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https://issues.apache.org/jira/browse/MATH-1386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15504074#comment-15504074
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Brian McCormick commented on MATH-1386:
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double epsilon = Double.longBitsToDouble(Double.doubleToLongBits(1) + 1) -
1;
Brian McCormick
MCB Systems Inc.
Phone: 918-749-5453
email: [email protected]
> 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: Bug
> Environment: win 7
> Reporter: Brian S. McCormick
> 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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