
> I can't imagine what benefit this trillion of activations is going to have
> for your application. Even if you have the memory for all that, assuming
> that firing of one of these activations and processing of the RHS statements
> can be done in one microsecond, this is going to take days to complete, and
> it'll create a huge data set of A/B/C combinations for just this one rule.
>
> Are you sure that you are on the right track?!
>
> -W
>
>
> On Mon, Mar 22, 2010 at 7:46 PM, Shah, Malay <Malay.Shah at morganstanley.com>
> wrote:
>>
>> Thanks W. Let me give you a rule that is causing us issues. Lets say we
>> have classes:
>>
>> class A
>> {
>>        int a;
>>        String id;
>> }
>> Class B
>> {
>>        int  b;
>>        String id;
>> }
>> Class C
>> {
>>        int c;
>>        String id;
>> }
>>
>> and we have 12000 objects each. These objects are connected using "id"
>> property.
>> If the rule is something like:
>>
>> Rule "ABC"
>> When
>>        Obj_A: A(a!=1)                  //10000 object "A" instances have
>> a!=1
>>        Obj_B: B(b!=2,Obj_A.id = id)            //10000 object "B"
>> instances have b!=2
>>        Obj_C: C(c!=3,Obj_B.id = id)            //10000 object "C"
>> instances have c!=3
>> Then
>>        System.out.println("Rule fired");
>> End
>>
>> This means there would be a join between A, B and C objects (10000 A's *
>> 10000 B's * 10000 C's) to evaluate the rule. In such cases, we see very high
>> org.drools.reteoo.LeftTuple object count while profiling the app. Is there a
>> way to make the rete algo perform this evaluation serially, or in batches,
>> or use some object swapping mechanism to limit creation of intermediate
>> LeftTuple objects? Would the rete algo use indexes in this case? That would
>> potentially decrease these intermediate objects. Currently, we use 5G heap
>> and that is not enough for evaluating this rule.
>>
>> Regards,
>> Malay
>>
>> -----Original Message-----
>> From: rules-users-bounces at lists.jboss.org
>> [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Wolfgang Laun
>> Sent: Monday, March 22, 2010 12:39 PM
>> To: Rules Users List
>> Subject: Re: [rules-users] Drools stateless session question
>>
>> You have misunderstood the documentation. All eight items in the
>> enumeration you cite from are steps performed internally by the Drools
>> engine. The only thing you have to do is request sequential mode.
>>
>> Without an idea about the rule set you are using it's difficult to advise
>> how to reduce memory consumption.
>>
>> -W
>>
>>
>> 2010/3/22 Shah, Malay <Malay.Shah at morganstanley.com>:
>> > Hi All,
>> >
>> > We have an application that uses drools stateless session over a set
>> > of 35000 objects (taking about 40 MB heap) of different types. During
>> > profiling, I saw that for rules that perform joins between two huge
>> > object types data sets, lots of org.drools.reteoo.LeftTuple objects
>> > causing out of memory errors. We are using 5G heap, and have set
>> > property drools.sequential=true too. Is there any way we can decrease
>> > the memory usage while applying these rules? Drools documentation
>> > mentions  for sequential mode, we should do the following, some of
>> > them I am not sure how to set:
>> >
>> >
>> > Turn off all node memories, except the right-input Object memory.
>> >
>> > Disconnect the LeftInputAdapterNode propagation, and have the Object
>> > plus the Node referenced in a Command object, which is added to a list
>> > on the WorkingMemory for later execution.
>> >
>> > Assert all objects, when all assertions are finished and thus
>> > right-input node memories are populated check the Command list and
>> > execute each in turn.
>> >
>> > http://downloads.jboss.com/drools/docs/4.0.7.19894.GA/html_single/inde
>> > x.html#d0e1295
>> >
>> > Do we need to set some properties in RuleBaseConfiguration to make
>> > sure node memories are switched off? It would be great if we can
>> > somehow decrease the memory usage for stateless sessions? Has anybody
>> > come across such memory issues before? Correct me if I am wrong, but I
>> > think 35000 objects is not a lot of data for causing such issues.
>> >
>> > Thanks
>> > Malay
>> > ________________________________
>> >
>> > NOTICE: If received in error, please destroy, and notify sender.
>> > Sender does not intend to waive confidentiality or privilege. Use of
>> > this email is prohibited when received in error. We may monitor and
>> > store emails to the extent permitted by applicable law.
>> >
>> > ________________________________
>> >
>> > NOTICE: If received in error, please destroy, and notify sender.
>> > Sender does not intend to waive confidentiality or privilege. Use of
>> > this email is prohibited when received in error. We may monitor and
>> > store emails to the extent permitted by applicable law.
>> >
>> > _______________________________________________
>> > rules-users mailing list
>> > rules-users at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/rules-users
>> >
>> >
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>> --------------------------------------------------------------------------
>> NOTICE: If received in error, please destroy, and notify sender. Sender
>> does not intend to waive confidentiality or privilege. Use of this email is
>> prohibited when received in error. We may monitor and store emails to the
>> extent permitted by applicable law.
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>
> ________________________________
>
> NOTICE: If received in error, please destroy, and notify sender. Sender does
> not intend to waive confidentiality or privilege. Use of this email is
> prohibited when received in error. We may monitor and store emails to the
> extent permitted by applicable law.
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>

More information about the rules-users mailing list