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From Mikkel Meyer Andersen <m...@mikl.dk>
Subject Re: svn commit: r1348024 - in /commons/proper/math/trunk/src: main/java/org/apache/commons/math3/stat/inference/MannWhitneyUTest.java test/java/org/apache/commons/math3/stat/inference/MannWhitneyUTestTest.java
Date Tue, 12 Jun 2012 06:13:41 GMT
2012/6/12 Thomas Neidhart <thomas.neidhart@gmail.com>:
> On 06/08/2012 01:04 PM, mikl@apache.org wrote:
>> Author: mikl
>> Date: Fri Jun  8 11:04:11 2012
>> New Revision: 1348024
>>
>> URL: http://svn.apache.org/viewvc?rev=1348024&view=rev
>> Log:
>> MATH-790: Patch applied to fix the overflow issue.
>>
>> Modified:
>>     commons/proper/math/trunk/src/main/java/org/apache/commons/math3/stat/inference/MannWhitneyUTest.java
>>     commons/proper/math/trunk/src/test/java/org/apache/commons/math3/stat/inference/MannWhitneyUTestTest.java
>>
>> Modified: commons/proper/math/trunk/src/main/java/org/apache/commons/math3/stat/inference/MannWhitneyUTest.java
>> URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/stat/inference/MannWhitneyUTest.java?rev=1348024&r1=1348023&r2=1348024&view=diff
>> ==============================================================================
>> --- commons/proper/math/trunk/src/main/java/org/apache/commons/math3/stat/inference/MannWhitneyUTest.java
(original)
>> +++ commons/proper/math/trunk/src/main/java/org/apache/commons/math3/stat/inference/MannWhitneyUTest.java
Fri Jun  8 11:04:11 2012
>> @@ -170,11 +170,11 @@ public class MannWhitneyUTest {
>>                                               final int n2)
>>          throws ConvergenceException, MaxCountExceededException {
>>
>> -        final int n1n2prod = n1 * n2;
>> +        final double n1n2prod = n1 * n2;
>>
>>          // http://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U#Normal_approximation
>> -        final double EU = (double) n1n2prod / 2.0;
>> -        final double VarU = (double) (n1n2prod * (n1 + n2 + 1)) / 12.0;
>> +        final double EU = n1n2prod / 2.0;
>> +        final double VarU = n1n2prod * (n1 + n2 + 1) / 12.0;
>>
>>          final double z = (Umin - EU) / FastMath.sqrt(VarU);
>
> just a small thing, but wouldn't it be better to do a long
> multiplication and convert the result to double?
>
> Thomas
>
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>
Do you mean for n1n2prod? Sorry for my ignorance, but what would that
help? Wouldn't that require more implicit conversions?

Cheers, Mikkel.

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