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

[Geoffrey De Smet (JIRA)]

Accumulate functions are highly unreliable for long's and BigDecimals
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                 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


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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