[rules-users] Performance issues with a rule that includes LHS functions

[Wolfgang Laun]

Looks like an anti-pattern to me: you can expect O(n^3) effort for
inserting Data facts.

This is something where a procedural/algorithmic solution is preferable to
a
rule based solution.

-W


On 4 May 2012 18:44, Mike Goldner <mike at thegoldners.com> wrote:

> I have a rule that is suffering severe performance degradation as I insert
> facts into the (stateful) session.  In my simplified example, the first
> 100 fact insertions take less than 10ms per fact.  By the 1000th fact,
> insertions are taking about 850ms per fact.  In production, the impact is
> much more severe, reaching 5000ms or more by the 1000th insertion.  The
> number of facts per execution can vary from a few hundred to a few
> thousand.
>
> I've created a simplified example that demonstrates the problem:  Imagine
> that there is a line plotted through a 3-dimensional plane and it is
> necessary to ensure that each plotted coordinate is an equal distance from
> the adjacent coordinates.  I realize that the math isn't correct, but it
> is sufficient for the example.
>
> The constraint (and source of performance degradation) imposed by my data
> source is that the plane (X, Y, or Z) is variable and it is defined by an
> separate index that serves as a pointer into the coordinate list.  If I
> remove the function calls, the problem disappears.
>
> Any suggestions on how I could rewrite the rule?
>
> Here is my rule:
>
> package test;
>
> declare Data
>        plane : int
>        coordinates : java.util.List
> end
>
> rule "Performance degradation with functions."
>        dialect "mvel"
>        when
>                $current : Data( $currentPosition : getPosByAxis(plane,
> coordinates) )
>                $before : Data( $beforePosition : getPosByAxis(plane,
> coordinates) <
> $currentPosition)
>                not Data( getPosByAxis(plane, coordinates) >
> $beforePosition && <
> $currentPosition)
>                $after : Data($afterPosition : getPosByAxis(plane,
> coordinates) >
> $currentPosition)
>                not Data(getPosByAxis(plane, coordinates) < $afterPosition
> && >
> $currentPosition)
>                eval ( ($currentPosition - $beforePosition) ==
> ($afterPosition -
> $currentPosition) )
>        then
>                System.out.println("Rule RHS fired.");
> end
>
> function Double getPosByAxis(int plane, java.util.List coordinates) {
>
>        return (Double) coordinates.get(plane);
>
> }
>
> Thanks,
>
> Mike Goldner
>
>
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