Gilles updated MATH-1386:
      Priority: Trivial  (was: Major)
    Issue Type: Wish  (was: Bug)

> EPSILON value in  org.apache.commons.math.util.MathUtils seems like half of 
> what it should be
> ---------------------------------------------------------------------------------------------
>                 Key: MATH-1386
>                 URL: https://issues.apache.org/jira/browse/MATH-1386
>             Project: Commons Math
>          Issue Type: Wish
>         Environment: win 7
>            Reporter: Brian S. McCormick
>            Priority: Trivial
>   Original Estimate: 1h
>  Remaining Estimate: 1h
> I've always used 1.1920929E-7 for dealing with float epsilon values. When 
> dealing with double I've always used 2.220446049250313E-16 for epsilon.
> You have it defined in org.apache.commons.math.util.MathUtils as 
> 1.1102230246251565E-16 which is half what I think it should be.
> I come up with these numbers using the following:
> float fEps = Float.intBitsToFloat(Float.floatToIntBits(1f) + 1) - 1;
> double dEps = Double.longBitsToDouble(Double.doubleToLongBits(1) + 1) - 1;
> Am I correct? I don't really know. I do know that float epsilon in every 
> legacy C/C++ compiler etc I have ever used is defined as about 1e-7 and this 
> is the value using the formula for fEps above. When I started doing comps 
> using doubles instead of floats I started using the formula for dEps above 
> which looks to me like the equivalent for double numbers. 

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