[rules-dev] Lazily Enabled Truth Maintenace (Project Propsoal)
Mark Proctor
mproctor at codehaus.org
Mon Sep 20 11:14:34 EDT 2010
On 20/09/2010 15:53, Leonardo Gomes wrote:
> I think I wasn't quite clear in my last email, so let me try to
> reformulate it:
>
> I also gave it a try to try to do what you suggested here
> (http://blog.athico.com/2010/09/lazily-enabled-truth-maintenace.html),
> Mark, and couldn't make it work due to the following situation:
>
> 1) Current code seems to rely on the equality map to know that a
> logical insert (insertLogical) for an object that has already been
> regularly inserted (insert) should be ignored;
You would need to lazily maintain an equality map. When the first
logical insertion is done we will have to first populate that map from
the Object Type Node set of FactHandles.
In the "insert" one of the first lines is:
ObjectTypeConf typeConf =
this.typeConfReg.getObjectTypeConf( this.entryPoint,
object );
So we get the ObjectTypeConf before we do anything with the object
itself, and we can check if TMS is being maintained for that Object Type.
>
> 2) If I apply the modifications that you suggested, from what I
> understood, things would start to be put in the equality map only when
> a logical insert is issued;
>
> *Problem*: How would I handle the situation described in item 1, if I
> don't have anything in the equality map at the moment a logical insert
> comes in and I have to "lazily activate" TMS?
final Rete source = this.ruleBase.getRete();
ClassObjectType cot = new ClassObjectType( MyClass.class );
Map<ObjectType, ObjectTypeNode> map = source.getObjectTypeNodes(
EntryPoint.DEFAULT );
ObjectTypeNode node = map.get( cot );
final ObjectHashSet memory = (ObjectHashSet)
workingMemory.getNodeMemory( node );
That "memory" is the set of currently asserted objects for that OTN. You
can now iterate that and populate the equality hash map. This is a one
off as the flag will be set on the ObjectTypeConf from then on and all
objects will be added to the equality map at the point of insertion.
Does that help? All the information is there, you should have to know
how to retrieve it :) We don't currently maintain TMS for anything other
than the default entry point. Although I think that was a mistake and we
will probably move all entrypoints to work with same, but for now you
can ignore that and just focus on the default.
Btw this should not be confused with "equality" mode where the equality
map has to be maintained by default from the start. Some would argue
that a rule engine should only under work and understand on the bases of
equality and thus all users must implement hashcode and equals correctly...
>
> --
>
> Moreover, I'm willing to attempt to implement the left and right
> un-linking and tried to start with this easier task to start to get
> familiar with drools-core. I already read the article you linked and
> your article. Would you have any document with an overview of the way
> drools implements rete?
not really no, Rete has already well documented in a number of papers.
The best thing to do is get onto irc and talk directly to edson and I
and we can walk you through classes.
http://www.jboss.org/drools/irc.html
Mark
>
> Thanks in advance!
>
> Cheers,
> Leo.
>
>
>
>
>
>
> On Sat, Sep 18, 2010 at 3:49 AM, Leonardo Gomes
> <leonardo.f.gomes at gmail.com <mailto:leonardo.f.gomes at gmail.com>> wrote:
>
> if you look at the AbstractWorkingMemory insert method you'll
> see one argument is whether it's a logical insertion or not.
> You'll also see it check the global maintainTMS configuration
> and also retrieve the ObjectTypeConf. So between those things
> someone should be able to get it working.
>
>
> Today, it enters a block where it operates on the equality map and
> also creates a default handle based on that TMS global option and
> *regardless* of whether it's a logical insert.
>
> If I'm *not* putting things in the equality map for regular
> inserts, when a logical insert comes in, but there were already
> stated inserts, how will I know that? I would create a new handle
> for the logical insert and do the tms.addLogicalDependency(...),
> even tough there were regular inserts before and this seems to be
> a wrong behaviour.
>
> Apparently, today, you can disable TMS and still use logical
> inserts in your drl, what, I believe, will lead to inconsistent
> behaviour, but you're at your own risk.
>
> Ideas? I feel that I missed something :)
>
> Cheers,
> Leo.
>
> P.S.: I reached the conclusions above based on the fact that
> LogicalAssertionTest started failing after I did the changes you
> suggested.
>
>
>
>
> On Wed, Sep 15, 2010 at 3:47 PM, Mark Proctor
> <mproctor at codehaus.org <mailto:mproctor at codehaus.org>> wrote:
>
> On 15/09/2010 14:35, Michael Anstis wrote:
>> Is this in drools-core; or drools-compiler?
>>
>> Whilst not undertaking to do the work; have a purpose to nose
>> through the code makes understanding easier.
> It's all in DroolsCore.
>
> It's a 5 minute hack for me and then 15 minute unit writing
> test. But I thought I'd write it up in a hope to bring someone
> else into the fold, we need more help writting the core engine
> someone else out there must want to work on current edge
> engine design :)
>
> if you look at the AbstractWorkingMemory insert method you'll
> see one argument is whether it's a logical insertion or not.
> You'll also see it check the global maintainTMS configuration
> and also retrieve the ObjectTypeConf. So between those things
> someone should be able to get it working.
>
> Mark
>
>>
>> On 14 September 2010 16:47, Mark Proctor
>> <mproctor at codehaus.org <mailto:mproctor at codehaus.org>> wrote:
>>
>> Here is another project proposal, this time simpler. I
>> think this one has Wolfgang's name on it ;)
>>
>> http://blog.athico.com/2010/09/lazily-enabled-truth-maintenace.html
>>
>> Three weeks ago I posted the project idea for "Left and
>> Right Unlinking"
>> <http://blog.athico.com/2010/08/left-and-right-unlinking-community.html>.
>> So far there are no takers, so if you are interested let
>> me know :)
>>
>> In the meantime I tried to think of a simpler enhancement
>> that we would like to see done.
>>
>> At the moment Drools has a user setting
>> "MaintainTMSOption" which can be true or false. It's a
>> small optimisation that when turned off avoids using the
>> equality hashmap that is maintained for all inserted objects.
>>
>> It would be a much better idea to remove this
>> configuration setting, thus simplifying things for end
>> users and have TMS lazily enabled on demand.
>>
>> For each object type there is an "ObjectTypeConf"
>> configuration object that is retrieved every time a
>> working memory action, such as insert, is executed. The
>> enabledTMS boolean should be moved there, so there is one
>> per object type, by default it is false.
>>
>> When a working memory action occurs, like insert, it
>> retrieved the ObjectTypeConf and checks the maintainTms
>> boolean there, instead of the current engine scoped
>> configuration. When a logical insertion occurs and the
>> ObjectTypeConf is retrieved if maintainTms is false it
>> sets the value to true and then iterates the associated
>> ObjectTypeNode memory lazily adding all the objects to
>> the TMS equality map. From then on for that ObjectType
>> all inserted objects are added to that equality map.
>>
>> With this you now have the advantage of TMS being laziy
>> enabled, so the minor hashmap operation is no longer used
>> and likewise a small memory saving from not populating
>> the map. There is a further advantage that this is now
>> fine grained and when enabled only impacts for that
>> specific object type.
>>
>> A further enhancement could use a int counter, instead of
>> a boolean. Each logical insertion for that object type
>> increases the counter, each retraction decreases the
>> counter; even if automatically retracted if the truth is
>> broken for that logical assertion. When the counter
>> reaches zero, TMS for that OTN can be disabled. We do not
>> however remove the objects from the equality map, as this
>> would cause "churn" if TMS is continuously enabled and
>> disabled. Instead when TMS is disabled record the current
>> fact counter id. Then if TMS is disabled on a retraction
>> but there is a counter id, we can check that counter id
>> to see if the fact is prior to TMS being disabled and
>> thus would need to be retracted from the equality map.
>>
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