<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
</head>
<body bgcolor="#ffffff" text="#000000">
Here is another project proposal, this time simpler. I think this
one has Wolfgang's name on it ;)<br>
<br>
<a
href="http://blog.athico.com/2010/09/lazily-enabled-truth-maintenace.html">http://blog.athico.com/2010/09/lazily-enabled-truth-maintenace.html</a><br>
<br>
Three weeks ago I posted the project idea for <a
href="http://blog.athico.com/2010/08/left-and-right-unlinking-community.html">"Left
and Right Unlinking"</a>. So far there are no takers, so if you
are interested let me know :)<br>
<br>
In the meantime I tried to think of a simpler enhancement that we
would like to see done.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
</body>
</html>