[jboss-jira] [JBoss JIRA] Commented: (JBRULES-1322) Build in accumulate functions are highly unreliable for long's and BigDecimals

[Geoffrey De Smet (JIRA)]

    [ https://issues.jboss.org/browse/JBRULES-1322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12602507#comment-12602507 ] 

Geoffrey De Smet commented on JBRULES-1322:
-------------------------------------------

IMO, The only decent way to fix this is by fixing JBRULES-1075.
But it's important, it means that accumulate of financial data (such as insurances or mortgages) is plain wrong.

> Build in accumulate functions are highly unreliable for long's and BigDecimals
> ------------------------------------------------------------------------------
>
>                 Key: JBRULES-1322
>                 URL: https://issues.jboss.org/browse/JBRULES-1322
>             Project: Drools
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: drools-compiler
>    Affects Versions: 4.0.3
>            Reporter: Geoffrey De Smet
>            Assignee: Edson Tirelli
>            Priority: Critical
>             Fix For: 5.2.0.CR1
>
>         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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