commons-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Luc Maisonobe <Luc.Maison...@free.fr>
Subject Re: [math] Complex Tanh for "big" numbers
Date Fri, 09 Dec 2011 09:14:35 GMT
Le 09/12/2011 08:51, Juan Barandiaran a écrit :
> Hi,

Hi Juan,

> 
> In Complex.java the tanh is computed with the following formula:
> 
> tanh(a + bi) = sinh(2a)/(cosh(2a)+cos(2b)) + [sin(2b)/(cosh(2a)+cos(2b))]i
> 
> The problem that I'm finding is that as soon as "a" is a "big" number,
> both sinh(2a) and cosh(2a) are infinity and then the method tanh returns in
> the real part NaN (infinity/infinity) when it should return 1.0.
> 
> Wouldn't it be appropiate to add something as in the FastMath library??:
> 
> if (real>20.0){
>       return createComplex(1.0, 0.0);
> }
> if (real<-20.0){
>       return createComplex(-1.0, 0.0);
> }

Yes, this does make sense. Could you open a Jira issue with this request ?

Thanks,
Luc

> 
> 
> Best regards,
> 
> JBB
> 


---------------------------------------------------------------------
To unsubscribe, e-mail: user-unsubscribe@commons.apache.org
For additional commands, e-mail: user-help@commons.apache.org


Mime
View raw message