6:25 p.m.
[ http://jira.jboss.com/jira/browse/JBRULES-1322?page=comments#action_12413726 ]
Geoffrey De Smet commented on JBRULES-1322:
-------------------------------------------
Actually, 45.1 and 40.0 are bad examples, because they get rounded by to the correct
double
Try this line of code:
System.out.println("0.05 + 0.01 = " + (0.05 + 0.01));
it gives
0.05 + 0.01 = 0.060000000000000005
Or try these numbers:
0.05 + 0.01 = 0.060000000000000005 not 0.06
0.06 + 0.01 = 0.06999999999999999 not 0.07
0.07 + 0.02 = 0.09000000000000001 not 0.09
0.07 + 0.04 = 0.11000000000000001 not 0.11
0.07 + 0.05 = 0.12000000000000001 not 0.12
0.08 + 0.07 = 0.15000000000000002 not 0.15
0.09 + 0.01 = 0.09999999999999999 not 0.1
0.09 + 0.08 = 0.16999999999999998 not 0.17
0.1 + 0.02 = 0.12000000000000001 not 0.12
0.1 + 0.05 = 0.15000000000000002 not 0.15
0.11 + 0.06 = 0.16999999999999998 not 0.17
0.11 + 0.1 = 0.21000000000000002 not 0.21
0.12 + 0.02 = 0.13999999999999999 not 0.14
0.12 + 0.05 = 0.16999999999999998 not 0.17
0.12 + 0.11 = 0.22999999999999998 not 0.23
0.13 + 0.08 = 0.21000000000000002 not 0.21
0.14 + 0.01 = 0.15000000000000002 not 0.15
0.14 + 0.04 = 0.18000000000000002 not 0.18
0.14 + 0.07 = 0.21000000000000002 not 0.21
0.14 + 0.08 = 0.22000000000000003 not 0.22
0.14 + 0.1 = 0.24000000000000002 not 0.24
0.15 + 0.02 = 0.16999999999999998 not 0.17
0.15 + 0.08 = 0.22999999999999998 not 0.23
0.15 + 0.14 = 0.29000000000000004 not 0.29
0.16 + 0.05 = 0.21000000000000002 not 0.21
0.16 + 0.13 = 0.29000000000000004 not 0.29
0.16 + 0.14 = 0.30000000000000004 not 0.3
0.17 + 0.01 = 0.18000000000000002 not 0.18
0.17 + 0.04 = 0.21000000000000002 not 0.21
0.17 + 0.05 = 0.22000000000000003 not 0.22
0.17 + 0.07 = 0.24000000000000002 not 0.24
0.17 + 0.12 = 0.29000000000000004 not 0.29
0.17 + 0.13 = 0.30000000000000004 not 0.3
0.17 + 0.14 = 0.31000000000000005 not 0.31
0.18 + 0.02 = 0.19999999999999998 not 0.2
0.18 + 0.05 = 0.22999999999999998 not 0.23
0.18 + 0.15 = 0.32999999999999996 not 0.33
0.18 + 0.16 = 0.33999999999999997 not 0.34
0.19 + 0.1 = 0.29000000000000004 not 0.29
0.19 + 0.15 = 0.33999999999999997 not 0.34
0.2 + 0.01 = 0.21000000000000002 not 0.21
0.2 + 0.04 = 0.24000000000000002 not 0.24
0.2 + 0.09 = 0.29000000000000004 not 0.29
0.2 + 0.1 = 0.30000000000000004 not 0.3
0.21 + 0.02 = 0.22999999999999998 not 0.23
0.21 + 0.12 = 0.32999999999999996 not 0.33
0.21 + 0.13 = 0.33999999999999997 not 0.34
0.21 + 0.2 = 0.41000000000000003 not 0.41
0.22 + 0.07 = 0.29000000000000004 not 0.29
0.22 + 0.12 = 0.33999999999999997 not 0.34
0.22 + 0.19 = 0.41000000000000003 not 0.41
0.22 + 0.2 = 0.42000000000000004 not 0.42
0.23 + 0.01 = 0.24000000000000002 not 0.24
0.23 + 0.06 = 0.29000000000000004 not 0.29
0.23 + 0.07 = 0.30000000000000004 not 0.3
0.23 + 0.18 = 0.41000000000000003 not 0.41
0.23 + 0.19 = 0.42000000000000004 not 0.42
0.23 + 0.2 = 0.43000000000000005 not 0.43
0.24 + 0.04 = 0.27999999999999997 not 0.28
0.24 + 0.09 = 0.32999999999999996 not 0.33
0.24 + 0.1 = 0.33999999999999997 not 0.34
0.24 + 0.17 = 0.41000000000000003 not 0.41
0.24 + 0.21 = 0.44999999999999996 not 0.45
0.24 + 0.22 = 0.45999999999999996 not 0.46
0.26 + 0.03 = 0.29000000000000004 not 0.29
0.26 + 0.15 = 0.41000000000000003 not 0.41
0.26 + 0.16 = 0.42000000000000004 not 0.42
0.26 + 0.17 = 0.43000000000000005 not 0.43
0.27 + 0.02 = 0.29000000000000004 not 0.29
0.27 + 0.03 = 0.30000000000000004 not 0.3
0.27 + 0.08 = 0.35000000000000003 not 0.35
0.27 + 0.14 = 0.41000000000000003 not 0.41
0.27 + 0.15 = 0.42000000000000004 not 0.42
0.27 + 0.16 = 0.43000000000000005 not 0.43
0.27 + 0.17 = 0.44000000000000006 not 0.44
0.27 + 0.2 = 0.47000000000000003 not 0.47
0.28 + 0.01 = 0.29000000000000004 not 0.29
0.28 + 0.02 = 0.30000000000000004 not 0.3
0.28 + 0.03 = 0.31000000000000005 not 0.31
0.28 + 0.07 = 0.35000000000000003 not 0.35
0.28 + 0.08 = 0.36000000000000004 not 0.36
0.28 + 0.13 = 0.41000000000000003 not 0.41
0.28 + 0.14 = 0.42000000000000004 not 0.42
0.28 + 0.15 = 0.43000000000000005 not 0.43
0.28 + 0.16 = 0.44000000000000006 not 0.44
0.28 + 0.17 = 0.45000000000000007 not 0.45
0.28 + 0.19 = 0.47000000000000003 not 0.47
0.28 + 0.2 = 0.48000000000000004 not 0.48
0.29 + 0.03 = 0.31999999999999995 not 0.32
0.29 + 0.04 = 0.32999999999999996 not 0.33
0.29 + 0.05 = 0.33999999999999997 not 0.34
0.29 + 0.11 = 0.39999999999999997 not 0.4
0.29 + 0.15 = 0.43999999999999995 not 0.44
0.29 + 0.16 = 0.44999999999999996 not 0.45
0.29 + 0.17 = 0.45999999999999996 not 0.46
0.29 + 0.28 = 0.5700000000000001 not 0.57
0.3 + 0.03 = 0.32999999999999996 not 0.33
0.3 + 0.04 = 0.33999999999999997 not 0.34
0.3 + 0.15 = 0.44999999999999996 not 0.45
0.3 + 0.16 = 0.45999999999999996 not 0.46
Build in 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: 5.0.0-M1
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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