[jboss-jira] [JBoss JIRA] Updated: (JBRULES-1322) Accumulate functions are highly unreliable for long's and BigDecimals

[Geoffrey De Smet (JIRA)]

     [ http://jira.jboss.com/jira/browse/JBRULES-1322?page=all ]

Geoffrey De Smet updated JBRULES-1322:
--------------------------------------

    Attachment: JBRULES-1322-testcase.patch

> Accumulate functions are highly unreliable for long's and BigDecimals
> ---------------------------------------------------------------------
>
>                 Key: JBRULES-1322
>                 URL: http://jira.jboss.com/jira/browse/JBRULES-1322
>             Project: JBoss Drools
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: Drl Parser/Builder
>    Affects Versions: 4.0.3
>            Reporter: Geoffrey De Smet
>         Assigned To: Edson Tirelli
>            Priority: Critical
>             Fix For: 4.1.0
>
>         Attachments: JBRULES-1322-testcase.patch
>
>
> When dealing with financial data, one should never ever use double's. Instead BigDecimal should be used.
> Not because BigDecimal is bigger (that's rarely a problem) but because it doesn't do any decimal to binary transformation.
> For example, it's impossible for a double to correctly represent "0.2", aka 1/5.
> Summing many doubles (or even a few differing in scale), can easily give wrong results (and for financial data this tends to be important).
> Using doubles to sum longs have the exact same problem.
> Attached is a testcase patch which proves this by checking if (MAX_LONG - 4L) and 3L sum up to be (MAX_LONG - 1L).
> Currently they don't.
> One possible way to solve this is to fix JBRULES-1075,
> which just happens to give drools-solver 3% more performance ;) what a coincidence ^^

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