[rules-dev] Lazily Enabled Truth Maintenace (Project Propsoal)

[Michael Anstis]

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.

On 14 September 2010 16:47, Mark Proctor <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.
>
> _______________________________________________
> rules-dev mailing list
> rules-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-dev/attachments/20100915/444ec347/attachment.html