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From "Thomas Neidhart (JIRA)" <>
Subject [jira] [Updated] (MATH-1269) FastMath.exp may return NaN for non-NaN arguments
Date Thu, 22 Oct 2015 21:22:27 GMT


Thomas Neidhart updated MATH-1269:
    Attachment: MATH-1269_fix_z.patch

I propose another patch for this issue.
The polynomial expansion for z = exp(epsilon) - 1.0 is actually returning wrong results in
case epsilon = 0.

The patch handles this case and further fixes the calculation of (1+z)(tempA+tempB) in case
z is 0 as well (in which case we only have to add tempA and tempB).

This would fix your case as well and other potential cases in the range [0, 709] for which
the epsilon is also 0.

> FastMath.exp may return NaN for non-NaN arguments
> -------------------------------------------------
>                 Key: MATH-1269
>                 URL:
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 4.0
>            Reporter: Otmar Ertl
>         Attachments: MATH-1269.patch, MATH-1269.patch, MATH-1269_fix_z.patch
> I have observed that FastMath.exp(709.8125) returns NaN. However, the exponential function
must never return NaN (if the argument is not NaN). The result must always be non-negative
or positive infinity.

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