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
