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Gilles commented on MATH905:

bq. Any specific reason why you prefer multiplication by 0.5 over division by 2, or just personal
preference?
I've doing that since having read that multiplication is simpler (thus potentially faster)
than division.
Never tried to benchmark.
> FastMath.[cosh, sinh] do not support the same range of values as the Math counterparts
> 
>
> Key: MATH905
> URL: https://issues.apache.org/jira/browse/MATH905
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.0
> Reporter: Thomas Neidhart
> Fix For: 3.1
>
> Attachments: MATH905.diff
>
>
> As reported by Jeff Hain:
> cosh(double) and sinh(double):
> Math.cosh(709.783) = 8.991046692770538E307
> FastMath.cosh(709.783) = Infinity
> Math.sinh(709.783) = 8.991046692770538E307
> FastMath.sinh(709.783) = Infinity
> ===> This is due to using exp( x )/2 for values of x
> above 20: the result sometimes should not overflow,
> but exp( x ) does, so we end up with some infinity.
> ===> for values of x >= StrictMath.log(Double.MAX_VALUE),
> exp will overflow, so you need to use that instead:
> for x positive:
> double t = exp(x*0.5);
> return (0.5*t)*t;
> for x negative:
> double t = exp(x*0.5);
> return (0.5*t)*t;

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