[jboss-jira] [JBoss JIRA] Commented: (JBRULES-1075) Support overloading of accumulate functions: Add int (or long) based sum's, int based avarage's, etc

[Edson Tirelli (JIRA)]

    [ https://issues.jboss.org/browse/JBRULES-1075?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12602586#comment-12602586 ] 

Edson Tirelli commented on JBRULES-1075:
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Geoffrey,

Just for documentation purposes for possible readers of this thread, I will state here what we discussed before: 

* the problem you describe is inherent to the accumulate function implementation of the default functions that ship with drools. On the other hand, anyone dealing with data that requires precision can easily implement their own accumulate functions using BigDecimal, BigIntegers or whatever data type best fits their requirement and they will have no rounding problems at all.

* the automatic selection of different functions based on the result type of the expression is tricky as it is not always possible to determine the result type. It would also be dangerous to those same users that you mention (like those doing financial calculations) as they must guarantee that a given function implementation is being used and not let the engine chose based on types that can mutate due to inheritance. Finally, it also requires users to always provide multiple function implementations for each datatype supported. I still intend to add a feature to do that, but at the moment I am not convinced this is the best way of doing it, so I haven't prioritized this ticket yet.

If anyone has a better suggestion, I am open to ideas.

Edson

> Support overloading of accumulate functions: Add int (or long) based sum's, int based avarage's, etc 
> -----------------------------------------------------------------------------------------------------
>
>                 Key: JBRULES-1075
>                 URL: https://issues.jboss.org/browse/JBRULES-1075
>             Project: Drools
>          Issue Type: Feature Request
>      Security Level: Public(Everyone can see) 
>          Components: drools-compiler
>    Affects Versions:  4.0.0.GA
>            Reporter: Geoffrey De Smet
>            Assignee: Edson Tirelli
>            Priority: Minor
>             Fix For: FUTURE
>
>         Attachments: JBRULES-1075.patch
>
>
> TTP nl10 solver has about a 3% performance increase when switching from sumDouble to sumLong (and possibly a bit more when switching to sumInteger)
> There are 2 ways I see to implement this:
> 1) Force the user to explicitly declare he wants to use an integer based sum and add a sumInteger.
> This is not so user-friendly. This is what I 've done in the patch.
> 2) Support overloading of accumulate functions based on the function arguments.
> AFAIK drl is strongly typed (at least with the java dialect), so it should be theoretically possible for the drl parser to see
>  sum($myInteger)
> and bind it to SumIntegerAccumulateFunction,
> while binding
>  sum($myInteger.doubleValue())
> to SumDoubleAccumulateFunction.
> And added advantage is that the drl compiler will also mark some bugs as compiler errors. For example
>   sum($myString)

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