2012/6/12 Thomas Neidhart <thomas.neidh...@gmail.com>: > On Tue, Jun 12, 2012 at 8:13 AM, Mikkel Meyer Andersen <m...@mikl.dk> wrote: > >> 2012/6/12 Thomas Neidhart <thomas.neidh...@gmail.com>: >> > On 06/08/2012 01:04 PM, m...@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 >> > >> > --------------------------------------------------------------------- >> > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >> > For additional commands, e-mail: dev-h...@commons.apache.org >> > >> Do you mean for n1n2prod? Sorry for my ignorance, but what would that >> help? Wouldn't that require more implicit conversions? >> > > I just quickly checked to make sure I had the right understanding, but the > line: > >>> + final double n1n2prod = n1 * n2; > > still does a int multiplication and may overflow (if n1 and n2 are too big). > > Maybe the overflow problem was not in this line but in this one: > >>> + final double VarU = n1n2prod * (n1 + n2 + 1) / 12.0; > > so the problem is hidden right now. > > Thomas Thomas, thanks for this. I have reopened the issue, https://issues.apache.org/jira/browse/MATH-790 . Would you be so kind to repeat your argument in there, and we can continue our discussion there?
Cheers, Mikkel. --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
